AGL/MISC/23/99
INTEGRATED SOIL MANAGEMENT FOR SUSTAINABLE AGRICULTURE AND FOOD SECURITY IN SOUTHERN AND EAST AFRICA AGL/MISC/23/99
INTEGRATED SOIL MANAGEMENT FOR SUSTAINABLE AGRICULTURE AND FOOD SECURITY IN SOUTHERN AND EAST AFRICA
PROCEEDINGS OF THE EXPERT CONSULTATION
Harare, Zimbabwe 8-12 December 1997
H. Nabhan A. M. Mashali
A. R. Mermut
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 1999
Preface
Land degradation, either natural or induced by humans, is a continuing process. It has become, however, an important issue through its adverse effects on national natural resources, food security, and the livelihood of the world population. Much has been said and documented about land degradation but there are still gaps of knowledge, due to the fact that only a few countries have really developed cost-effective technologies for mitigation. Inappropriate land use is a major cause of declining soil quality. In many countries, especially in sub Saharan Africa, there is continuous stress on the limited land resources due to population pressure. Food security is directly related to the ability of land to support the population.
Causes for land degradation are numerous and include decline of soil fertility, development of acidity, salinization, alkalization, deterioration of soil structure, accelerated wind and water erosion, loss of organic matter and biodiversity. Efforts to restore productivity of a degraded land must be coupled with efforts to recognize productive capacity of soil resources. Restoring the soil quality for crop production through the appropriate soil management and conservation techniques is important for all nations, primarily those at risk with respect to food security. Although cost effective options are available to restore the soil quality and productivity, there is a need to increase awareness at high policy-making level with sound scientific evidence. It is, therefore, important to develop spatial or other databases about the extent of soil degradation, its biophysical, economic and social impacts, as well as successful examples of soil productivity improvement programmes.
The FAO Land and Water Development Division (AGL), in collaboration with the Subregional Office for Southern and East Africa (SAFR) and the Agricultural Technical and Extension Services (AGRITEX) of Zimbabwe, organized this expert Consultation on "Integrated Soil Management for Sustainable Agriculture and Food Security" with the following main objectives: · examine the status of land degradation under contrasting agro-ecological conditions; · exchange experiences on constraints for controlling land degradation and examine possible solutions to overcome these constraints; · discuss proposals for national and subregional programmes in support of land development schemes to enhance soil productivity, in support of food security in sub- Saharan Africa.
During the Consultation, held in Harare from 8 to 12 December 1997, overview and country papers were presented by senior specialists from Eritrea, Ethiopia, Kenya, Malawi, Namibia, South Africa, Tanzania, Uganda, Zambia, and Zimbabwe, FAO Headquarters and from many national and international institutions. Besides the representatives from the ten countries, an additional ten soil scientists, agricultural land development planners, extensionists and farmers’ union officials from various Ministry of Agriculture departments of Zimbabwe, as well as eight scientists from the Tropical Soil Biology and Fertility Programme (TSBF), and FAO consultants and resource persons from the UK, Sweden and the International Soil Research and Information Centre (ISRIC) participated in the Consultation. The wide range of participants in the iv
consultation reflects the international interest in land degradation in sub Saharan Africa. These proceedings provide very useful information about land degradation in general and the situation in the ten countries of the region.
In the light of discussions, recommendations are made to increase exchange of experience and activities in the area of research and technology development, especially the assessment methodologies, extension and training, policies and legislation, strategies, publications and networking. Integrated soil management for sustainable agriculture and food security in Southern and East Africa v
Contents
page
SUMMARY REPORT 1
OVERVIEW PAPERS 15
Land degradation with focus on salinization and its management in Africa, by A.M. Mashali 17
Land degradation in relation to food security with focus on soil fertility management, by H. Nabhan 49
Erosion-induced loss in soil productivity and its impacts on agricultural production and food security, by M. Stocking and A. Tengberg 91
Soil degradation assessment and soil conservation inventory on a SOTER basis: Asian experience, by G.W.J. Van Lynden 121
Socio-economic impacts of soil management for sustainable agriculture and food security in Africa; with particular reference to Zimbabwe, by D. Tawonezi and P.N. Sithole 127
Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe, by G. Nehanda 153
COUNTRY REPORTS 177
Eritrea 179 Ethiopia 197 Kenya 211 Malawi 231 Namibia 247 South Africa 263 Tanzania 295 Uganda 319 Zambia 337 Zimbabwe 355 vi
Annex 1 Opening and closing addresses 383
Annex 2 Programme 389
Annex 3 List of participants 393
Annex 4 Maps 397 Integrated soil management for sustainable agriculture and food security in Southern and East Africa vii
Acknowledgements
The contribution through country and overview papers by the country specialists and resource persons is greatly acknowledged.
The efforts of AGRITEX staff, Messrs H.Nabhan, A.Mashali, C.F Mushambi, A.Savva and Ms K. Franken in the organization of the Expert Consultation are highly appreciated .
Special thanks are due to Messrs H.Nabhan, A.Mashali, M.Gosi ,and A.R. Mermut for the compilation, review and editing of these proceedings . Integrated soil management for sustainable agriculture and food security in Southern and East Africa 1
Summary report
Nearly one thousand million ha of vegetated land in developing countries are subjected to various forms of degradation, resulting in moderate or severe decline in productivity. About 490 million ha in Africa are affected by different types of degradation from the approximately 2 976 million ha total land area in Africa. Of this total land, 72% (2 146 million ha) are problem soils with different production constraints (soil acidity, vertic properties, low fertility, shallow soils, saline and poorly drained soils). Poor and inappropriate soil management is the main cause of physical and chemical degradation of cultivated land. Soil degradation is the most serious environmental problem affecting sub-Saharan Africa (SSA). In many parts of SSA fallow periods are being reduced considerably and farmers are increasingly cultivating marginal lands susceptible to various forms of degradation. Increasing population pressure, particularly in vulnerable regions has caused serious soil productivity decline especially under extensive farming practices. This is manifested by declining yields, decreasing vegetation cover, salinization, fertility decline and increasing erosion. With recent emphasis on the priority programme of FAO on Food Production in Support of Food Security (SPFS), issues related to land degradation and its negative impact on food production as well as land improvement for enhanced productivity are receiving special attention. Rectifying soil degradation and sustaining crop production through appropriate management and conservation are, therefore, important components in the effort towards security. Successful experience and initiatives for soil improvement in specific countries or socio-economic and agro- ecological environments have taken place but their wider dissemination for the benefit of other countries, even in the same region, is rather limited. There is an urgent need to develop and implement sub-regional and national programmes, as well as projects at community level to control land degradation and to improve land productivity. Therefore, the FAO Land and Water Development Division (AGL), in collaboration with the Subregional Office for Southern and East Africa (SAFR) and the Agricultural Technical Extension Services (AGRITEX) of Zimbabwe, has organized this Expert Consultation The FAO Subregional Office for Southern and East Africa represents 21 countries. Of these, four are in the Indian Ocean and 17 are within the continent of Africa (Figure 1).
Out of the 21 countries, ten were given the opportunity to participate in this important Expert Consultative Workshop on Integrated Soil Management for Sustainable Agriculture and Food Security. The main objectives of the workshop were: · Discuss the status of land degradation under contrasting agro-ecological and socio-economic conditions. · Exchange experiences on constraints for controlling land degradation and examine possible solutions to overcome these constraints. · Develop national and sub-regional programmes in support of land development schemes to enhance productivity in support of food security in the region. 2 Summary report
FIGURE 1 Countries served by the FAO Subregional Office for Southern and East Africa
Reversing the process of soil degradation and sustaining crop productivity through soil management and biodiversity conservation are important aspects of food security. Although cost effective options are available, there is a need to increase the awareness campaign at high policy- making level as well as maintain the determination of agriculturists to achieve their goals. It is, therefore, important to document the information on the extent of soil degradation, its biophysical, economic and social impacts as well as successful examples of soil improvement programmes within the region.
ATTENDANCE The Expert Consultation was attended by senior specialists from ten African countries of the Subregion for Southern and East Africa: Eritrea, Ethiopia, Kenya, Malawi, Namibia, South Africa, Tanzania, Uganda, Zambia and Zimbabwe. Besides representatives from the mentioned countries, some ten soil scientists, agricultural land development planners, extension and farmers' Integrated soil management for sustainable agriculture and food security in Southern and East Africa 3
unions from relevant departments of Zimbabwe, as well as eight scientists from the Tropical Soil Biology and Fertility Programme (TSBF) - Kenya, Malawi, Tanzania Zambia, Zimbabwe and Uganda - and officials from FAO Headquarters (2), FAO Subregional Office for Southern and East Africa (2), Regional Office for Africa (1) and FAO consultants and resource persons from England, Sweden and the International Soil Research and Information Centre (ISRIC) participated in the Consultation, with a total of 35 participants.
OPENING OF THE EXPERT CONSULTATION On Monday, 8 December, after registration of the participants, the Opening Session took place at St. Lucia Park Training and Development Center, where H.E. the Minister of Lands and Agriculture, Cde Kumbirai Kangai and the Chief of the Soil Resources, Management and Conservation Service of FAO Headquarters, Dr P. Koohafkan (on behalf of the Land and Water Development Division of FAO, and the Southern and East Africa Subregional FAO Representative, Ms V. Sekitoleko), addressed the Expert Consultation. The opening session was followed by three overview papers on (i) Land degradation and its impact with focus on salinity and fertility decline and their management; (ii) Erosion induced loss productivity, its implication on land use and food security; and (iii) Methodologies of soil degradation assessment with focus on GLASSOD /SOTER using the Asian experience (ASSOD).
COUNTRY PAPERS Three technical sessions were devoted to discussion of country papers on: · Evaluation of country production and projected demands · Evaluation of per caput arable land, crop yields and causes of yield stagnation · Assessment of soil degradation: its causes and its bio-physical and socio-economic impact · Available technological options for controlling soil degradation and for productivity · Successful cases on improved soil management scheme and reasons for success · Institutional, socio-economic and policy issues related to land resources and degradation.
Three papers were also presented from Zimbabwe on: · Socio-economic aspects of soil management for sustainable agriculture and food security in Africa · Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe · Water harvesting and small-scale irrigation.
OTHER BUSINESS A video show of the 14th meeting of the Soil Science Society of East Africa (SSSEA) on "Enhancing farmers efforts to combat soil degradation has been demonstrated to the Consultation participants. The video indicated that scientists, administrators, policy makers and farmers were concerned with the issue of soil degradation in the sub-region (Uganda and Tanzania participated in that meeting). Commitment of Uganda Government and other sub-regional governments to the issue of soil degradation was outlined. The SSSEA members were happy to note that FAO would 4 Summary report
respond to the deterioration of soil productivity through the establishment of a new Southern and East Africa Subregional Network on Management of Degraded Soils.
One day (10 December) was devoted to field visits and on-site discussions. The participants were driven to Mangwende Communal Area in Murehua and shown three programmes on soil fertility: · The effect-of low and high quality manure on the improvement of soil fertility on crop. · The effect of storage practices on the quality of communal area manure. · The use of legume inoculant on a crop of soybeans and the effect of residual N (Nitrogen) on crop rotation.
After discussions on each programme, the participants were shown active and reclaimed gullies in the same area. Lastly, the group visited a stream bank conservation programme, where farmers are encouraged to cultivate pieces of land situated away from the river bank. On this piece of land, these farmers were provided with fencing materials by the Department of Natural Resources and a well for drawing water was dug using funds from a donor agent. The water is used for irrigating the gardens.
PARTICIPATORY WORKING GROUP DISCUSSIONS One and-a-half days have been devoted to group discussions. The participants were divided into three groups to discuss the following issues: · present and outlook for food production and security in the participating countries, · identification of land degradation and degraded soils - quantification of magnitude and distribution, · assessment of human-induced soil degradation, proposals, methodologies for assessment. Soil vulnerability to different degradation processes (as early warning system). If methodologies are available, how they can be used for the sub-region (data availability to carry out such assessment), · dominant types of land degradation, (chemical, physical, biological), causes and processes, · research, measuring, interpretation and prediction methods including new technologies (modelling, GIS, expert system, decision support system, remote sensing, etc.), · bio-physical-environmental and socio-economic impacts of soil degradation: (i) evidence and indicators of impacts of degradation on productivity, and (ii) assessment of economic impacts of degradation, · technologies available for improving the productivity of degraded soils: constraints and solutions. Sustainable integrated management of degraded soils (techniques): (i) available technologies for addressing or controlling various types of degradation: and physical degradation - fertility decline – salinization and (ii) analysis of factors which are limiting wider adoption of improved technologies to above major types of degradation, · policy and land tenure issues: institution set-up and coordination at local subnational and national level, farmers' participation in land improvement schemes, role of associations, cooperatives, extension services: (i) government responsibility: monitoring of soil degradation, control at country and regional level (regulation, legislation, etc.) and (ii) Integrated soil management for sustainable agriculture and food security in Southern and East Africa 5
influencing, decision makers/increasing awareness about land degradation and solutions for land productivity improvement, · research and monitoring requirements: (i) applied research, decision support system, integrated approach, monitoring system, requiring more research, mechanism, programmes and government support and interest, (ii) the role of private (multinational) companies, large farms, and (iii) the role of farmer associations, organizations, · national and regional plans for improvement and control of soil degradation, · proposal for a network on management of degraded and problem soils in the subregion - objectives, activities, mechanisms, membership and expected outputs including newsletters/publications, pilot field activities (demonstration of trials on improved management techniques), training, workshop, etc.
At the end of these group discussions, three summary reports were produced.
RECOMMENDATIONS In the light of the discussions, the Expert Consultation agreed on the following recommendations as the basis of future activities.
Technologies and Research · Further investigation and understanding of existing indigenous technologies, · Compiling available technologies, · Pursue integrated and sustainable soil management issues such as biophysical, economic and social viability, · Develop problem oriented and farmer participatory research approach to tackle land degradation problems in the sub-region.
Extension and Training · Both demonstrations and training of people (research, extension, farmer) should be part of the introduction of new technologies, · Technologies should be made available to farmers through extension programmes in the country wherever applicable, · Support for farmer conservation groups.
Policies, Institutions and Laws · Formulate effective land tenure and land use policies to create conducive environment for improved integrated management technology for land degradation control, · Creation of enabling policies to encourage management, conservation and sustainability of land resources should include land tenure, environmental protection and a set of framework for conservation, · Countries should commit themselves to review natural resources and implementation of the policies, 6 Summary report
· People should be trained to implement these policies, · Create strong institutions to backstop management and conservation initiatives at local level, · Strengthen institutional capacity to adopt and utilize new and improved technologies.
Strategies · Causes of food insecurity should be identified as well as strategies to address these causes and the possible constraints to these strategies.
Models · Prediction models should be used as possible scenarios to monitor land degradation.
Standard Analytical Methods · Quality control and standardized analytical methods are required to make comparison of results between countries within the sub-region.
Assessment of methodologies · Available methodologies for the assessment of land degradation include WOCAT, GLASOD, ASSOD, etc. It is recommended that in using similar methods for the sub-region, the following should be considered: · The scale on which the information is presented should be revised on a regional basis, utilizing the polygon concept as is done in Asia studies (ASSOD), · Countries should concentrate on the quantification of land degradation processes, · Countries should consider the utilization of the ASSOD impact evaluation methodology and modify it when deemed necessary for the sub-region conditions, · Existing impact assessment technologies may be reviewed and utilized wherever applicable (reference Jan de Graaff, Stocking, etc.), · The state-of-the-art of existing technologies should be compiled through modified and more effective mechanisms suitable for the sub-region, i.e. modification of WOCAT methodologies.
Projects · First priority: projects to keep good land conserved. Dissemination and implementation of good practices, · Rehabilitation of degraded land - target "hot spots" and "potential hot spots”. Use of best technologies (irrigation, improved fallow, etc., adapted to local social and economic circumstances), · Use of food security scenarios as tools to design and target implementation projects and appropriate interventions.
Publications · Prepare a state-of-the-art/overview document on management of degraded soils in Africa with particular reference to the Southern and East Africa sub-region conditions. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 7
Networking · The group agreed to create a new network on the management of degraded soils. The first activity of this network should include the evaluation of ongoing networks in the region as TSBF (Tropical Soil Biology and Fertility), ALASA, CIMMYT (soil fertility), etc. Based on this evaluation, activities of the proposed network will be identified including supplementary field work to control other land degradation processes not included ongoing networks, newsletters, internet, workshops, farmer-to-farmer visits and prediction models.
GROUP DISCUSSION REPORTS Group discussion report for Group One (Tanzania, Kenya, Ethiopia, Eritrea) Outlook of food situation Eritrea and Ethiopia experience food deficit. Tanzania and Kenya are self-sufficient at country level but not at household level. All countries require improved technology for future food production.
Types and extent of soil degradation Type Eritrea Ethiopia Kenya Tanzania Erosion +++ +++ +++ +++ Fertility decline ++ ++ ++ ++ Acidification + + + + Sodicity/salinity ++ ++ ++ ++ Compaction and crusting + + ++ + Water logging ++ + + : Low, ++ : Moderate, +++ : High
Technologies applied to control degradation Technology Eritrea Ethiopia Kenya Tanzania Soil & water conservation ++ ++ +++ +++ Minimum tillage + + Inorganic fertilizer + + +++ + Liming + Manure & organic + fertilizer ++ ++ BNF + + ++ + Agroforestry ++ + + : Low, ++ : Moderate, +++ : High
Assessment of land degradation · Kenya has identified indicators of land degradation but the assessment techniques need to be developed in the four countries. · Modelling and GIS facilities are in place but need to be utilized effectively. · The socio-economic impact of degradation in the four countries is high. However, the quantitative assessment has not been adequately undertaken.
Soil degradation indicators identified · Yield decline · Reduced fallow periods 8 Summary report
· Deforestation · Encroachment on marginal land · Erosion features (gullies, siltation of dams) · Loss of biodiversity · Shrinkage of agricultural land
Availability of technology
Technologies Eritrea Ethiopia Kenya Tanzania Soil & water conservation ++ ++ +++ ++ Minimum tillage + + +++ + Inorganic fertilizer ++ ++ +++ ++ Liming + + + + Manure & organic + fertilizer ++ + + ++ BNF + + ++ + Agroforestry + + + + Salinity reclamation + + + + + : Low, ++ : Moderate, +++ : High
Adoption of technologies
Technologies Eritrea Ethiopia Kenya Tanzania Soil & water conservation + + ++ ++ Minimum tillage + + + + Inorganic fertilizer + + ++ + Liming + + + + Manure & organic + fertilizer + + ++ ++ BNF + + ++ + Agroforestry + + + + Salinity reclamation + + + + + : Low, ++ : Moderate, +++ : High
Constraints limiting adoption · Soil and Water Conservation: Labour shortage, lack of training, lack of awareness, decrease in size of agricultural land, lack of credit, poor extension, poor infrastructure, poor linkage, land tenure systems · Minimum Tillage: Lack of information, lack of extension services, lack of inputs (herbicides and equipment) · Inorganic Fertilizers: High costs, limited availability, lack of knowledge, adverse effects on soils · Liming and Liming Materials: Not adequately researched, lack of information, high costs, lack of awareness on acidity problems · Manure and Organic Fertilizers: Unavailability, alternative uses (fuel), lack of transport, poor storage, preservation, ow nutrient content · Biological Nitrogen Fixation: Lack of adequate research, lack of seed inoculants, poor fixation (low P), lack of information Integrated soil management for sustainable agriculture and food security in Southern and East Africa 9
· Agroforestry: Competition with crops (light, moisture nutrients), incomplete package, lack of awareness, land shortage, lack of seedlings, lack of convincing results · Salinity reclamation: Lack of awareness, technology not well developed, high input costs
Policy issues · Land use policies and tenure systems exist in the four countries but they vary · Existing instruments to enforce land use policies are not effective · Farmer participation in all countries exists, but needs to be further promoted · Cooperatives and farmer associations exist but they are poorly managed · The ratio of extension/farmers is very wide and at the same time facilities for effective extension are very limited
Research and monitoring requirements · Private sector supports research on cash crops in Kenya and Tanzania · All research in Ethiopia and Eritrea is supported by Government · NGOs are actively involved in research in all countries · Applied research, decision support and monitoring systems are in place in the four countries, but they need to be strengthened
National and regional plans · Regional Programmes in Soil and Water Conservation include IGAD, ICRAF, CAHI (AHI, AFRENA), SWNM (soil, water, nutrient management and others)
Group discussion report for Group Two (Zambia, Zimbabwe and Uganda) Status of food security · Issues and problems · National: seasonal fluctuations in food security - imports of food, post-harvest storage and distribution · Subnational: accessibility and availability, post-harvest storage and distribution · Type of food, preference: Matoke (Uganda), Maize - monocrop (Zimbabwe and Zambia) · Household: affordability and availability e.g. draught power h/h structure, entrepreneurship/resources/land, labour, capital, seasonal deficits, access to technology
Does land degradation cause food insecurity? · How? · Fertility decline · Population migration 10 Summary report
· Shift from cropping to livestock which promotes overgrazing · Higher albedo and higher soil surface temperatures · Greater vulnerability to drought
Positive effects of land degradation (trigger) · Adaptation · Diversification · Technology uptake and intensification
Examples from the region: smallholder irrigation (Zimbabwe - Mvuma), banana mulching (Uganda - Kabale), agroforestry (Zambia, Chipata), smalholder irrigation (Uganda - Mbuka).
Conditions for positive outcome · Enabling policy environment · Institutional and legal framework · Political (in)stability · Marketing and economic incentives
Degradation Case Studies
‘Hot Spots’ Zambia: Southern province, smallholder rainfed monocropping of maize (fertility decline and soil erosion) (4 to 5 years of cropping before critical level is reached). Farm size: 2.5-5 ha Soil type: Acrisol Crop: maize Erosion rates: 20 tonnes/ha/year Farm family: 2 adults + 4 children Production potential: 3,600 kg/ha
Zimbabwe: North eastern part (Mutoko), natural region 4, soil erosion Soil type: Acrisols Farm size: 1-2 ha Erosion rates: 50-60 tonnes/ha Crop: Maize Farm family: 2 adults + 4 children Production potential: 3 tonnes/ha
Uganda: Kabale, soil erosion because of steep slopes (water erosion) Crop: Sorghum (less susceptible to bad conditions than maize) Soil type: Ferralsol Erosion rate: 10-30 tonnes/ha Yield potential: 2 tonnes/ha Farm size: 1 ha Integrated soil management for sustainable agriculture and food security in Southern and East Africa 11
Successful Spots Uganda: Nangabo (near Kampala) Local institutions and strong farmer-to-farmer interaction Access to technology Good marketing infrastructure Crop: sweet potatoes Management: crop rotation, mulching, livestock interaction
Zimbabwe: smallholder irrigation in Mushandike near Maswingo, 1 ha per farmer, abandoned dryland farming in surrounding areas Crops: maize and rice Soil type: Cambisol Erosion rate: 10-20 tonnes/ha Yield potential under irrigation: 6-7 tonnes/ha
Zambia: Eastern Zambia, Saeli, Chipata South, maize - previously serious soil erosion Soil type: Cambisols, 5% slope (pockets of Acrisols) Agroforestry technology approach Farm Size: 0.25 ha Erosion rate: 45 tonnes/ha before, now 5-10 tonnes/ha lots of biological measures Yields now: 4.5 tonnes/ha (formerly 1.5 tonnes/ha) crop rotation
‘Potential’ Hot Spots: Zambia: northern province (acidification) Soil type: Ferralsol/Acrisol Sub-humid, shifting cultivation zone
Uganda: Mount Elgon/ Mbale area (water erosion on steep slopes)
Zimbabwe: Zambezi Valley, shallow and erodible soils, tsetse clearance encourages immigration
General Degradation Issues
· Fertility depletion - presently N, P, and S deficits (cropping, erosion, leaching, humification), potentially K by the same processes
· Organic matter depletion - affects plant available water, soil structure, erodibility, nutrient supply, biodiversity, soil moisture and soil humidity (erosion, burning, conventional ploughing)
· Acidification - Al toxicity, nutrient imbalance, P-fixation (leaching, acid parent material, cropping and organic matter depletion, fertilizers)
· Devegetation - wind and water erosion, siltation, desertification, reduced base flow of rivers, reduced biodiversity and ozone depletion, organic matter and nutrient supply (shifting cultivation and shortened fallow cycle, wood fuel, overgrazing, construction, fire, land clearing) 12 Summary report
Recommendations Technologies, research and monitoring · Further investigation and understanding of existing indigenous technologies · Compiling (inventorying) available technologies · Integrated sustainable soil management - biophysical, economic and social viability
Policies, Laws, Institutions, and Extension · Formulation/ Creation of enabling policies to encourage conservation and sustainable land use should include: land tenure, support for farmer conservation groups - need to set a legal framework for conservation rather than setting it against degradation · Creation of strong institutions to backstop conservation initiatives at local level
Networking · Sharing information, experiences, good practice and expectations · Formalize and strengthen existing networks between and among all stakeholders (not only between scientists), e.g. newsletters, internet, forums, workshops, farmer-to-farmer visits · Networking the networks at local level
Projects · First priority: projects to keep good land conserved through dissemination and implementation of good practice · Rehabilitation of degraded land to target ‘hot spots’ and potential ‘hot spots’ through use of best technologies (irrigation, improved fallows etc. adapted to social and economic circumstances - see Table 1) · Construction of food security scenarios to design and target implementation projects and appropriate interventions
Group discussion report for Group Three (Malawi, Namibia, Zimbabwe, South Africa)
Identification, quantification, extent, distribution and assessment of land degradation · For Malawi, Namibia, Zimbabwe and South Africa the major forms of degradation are erosion and fertility decline and depending on the country soil acidity (South Africa), sodicity and salinity (Namibia). · There is doubt on the validity of the assessments since it was done for some countries qualitatively and also only for cereal production. · With certain reservations the countries agreed that the information on the above topics is acceptable when the heading of Table 3 (given in Summary analysis of country papers by C.F. Mushambi; page 175) is changed to include “for cereal production” and the footnotes may be changed as follows: (i) sodicitv/salinity to sodication/salinization; (ii) causes of degradation be changed to include impacts; (iii) nutrient loss due to erosion be added as an indicator of soil fertility decline and (iv) that improper irrigation management be added as a cause of sodification and salinization. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 13
TABLE 1 Examples of best practice technologies Technology (examples) Conditions Conservation tillage (minimum tillage, including - Weed control - herbicidal or mechanical ripping, subsoiling and residue management and - Grazing control ridging) - Appropriate equipment Improved fallow (green manure, cover crops - Stylo) - Research station only to date/ more on-farm research is needed - Sufficient land - Not becoming invasive/ a weed - Integration with livestock Soil amelioration (liming, manuring, composting, - Availability and cost of materials inorganic fertilizers, termite earth) - Expert knowledge - Analytical services Grazing management (zero grazing, short duration, - Skills, technical knowledge paddocking, improved pastures - legumes, perennial - Materials grasses) - Sufficient land - Water - Community participation - Veterinary service Irrigation (surface - canals, borders, basins; - Water availability sprinkler; trinkler/drip (micro)) - Capital - Knowledge and technology - Suitable land and soil - Community participation - Institutional support Contour bunds; grass strips and terraces - Labour - Equipment - Land Crop rotation (grass fallow, sweet potatoes) - Enough land - Labour for mounding
Bio-physical and economic impacts Quantitative data on impacts are not available for many degradation processes.
Outlook for food production and security · The production and requirement data (see below) presented are open to criticism. A certain time frame might not be representative of the true picture. · We should not get involved in detailed food production scenarios since other institutions are already doing this. · It is not to say that national food security figures are relevant to household food security figures.
Technologies available for improving the productivity of degraded soils · Networks are absent for inventories of existing technologies. · Factors limiting application of technology are: (i) lack of information; (ii) cost and (iii) lack of knowledge with respect to cost-benefits (illiteracy).
Research and monitoring requirements · There is in general a lack of expertise/skills to utilize new technologies and also an unavailability of these technologies exists. 14 Summary report
Policy and land tenure issues, national and regional plans · There is a need for countries to make evaluations of existing policies on land use planning, incorporating sustainable utilization of natural resources.
Networks and project proposals/programmes · RSA Sustainable Utilization of Natural Resources; Biodiversity · Namibia Ecosystems Conservation and Protection Programme; Agro-ecological Zone Programme · Regional ELIMS Integrated soil management for sustainable agriculture and food security in Southern and East Africa 15
Overview papers 16 Integrated soil management for sustainable agriculture and food security in Southern and East Africa 17
Land degradation with focus on salinization and its management in Africa
Recent estimates indicate that the global demand for food, fibre and bio-energy products is growing at an annual rate of 2.5% and that of developing countries at 3.7% (FAO 1993). World population has doubled in the past 40 years and may double again in the next century to approach 11 thousand million by the year 2100 (World Resources Institute 1992). The population in Africa is expected to increase to 2 193 million in 2100. Historical evidence suggests that an annual growth in output of only 1% can be expected from area increase at global level. Hence optimization of the productive potential of land including degraded land must form a major contribution to meeting the increased demand. However, the greatest challenge for the coming decades lies in the fact that many production environments are unstable and degrading. At risk from starvation, farmers are forced to strive for maximum production from the limited land resources available; this is leading to neglect of the long-term husbandry needs of the soil and water resources. Exhaustion of these resources is the result: decrease of inherent soil fertility, erosion by wind or water and salinization. Africa's lands are suffering from poor and inappropriate land management resulting in rapid land degradation, massive soil loss, falling yields, deforestation, the disruption of water resources and the destruction of natural pastures. About 490 million hectares in Africa are affected by different types of degradation.
In rainfed areas, fallow periods are declining below safe limits and marginal land and problem soil with severe production constraints are being put under cultivation in an attempt to meet demands without adoption of proper and efficient water and soil management practices. Of the approximately 2 976 million hectares total land in Africa, 2 146 million hectares are problem soils (72%) with different production constraints (soil acidity, vertic properties, low fertility, shallow soils, saline and poorly drained soils). On irrigated lands, improper water use and system management not only detract from attainment of potentials, but also cause productive land to be withdrawn from cultivation through waterlogging and increasing salinity and sodicity. Salinization in Africa is one of the degradation processes and affects widespread areas mainly in arid and semi-arid regions. Drought combined with the different forms of land degradation is seriously contributing to considerable yield decline and loss in food production, and hence the food security at household and country level, particularly in countries which cannot easily finance increased need of food imports. Land degradation is proceeding so fast that few African countries can hope to achieve sustainable agriculture in the foreseeable future.
A.M. Mashali Technical Officer, Soil Reclamation, Soil Resources, Management and Conservation Service, Land and Water Development Division, FAO, Rome, Italy 18 Land degradation with focus on salinization and its management in Africa
Neither traditional systems of using the land, nor the responses of traditional societies to increasingly severe pressures on the land, have been able to cope with the rapid growth of population and degradation processes in Africa for most of this century. The problem is usually identified only after the situation has become serious. Large quantities of soil have already been lost and the productivity of land seriously impaired. Governments have to recognize that their productive land is a limited and irreplaceable resource which should be carefully managed and protected against all forms of degradation and thus desertification. Only when the seriousness of degradation is recognized and its causes properly identified is it possible to develop agricultural practices and management measures that will ensure safe use of the land. Unfortunately wider dissemination of results from successful experiments and initiatives for soil improvement of degraded land in one country for the benefit of other countries (even in the same region) is rather limited. In order to alert policy makers, there is a need to provide evidence and justification for corrective methods which are based on in-depth assessment of the extent, severity of land degradation and their economic and social impacts. Issues related to land degradation and its negative impacts on food production and food security as well as development of appropriate technologies to enhance productivity of degraded soils are receiving special attention and are an important part of the priority programmes of FAO.
DEFINITION OF SOIL DEGRADATION, DESERTIFICATION AND SALINITY PROBLEMS Soil degradation and desertification Soil degradation is defined as a "process which lowers the current or the potential capability of soil to produce (quantitatively or qualitatively) goods or services". Soil degradation implies a regression from a higher to lower state - a deterioration in productive capability. The process is not necessarily continuous and may take place between periods of ecological stability or equilibrium. It is usually a complex process in which several features can be recognized as contributing to a loss of productive capacity. It can result from land uses or from processes arising from human activities such as: erosion, deterioration of physical, chemical and biological properties of the soil or long-term loss of natural vegetation. Recently degraded land is defined as land which due to natural process or human activity is no longer able to properly sustain an economic function or the original natural ecological function. Vast areas of Africa continue to be eroded and the degradation of the arid and semi-arid and dry sub-humid regions becomes so serious (resulting from adverse human activities and climate variations) that a new word, desertification, was coined to describe the gravity of the situation. Soil degradation processes whether chemical, biological or physical may occur simultaneously or sequentially and they are interrelated. A definition of desertification is "the intensification or extension of desert conditions". It is a process leading to reduced biological productivity with consequent reduction in plant biomass and destruction of the equilibrium of soil, vegetation, air and water in the areas subject to edaphic or climatic aridity (FAO 1984). Desertification hazards refer to the natural susceptibility of the land to desertification and manmade factors (ISRIC/UNEP 1990). It is considered as a comprehensive expression of economic and social processes as well as those of natural or man-induced processes. An important difference between soil degradation and desertification is that soil degradation is not necessarily continuous; it takes place over relatively short periods and can be reversed. Also desertification or the danger of it, is confined to the arid, semi-arid and sub-humid areas, whereas soil degradation can occur in all climates. Furthermore, certain processes important to the concept of soil degradation are not considered desertification, i.e. waterlogging, depletion of plant nutrients and acidification. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 19
Soil salinization Soil salinization as a process of land degradation is defined as the accumulation of excess salts in the root zone resulting in partial or complete loss of soil productivity and eventual disappearance of the vegetation. Salt-affected soil is simply defined as a soil that has been adversely modified for the growth of most crop plants by the presence of soluble salts, exchangeable sodium or both. Any quantitative definition, however, must be arbitrary because of the broad range of crop salt tolerance. Salt-affected soils are normally divided into three broad categories: saline, sodic and saline sodic. Other categories of salt-affected soils though less extensive are commonly met in different parts of the world and include acid sulphate soils, acid soils, degraded sodic soils and magnesium solonetz. The problems of soil salinity occur in all continents and under all climate conditions. They are most widespread in the arid and semi-arid regions, but salt-affected soils also exist extensively in sub-humid climates, particularly in coastal regions where intrusion of seawater through estuaries and rivers, and through groundwater, causes large-scale salinization. Soil salinity is a problem in irrigated lands particularly where saline water is used for irrigation. Salinity problems occur as well where crops are grown under rainfed conditions. There salinity has several local names, but is most commonly known as dryland salinity or saline seeps. Although weathering of rocks and primary minerals is the main source of all salt, salt-affected soil rarely forms through accumulation of salts in situ.
EXTENT OF LAND DEGRADATION, DESERTIFICATION AND SALINIZATION Land degradation and desertification Though soil degradation is largely manmade, its pace being governed primarily by the speed at which population pressure mounts, irregular natural events, such as droughts, exacerbate the situation. Such a sequence of events is not just a thing of the past. In many countries of the tropics and sub-tropics it is happening right now, and at an alarming scale. The 1982/1985 drought, for example, had a dramatic effect on the speed of land degradation in most African countries. Human activities usually aggravate the effect of the physical processes leading to desertification through an inadequate system and policy of land tenure, bad communications, and lack of awareness of acute problems and economic and social conditions. Much of Africa's land base is environmentally delicate and easily damaged. Large areas of cropland, grassland, woodland and forest are already seriously degraded. FAO reported in 1981 that in Africa north of the Equator more than 35% of the land was affected by either erosion or salinization. While it is now generally recognized that land degradation in general, and soil erosion and salinization in particular, are widespread and serious, very few reliable data are available on its extent or degree. Part of the problem is that much of the available data are reported in different ways and not in readily comparable forms (Sanders 1991). An indication of the extent to which the African continent (Figure 1) is subject to soil constraints is given in Table 1. It should be noted that the extents shown in this table are not cumulative since certain constraints overlap one another (FAO 1986). The table indicates that major constraints are caused by steep slopes and erosion. In semi-arid areas where exploitation of the land has continued for thousands of years, accumulation of soluble salts created a serious constraint to production, particularly in Egypt, Libya, Morocco, Tunisia, Somalia, Algeria, Sudan, Ethiopia, Eritrea, Botswana, Chad, Kenya, Tanzania and South Africa. Table 2 gives a summary of most degradation problems in the six climatic regions of Africa. 20 Land degradation with focus on salinization and its management in Africa
FIGURE 1 Main agro-ecological zones of sub-Saharan Africa
More recently ISRIC (International Soil Reference and Information Centre), under the aegis of UNEP and in collaboration with FAO, has produced a World Map of the Status of Human- Induced Soil Degradation at a scale of 1:10 m (ISRIC/UNEP 1990) known as GLASOD. It identifies 4 degrees of degradation (light, moderate, strong and extreme). Five types of human intervention were identified as resulting in soil degradation: deforestation and removal of natural vegetation (579 million hectares), overgrazing of vegetation by livestock (679 million hectares), improper management of agricultural land (552 million hectares), over exploitation of vegetative cover for domestic use (133 million hectares), and industrial activities leading to chemical pollution (32 million hectares). According to GLASOD, 1964 million hectares of agricultural land worldwide are degraded (Table 3), of which 494 million hectares (25%) in Africa. Table 4 gives an indication of the extent and severity of land degradation problems in Africa. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 21 22 Land degradation with focus on salinization and its management in Africa
TABLE 2 Summary of most serious degradation problems by region Region Arable land Grazing land Forest land Mediterranean Declining soil fertility General degradation of Degradation of vegetation and North Africa Wind and water erosion vegetation both in quality as the deficit in fuelwood Salinization on irrigated and in quantity and timber increases lands Wind and water erosion Water erosion on degraded forest land Sudano-Sahelian Decline in nutrient levels of General degradation of Degradation of vegetation Africa the soils vegetation both in quality Decline in soil physical and in quantity properties Wind erosion in sub- Wind and water erosion humid areas Humid and Sub- Decline in nutrient levels of Degradation of Degradation of vegetation humid Africa the soils vegetation Decline in soil physical Wind erosion in sub- properties humid areas Water erosion Humid Central Degraded soil physical Africa properties Degraded soil chemical properties Sub-humid and Water erosion Degradation in quality Degradation of vegetation mountain East Degradation of soil physical and in quantity of Water erosion Africa properties vegetation Degradation of soil Water erosion chemical properties Sub-humid and Water erosion Degradation in quality Degradation of vegetation semi-arid Degradation of soil physical and in quantity of Erosion Southern Africa properties vegetation Degradation of soil Wind erosion chemical properties Water erosion
TABLE 3 Human-induced soil degradation for the world (GLASOD) Type Light Moderate Strong Extreme Total Total (Mha) (Mha) (Mha) (Mha) (Mha) (%) Loss of topsoil 301.2 454.5 161.2 3.8 920.3 Terrain deformation 42.0 72.2 56.0 2.8 173.3 WATER 343.2 526.7 217.2 6.6 1093.7 55.7 Loss of topsoil 230.5 213.5 9.4 0.9 452.2 Terrain deformation 38.1 30.0 14.4 - 82.5 Overblowing - 10.1 0.5 1.0 11.6 WIND 268.6 253.6 24.3 1.9 548.3 27.9 Loss of nutrients 52.4 63.1 19.8 - 135.3 Salinization 34.8 20.4 20.3 0.8 76.3 Pollution 4.1 17.1 0.5 - 21.8 Acidification 1.7 2.7 1.3 - 5.7 CHEMICAL 93.0 103.3 41.9 0.8 239.1 12.2 Compaction 34.8 22.1 11.3 - 68.2 Waterlogging 6.0 3.7 0.8 - 10.5 Subsidence of organic 3.4 1.0 0.2 - 4.6 soils PHYSICAL 44.2 26.8 12.3 - 83.3 4.2 TOTAL (Mha) 749.0 910.5 295.7 9.3 1964.4 100 (percent) 38.1 46.1 15.1 0.5 Integrated soil management for sustainable agriculture and food security in Southern and East Africa 23
TABLE 4 Human-induced soil degradation in Africa, GLASOD (in million hectares) Type/Degree Light Moderate Strong Extreme ~Total Water erosion 57.5 67.4 98.3 4.3 227.4 (46%) Wind erosion 88.3 89.3 7.9 1.0 186.5 (38%) Chemical deg. 26.0 27.0 8.6 - 61.5 (12%) Loss of nutrients 20.4 18.8 6.2 - 45.1 Salinization 4.7 7.7 2.4 - 14.8 Pollution - 0.2 - - 0.2 Acidification 1.1 0.3 - - 1.5 Physical degr. 1.8 8.1 8.8 - 18.7 (4%) Compaction 1.4 8.0 8.8 - 18.2 Waterlogging 0.4 0.1 - - 0.5 Total* 174 (35%) 192 (39%) 124 (25%) 5 (1%) 494 (100%)
TABLE 5 Regional distribution of salt-affected soils in 1 000 hectares Regions Solonchaks/ Solonetz/ Total % of the total saline phase sodic phase area affected North America 6,191 9,564 15,755 1.65 Mexico and Central America 1,965 - 1,965 0.21 South America 69,410 59,753 129,163 13.55 Africa 53,492 26,946 80,438 8.44 South and West Asia 83,310 1,798 85,108 8.92 South East Asia 19,983 - 19,983 2.09 North and Central Asia 91,621 120,065 211,686 22.20 Australasia 17,359 339,971 357,330 37.48 Europe* 9,121 21,105 52,082 5.46 Total 352,452 579,202 953,510 100.00 * The difference between the total salt-affected soils and existing saline and sodic soils in Europe represents the potential salt-affected soils (20 856 million hectares).
Salinization Land salinization has been identified as a major process of degradation. Information on the exact extent, distribution and degree of degradation is not available for all soils of countries affected by salinity. In some countries, even the existence of these soils was discovered only through a survey or the pressing demand for agricultural utilization of a region. As a general figure about 7% of the total soil surface of the world is covered by salt-affected soils: Australia 45%, Asia 21%, South America 7.6%, Africa 8.5%, North America 0.9%, Central America 0.7%, and Europe 4.6%.
Based on the FAO/UNESCO Soil Map of the World, Table 5 shows regional distribution and percentage of salt-affected soils. It should be borne in mind that areas given in Table 5 are not necessarily arable but cover all the salt-affected lands. In Africa the problem is particularly serious in the countries north of the Sahara, in the Sahel, in East Africa, Botswana, South Africa and Namibia. Salt-affected soils are known also in Ethiopia, Kenya, Tanzania and Zimbabwe (Table 6). Table 7 shows that globally more than 76 million hectares of land is human induced salt-affected soil, out of which 52.7 million hectares (69%) is in Asia, 14.8 million hectares (19%) in Africa and 3.8 million hectares (5%) in Europe (Oldeman et al 1991). The four degrees of light, moderate, strong and extreme salt-affected land cover 34.6 million hectares, 20.8 million hectares, 20.4 million hectares and 0.8 million hectares, respectively. 24 Land degradation with focus on salinization and its management in Africa
TABLE 6 Distribution of salt-affected areas in the countries of the FAO Subregion for Southern and East Africa Country Area (000 hectares) Total Saline/Solonchaks Sodic/Solonetz Angola 581 81 662 Botswana 6 765 906 7 671 Comoros 0 0 0 Ethiopia 8 084 2 714 10 798 Kenya 5 838 2 838 8 676 Lesotho 0 153 153 Madagascar 512 520 1 032 Malawi 69 0 69 Mauritius 0 0 0 Mozambique 1 203 113 1 316 Namibia 3 478 1 657 5 135 Rwanda 0 0 0 South Africa 1 158 5 714 6 872 Swaziland 0 39 39 Tanzania 1 963 325 2 288 Uganda 26 87 113 Zimbabwe 349 957 1 306
TABLE 7 Global extent of human-induced salinization Continent Light Moderate Strong Extreme Total (Mha) (Mha) (Mha) (Mha) (Mha) Africa 4.7 7.7 2.4 - 14.8 Asia 26.8 8.5 17.0 0.4 52.7 South America 1.8 0.3 - - 2.1 North and Central America 0.3 1.5 0.5 - 2.3 Europe 1.0 2.3 0.5 - 3.8 Australasia - 0.5 - 0.4 0.9 Total 34.6 20.8 20.4 0.8 76.6
ASSESSMENT OF LAND RESOURCES IN AFRICA RELATED TO LAND DEGRADATION AND DESERTIFICATION The need for a systematic global assessment of land degradation and desertification has been highlighted on many occasions and the following are some of FAO's activities in this regard. · A provisional methodology was developed for the assessment and mapping of land degradation. Two types of assessment were made, i.e. present degradation and degradation risk. Six groups of soil degradation were recognized - water erosion, wind erosion, excess of salt, chemical degradation, physical degradation and biological degradation (FAO 1979). · A provisional methodology for assessment and mapping of desertification was developed (FAO 1984). Seven desertification processes were identified (degradation of the vegetation cover, water erosion, wind erosion, salinization, reduction in soil organic matter, soil crusting and compaction and accumulation of substances toxic to plants or animals. Three different aspects were considered, i.e. status, rate and inherent risk of desertification. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 25
· A more comprehensive and detailed set of information has been assembled and analysed for the African continent. The information shows that only 5% of total area in Africa has none to slight soil constraints while 55% has severe or very severe constraints (Table 8). Six maps on desertification hazards in Africa, scale 1:5-25 m, resulted from these analyses (soil constraints, water action, wind action, salinization, animal pressure, population pressure (see six maps by UNEP, 1984) and desertification hazards (window) (UNDP/FAO 1984). Table 9 shows the degree of desertification hazards by country in the FAO Subregion of Southern and East Africa.
· A recent study undertaken by the Winand Staring Centre of the Netherlands (Stoorvogel and Smaling 1990) for FAO covering 38 Sub-Saharan African countries, was based on the net removal of the micro-nutrients, N, P and K from the rootable soil layer. The results of this study show that nutrient depletion is quite severe in Sub-Saharan Africa. In almost all 26 Land degradation with focus on salinization and its management in Africa
of the 38 countries more than 10 kg of N, 4 kg of P205 and 10 kg of K20 per ha per year are being lost from the soil. The highest nutrient depletion rates were found in East Africa as compared to West Africa (moderate), Central Africa and the Sahelian Region (moderate to low). Countries with the highest depletion rates were found in most cases associated with high degrees of erosion as in Kenya and Ethiopia. · ISRIC (International Soil Reference and Information Centre) has produced a World Map of the Status of Human-induced Soil Degradation (GLASOD) at a scale of 1:10 m (ISRIC/UNEP 1990) for UNEP and in collaboration with the Winand Staring Centre, ISSS, FAO, ITC, UNEP (1992) has published an atlas on desertification with maps indicating soil degradation severity in general and specifically water erosion, chemical deterioration, and overgrazing and deforestation (see Maps Annex 4). The results of the above studies show that the constant feature of land resources in Africa is the high degree of variation observed amongst countries. If land itself is taken as the base resource it appears that some countries are better endowed in terms of availability of productive land than others. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 27
TABLE 8 Average data for Africa by process Component Rating class analyses None to slight Moderate Severe Very severe (000 km2) % (000 km2) % (000 km2) % (000 km2) % Soil constraints 1,258 5 11,261 40 11,962 43 3,446 12 Water action 23,573 84 3,514 13 550 2 290 1 Wind action 19,043 68 6,361 23 1,057 4 1,466 5 Salinization 20,932 75 2,167 8 1,802 6 3,026 11 Animal 10,952 39 11,865 43 2,871 10 2,239 8 pressure Population 15,335 55 8,924 32 2,952 10 716 3 pressure Source: UNEP/FAO 1984 28 Land degradation with focus on salinization and its management in Africa
· To categorize the agroclimatic and soil resources initially by country, and subsequently for the region, with a view to identifying constraints to agricultural production and by inference to the horizontal expansion of cultivated area, a common classification and system of interpretation could be employed. Fortunately, a common base exists in the forms of the FAO/UNESCO Soil Map of the World which characterizes and delineates the soils in a uniform manner. Therefore FAO could carry out assessment of land resources in Africa. The method used is based on soil data from the FAO GIS (Geographic Information System) using the FAO/UNESCO Soil Map of the World, the Fertility Capability Classification (FCC) developed by the North Carolina State University, and agroclimatic data from FAO's Global Agro-ecological Zones Study (World Soil Resources Reports 48/1-4, 1978-81, Land and Water Development Division, FAO). However, the process of grouping land areas according to constraints to agricultural production is particularly complex because in many cases individual tracts of land will Integrated soil management for sustainable agriculture and food security in Southern and East Africa 29
exhibit a combination of soil and agroclimatic constraints. At the same time the environmental requirements of individual crops vary considerably so that what is a severe constraint for one crop may be less severe or no constraint to another. Where a combination of constraints occurs, grouping may be enhanced by identifying the most limiting of these constraints. However, this becomes difficult when, as is the present case, the base data and mapping scale (1:5 million) are of rather a general nature. Despite these drawbacks an attempt has been made to identify the major natural constraints to agricultural production and their extent by country, in the continent. Extents listed include all soils whether occurring as dominant soils or associated soils, or as inclusions. Areas of non-soils such as Calciers, bare rock or moving dunes are excluded. Sixteen categories of natural constraints to agricultural production have been identified (Table 10). This study shows that the main agricultural production constraints in Africa are in the following order: low K reserves (20.4%) > acid soil (15.9%) > Al toxicity (15.0%) > low nutrient retention (13.2%) > shallow soil (11.7%) > free CaCO3 (11.1%) gravel (10.2%) > steep slopes (8.7% > poor 30 Land degradation with focus on salinization and its management in Africa
drainage (6.7%) > P fixation (6.8%) > salt-affected soil (3.9%) (this figure for salt-affected soil is lower comparing it with 8.5% given in Table 6 because it does not include waterlogged areas due to poor drainage conditions) > Vertisol (3.7%) > amorphous materials (0.2%) > acid sulphate soils (0.1%). · A two-year project on Mapping of Soil and Terrain Vulnerability in Central and Eastern Europe (SOVEUR) was signed between FAO and the Government of the Netherlands within the framework of the FAO/Netherland Government Cooperative Programme. The objectives of the project are the establishment of a geographic database and production of associated maps at a scale of 1:2.5 million on human induced soil degradation and soil vulnerability for Central and Eastern Europe as a tool for targeting appropriate corrective actions. Like the previous assessment of soil degradation at a global level, GLASOD 1:10 million and Asia Regional (ASSOD 1:5 million scale), the assessment of soil degradation in Central and Eastern Europe will serve as a means to increase awareness of soil degradation. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 31
In view of the scale and the anticipated available data, the inventory is like GLASOD based on experts' estimates. Together with the Soil and Terrain Data (SOTER) to be collected and the soil vulnerability assessment, the status of soil degradation will be produced. The assessment will be based on the SOTER map (Soils and Terrain Digital Database) at scale of 1:2.5 million. Same methodologies and the produced guidelines can be applied for assessment of the status of soil degradation in Africa.
TABLE 9 Degree of desertification hazards by country in the FAO Subregion for Southern and East Africa Country Desertification hazards rating None to Slight* Moderate Severe Very severe % area % area % area % area Angola 85.8 11.4 2.6 .2 Botswana 39.3 60.7 0 0 Burundi 100.0 0 0 0 Comoros Islands 100.0 0 0 0 Ethiopia 44.4 36.2 15.0 4.4 Kenya 13.0 64.3 21.0 1.7 Lesotho 26.9 57.2 0 15.9 Madagascar 91.4 6.1 2.4 <.1 Malawi 94.5 5.5 0 0 Mauritius 100.0 0 0 0 Mozambique 79.9 20.1 .1 0 Namibia 25.5 50.2 24.3 .1 Rwanda 100.0 0 0 0 South Africa 11.4 17.5 33.3 37.8 Swaziland 69.6 30.4 0 0 Tanzania 65.4 33.4 1.2 0 Uganda 80.2 19.2 .6 0 Zambia 97.1 2.9 0 0 Zimbabwe 39.2 55.0 5.8 0 Note: *Includes areas not rated for desertification hazards. Land degradation hazards may occur.
CAUSES OF DEGRADATION, DESERTIFICATION AND SALINIZATION It is necessary to identify the causes and origin of degradation so that the real causes and not the symptoms are controlled. In the past the problems were usually treated from an engineering perspective, the planners seldom paid much attention to incorrect land management and use, of which surface runoff and soil loss were only the symptoms. They attacked the symptoms of the problems, not the causes. A sound understanding of the causes of land degradation and desertification can prevent governments embarking on costly but unsuccessful programmes. For example, an analysis of badly eroded areas may lead to the conclusion that the problem is excessive population pressure on the land and that little can be done unless this pressure is reduced.
Degradation and desertification Degradation and desertification have taken place in various regions of the globe, and due to various causes. However, most if not all of these causes are closely interrelated, the occurrence of one usually leading to the occurrence of one of the others. Major processes causing soil degradation can be defined as follows: 32 Land degradation with focus on salinization and its management in Africa Integrated soil management for sustainable agriculture and food security in Southern and East Africa 33
a. Plant cover degradation and deforestation. From time to time unusual events may occur, such as fires, drought or floods, but usually the natural ecological system is able to quickly recover without any, or very little, permanent damage being done, Problems arise when man tries to alter a stable environment to meet one or more of his needs. In rainfed agriculture many areas, particularly those in the lower rainfall areas in the tropics, are very fragile and the removal of the natural vegetation, growing different types of plants at a lower density than would be found under natural conditions, and introducing more animals, create conditions which are likely to lead to land degradation and desertification. Overstocking and overgrazing are serious problems on their own in many countries in Africa and are one of the principal causes of desertification, but they also aggravate the effects of drought. The main effect of the degradation of the vegetation cover is then the exposure of the soil to other processes which, in turn, may destroy the soil structure, leaving the land less productive and with its productive potential seriously impaired and becoming subject to desertification. The increasing use of trees and brushwood for fuel, leading progressively to deforestation, has accelerated desertification over much of semi- arid Africa. At present deforestation is proceeding 30 times faster than reforestation. In the early 1980s it was estimated that 3.7 million hectares were being lost each year. The destruction of the forests is mainly a result of clearance for agriculture. In brief, incorrect land use and bad land management (from the land being used in a manner incompatible with its capacity) are main factors causing deterioration of land cover and thus land degradation. b. Wind erosion. Wind erosion in Africa occurs most frequently in the arid and semi-arid regions of the tropics, but wind erosion is also a problem in lands even up to rainfalls of 750 or 800 mm. Especially areas where dryland agriculture is being practised with little or no vegetation, light-textured soils easily become subject to wind erosion. Wind erosion frequently leaves the land subject to other forms of degradation such as water erosion. In (semi-) arid climates natural wind erosion is often difficult to distinguish from human induced wind erosion, but natural erosion is often aggravated by human activities. c. Water erosion. Water erosion is another spectacular form of land degradation which can also play an important part in the formation of deserts. Large areas of once productive river flats may become covered with a layer of fresh deposit, rivers and irrigation canals may become blocked, while dams and lakes may fill with silt. Once the process of water erosion has started, runoff increases with an accompanying damage to soil property and even possible loss of life. Water erosion is most likely to occur when the land is used for arable agriculture as the soil is then exposed without vegetative cover at certain times of the year. Loss of topsoil itself is often preceded by compaction or crusting causing a decrease in infiltration capacity of the soil and leading to accelerated runoff and soil erosion. A joint FAO/UNDP study on land degradation found that 11.6% of Africa's land north of the equator was affected by water erosion. d. Soil crusting, sealing and compaction (physical deterioration). Compaction, sealing and crusting occur in all continents, under nearly all climates and soil physical conditions. Soil crusting and compaction has been identified as one of the processes of desertification, the main reason being that if land is not cultivated correctly, the structure of the surface soil can be broken down and destroyed. In addition, the heavy action of some implements tends to pulverize and break down the structure of soils, leaving them subjected to both surface crusting and compaction. Closely related to crusting is soil compaction. Cultivated soils 34 Land degradation with focus on salinization and its management in Africa
can become compacted in a number of ways. For example, the wheels of heavy machines can quickly compact soils. Soil crusting and compaction tend to increase runoff, decrease the infiltration of water into the soil, prevent or inhibit plant growth and leave the surface bare and subject to other forms of degradation. e. Reduction of soil organic matter and biological degradation. In the tropics in Africa, i.e. in warm or hot climates, oxidation of the organic matter is rapid and most of the soils are relatively low in organic matter (FAO 1983). About 1.7 billion hectares of tropical soils are low in organic matter and nutrient reserves. In the tropics organic matter decomposes about five times faster than in temperate climates. Unfortunately, in many of the areas which are subject to desertification there is a general shortage of vegetation, crop residues are not returned to the soil but are used as animal feed or fuel; animal manure is not spread on the fields but is used as fuel, and the pressure on the land to produce grain crops is intense. Under such conditions the organic matter level and the volume of vegetation cover drop, the fertility of the land declines and the soil becomes subject to other processes such as surface crusting, wind and water erosion. f. Excessive toxic substances, other than salinization (chemical degradation). Soil toxicity can be brought about in a number of ways, but typical examples are from municipal or industrial wastes, oil spills, the excessive use of fertilizer, herbicides and insecticides, or the release of radioactive materials and acidification by airborne pollutants. While soil toxicity may be a relatively minor problem at present, it is likely to become of increasing importance in future years. g. Cultivation practices and improper management. Cultivation practices introduced in many developing countries have often been unsuccessful because practices have been copied from systems that are appropriate elsewhere in very different conditions and circumstances. This causative factor is defined as improper management of agricultural land. In Africa, there are many examples of unsuccessful mechanization projects which have failed as a result of ill-adapted land clearing and cultivation systems, inappropriate equipment and poor support services, policies and strategies. h. Shifting cultivation. Shifting cultivation is popularly blamed as unproductive and a serious cause of desertification. However, many shifting cultivation systems were appropriate and sustainable at low population pressures. Various kinds of shifting cultivation are practised by the vast majority of farmers in the least developed countries and most vulnerable countries of different regions. Generally they are no longer adequate to meet current demand because of increases in population. However, until practical feasible alternatives are proved and the conditions for their adoption facilitated, serious problems will persist. i. Land users' involvement. In Africa, farmers, pastoralists and those who relied on woodland and forests or agricultural land for their livelihoods were often regarded as part of the problem, rather than as the potential solution. Few attempts have been made to analyse the real causes of land misuse, such as land tenure systems, labour shortages and lack of economic incentives, information and advice (FAO 1990). Population pressures may be high, agricultural pricing and policies inappropriate, inputs unavailable, or land tenure systems may be forcing farmers to over-exploit or neglect the long-term husbandry needs of the soil to prevent degradation. Other causes may be identified as growing the wrong crop on the wrong land, subsidies systems, taxes or outmoded laws or social customs. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 35
Causes of salinization and sodication It is necessary to identify the causes and origin of salinity and sodicity so that the causes and not the symptoms are controlled.
Salinization In semi-arid and arid areas of the world, the scarcity, variability and unreliability of rainfall and high potential evapotranspiration affect water and salt balance of the soil. Low atmospheric humidity, high temperature and wind velocity promote the upward movement of the soil solution and the precipitation and concentration of the salts in the surface horizons. In arid regions, various types of Na, Mg and Ca salts are concentrated, mainly chloride and sulphate. In more humid climates, salts are less concentrated and Na dominates in carbonate and bicarbonate forms which enhance the formation of sodic soils. In the geography and geochemistry of the formation of saline soils, the following salt accumulation cycles can be distinguished. They are not necessarily exclusive (Mashali 1989).
Natural cycles · Marine cycles connected with the accumulation of marine salts in areas lying near the sea or saline lake and lagoon ecosystems: The sea water influences, directly or indirectly, soils and groundwater of these areas, giving rise to saline soils and groundwater with salt concentration ranging between 25 and 100 g/l. In coastal aquifers including lagoon ecosystems freshwater usually overlies a transition zone which in turn overlies the saline seawater. The rising water tables of saline aquifers due to increased recharge or the upward leakage from deeper aquifers not only causes land salinization but will also increase the seepage of saline groundwater into rivers and watercourses and enhance their salinization. · Continental cycles in which salinization results from the migration and redistribution of salt accumulated earlier in sedimentary salt bearing rocks, or from the deposition of salts during the process of weathering and soil formation in surface and groundwater: The result is the accumulation of carbonates, sulphates and chlorides in regions without natural drainage. This is more commonly in depressions and low-lying areas than in higher parts of the landscape. The discharge of saline effluents from drainage schemes, or from evaporation basin (ponds), lagoon ecosystems or runoff from land affected by salinization can also contribute to increased salinity of the watercourses. · In rainfed agriculture, development of saline seeps involves recharge and discharge areas. In discharge areas, groundwater rises to soil surface creating a seep. As water evaporates from seepage area, salt accumulates and forms saline soils. The most important contributory factors which may aggravate the saline seep problem are fallowing practices, denudation of vegetation by overgrazing, drought or fire, when replacing native vegetation including grasses with agricultural fields and cropping systems with lower potential evapotranspiration requirements, or other practices which result in the accumulation of water in the recharge areas. · Artesian cycles: If salts migrate with artesian waters through aquifers in, e.g. tectonic fault areas or in vast, deep continental depressions, salinity may develop as a result of evaporation under arid desert conditions. 36 Land degradation with focus on salinization and its management in Africa
Soil and water mismanagement cycles Anthropogenic cycles in which man, through poor soil and water management and agronomic practices, aggravates soil salinization and sodication. These practices include the following: · Irrigation cycles are characterized by a complex combination of salt movements. In irrigation areas with insufficient drainage, water table rises leading to waterlogging and secondary salinization. In irrigated areas the following can cause soil salinization: * Insufficient water applications, to the extent that crop water requirements and salt leaching requirements are not met. * Irrigation at low efficiency: the efficiency of water use is generally low, less than 30- 40%, due to seepage losses from canals during conveyance and distribution of irrigation water, and water losses on the farm due to poor irrigation practices. Most of the water lost finds its way to groundwater, thus gradually raising the water table leading to waterlogging and its effects on soil aeration, root penetration and nutrient availability, and to soil salinization under arid and semi-arid environments. Over-irrigation contributes to the high water table, increase in the drainage requirement and is a major cause of salinity build-up in many irrigation projects of the world. Therefore, a proper relationship between irrigation, leaching, and drainage must be maintained in order to prevent irrigated lands from becoming excessively waterlogged and salt-affected (Rhoades, Kandiah and Mashali 1992). * Irrigation with saline water or marginal quality water: Since good quality water is not always available, there has been a trend in some countries to use water of marginal quality for irrigation. Overpumping in the freshwater zone which overlies the saline seawater in coastal aquifers and lagoon ecosystems changes the equilibrium between the fresh and saline water, and causes the intrusion of seawater in aquifers degrading the quality of the fresh groundwater zone. Continued irrigation with such low quality groundwater has contributed to the expansion of land salinization. Drainage water is mixed with fresh water and used for irrigation in different countries. Treated municipal wastewater has been used on small scale for irrigation. Using saline water or marginal quality water for irrigation without proper soil and water management and agronomic practices, encourages soil degradation by salinization and sodication. The effect depends on salt concentration and composition, quantity and method of irrigation water application and soil properties. · Poor levelling: Variations of macro and micro relief also contribute to soil degradation in different ways. Small differences in elevation may result in salinization of the lower parts as the water table is closer to the surface and becomes more subjected to evaporation. On the other hand, changes in the micro relief in the order of 30 cm result in increasing salt content on raised spots and better leaching in dips which may explain the spotty nature of salinity observed in poorly levelled but otherwise normal fields. · Dry-season fallow practices in the presence of shallow water table. · Misuse of heavy machinery leading to soil compaction and poor drainage conditions. · Excessive leaching during reclamation techniques with insufficient drainage. · Use of improper cropping patterns and rotations. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 37
Sodication The sodication process involves the presence of soluble sodium salts in the soil solution and their adsorption on the exchange complex. The following processes responsible for the formation of sodic soils in the Near East Region have been given by El-Gabaly (FAO 1971): · desalinization in the absence of enough divalent cations and with insufficient drainage;
· evaporation of groundwater rich in NaHC03 and Na2C03 formed under particular geologic structure in areas having regional faults;
· decomposition of sodium alumino silicates which may lead to the formation of NaHC03 and Na2C03 and silica; · denitrification and sulphate reduction under anaerobic conditions; · migration and accumulation of sodic salts in arid climates;
· use of water with low salinity, in the order of 100-300 ppm, but with dominantly HC03- ions, especially in heavy textured, slowly permeable soils.
BIO PHYSICAL AND SOCIO-ECONOMIC IMPACTS OF DEGRADATION The impact of land degradation affects both production and people.
Effects on production · Various forms of degradation can cause serious and severe decline in soil productivity and crop yields. · To overcome reduction in yield farmers will increase inputs including seeds, fertilizers, etc. · Degradation can reduce response to any inputs, for example in salt-affected soil crop yield response to fertilizer application will be less as salinity is a limiting factor. · Degradation processes may reduce possibility for alternative land use. For example in salt- affected soils farmers are forced to cultivate only salt tolerant crops which might not always be high-income cash crops. · Irrigation schemes may fail because of the development of one or more of the degradation processes. For example salinity will reduce efficient use of water (i.e. crop yield per unit water) causing reduction in return from capital investment and labour inputs. · Degraded soil is more fragile with greater risk and always subjected to other forms of degradation. For example biological or physical degradation (soil crusting, compaction, etc.) will reduce organic matter level and level of vegetative cover and with decline in fertility (chemical degradation) and soil becoming subject to other processes such as wind and water erosion. · Siltation of reservoirs due to water erosion, for example, will reduce the available water for irrigation. An off-site effect of deforestation and erosion of watershed areas is the destabilization of river flow, causing flooding after rain and reduced flow in subsequent periods. Downstream irrigation and drainage system can also be damaged as a result of sedimentation caused by erosion. In salt-affected soil, saline water table through seepage into river and watercourses can enhance salinity of fresh river water. · When degradation is identified the required rehabilitation programme will need high investment cost such as in reclamation projects of salt-affected soils. In economic terms the 38 Land degradation with focus on salinization and its management in Africa
cost of degradation by erosion or soil fertility decline may reach a 5-10% production loss for a light degree of degradation or 20% for moderate, and 75% for severe degradation. Degradation by salinity may reach 65% in moderate conditions or even 100% in severe conditions.
Effect on the people · Abandonment of the land where severe degradation occurred which increased the number of landless farmers. · Reduction in food production, food supply, low food security leading to famine in some cases. The famines in Ethiopia in the 1970s and 1980s were at least partially due to the effect of land degradation brought about by years of soil erosion (Sanders 1987). · Increased labour requirement: for example, deforestation and erosion forces farmers to go for long distances to collect their fuel or water which means more labour required to do the same job. More labour is required for rehabilitation of degraded land. Reduced crop yields and more required inputs in degraded soils will reduce labour use efficiency. · Lowered income of the poor small scale farmers from agriculture: as a consequence farmers will be forced to work on land of others or migrate to cities searching for other sources of living or ultimately depend on famine relief. During the Sahel drought of the early 1970s, nearly one million "environmental refugees", a sixth of the population, were forced to leave Burkina Faso. Half a million more left Mali because of desertification processes (FAO 1990).
LAND RECLAMATION AND MANAGEMENT TECHNIQUES Land degradation The restoration of soil degradation and the protection from the causes of desertification call for the application of certain management and conservation measures and the undertaking of necessary precautions. Measures such as contour cultivation, tied ridging, terracing, strip cropping, dense vegetation and planting cover crops, mulches, fast growing trees, selection of proper crop rotation, quick growing species and integrated cropping system, provision of alternative fuel sources, check structures, protected watersheds, proper land preparation and ploughing, application of fertilizer, amendments and organic manures, and drainage systems are quite often mentioned as the techniques which help to protect and improve the land. However, the following are among the priorities: · In dryland agriculture, improving soil productivity and water conservation by promoting dryland farming and water harvesting techniques: communities can build devices such as small dams to conserve water and can plant trees to protect the upper slopes of their land. Farmers can be persuaded to use dryland farming techniques such as early ploughing, strip farming with the minimum of soil disturbance (minimum tillage), Conservation tillage, as compared to clean tillage, could promote the maintenance of soil structure and aggregates at the surface and thus reduce wind and water erosion. However, under specific conditions conventional tillage could promote water infiltration, control weeds and reduce mechanical impedance to root growth. Also short-season drought-tolerant cultivars can be used. Several are available, though not yet adopted, that have appropriate agro-ecological adaptation and meet people's consumption preferences. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 39
· Controlling wind erosion with fast growing trees and shrubs as windbreaks and shelter belts, live fencing and roadside planting: studies have shown that spacing of the shelterbelts can be 20 times the height of the tallest growing trees, this being the zone of protection. Narrow belts, 1-3 rows wide, already have a considerable effect. Shelterbelts improve the microclimate, prevent soil erosion, reduce the quantity of irrigation water used and protect the crop from desiccation. On the other hand, shelterbelts occupy a portion of the land, use plant nutrients, and shade the plants grown adjacent to the windbreak rows. · Integrating trees and livestock with arable farming, maintaining a good cover, protects the soil. On flat farmland, a good method of soil protection is to leave stubble and leaves on the surface after harvest and at planting. In this regard, maximum recycling of organic product should be encouraged both from within and from outside the farm (crop residues, animal manure, composts, urban wastes). Improve land use systems including appropriate crop rotation, intercropping, agroforestry and related tree based farming systems; species that fix nitrogen should be considered. · Applying dune stabilization measures: it is common practice to start with planting grasses followed by bushes and then by trees. However, in several areas afforestation starts after mechanical fixation, i.e. the surface of the dune might be fenced with dry grasses and the like in a checkerboard system. Plant species used for afforestation must be able to withstand drought, salinity, low soil fertility and fluctuations in surface temperature and have deep root systems capable of reaching the moisture in deep layers, or horizontal spread that allows for efficient use of surface rain and any dew. Chemical fixation using chemicals such as crude oil, asphalt and synthetic rubber latex is recommended when cost of labour is very high and the areas need to be stabilized in a short period. · Water erosion can be checked by many agronomic methods such as terraces to stop water erosion on steep slopes, level terraces to interrupt the rain flow and filter the water into the soil, and waterways lined with concrete, stone or even grass to direct the water down and ploughing along the contour of gentle slopes to check erosion. Studies shown that if contouring and strip cropping are combined, soil loss is reduced by 75% compared to up- and-downhill cultivation. Mulches reduce the impact of raindrops and hold moisture and allow it to infiltrate into the soil. · Grazing strategies should give attention to localized concentration of stock as around salt licks, watering points and settlements, and measures should be taken to avoid intensive local grazing and trampling and to propose a system to limit numbers of stock - which only appears feasible with the grazers' cooperation. · Techniques that directly increase range productivity are disease control and animal health improvement, pasture regeneration through grass seedling and forage plantation. · Management plan must be site specific. Participative approach in which both the selection of solutions and their implementation are decided in cooperation with the beneficiary groups including farmers, all land users and farmer associations. Identification, selection and farmer's adoption through participatory approach of improved and alternative packages of low-cost, low-risk soil management and conservation practices are required therefore to address and control land degradation. In this regard, integrated approach should be encouraged whenever feasible. Issues like changing in pricing policy, subsidy of inputs, market liberalization, land tenure reforms, infrastructures, policy and socio-economic aspects, environmental aspects should be considered in any management plan. 40 Land degradation with focus on salinization and its management in Africa
· Promotion of quantitative assessment of the impacts of degradation on productivity at regional, sub-regional and national level: this includes survey of the present state of degradation, potential risks of degradation, and monitoring of soil changes. · Promoting research and encouraging national coordination between government departments, local non-government organizations, parastatal bodies, universities and research institutions. · Rehabilitating irrigation schemes suffering from salinization or sodication. Summaries of the hydraulic, physical, chemical and biological technologies to control salinity and sodicity are described below.
Management practices for salt-affected soils Salt-affected soils exist under a wide range of hydrological, physiographical conditions, soil types, rainfall regimes and socio-economic settings. Therefore, there is no single technique or agricultural system that will be applicable to all areas. Management of salt-affected soil for agricultural purposes requires a combination of agronomic and management practices depending on a careful definition of the main production constraints and requirements based on a detailed, comprehensive investigation of soil characteristics, water monitoring (rainfall, surface water and groundwater), and a survey of local conditions including climate, crops, economic, social, political and cultural environment and existing farming systems. Management of salt-affected soils for agricultural use is largely dependent on water availability, climatic conditions, crop standing and the availability of resources. Several practices should be combined into an integrated system according to requirement. Summaries of the hydraulic, physical, chemical, biological and human aspects to improve productivity of salt-affected soils and other alternative forms of land use rather than crop production are discussed in Table 11.
Hydraulic practices Leaching To prevent the excessive accumulation of salt in the root zone, extra water (or rainfall) must, over the long term be applied in excess of that needed for ET and must pass through the root zone in a minimum net amount. This amount, in fractional terms is referred to as "the leaching requirement". The recent trend is to minimize these leaching requirements in order to prevent raising the groundwater and minimize the total load to the drainage system. Methods to calculate the leaching requirement and predict crop yield losses due to salinity were described by Rhoades, Kandiah and Mashali (1992). The quantity of salts removed per unit water can be increased by intermittent flooding or even more by sprinkler and frequent irrigation. Leaching should preferably be done when the soil moisture is low and water table is deep. Leaching should be timed to precede the critical growing stages. Leaching at times of low evapotranspiration demand is recommended, as at night, during high humidity, in cooler weather or outside the cropping season.
Irrigation practices Management of water should ideally maintain a relatively high soil moisture content (as in drip irrigation) during the cropping season and at the same time allow for periodic leaching. Good irrigation management has two objectives, the achievement of high crop yields with high water use efficiency, and the protection of land from waterlogging and salinization. The methods and frequency of irrigation and amount of water applied are of prime importance in controlling Integrated soil management for sustainable agriculture and food security in Southern and East Africa 41
salinity. They are determined by such factors as potential evapotranspiration, root proliferation and depth of root penetration, capacity of soil to store and transmit water and nature of plant responses to soil moisture stress. Sprinkler irrigation allows a close control of the amount and distribution of salts and water. Drip irrigation results in salt accumulation at the outside edge of the zone moistened by the emitters. Improvement in salinity control generally comes hand in hand with improvements in irrigation efficiency. The key is to provide the proper amount of water to the plant at the proper time. The distribution system of irrigation water should be designed and operated so as to provide water on demand and in metered amounts as needed, particularly when saline water is used for irrigation. Seepage losses from irrigation canals should be reduced by lining the canals with impermeable materials or by compacting the soil to achieve a very low permeability.
TABLE 11 Management practices and human aspects of management related to uses of salt-affected lands HYDRAULIC: - Leaching (requirement, frequency) - Irrigation (system, frequency, cyclic "dual rotation" strategy in irrigation with saline water, operating delivery system efficiently and lining irrigation canals - Drainage (system, depth, spacings, purpose, intercepting drainage, reuse drainage water for irrigation)
PHYSICAL: - Land levelling - Tillage, land preparation, deep ploughing, subsoiling - Seedbed shaping (planting procedures) - Sand or mineral soil material cover - Salt scraping
CHEMICAL: - Amendment - Soil conditioning - Mineral fertilization
BIOLOGICAL: - Organic, green manure and legumes - Crop rotation and pattern - Growing suitably tolerant crops "varieties" - Mulching - Crop residue
HUMAN ASPECTS OF MANAGEMENT: - Socio-economic aspects including farmers involvement, needs and preferences - Policy - Environment - Institution, organization, operation and maintenance
POSSIBLE ALTERNATIVE LAND USES IN COASTAL AND LAGOON ECOSYSTEMS: - Fish farms, rice-shrimp systems - Halophytes, mangroves, timber and fuelwood - Chemicals, industrial raw material production and salt making - Recreation parks - Preservation zone (swamp forest) 42 Land degradation with focus on salinization and its management in Africa
The "dual rotation cycle" management strategy (Rhoades 1984) can be used to enhance the feasibility of re-using drainage waters for irrigation: in this system: sensitive crops in the rotation are irrigated with low salinity water (fresh water) and salt tolerant crops are irrigated with saline drainage water. For the salt-tolerant crops, the switch to saline water is usually made after seedling establishment; pre-plant irrigation and initial irrigation being made with low salinity irrigation water. The secondary drainage resulting from such re-use should also be isolated and used successively for crops (including halophytes and tolerant trees) of increasingly greater salt tolerance. The ultimate unusable drainage water, which in this strategy will be reduced to the minimum, should be disposed of to some appropriate outlet or treatment facility.
Drainage practices Leaching and drainage are the basic requirements for successful amelioration of saline or sodic soils. When underlying layers are permeable and relief is adequate, natural drainage may function well. Since such conditions are rare in areas where saline and sodic soils occur, a drainage system will usually be required. Methods adopted to remove excess salt from the root zone include scraping, which removes the salt accumulated on the soil surface by mechanical means; washing away the surface salt crusts through flushing water over the surface in the rare cases with soils of low permeability and adequate slope; and, most commonly, leaching. Various types of drainage are used all over the world: surface drainage in which ditches are provided so that excess water will run off before it enters the soil; subsurface drainage for the control of the groundwater table at a specified safe depth, consisting of open ditches or tile drains or perforated plastic pipes; mole drainage where shallow channels left by a bullet shaped device pulled through the soil can act as a supplementary drainage system connected to the main drainage system (open or closed); and vertical drainage by pumping out excess water from tubewells when the deep horizons have an adequate hydraulic conductivity. Reducing deep percolation of excess water by drainage will generally reduce the salt load returned to river as well as reduce water loss. Saline drainage water should be intercepted as mentioned through drainage systems. Such drainage water can be disposed of by pond evaporation or by injection into some isolated deep aquifer, or it can be used as water supply where use of saline water for irrigation is appropriate.
Physical management Several mechanical methods have been used to improve infiltration and permeability in the surface and root zone and thus to control saline and sodic conditions (Mashali 1995)
Land levelling Careful levelling of land makes possible a more uniform application of water for better leaching and salinity control. For coarse levelling, simple scrapers or levellers may be used, while for fine levelling, use of laser guidance has recently been adopted which is more effective (precision 1 to 3 cm) but more expensive and time consuming. Land levelling causes a significant amount of soil compaction by the weight of heavy equipment and it is advisable to follow this operation with subsoiling, chiselling or ploughing to break up the compacted layer and restore or improve water infiltration.
Deep ploughing and tillage Tillage is usually carried out for seedbed preparation and soil permeability improvement, but if improperly executed might form a plough layer or turn a saline layer and bring it closer to the Integrated soil management for sustainable agriculture and food security in Southern and East Africa 43
surface. Deep ploughing is most beneficial on stratified soils having an impermeable layer. It loosens the soil aggregates, improves the physical condition of this layer and increases air space and hydraulic conductivity. Deep ploughing in sodic soils should only be carried out after eliminating the sodicity, otherwise the mechanical disturbance may cause collapse of the soil structure. The selection of the right plough type, tillage sequence, ploughing depth and moisture content at the time of ploughing and subsoiling should provide good soil tilth and improve soil structure.
Subsoiling Subsoiling opens channels to improve soil permeability. The shape of the subsoiler's shank and the space between shanks depends to a large extent on the depth, thickness, hardness and continuity of the impervious layer.
Sanding Sanding is used in rare cases to make a fine textured surface soil more permeable by mixing sand into it, thus a relatively permanent change in surface soil texture is obtained. Adding sand to the soil surface (10-20 cm on the surface) as a better media for plant establishment is used as a physical management practice in some saline conditions.
Planting procedures Special planting procedures that minimize salt accumulation around the seed are helpful in getting better stands under saline conditions. Certain modification of the furrow irrigation method are recommended including planting in single or double rows or in sloping beds.
Chemical practices Chemical amendments Chemical amendments are used to neutralize soil reaction to react with sodium carbonate and replace exchangeable sodium by calcium, followed by leaching for removal of salts derived from the reaction of the amendments with sodic soil. Gypsum is by far the most common amendment for sodic soil reclamation. Calcium chloride is highly soluble and would be a satisfactory soil amendment, especially when added to irrigation water, but is difficult to handle and generally expensive. Lime is not an effective amendment for reclamation of sodic soils when used alone, but has a beneficial effect when combined with a large amount of organic manure. Sulphur, too, is effective. It is inert until it is oxidized to sulphuric acid by soil micro-organisms. All other sulphur containing amendments (sulphuric acid, iron sulphate, aluminium sulphate) are effective because of the sulphuric acid originally present or formed upon microbial oxidation or hydrolysis. The choice of an amendment at any place will depend upon its relative effectiveness as judged from improvement of soil properties and crop growth, availability of the amendments, relative costs involved, handling and application difficulties and time allowed and required for an amendment to react in soil and effectively replace adsorbed sodium. The dosage of amendments must be equivalent to the quantity of exchangeable sodium to be removed considering the purity and type of the different amendments. The effectiveness of the amendment depends on the application method, i.e. broadcasting, incorporation in the soil by disking or ploughing, mixing to greater depth, metering into irrigation water or spraying on the soil surface in case of sulphuric acid. 44 Land degradation with focus on salinization and its management in Africa
Soil conditioning Attempts have been made to coagulate soil particles and provide aeration and better permeability and water infiltration by using soil conditioners. Factors limiting the use of soil conditioners are high costs, the difficulty of achieving intensive mixing during incorporation in the soil and limitation of beneficial effects to a shallow surface layer.
Mineral fertilization Salt accumulation in soil may affect nutrient contents and availability for plants in one or more of the following ways: by changing form in which nutrient is present in soil; by enhancing loss of nutrients from soil; through cation and anion interaction effects; through effects on non- nutrient (complementary) ion on nutrient uptake - all, adverse interactions between salt present and fertilizers, decreasing fertilizer use efficiency. The benefits expected from reclamation of salt-affected soils will not be obtained unless adequate plant nutrients (but not in excess) are supplied as fertilizer or by other means. The type of fertilizer used in salt-affected soils should preferably be of acid reaction and contain calcium rather than Na. It may also be necessary to take into account the complementary anions present.
Biological practices
· Incorporating organic matter in soil has two principal beneficial effects on saline and sodic soils, improvement of soil permeability and release of carbon dioxide and certain organic acids during decomposition. This will help in lowering pH, release of cations by solubilization of CaCO3 and other soil minerals, thereby increasing the EC, and replacement of exchangeable Na by Ca and Mg which lowers the ESP.
· Farm manure acts both as a source of nutrients and to improve soil structure and conditions. Green manure has a similar effect on soil properties and as a source of nutrients as organic matter.
· Fallowing encourages upward movement of salts. Therefore, it is advisable to crop land continuously, particularly when a wetland crop is one of the components of the cropping sequence. Growing legumes will improve soil structure.
· Mulching to reduce evaporation losses will also decrease or prevent soil salinization.
· Crop residue application is one of the easiest methods to improve water infiltration, especially for small farmers who do not have the resources to implement more costly corrective measures. Unfortunately in many instances, the small farmers use crop residues for other purposes and little, if any, is returned to the soil. Both crop residue left on the soil surface as well as the root system of the crop improve soil structure.
· Judicious selection of crops that can produce satisfactorily under moderately saline or sodic conditions has merit in some cases. In areas where it is not practical to reclaim salt-affected soils completely, or even to maintain conditions of low salinity and adsorbed sodium, so that farmers have to live with the existing conditions for some time, an alternative crop can be selected that is more tolerant of the expected soil salinity or sodicity and can produce economic yields. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 45
The factors that affect plant response to salt-affected soils include stage of crop growth, root stock in the case of fruit trees, crop varieties and climatic conditions.
Human aspects Farmers should become active participants in the development of appropriate management systems and should become the main originators of technical solutions to their environmental problems. The technological package available should be field tested under farmers' conditions and acceptance of newly developed technologies ascertained. Extension officers, project staff and farmers should be trained in all aspects of crop tolerance and management practices. Other factors such as pricing and marketing policies, labour, infrastructure development, intensive training and extension programmes should be considered. It is now recognized that social and economic factors have a decisive influence on farmers' decisions to accept any new technology and therefore have to be fully taken into account. An environmental impact assessment should be undertaken to identify the possible impacts of the proposed activities on the environment. It is, in essence, a tool in the decision making process. A sufficient budget of local funds for operation and maintenance should be reserved. Various aspects of a large management and development scheme should be controlled by a special development authority under the political responsibility of one minister.
Alternative forms of land use In some cases, instead of reclaiming salt-affected soils to suit the existing crops, some plant species could be selected to suit the environment. Such plants can be introduced on barren saline wasteland and lagoon ecosystems. The green matter (biomass), or seed produced on these lands could be used in numerous ways such as forage, manure and for making pulp for paper, and could also be converted into other value added products such as chemicals, medical products, methane gas or alcohol for fuel and solvent purposes. Of these plants the jojoba (Simmondsia chinensis) is an example. Halophytes can be grown under very saline conditions, the culms provide fibre for high quality paper production, and the seeds can have medical value (Juncus vigidus). Mangroves provide fuel in parts of the world that are chronically short of firewood.
In very saline soils, fish farms and salt making are practised particularly in coastal and lagoon ecosystems.
NETWORK ON INTEGRATED SOIL MANAGEMENT FOR SUSTAINABLE USE OF SALT- AFFECTED SOILS Although many countries are using salt-affected soils because of their proximity to water resources and the absence of other environmental constraints, there is a clear need for a sound scientific basis to optimize their use, determine their potential, productivity and suitability for growing different crops, and identify appropriate integrated management practices. Because of this and the increasing awareness of continuing soil salinization and sodication, FAO's Regular Programme is supporting national institutes in countries having problems of salt-affected soils to strengthen their experimental programmes on adapted soil management practices. Since 1990, collaborative projects have been identified to develop management practices for sustainable use of salt-affected soils: experiments and demonstrations on pilot farms are ongoing in twenty-one countries in different regions - Near East Region (Egypt, Iran, Syria and Tunisia); Asia and Pacific Region (China, Indonesia, Pakistan, Philippines, Thailand and Vietnam); Latin America 46 Land degradation with focus on salinization and its management in Africa
Region (Argentina, Brazil and Mexico); Europe Region (Hungary, Italy, Spain and Turkey); North America (Canada) and Africa Region (Kenya, Nigeria and Tanzania).
To avoid the fragmentation of technical research and development efforts in soil management of salt-affected soils in developing countries and to stimulate coordination of work between different international and national organizations in the field of salt-affected soils, a Network was established by FAO in association with the Subcommission of Salt-affected Soils of ISSS, on Integrated Soil Management for Sustainable Use of Salt-affected Soils. Twenty-one countries are now participating in the Network - those involved in the ongoing collaborative projects. The objectives of the Network are the dissemination of information, improved coordination among scientists and extension staff, strengthening field experimental programmes, and extension of appropriate management practices to increase productivity of salt-affected soils or land irrigated with saline water in participating countries. Activities of the Network include the above mentioned collaborative projects through experiments and demonstration pilot farms, publishing of a six-monthly Newsletter (SPUSH), and every two years holding an International Workshop.
CONCLUSIONS Africa is a vast continent with 55 countries covering a large range of environmental conditions, cultures, political systems and economies. It is therefore impossible to produce a conservation blueprint that can be applied without modification to all parts of the continent. If the problems of land degradation are to be overcome, each country must develop its own conservation strategy, policies and programmes, and tailor them to its own unique circumstances. National action is needed to identify for each country the seriousness and causes of degradation and to accordingly suggest solutions based on techniques designed both to raise yields and to prevent degradation. It is important that reasons for the problems be understood. Failure to do so can waste a great deal of time, effort and money.
Physical conservation measures will still be needed such as terracing, proper drainage systems, provision of alternative feed sources, check structures, protected watersheds, water harvesting techniques, live fencing and roadside planting, applying dune stabilization methods, etc. However, much greater emphasis should be placed on increasing and maintaining the land's vegetation cover through appropriate agronomic and forestry techniques and introducing sound management practices through proper land preparation and ploughing, amendment using crop residues, mulching, quick growing species and integrated cropping systems, conservation of soil moisture, preventing foundation of bad soil structure, tolerance of crop and livestock, etc. This approach protects the land surface from wind and water erosion and improves soil conditions by increasing fertility and organic matter content. Schemes that encourage better use of land should be implemented such as relocating land users, proper land tenure system, encouraging the use of farm inputs, working with farmers, providing technical advice and training, encouraging participation of land users, development of national institutions, coordinating international action and catalyzing regional programmes.
REFERENCES El-Gabaly, M. 1971. Salinity and waterlogging in the Near East Region. Ambio, 6:36. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 47
FAO. 1979. A provisional methodology for soil degradation assessment. FAO, Rome. ISBN 92-5- 100869-8. FAO. 1983. Keeping the land live - soil erosion: its causes and cures. Herbert W. Kelley. Soils Bulletin 50, FAO, Rome. FAO. 1984. A provisional methodology for assessment and mapping of desertification. FAO, Rome. ISBN 92-5-101442-6. FAO. 1986. African agriculture: The next 25 years. The land resource base. Annex II: pp. 116. FAO. 1990. The conservation and rehabilitation of African lands - An international scheme. ARC/90/4. FAO, Rome. FAO. 1993. Agriculture: Toward 2010. FAO Conference, Twenty-seventh Session, November 1993. FAO, Rome. ISRIC/UNDP. 1990. World map of the status of human-induced soil degradation. An explanatory note. Mashali, A.M. 1989. La salinizzazione e la desertificazzione del suolo. Genio Rurale N. 11:50-62. Italy Mashali, A.M. 1995. Integrated soil management for sustainable use of salt-affected soil and network activities. Paper presented in the International Workshop on Integrated Soil Management for Sustainable Use of Salt-affected Soils, held in Manila, the Philippines, 8-10 November 1995. Proceedings of the Workshop, pp. 55-75. Oldeman, L.R., Hakkeling, R.T.A. and Sombroek, W.G. 1991. Second revised edition. World map of the status of human-induced soil degradation. An explanatory note. Wageningen. International Soil Reference and Information Centre (ISRIC). 35 pp. Rhoades, J.D. 1984. New strategy for using saline water for irrigation. Proc. ASCE Irrigation and Drainage Speciality Cong., Water Today and Tomorrow, 24-26 July 1984, Flagstaff, Arizona. pp. 231-236. Rhoades, J.D., Kandiah, A. and Mashali, A.M. 1992. The use of saline water for crop production. Irrigation and Drainage Paper 48. FAO, Rome. 133 pp. Sanders, D.W. 1987. Food and Agriculture Organization activities in soil conservation. In: Conservation Farming on Steep Lands. Ed. Moldenhauer and Hudson. Soil and Water Conservation Society and the World Association of Soil and Water Conservation, Ankeny, Iowa, USA. ISBN 0-935734-19-8. Sanders, D.W. 1991. International activities in assessing and monitoring soil degradation. Paper presented to the International Workshop on Assessment and Monitoring of Soil Quality, Rodale Research Center, Emmaus, Pennsylvania, USA, 11-13 July 1991. Stoorvogel, J.J. and Smaling, E.M.A. 1990. Assessment of soil nutrient depletion in Sub-Saharan Africa: 1983-2000, Vol. 1: Main Report, Report 28. The Winand Staring Centre, Wageningen, The Netherlands. UNEP. 1984. Assessment of desertification. Environmental Conservation Special Issue 11, 1. UNEP/FAO. 1984. Map of desertification hazards. Explanatory note. UNEP. May 1984. UNEP/FAO. 1992. World Atlas of Desertification. Edward Arnold. A Division of Hodder and Stoughton, London. World Soil Resources Institute 1992. World resources 1992-93. A report by the World Soil Resources Institute in collaboration with the United Nations Environmental Programme and the United Nations Development Programme, New York. Oxford University Press. 385 pp. 48 Land degradation with focus on salinization and its management in Africa Integrated soil management for sustainable agriculture and food security in Southern and East Africa 49
Land degradation in relation to food security with focus on soil fertility management
The majority of developing countries are faced with difficulties of securing enough food for their rapidly growing population. Countries with limited land and water resources, particularly those which cannot easily finance increased food imports, will be faced with serious problems. Land degradation, in different forms, is seriously affecting the soil resources and contributing to considerable yield decline, loss in food production, and hence the food security at household and country levels. Food security cannot be achieved without effective planning and improved management strategies of soil, water and nutrient resources. Appropriate soil management and conservation practices are now available, for correcting or minimizing the degradation that also enhances land and labour productivity.
Nearly 1.4 thousand million ha of vegetated land in developing countries are subjected to land degradation, resulting in moderate or severe decline in productivity known as soil impoverishment. Some 9 million ha lands in the world have had their original biotic function fully destroyed and reached the point that rehabilitation is likely uneconomic. About 490 million ha, in Africa alone, are affected by various forms of degradation.
Poor and inappropriate soil management systems are the main causes of physical and chemical degradation of cultivated lands. Increasing population pressure, particularly in vulnerable regions, has resulted in serious soil fertility decline, especially under extensive farming practices. Decreasing yields and vegetation cover and increasing erosion are the typical manifestations of mismanagement practices. As a result, farm labour productivity and revenues from agriculture are falling, migration to urban areas is increasing. There is a need to increase efforts to encourage countries utilizing already known methods and continue to develop new ones to conserve resources, to secure food for mankind.
With recent emphasis and priority programme of FAO on food production in support of food security, issues related to land degradation and its negative impacts on food production, as well as land improvement for enhanced productivity, are now receiving a special attention. Rectifying soil degradation and sustaining crop production through appropriate soil management and conservation technologies are, therefore, important components of food security. FAO (AGL) with its lead technical, catalytic and coordinating role, has been and will continue to assist member countries in that direction, e.g. strengthening country efforts to combat land degradation and to improve land productivity.
H. Nabhan Senior Officer, Soil Management, Land and Water Development Division, FAO, Rome, Italy
The author of this paper did not participate in the Expert Consultation due to unavoidable circumstances. The paper, however, was presented by Dr A. Mashali of the same Division 50 Land degradation in relation to food security with focus on soil fertility management
So far, assessment of the extent of soil degradation has been attempted at global and/or small-scale level (1:10 or 1:5 million mapping). While such global assessment is useful, it has its limitation, if effective programmes or policy measures have to be implemented in a given country to address soil degradation and to promote soil improvement schemes. Successful experiences and initiatives for soil improvement in a specific country or socio-economic and agro-ecological environment have taken place, but their wider dissemination for the benefit of other countries, even in the same region, is rather limited. Despite the availability of cost-effective technical options for soil management and conservation, little would be achieved without a policy at high level and promotion of this policy for the implementation of effective programmes, which are designed to address the direct and underlying causes of soil degradation. In order to alert policy and decision makers, there is a need to provide evidence of degradation and justification for corrective measures, based on in-depth assessment of the extent, severity of land degradation and their economic and social impacts. Well-documented information on successful examples of soil improvement technologies and initiatives are also required. Half of the low income food deficit countries (LIFDCs), where the Special Programme for Food Security (SPFS) is or will be implemented, are in sub-Saharan Africa (SSA). In the short and medium-terms, the technological packages for enhancing productivity in these SPFS may heavily rely on low-cost, low-risk options. As such, appropriate and integrated soil and nutrient management for conservation and improvement of the soil resource, in addition to proper water harvesting and irrigation management, are among the essential elements for enhancing crop production and ensuring food security. Land degradation, is recognized as the most critical problem affecting the agricultural growth and causing increased rural poverty in SSA. In many parts of SSA, fallow periods are being reduced considerably and farmers are increasingly cultivating marginal lands susceptible to various forms of degradation. The high potential agricultural lands play a vital role in food, fodder and forest products, and are increasingly under threat due to loss of soil fertility. Without restoration of soil fertility, and controlling further degradation on land currently under cultivation, SSA countries will face the chronic food insecurity and hunger. Soils in most SSA countries have inherent low fertility and are characterized by: (i) deficiencies in major nutrients, particularly N and P; (ii) low soil organic matter; and (iii) poor structure and low water holding capacity. In addition, these soils do not receive adequate external nutrient replenishment since SSA countries have the lowest fertilizer consumption in the world, estimated at 10 kg nutrients/ha (as compared to 90 kg/ha of world average, 1990/93; 60 kg/ha in the Near East and 130 kg/ha in the Far East). The deficiencies in plant nutrients and organic matter are manifested in: (i) low plant and livestock productivity; (ii) low efficiency in using water from rain and irrigation; (iii) low efficiency in using inorganic and organic fertilizer; and (iv) high incidence of erosion. Agricultural growth in many SSA countries has been stagnant over the past three decades, averaging below 2% annually. Cereal production, for example, has decreased from 150 to 130 kg/person over the same period. Food production per capita has been declining in SSA since the 1970s, in contrast with the increase in Asia and South America (Figure 1). Under the current rate of population growth (estimated over 3% annually), it is essential to attain an agricultural growth rate of at least 4% per year to counter this food imbalance and reduce poverty. This can be attained mainly through increased productivity in areas presently under cultivation. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 51
FIGURE 1 World food production per caput
There is a convincing reason to believe that this poor performance in agricultural productivity in SSA countries is related to declining soil productivity. This paper focuses on the degradation of soil resources in sub-Saharan Africa.
TYPES AND CAUSES OF LAND DEGRADATION Definitions Land is defined as the terrestrial bio-productive system that comprises soil, vegetation, and water resources, other biota and the ecological and hydrological processes that operate within the system. It refers to all natural resources that contribute to agricultural production, including livestock and forestry (FAO, 1976; UNEP, 1992). Land degradation is the temporary or permanent lowering of the productive capacity of land (UNEP, 1992). It refers to reduction in productivity of croplands, range and pastures, forest and woodlands, resulting from land uses or from processes arising from human activities such as: erosion; deterioration of physical, chemical and biological properties of soils; long-term loss of natural vegetation. A new definition was recently given to land degradation as "Land which due to natural processes or human activity is no longer able to properly sustain an economic function and/or the original natural ecological function". Desertification: because of the considerable controversy about the term, the definition given in the Convention to Combat Desertification may be retained: it is land degradation in arid, semi- arid and dry sub-humid areas resulting from adverse human activities and climatic variation (UNEP, 1992).
Recognition of land degradation at different levels Traditionally land degradation is identified at three levels: 52 Land degradation in relation to food security with focus on soil fertility management
FIGURE 2 Relationship between population pressure and soil productivity
· at field level, land degradation results in reduced productivity; · at national level, land degradation results in a range of problems such as damage to downstream infrastructure through flooding and sedimentation, reduction in water quality and changes in the timing and quality of water flows. · at global level land degradation can contribute to: - climate change (through increased emissions of greenhouse gases - carbon dioxide "CO2", methane "CH4" and nitrous oxide "N2O" - and changes in the ability of terrestrial ecosystems to serve as carbon sinks), - damage the bio-diversity (both directly in degraded areas and indirectly by inducing expansion of cultivated land), and - pollute international waters (through sediment loads and changes in hydrological cycles).
Forms and causes of soil degradation Major forms of soil degradation are water and wind erosion, other physical degradation, and chemical degradation. Major causes: deforestation, overgrazing, agricultural mismanagement/over exploitation of cultivated lands. The forms of physical degradation would include crusting, compaction, waterlogging, reduced infiltration, removal or decline in organic matter due to de-vegetation. The forms of chemical degradation would include acidification, salinization/sodication, nutrient depletion or excessive leaching, pollution from industrial wastes, mining, and application of agro-chemicals. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 53
It must be underlined that soil degradation FIGURE 3 processes, whether chemical, physical, or The downward spiral to the poverty trap biological may occur simultaneously or sequentially, and they are interrelated. As such, a clear distinction cannot often be made among the various forms of degradation: examples are waterlogging and salinization, erosion and decline in organic matter content, erosion and nutrient loss, etc. Figures 2 and 3 show the interrelationship and causes of soil degradation.
In order to understand the dynamics, relationship of these processes, and forms of degradation, a brief description of the prominent ones is given below:
Soil erosion is defined as the detachment and lateral transport of soil particles on the soil surface by water and by wind. Determinants of erosion are rainfall, vegetation/ground cover, topography, and properties (erodibility) and slope inclination. Soil erosion causes loss of organic matter, nutrients and utility water and structural deterioration, which result in lower yield and soil fertility. The amount of productivity declines depends on the crop planted (example maize as high input crop is more sensitive than low input crop such as cassava). Decline in productivity due to erosion will also depend on the soil properties that curtail yield. Soils in the humid tropics (Oxisols, Ultisols) usually suffer far greater yield loss than less intensively weathered soils (Alfisols, Inceptisols). Compacted surface or iron crusts or deterioration of soil structure would promote water runoff and increase erosion, resulting in reduction of groundwater recharge and lowering the water table. Erosion has also serious off-site damage through sedimentation on cropland and downstream infrastructure.
Compaction is an increase in bulk density due to external load leading to deterioration of soil physical properties such as root penetration, hydraulic conductivity and aeration. The main causes are mechanized farming systems, forest clearance machinery, grazing. In agricultural engineering there are many methods to reduce compaction, for example, to loosen the soil mechanically or biologically, to reduce the load on the surface of the soil (combined tillage, wide tyres, etc.).
Crusting is due to destruction of aggregates in the topsoil by rain and it is closely linked to soil erosion. Crusting reduces infiltration and promotes surface runoff. It inhibits germination and emergence. Lower infiltration rates reduce water retention and aggravate drought stress. Surface crusting increases with lack of organic matter application to the soil or insufficient recycling of harvested crop residue (Stainer,1996).
Waterlogging/Salinization: Waterlogging is the lowering in land productivity through the rise in groundwater close to the soil surface. Waterlogging is linked to salinization, both are often brought about by incorrect irrigation management. Salinization refers to all types of soil degradation brought about by the increase of salt content in the soil. It thus, covers the build-up 54 Land degradation in relation to food security with focus on soil fertility management
of free salts and sodication due to the development of dominance exchange complex by sodium. Salinization can also be caused by the incursion of sea -water into coastal areas. Human-induced salinization is the result of improper irrigation, soil and water management. Due to the high osmotic potential of the water, salinization reduces the amount of water available to plants, results in phytotoxicity, damages soil structure due to high sodicity, impairs infiltration capacity and consequently causes serious decline in yields. If the salinity/sodicity level is high, the soil could be completely lost from agricultural production. There are some 77 million ha, worldwide, affected by various degrees of salinization, including about 19 million ha in SSA.
Acidification and Al Toxicity: Soil acidification takes place during the agricultural/cropping use of land. The direct causes are heavy leaching and nutrient export, decomposition of organic matter, and the considerable application of acid reacting fertilizers (NH4SO4, urea). About a quarter of tropical soils are acidic soils with pH values below 5.5 in the upper horizon, but with no Al phytoxicity (Sanchaez and Logan, 1992) About 1.5 billion ha of tropical land are associated with highly acidic soils, which contain phytoxical Al in solution. Al saturation in these soils exceeds 60% of the upper 50 cm. The Al ions directly damage the roots and thus reduce nutrient and water uptake and consequently reduce yields significantly.
Decomposition of Organic Matters and its Impact on Nutrient Retention: Soil organic matter plays a key role in soil fertility. The linkages between soil degradation and carbon storage in soils are complex (Figure 4). Organic matter ensures favourable physical conditions, including water retention capacity. It provides a balanced and slow-flowing source of nutrients and a base for cation exchange.
FIGURE 4 Soil carbon cycle and some effects of degradation
In cropping systems involving tillage, organic matter diminishes rapidly. Some forms of tillage, particularly in arid and semi-arid environment, encourage oxidation of organic matter throughout the profile, resulting in carbon being released to the atmosphere rather than its build up in the soil. Lower production of crops or pastures (due to degradation or soil erosion or Integrated soil management for sustainable agriculture and food security in Southern and East Africa 55
nutrient depletion) will result in lower carbon inputs in subsequent period (e.g. less root material, less leaf litter, less crop residues, etc.). In the tropics organic matter, on average, decomposes about five times faster than in the temperate climate.
About 1.7 thousand million ha of tropical soils are low in organic matter and nutrient reserves, they contain <10% weatherable minerals in the sand and silt fractions. These soils can supply only a limited amount of N, P, K, Ca, Mg and S. They are particularly common in the humid tropics (66% of the surface) and the savannahs (55% of the surface).
Because of leaching, particularly in the humid areas, soluble nutrients from the root zone can be transported into deeper soil layers. The consequent acidification produces Al and Fe- oxyhydroxides leading to P fixation. This P fixation which is more frequent in humid tropics, but also takes place to significant degree in savannahs and steep highlands. If the exported nutrients from the soil are not compensated by mineral and organic sources of plant nutrients or by subsequent delivery through weathering of soil minerals, the nutrient content of the soil will decline rapidly.
Soil Fertility Decline: In general, this is defined as short term deterioration in soil chemical, physical and biological properties. Sometime it could be referred to as soil fertility or soil productivity decline. Though erosion adversely affects soil fertility, because of loss of nutrients, the main processes other than erosion, which contribute to soil fertility decline are: · lowering of soil organic matter, with associated decline in soil biological activity; · degradation of soil physical properties (structure, aeration, water holding capacity) as a result of reduced organic matter; · adverse changes in soil nutrient resources, including reduction in availability of major nutrients (N, P, K), existence of micro-nutrient deficiencies and development of nutrient imbalances; · build up of toxicity due to acidification and/or pollution.
SOIL NUTRIENT DEPLETION IN SSA Winand Staring Centre in the Netherlands undertook an assessment of the state of soil nutrient depletion in Sub-Saharan Africa, and the results were published in 1990 (Stoorvogel and Smaling, 1990). Nutrient balances were calculated, through a Model, for the arable lands of 38 countries in SSA. The assessments were made for 1983 and the year 2000 and provided, on a country to country basis, data on the net removal of the macro-nutrients, from the rootable soil layer. Assumptions were made to quantify the various mechanisms that contribute to the flow of N, P and K into and out of the soil. A simple model was established for the purpose of simulating the processes of nutrient inputs and nutrient outputs from the soil. The inputs used in the above-mentioned assessment were mineral fertilizers, manure, deposition by rain and dust, biological nitrogen fixation. The outputs were harvested products, crop residues, leaching, gaseous losses and erosion (Figure 5). The results of the study showed that nutrient depletion is quite severe in SSA. An annual average nutrient loss in SSA was estimated at 24 kg nutrients per hectare (10 kg N, 4 kg P205 and 10 kg K20). The average loss in the year 2000 was estimated at 48 kg nutrients per hectare per year (i.e. a loss equivalent to 100 kg fertilizer product per ha per year). 56 Land degradation in relation to food security with focus on soil fertility management
FIGURE 5 Nutrient flows in the soil
Input and output factors governing nutrient flows in the soil
Classes of nutrient loss rates (in kg/ha) were established for 38 countries (low, moderate, high, and very high; Table.1). The highest nutrient depletion rates were found in East Africa as compared to West Africa (moderate), Central Africa and the Sahelian Region (moderate to low). Countries with the highest depletion rates were found to be in most cases associated with high degrees of erosion (e.g. Kenya and Ethiopia). Classes of nutrient loss and distribution of countries in 1983 are given in Table 2. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 57
TABLE. 1 Classes of nutrient loss rates (in kg/ha/year) Class N P205 K20
Low <10 <4 <10 Moderate 10-20 4-7 10-20 High 21-40 8-15 21-40 Very high >40 >15 >40
TABLE 2 Countries classified by nutrient depletion rate in 1983 Low Moderate High Very High Angola Benin Côte d'Ivoire Burundi Botswana Burkina Faso Ghana Ethiopia Central African Republic Cameroon Madagascar Kenya Chad Gabon Mozambique Lesotho Congo Gambia Nigeria Malawi Guinea Liberia Somalia Rwanda Mali Niger Swaziland Mauritania Senegal Tanzania Mauritius Sierra Leone Uganda Zambia Sudan Zimbabwe Togo Zaire
As an example, Figure 6, shows the nutrient inputs/outputs and the net removal in Zimbabwe and Swaziland (62 and 55 kg of nutrients net removal/ha/year, respectively).
It may be noted that this "study" (Stoorvogel and Smaling, 1990) was the first global assessment of nutrient depletion. It draws attention to issue and the need of corrective measures, and its results are quoted by various scientists and policy makers since the publication of the report.
Some scientists, however, raised concern about the methodology and approach used in the study, as it implies a lot of approximation and aggregation at country level, which could be misleading and mask the "bright" spots and the "hot" spots where urgent nutrient replenishments are required. It would be more appropriate, however, to carry out the assessment of nutrient balances (using the same concept of the model) at watershed or community level, in view of the complicated dynamics of nutrient flows and transfer of fertility, in small geographical areas and/or specific farming systems.
Considering the scale-inherent simplification of nutrient balance assessment at country level, a study was undertaken in Kisii District in South-West Kenya, 1992 (Smaling et. al, 1992). Land use types and land/water classes (combinations of rainfall zones and soil units) were combined into geographically well-defined land use systems, with NPK inputs by mineral fertilizers, manure, wet and dry deposition, biological N fixation, outputs by above-ground crop parts, leaching, denitrification, and erosion. The aggregated nutrient balance (net removal) for the Kisii District was - 185 kg nutrients/ha/year. For all nutrients, removal of harvested product was the strongest negative contributor, followed by erosion. Sensitivity analysis revealed that changing mineralization rate and soil N content had an important impact on the N balance. (The net nutrient removal for the whole of Kenya was earlier estimated by Stoorvogel and Smaling at 85 kg nutrients/ha/year). 58 Land degradation in relation to food security with focus on soil fertility management
FIGURE 6 Nutrient balance for Zimbabwe and Swaziland in 1983 in kg/ha/year
The study also revealed that practices such as zero tillage, mulching, strip cropping, alley cropping, and considerably reduce erosion and consequently the nutrient's loss. Integrated nutrient management approach was also emphasized, as a combination of mineral fertilizers, manure and crop residues gave the highest maize yields (long-term trial, 5-10 years) as compared to different/individual treatments of each. The results of such a study at "district level" could be translated into packages to provide advice on land use planning and management issues. The methodology used in the study could be applied in other districts (or countries) and proved to be valuable for researchers, policy makers and farmers in understanding the systems of integrated soil and nutrient management. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 59
Other studies estimated that 4 million tonnes of nutrients are harvested annually in Sub- Saharan Africa, while only ¼ of it is returned to the soil in the form of fertilizers. For example, on the 6.6 million ha of land cultivated in Burkina Faso, an estimated 95 000 tonnes of N, 28 000 tonnes of P205 and 79 000 tonnes of K20 are lost annually as a result of nutrient mining. In the Gambia, for example, the estimated nutrient removal by the major crops amounted to 26 000 tonnes of nutrients - N, P205, K20 - per annum, against nutrient inputs of only 2 850 tonnes from inorganic fertilizers and 5 640 tonnes from organic manure. Besides declining yields due to nutrient mining, this type of degradation would also contribute to deterioration of soil structure due to reduction in biomass and organic matter, reduced water infiltration and increased erosion. With population pressure and low level of fertilizer or nutrients use, farmers may be forced to cultivate marginal/low productive lands and hence the continuation of the vicious circle of land degradation. The attempt to maintain crop yields through application of commercial fertilizers, without due consideration to corrective soil management practices, such as the maintenance of soil organic matter and improving both physical and chemical soil conditions with low-cost packages and local resources is inappropriate. Emphasizing fertilizer use alone to address the nutrient mining may not be applicable/relevant in many countries in Sub-Saharan Africa, where fertilizer use is still very limited and is almost stagnant for the last 15 years.
ASSESSMENT OF SOIL DEGRADATION GLASOD For the first time, an attempt was made to map the severity of soil degradation at Global level, under the project "Global assessment of human-induced soil degradation", known as GLASOD (Oldeman et al., 1990b). The project was undertaken by the International Soils Research and Information Centre (ISRIC), under the aegis of UNEP and in collaboration with FAO. The map was at the scale of 1:15 million at the equator and 1:13 million at 30o latitude. A standardized methodology, including definitions, was developed through international consultations. Data from individual countries was provided by leading experts in the field. The authors of GLASOD acknowledge, however, that there are certainly some deficiencies and that the assessment should be regarded as first approximation (Oldeman et al., 1990a,b) (Table 3). An estimated 2 thousand million ha of agricultural land worldwide are degraded (Table.3).
TABLE 3 Major terrain division of the GLASOD map (in million ha) Continents Non used Stable Other terrain (non Human induced, Total land wasteland land degraded) soil degradation surface Africa 732 441 1 299 494 (17%) 2 966 Asia 485 1 426 1 597 748 (18%) 4 256 South America 28 368 1 129 243 (14%) 1 768 Central America 53 27 163 63 306 North America 75 1 043 672 95 1 885 Europe 1 116 614 219 950 Australia 95 250 434 103 882 World 1 469 3 671 5 909 1 (15%) 13 013 964 60 Land degradation in relation to food security with focus on soil fertility management
GLASOD identifies four categories or "Degrees" of degradation (light, moderate, strong and extreme). About 749 million ha is identified as light degree of soil degradation, implying a somewhat reduced productivity, but manageable in local farming system (including some 25 million ha in Asia and 174 million ha in Africa). About 910 million ha are classified as moderately degraded, which require major improvements to restore productivity, often beyond the means of small scale farmers in developing countries. Some 340 million ha of this moderately degraded land is found in Asia and over 190 million ha are located in Africa. Strongly degraded soils cover an area of 296 million ha worldwide, of which 108 million ha in Asia and 124 million ha in Africa. These soils are not any more reclaimable at farm level and are virtually lost. Major engineering work is required to restore their productivity. Extremely degraded soils are considered unreclaimable and beyond restoration. Their worldwide coverage is almost 9 million ha, of which 0.5 million ha in Asia and 5 million ha in Africa. Direct causes of degradation. GLASOD estimates soil erosion to be the most important form of soil degradation, because about 56% of the degraded lands are affected by water erosion and 28% by wind erosion (Table 4). The most important causes of water erosion are deforestation (43%), overgrazing (29%), and agricultural mismanagement (29%). For wind erosion the major causes are overgrazing (60%), agricultural mismanagement (16%), over exploitation of natural vegetation (16%) and deforestation (8%). The most important forms of chemical degradation are loss of nutrients and organic matter (mainly in South America and Africa) and salinization (in Asia). The main reasons for chemical degradation are agricultural mismanagement (56%) and deforestation (28%). GLASOD maps also show physical degradation in temperate zones, mainly attributed to compaction because of the use of agricultural machinery. Some of the basic data of GLASOD, particularly for Africa, are given in Tables 3, 4, 5, and 6. It may noted that individual country tables showing the overall severity of degradation and main causes can be retrieved from GLASOD database. It may be concluded that while the assessment provided by GLASOD is useful at a global level, it has its limitations (because of the very small scale) to be used at country level for concrete planning of agricultural production and/or degradation control measures. More detailed and in-depth assessments are required per country (example the recent assessment carried out in Togo at scale of 1:500 000) (Brabant et al., 1997).
TABLE 4 Human-induced soil degradation for the world, GLASOD (in million ha) Type/Degree Light Moderate Strong Extreme ~Total* Water erosion 343.2 526.7 217.2 6.6 1 094 (56%) Wind erosion 268.6 253.6 24.3 1.9 548 (28%) Chemical degradation 93.0 103.3 41.9 0.8 239 (12%) ·Loss of nutrients 52.4 63.1 19.8 - 135 nutrients ·Salinization 34.8 20.4 20.3 0.8 76 ·Pollution 4.1 17.1 0.5 - 22 ·Acidification 1.7 2.7 1.3 - 6 Physical degradation 44.2 26.8 12.3 - 83 (4%) ·Compaction 34.8 22.1 11.3 - 68 ·Waterlogging 6.0 3.7 0.8 - 11 Total* 749 (38%) 910 (46%) 296 (15%) 9 (1%) 1 964 (100%) *rounded figures for the totals Integrated soil management for sustainable agriculture and food security in Southern and East Africa 61
TABLE 5 Human-induced soil degradation in Africa, GLASOD (in million ha) Type/Degree Light Moderate Strong Extreme ~Total Water erosion 57.5 67.4 98.3 4.3 227.4 (46%) Wind erosion 88.3 89.3 7.9 1.0 186.5 (38%) Chemical degradation 26.0 27.0 8.6 - 61.5 (12%) ·Loss of nutrients 20.4 18.8 6.2 - 45.1 ·Salinization 4.7 7.7 2.4 - 14.8 ·Pollution - 0.2 - - 0.2 ·Acidification 1.1 0.3 - - 1.5 Physical degradation 1.8 8.1 8.8 - 18.7 (4%) ·Compaction 1.4 8.0 8.8 - 18.2 ·Waterlogging 0.4 0.1 - - 0.5 Total* 174 192 124 5 (1%) 494 (100%) (35%) (39%) (25%)
TABLE 6 Human-induced soil degradation in Asia, GLASOD (in million ha) Type/Degree Light Moderate Strong Extreme ~Total Water erosion 124.5 241.7 73.4 - 440.6 (59%) Wind erosion 132.0 74.6 14.4 0.2 221.2 (30%) Chemical degradation 31.8 21.5 19.5 0.4 73.2 ( 1%) ·Loss of nutrients 4.6 9.0 1.0 - 14.6 ·Salinization 26.8 8.5 17.0 0.4 52.7 ·Pollution - 1.5 0.3 - 1.8 ·Acidification 0.4 2.5 1.2 - 4.1 Physical degradation 5.7 6.0 0.4 - 12.1 ( 2%) ·Compaction 4.6 5.0 0.2 - 9.8 ·Waterlogging 0.4 - - - 0.4 Total* 294 344 108 0.5 747 (100%) (39%) (46%) (14%) (1%)
ASSOD Based on the recommendations of the Expert Consultation of the FAO Asian Network of Problem Soils (1993), UNEP formulated a project under the title: Assessment of the Status of Human- induced Soil Degradation in South and Southeast Asia (ASSOD). The project was financed by UNEP and the responsibility for coordination and implementation was entrusted to the International Soil Reference and Information Centre (ISRIC), in close collaboration with FAO and national natural resource institutions in 17 countries of the sub-region. FAO provided facilities, technical and financial support during the implementation of the project. The assessment of degradation was undertaken at a scale of 1:5 million, using refined GLASOD methodology, computerized database linked to GIS, physiographic maps and databases constructed along the lines of the internationally endorsed SOTER (Soils and Terrain Digital Database) approach (FAO, WSRR no 78, 1994). Besides detailed geo-referenced maps and information on dominant degradation types, which can be derived from the ASSOD database, the extent and impacts of degradation can be more precisely assessed. ASSOD maps and database provide credible and valuable contribution to the worldwide concern about soil degradation and its negative impact on agricultural productivity. An obvious next step would be to prepare these kinds of maps and evaluations at higher resolution for specific regions of countries of concern. An initiative/project similar to ASSOD for Southern and East Africa is recommended. 62 Land degradation in relation to food security with focus on soil fertility management
HIGHLIGHTS OF STUDY ON LAND DEGRADATION IN SOUTH ASIA Through the inter-country project RAS/93/560, and collaboration between FAO, UNEP and UNDP, a supplementary study (to GLASOD) was undertaken. The results were published in 1994, in the FAO World Soil Resources Report ("Land degradation in South Asia, its severity, causes and effect upon the people; FAO, WSRR No 78, 1994). Besides the GLASOD data, additional information derived from surveys or estimates by government institutions and specialists was used for the study. It is also the first time that an attempt was made (by this study) to quantify (even with a lot of approximation) the economic loss caused by the various forms of degradation at a regional level. Comparison and cross checking were made with the standard GLASOD data and methodology and adjustments/corrections were made, as appropriate. The main countries covered by the study were: Afghanistan, Bangladesh, Bhutan, India, Iran, Nepal, Pakistan and Sri Lanka. In addition to the elaborated estimates on soil erosion and its impacts, the report provided more information (though not very conclusive) on "evidence of soil fertility decline". On the basis of this study, however, the GLASOD estimates for soil fertility decline (degradation) were revised in India and Pakistan. For promoting exchange of experiences among the Regions, items related to land degradation, fertility decline, their causes and impacts are highlighted below.
Causes The following direct and underlying causes of soil degradation have been identified: Direct Causes are the unsuitable land use and the inappropriate soil management practices (they vary with the type of degradation): · deforestation of fragile land, unsuitable for sustained agricultural use · overcutting of vegetation · shifting cultivation without adequate fallow period · overgrazing · non-adoption of soil and water conservation practices · extension of cultivation into lands of low potential or high natural hazards (marginal lands) · improper crop rotations · deficient plant nutrients and negative nutrient balance · unbalanced fertilizer use · problems arising from planning and management of irrigation schemes · over pumping of groundwater, in excess of capacity for recharge.
Underlying Causes · population increase · land shortage · land tenure, short-term or insecure tenancy · poverty and economic pressure. The underlying causes are linked (Figure 7). The two external, or driving, forces are "limited land resources" and "increase in rural population". These combine to produce "land shortage", resulting in small farms, low production per farm and increasing landlessness. The consequence of land shortage is "poverty". Land shortage and poverty, taken together, lead to "unsustainable land management practices", which are the direct cause of degradation Integrated soil management for sustainable agriculture and food security in Southern and East Africa 63
FIGURE 7 Causal nexus between land, population, poverty and degradation
Soil fertility aspect, Asian experience The problem of soil fertility decline has not previously received enough attention. On a national scale, increases in crop yields are falling behind rates of increase in fertilizer use. Surveys have shown that application of soil organic material is declining. Micronutrient deficiencies are widely reported, where farmers have attempted to sustain yield by application of major nutrients only. In long-term experiments, yield responses are declining except where fertilizers are applied in conjunction with organic manure. This form of degradation is found in both the humid and dry zones. Whilst its widespread occurrence is not in doubt, more precise and quantitative estimates of its extent and severity will require further surveys and monitoring of soil changes.
Evidence and factors that are contributing to soil fertility decline are summarized below: · Organic matter depletion: Crop residues are widely used for fuel and fodder and not returned to soil. Use of farmyard manure is limited. In Bangladesh, for example, the average OM content declined by 50%, from 2% to 1% over the past 20 years. · Continuing negative plant nutrient balance (nutrient mining): Removal of nutrients from the soil by the harvested crops appears substantially to exceed inputs as fertilizers or natural replenishment. · Imbalanced fertilizer application: Fertilizer use in the region is concentrated on N, for example, the N:P:K ratio for India was (in 1992) 1.00:0.33:0.17, compared with 1.00:0.52:0.40 for the world. Imbalanced fertilizer use is considered to be among the principal causes of low fertilizer use efficiency and yield stagnation. · Secondary and micronutrient deficiencies: An increasing incidence of S and Zn deficiencies is occurring in the region, thus limiting yields and crop response to fertilizers. · Lower response to fertilizers: Increases in fertilizer use is not matched by increases in crop yield: a levelling off, or plateau, in crop yield increases which took place in the 1960s and 64 Land degradation in relation to food security with focus on soil fertility management
1970s is continuing in the region. The Grain Nutrient Ratios are falling. A striking example from a 33-year fertilizer experiment (at Bihar, India) showed that despite changes in improved varieties, wheat yields have declined substantially over the period with N, NP, and NPK fertilization, whereas they have risen with farmyard manure (Goswami and Rattan, 1992). Despite the above indicators, it is difficult to establish any significant trends in soil fertility. That is mainly because of the lack of long-term monitoring. Drawing from the experience in Asia, which certainly has some similarities in some African countries, there is a need to study the soil fertility decline trends. Two methods are appropriate: · long-term experiments with standardized methodology through well established network; · monitoring of changes in soil properties and relevant land quality indicators, over long period on a statistically-based selection of on-farm sites (Young, 1991).
Bio-physical and socio-economic impacts of degradation The effects of land degradation may be grouped as effects on (i) production and (ii) consequences on the people:
Effects on production · Reduced crop yields. · Increased inputs and greater costs where farmers, out of necessity, attempt to combat reduction in yields with increased inputs, particularly fertilizers. · Reduced response to inputs, for example lowering of organic matter content as a result of degradation will lower the response to fertilizers. · Reduced productivity of irrigation systems because of salinization for example, thereby leading to less efficient use of capital investment and labour inputs into the development of irrigation schemes. · Lower flexibility of land use, for example reduced crop yields may force farmers to grow only cereals, and this can lead to further decline in soil fertility. · Greater risk, degraded soil is less resilient and less able to recover from production risks such as drought, erosion will reduce OM content and water holding capacity of the soil. · Loss of water for irrigation, an off-site effect of deforestation and erosion of watershed areas, is the destabilization of river flow, causing flooding after rain and reduced flow in subsequent periods. Downstream irrigation and drainage infrastructure can also be damaged as a result of sedimentation caused by erosion.
Effects upon the people · Increased landlessness, abandonment of land, where degradation has reached severe degree. · Reduced and less reliable food supplies, lowering of crop yields means reduced production of food crops, increased risks, lower supplies and lowered food security. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 65
· Increased labour requirements. erosion, deforestation, drying up of rivers caused by destabilized flow, forces farmers to collect fuel-wood and water from long distances (e.g. more labour); labour used in reclamation and rehabilitation of land is labour lost from production; reduced crop yields and increased inputs both have the effect of reducing farmers' return from labour. · Lower incomes and welfare, out of all consequences of land degradation is lowering of incomes of the resource poor/small scale farmers as a result of: "increased inputs or reduced outputs". With land degradation occurring, it becomes a declining resource and as a consequence, labour and capital are less efficiently applied and productivity is lowered. Land degradation means that farmers must either accept a lowered productivity of food or else put in greater effort and resources to maintain production. It is the poor who suffer most from land degradation. Poor farmers, particularly those with small landholding, have neither the resources to combat land degradation and enhance productivity, nor the options to meet short- term disasters such as flood, drought, pest attack, etc. Because of land shortage and declining productivity, accentuated by degradation, the poor farmers may have only limited options: clearance (or deforestation) of fragile lands for agricultural production which cannot be sustained because they have not the required resources; work on the land of others; migrate to cities or ultimately depend on famine relief.
Economic cost of degradation The estimates of cost could be based primarily on the measurement of two variables: production loss or replacement cost. i. Production loss is the reduced productivity of the soil as a consequence of degradation, which could be expressed as a percentage of production from the undegraded soil. For erosion and soil fertility decline, the assumptions are: a 5-10% production loss for a "light" degree of TABLE 7 degradation, 20% for "moderate" and 75% for Estimated cost of land degradation "strong" degradation. In the case of salinity, the in South Asia. Type of Cost US$ respective assumed losses based on experimental degradation thousand million data, are 15%, 65% and 100%, respectively. per year ii. Replacement cost is the cost of additional inputs water erosion 5.4 (basically fertilizers) used by farmers in order to wind erosion 1.8 maintain production levels on the degraded soils. fertility decline 0.8 waterlogging 0.5 Based on the method of production loss, the cost of salinization 1.5 land degradation in South Asia region was estimated at some US$10 thousand million per year (FAO WSSR No.78, 1994) (Table.7). Addition of the off-site effects of erosion would substantially increase this figure. The on-site cost is equivalent to 2% of the Gross Domestic Product of the region, or 7% of its Agricultural Gross Domestic Product.
For indicative purposes, other estimated costs due to land degradation are: · Australia: Annual loss of production was estimated at US$300 million due to salinity/waterlogging, US$200 million due to soil structure deterioration, and US$80 million due to erosion. 66 Land degradation in relation to food security with focus on soil fertility management
· Zimbabwe: Total financial cost, due to annual loss of nutrients by erosion, from arable lands (i.e. equivalent cost of fertilizers) was estimated at US$150 million (1986). · Burkina Faso: The estimated annual loss of nutrients (mining) amounted to US$159 million in terms of N, P, K fertilizers (1983). · Desertification costs the world an estimated US$42 billion a year.
Despite the approximation in the estimations of costs of degradation, they are required to provide evidence in order to alert policy and decision makers (at regional, national and sub-national level) for promoting conducive policies and for implementing appropriate programmes for addressing soil degradation and improving productivity, and where possible, to reverse the effects of past degradation (i.e. reclamation and rehabilitation). In this respect, sub-regional and/or national studies for estimation of economic costs of degradation, in Africa, are recommended.
LIMITATIONS OF DATA AND GAPS RELATED TO LAND DEGRADATION Despite years of concern over the effects of land degradation on crop lands, critical gaps remain with respect to the data and information.
· The data and information are highly fragmented, incomplete and often unreliable; the information on land degradation often stops short of addressing the productivity issues which are of fundamental interest to policy makers, agricultural planners as well as the farmers. · Much of the data is purely qualitative. Land is classified as "undegraded", "degraded" or "severely degraded" but the meaning of these labels and the magnitude of each category are seldom made precise.
Examination of available data on crop yields, at national level, does not often provide strong evidence that degradation is affecting productivity. In many countries, the yields appear to have increased over the last decades, even in SSA (though per capita production has fallen). These data, however, do not mean that there is no land degradation. Some examples are: · Data on average national yields may well conceal significant regional or sub-national variations. · National yield data are often suspect, both in terms of quality and in terms of representation. If data collection tends to favour the more prosperous farmers using improved techniques, for example, it may miss degradation problems experienced by the bulk of farmers. · Agricultural technology has improved and input levels have been increasing and this may have offset some of the effects of degradation, e.g. in the absence of degradation, yield increases might have been faster. · Expansion of agriculture into new, as yet undegraded areas, may mask the effects of degradation on existing agricultural land.
As such, it should be emphasized that assessment of degradation and its impacts on productivity at a national/aggregated level could be misleading. For meaningful advisory services and planning purposes for enhancing agricultural production and for implementation of measures to control degradation, attention should also be paid Integrated soil management for sustainable agriculture and food security in Southern and East Africa 67
to the site-specificity of the problem. It is not usually necessary to have complete information in the entire country. What is needed is information on the specific area "hot spot" where interventions have to be envisaged. There is also a need for more quantitative data on the effects of degradation on productivity. Long-term, on-farm trials and more precise monitoring mechanisms are required in this respect.
Since the global assessment of human induced soil degradation (GLASOD) and the study on nutrient depletion in sub-Saharan Africa were disseminated in 1990, considerable debate has arisen, however, over the magnitude of the problem. Recent reviews and detailed studies, for example in Ethiopia, Kenya, El Salvador or Togo, (Pagiola, 1997; Brabant et al., 1997) challenge the "more catastrophic views" of the nature, extent and severity of land degradation, particularly the erosion. None of these studies, however, suggests that land degradation is not a problem.
For example, the detailed assessment of land degradation in Togo (at a scale of 1:500 000) showed that 77% of the land has "minor" degradation caused mainly by farming activities and only 1.6% of the country is severely degraded. The study also confirmed the hypothesis that the main cause of chemical degradation is the change in farming system due to population pressure. In this respect, however, no quantitative relationship was established, but indicators for monitoring were suggested: the ratio of crop fields to fallow land, as main indicator of population pressure on the land. Population distribution and cropping density are, therefore, two factors to be monitored attentively; the former through periodic census results, and the latter by interpreting satellite images.
CONTROLLING LAND DEGRADATION, CHANGES IN APPROACHES/PROJECT DESIGN Approaches for addressing land degradation These may include: · Changing production technology, for example, by introducing practices such as minimum or conservation tillage, application of manure, or agroforestry. · Adding conservation techniques to production systems, for example, by introducing terraces in steeplands. · Changing patterns of land use, for example, by relocating cropland and pastures to lower slopes and reforesting steeper slopes or by changing stocking rates on grazing land. Such efforts are often undertaken on a watershed scale.
If degradation is far advanced, such measures might have to be preceded by reclamation and/or rehabilitation of the affected areas (as in case of moderate or strong degree of salinization).
Any land degradation control effort must begin with the diagnosis of the problem, i.e. an assessment of the extent and severity of land degradation (in a more quantitative manner) and a diagnosis of the main causes of this degradation. Some countries that are seriously affected by land degradation have already started the diagnosis process through, for example, preparation of their National Environmental Action Plans (NEAPs) or National Action Programmes (NAPs). 68 Land degradation in relation to food security with focus on soil fertility management
These allow combating desertification within the framework of CCD, e.g., providing new opportunities to review land degradation problems and prioritize interventions.
Changes in approaches and project design Historically, the approach taken by most land degradation control projects has been to encourage land users to adopt some specific conservation measures. The proposed measures were generally centrally selected by specialists. Various forms of incentives were introduced ranging from subsidy, credit, free inputs or payment of even all the cost of implementation of heavy structures (for erosion control for example). Many recommended conservation measures, while technically sound in terms of preserving land, were inappropriate to farmers' conditions. Insufficient attention was paid to the constraints faced by the land users and causes of their use of degrading practices. Moreover, insufficient attention was paid to the policy and socio-economic environment. In many cases such approach has failed; adoption of the recommended practices was low, in other cases the practices were abandoned once the project ceased, seldom did adoption spread to other land users who did not receive subsidies, or financial incentives. Therefore, emphasis of land degradation control projects has recently changed, to take into account the following basic principles: i. Land degradation control efforts or projects have been moving toward a more participatory approach, in which both the selection of solutions and their implementation are decided upon and executed in cooperation with beneficiary groups. An example is the approach of "Gestion des terroires" or the so called "Community-Based Natural Resource Management" (Pagiola, 1997). In this approach, communities design and implement a resource management plan with the help of a multidisciplinary team of technicians. The plan includes rules governing access to and exploitation of common resources such as pasture, forest and water, and specific land improvement work mainly on common lands but also on individual holdings. The new approach also includes: · management plan must be site-specific, e.g. there are no "blue prints"; · management units must be based not only on social units (e.g. villages) but on natural resources units (such as watersheds) that need to be treated together for management purposes; · when a resource is shared by several communities, the management unit needs to include all users; · a multidisciplinary production system approach is considered, even where one activity such as grazing is dominant; · government departments and relevant farmers advisory services have to be adapted to the approach and directed to support the schemes at community level or decentralized structure. ii. Much greater attention is now paid to changing the incentive framework within which land resource management decisions are made; such as change in pricing policy, market liberalization, land tenure reforms, etc. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 69
The World Bank and other agencies, such as IFAD, have already devoted considerable resources to assist countries in implementation (with the new approach described above) of projects aiming at controlling land degradation and improving its productivity. Projects using this approach are already implemented in West Africa. Similar watershed land management projects have also been carried out in Latin America with technical assistance from FAO.
PROPOSALS FOR MONITORING AND STRENGTHENING EFFORTS TO COMBAT LAND DEGRADATION If comprehensive and integrated action is not taken to combat both direct and underlying causes of land degradation: land resources would be destroyed and there will be further economic losses at national level, negative consequences on the environment at global level; and the poor farmer will suffer. In order to enhance the knowledge and monitor the status of land degradation and to strengthen the efforts for combating degradation, the following proposals may be considered: i. Establishment of regional or sub-regional Collaborative Programme and guidelines for in- depth assessment of land degradation, which would include survey of the present state of degradation and monitoring of soil changes. ii. Study of the economic and social effects of degradation upon the people, which will require collaboration between land resources and management specialists as well social scientists.
In this respect, initiating a sub-regional project on the assessment of soil degradation and its impacts in Southern and East Africa (in line with ASSOD "Soil degradation in South and South-East Asia") would be useful.
Moreover, there is a need for harmonization of methodologies and promotion of quantitative assessment of the impacts of degradation on productivity at national/sub- regional level, using 1:1 million SOTER database (example: impact of erosion or fertility decline, Case Study/Project in Kenya, Argentina and Uruguay -UNEP/ISRIC). This of course is subject to the concerned countries' interest, commitment and eventually the possibility of donor's support. iii. Design and implementation of programmes and measures to combat land degradation would include: · Clarify institutional responsibilities, and perhaps the establishment of high-level advisory committees on policies related to land degradation and its combat. · Identify focal institutions and coordination mechanisms for land degradation assessment and monitoring. · Identify priorities with respect to type of degradation, critical and "hot" spots. · Plan and implement national, sub-national and/or community-based programmes for controlling degradation and for enhancing productivity, such as: - watershed land management and conservation projects; - community-based natural resources management projects "Gestion des terroires"; 70 Land degradation in relation to food security with focus on soil fertility management
- elaboration and implementation of National Action Programmes for combatting desertification and drylands development projects; - promoting the adoption of ISCRAL (Soil conservation and rehabilitation schemes) at national, sub-regional and regional level.
Allocation of national resources, increased funding and international support would be required.
In this respect, there is a need of: more effective regional and/or sub-regional co- operation, networking for exchange of experience and technologies, increasing awareness and dissemination of information on land degradation and corrective measures for its control; mobilization of national financial resources and commitment to the issue; promotion of donor support, technical assistance from bilateral and international relevant agencies (such as FAO) for the implementation of land development programmes.
Networks Networks established through regional collaborative programmes, with the support of FAO and UN Agencies, continue to play an important role in exchange of ideas, experiences and technologies as well as assistance in policy and project formulation related to land degradation control and land productivity improvement.
While several relevant networks are still operating in Asia, with the support of UN agencies particularly FAO, not much attention has been given to the Africa region with respect to networks, which specifically deal with land degradation and land improvement issues. Moreover, if a specific network is established in Africa, with technical support of FAO, the participating countries would benefit from global exchange of information, technologies and methodologies etc., through interlinks with existing global and regional networks, in Asia and Latin America, which are supported by FAO.
The FAO Soil Resources, Management and Conservation Service (AGLS) has provided and disseminated to FAO member countries and partner institutions: technical assistance, information, methodologies, concepts and frameworks, technologies and global assessment related to land resources, management and conservation. In addition, AGLS has been at the forefront of creating international linkage and networks concerned with land management and conservation. Examples of relevant ongoing networks (supported by FAO/AGLS) are given below: · Asian Network on Problem Soils · Asian Bio and Organic Fertilizer Network · Asia Soil Conservation Network for the Humid Tropics (ASOCON) · Network on conservation tillage in Latin America (RELACO) · Association with WOCAT (World Overview of Conservation Approaches and Technologies) · Global Network on Integrated Soil Management for Sustainable Use of Salt Affected Soils · The Network on the Management of Gypsiferous Soils (Near East and Mediterranean). Integrated soil management for sustainable agriculture and food security in Southern and East Africa 71
* It is, therefore, proposed, subject to debates and endorsement of this consultation, to create an "African Network on Degraded and Problem Soils". Such a network would deal with issues related to soil degradation, its assessment and promotion of soil management and productivity improvement technologies. The Network could also promote, through TCDC mechanisms, transfer of knowledge and experience in areas related to sustainable management of problem soils, such as: acid soils, saline soils, gypsiferous soils, calcareous soils and vertic soils. This African Network will be interlinked with the above mentioned ongoing networks (assisted by FAO) to ensure global and intra-regional exchanges of experience and know-how. The proposed Network, however, could cover at initial stage some countries in Southern and East Africa (i.e. countries under SAFR).
THE SPECIAL PROGRAMME FOR FOOD SECURITY (SPFS) At present, there are 86 low-income food deficit countries (LIFDCs), including 43 countries in Africa and 9 in Latin America and the Caribbean. These countries are home to the vast majority of the world’s 800 million chronically undernourished people. Many LIFDCs, particularly in Africa, do not grow enough food to meet their needs and lack sufficient foreign exchange to fill the gap by purchasing food on the international market. After the approval of the Council in June 1994, the SPFS was launched by FAO and at present it is operational in 20 countries. Initially launched with modest FAO Regular Programme funds, the SPFS is now supported by several donor countries and international agencies, including the World Bank, African Development Bank, IFAD, WFP and UNDP.
The SPFS helps farmers increase food production and productivity in LIFDCs. It responds to the urgent need to boost food production in these countries in order to meet the growing market demands and help eradicate food insecurity. The SPFS implementation consists of two phases: a "pilot phase" of some 3 years’ duration, followed by an "expansion phase" that takes place after results of the 4 components of the pilot phase have been assessed and the policy and investment plan have been prepared and approved at national level. The pilot phase, which usually starts with participatory on-farm demonstrations, consists of 4 interrelated components: · Improved water control, including low-cost small-scale irrigation. · Sustainable intensification of crop production systems, through improved technologies1 and agricultural inputs. · Diversification of production, including aquaculture, small animal and horticulture. · Removal of constraints to increased food production, through participatory approach
World Food Summit (WFS) The successful expansion of the SFPS will play an important role in achieving food security objectives, set out by the World Food Summit (WFS), held in Rome, November 1996. Representatives of 186 countries approved the Rome Declaration and the WFS Plan of Action that included recognition of the need to pursue, through participatory means, sustainable intensified and diversified food production:
1 Including Integrated Soil, Water and Nutrient Management. 72 Land degradation in relation to food security with focus on soil fertility management
"Objective 3.2, Commitment Three of the Plan of Action is: to combat environmental threats to food security, in particular, drought and desertification, pests and erosion of biological diversity and degradation of land and aquatic-based natural resources, restore and rehabilitate the natural resource base, including water and watersheds, in depleted and over exploited areas to achieve greater production".
Complementarity and the place of ISWNM1 in the SPFS Sustainable increase of food production is critical for achieving household food security particularly in resource poor areas. Improper land use and management, over cultivation, physical, chemical and biological soil degradation cause serious decline in productivity, especially in countries or areas subjected to increased population pressure on limited and/or fragile lands. Identification, selection and farmers’ adoption, through participatory approach, of improved and alternative packages of low-cost, low-risk soil management and conservation practices are, therefore, required to address/control land degradation, to maintain and enhance soil fertility and hence, soil productivity and food production.
The adoption of improved packages of technologies related to soil, water and nutrient management at farm level is rather limited, particularly in LIFDCs, because the development of these technologies has often not taken into due consideration the socio-economic environment of the farmers nor the specific potentials and constraints of the natural resources base at farm and at community level.
Despite the availability of segmented technologies on soil, water and plant nutrition management; the holistic approach and integrated packages are still lacking. In addition, effective approaches and mechanisms for participatory technology development and transfer to farmers are inadequate. Field level technicians and grass-root extension workers still lack training in such integrated approach to facilitate farmers’ adoption.
The sustainable intensification of production systems in agriculture is a key for food security and requires a coherent and integrated development of appropriate technologies, know- how and tools related to soil, water and plant nutrition management. Assisting farmers’ decision- making for increasing their income, optimizing the use of their natural resources and inputs and improving and/or conserving the productivity of their resource base is a prerequisite for such sustainable intensification and food security.
Intensification of production systems, usually requires an increased supply of plant nutrients. Monitoring of plant nutrient balance and supply to the crops, control of losses, arresting depletion and ensuring accumulation are essential for increased productivity, income and safe environment.
Poor water and irrigation management at farm level result in substantial losses in productivity and scarce water resources. In irrigated areas, the misuse of water and poor irrigation practices are causing moisture deficit, induced waterlogging, soil degradation/salinization and declining productivity. Poor water control and harvesting in rainfed agriculture result in poor yields per unit area and do not allow any meaningful intensification. As such, water management at farm level is an essential element in crop production intensification.
1 ISWNM: Integrated Soil, Water and Nutrient Management. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 73
Optimizing the physical, chemical and biological conditions of the soil will also provide the synergy and base of successful crop identification. Improving the soil conditions will enhance the efficiency of agricultural inputs (seeds, fertilizers and other sources of plant nutrients), will promote water use efficiency (either rain or irrigation water through increase in infiltration, improvement in water-holding capacity and reduction in runoff), and will reduce pest attacks (through appropriate tillage practices, aeration and optimal soil organic matter and plant residue management).
It is evident that there are interactions and complementarities among the various components of a pilot project (under the SPFS or land improvement schemes). Segmented interventions or separate schemes (for water control or soil fertility/productivity improvement, etc.) would not necessarily result in a significant or sustainable yield increase.
An integrated approach (and intervention/project implementation) of soil, water and nutrient management, and wherever feasible to be linked with integrated pest management, should be promoted in order to address soil degradation and declining productivity, and to enhance agricultural production and food security.
FERTILIZERS USE DEVELOPMENT IN SSA, THE CONTRAST WITH ASIA AND RELATED ISSUES The average world fertilizer consumption during the period 1990/1993 was 130 million metric tonnes of nutrients. It declined to 121 million metric tonnes (MMT) in 1993 and it reached 131 MMT in 1995/96. Africa, comprising 58 countries, accounts to only 2.6% of world fertilizer consumption, and the share of Sub-Saharan Africa(SSA) is 1.2%. Fertilizer consumption in Africa continues to be restricted to some 12 major consumers1; about 63% of the regional total fertilizer consumption occur in Egypt, Morocco and South Africa. The average fertilizer consumption in SSA during 1990/93 was only 2.16 MMT, compared to 51.2 MMT in Far East developing countries and 5.4 MMT in Near East. The contrasting evolution of fertilizer consumption in Asia and in SSA could be depicted from Figure 8. While fertilizer consumption has developed rapidly in Asia, there is an alarming stagnation of fertilizer consumption in SSA (Table 8). There is also a great disparity in fertilizer consumption among the countries of SSA (Figure 9). With the exception of 12 countries2 in SSA, the average fertilizer use is below 10 kg nutrients/ha of arable land (compared to 130 kg/ha in the Far East and 60 kg/ha in the Near East, and about 90 kg/ha as world average). The stagnation of fertilizer use in SSA could be attributed to the following constraints: · lack of coherent medium and long-term policy for fertilizer use development; · inefficient input procurement and distribution systems and inexperienced organizations; · shortage of foreign currency and balance of payment problems; · low price of agricultural produce;
1 Algeria, Egypt, Kenya, Libya, Malawi, Morocco, Nigeria, South Africa, Sudan, Tunisia, Zambia and Zimbabwe. 2 Zimbabwe, Kenya, Mauritius, Swaziland (>40 kg nutrient/ha); Malawi (20-40 kg/ha); Ivory Coast, Lesotho, Mauritania, Nigeria, Tanzania, Togo, Zambia (10-20 kg/ha); Burkina Faso, Congo, Ethiopia, Gambia, Mali, Senegal (5-10 kg/ha); the remaining 26 countries of SSA (< 5 kg/ha). 74 Land degradation in relation to food security with focus on soil fertility management
FIGURE 8 Evolution of fertilizer consumption: Asia, South America and sub-Saharan Africa
· inconsistent agricultural input pricing and subsidy policies; · limited access of smallholders to agricultural credit and poor purchasing capacity; · inadequate advisory institutions and supporting data/information base; · poor infrastructure facilities.
Between 1980 and 1991, fertilizer consumption in India1, China2 and other Asian developing countries almost doubled, in contrast with the alarming stagnation in SSA over the same period. The unbalanced fertilizer use in Asia (N:P205 ratio of 3.19 and P205:K20 of 2.65 in 1993 for example), however contributes to the limited increase in yields and the low fertilizer use efficiency in some countries of the region.
TABLE. 8 Fertilizer consumption, Asia and SSA (1000 M tonnes of nutrients) 1. India, China and South East Asian Countries 1980 1982 1984 1986 1988 1990 1991 1992 1993 N 19 887 20 177 25 904 25 544 32 903 34 669 35 558 37 286 34 846
P205 5 544 6 570 7 884 7 471 10 596 12 087 13 433 12 615 10 909
K20 1 924 2 140 2 659 2 621 3 991 4 499 5 139 4 408 4 109 Total 27 335 28 887 36 447 35 636 47 490 51 255 54 130 54 309 49 864 2. Sub-Saharan Africa 1980 1982 1984 1986 1988 1990 1991 1992 1993 N 995 1 017 907 948 997 1 073 1 054 1 137 1 193
P205 719 782 734 668 687 644 625 639 782 K20 305 339 336 312 330 361 363 367 385 Total 2019 2 138 1 977 1 928 2 014 2 078 2 042 2 143 2 360
1 In India from about 6.5 million tonnes in 1980/83 to 12 million tonnes in 1990/93. 2 In China from some 16 million tonnes in 1980/83 to 29 million tonnes in 1990/93. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 75
The lack of important fertilizer industry in SSA has certainly contributed to the slow and low fertilizer use development.
About 87% of the production of N fertilizers takes place in South Africa and Nigeria and very small units are also operational in Zimbabwe, Senegal, Mauritius and Zambia. Some 85% of the production of P fertilizers takes place in South Africa and Nigeria, small units exist in Zimbabwe and Senegal. There is no production of potash fertilizers in the continent. On the contrary, with the development of the fertilizer sector in Asia and the Near East, the development of the fertilizer industry did not take place in SSA, though ample raw materials are available: rock phosphates, natural gas, naphtha.
For the development of the fertilizer sector in Africa, a combination of the following would be required: · the organization of sub-regional fertilizer markets, justifying plants of viable size; · the connection of those markets with joint ventures (for fertilizer production facilities) providing the capital and the security of sales; · revision of the actual taxation, banking rates, margins of distribution, etc.; · a proactive national programme for fertilizer demonstration and technical advice on intensification to farmers; · a re-organization of the marketing of agricultural produce and inputs, improvement of infrastructure, providing fair on farm prices and lower distribution costs.
Structural Adjustment Programmes (SAPs) Since 1980, the major lending international institutions introduced Structural Adjustment Programmes (SAPs) in many countries in Africa. More than 80% of these programmes included a condition related to agricultural pricing/subsidy and/or parastatal institution reforms. The relevant impacts of these SAPs were: · devaluation of local currencies; · decline or removal of subsidies on agricultural inputs; · suppression of government/parastatal monopolies in input import and distribution; · increased interest rate on agricultural credit; · decrease in output/input price ratio and decrease in the profitability of fertilizers; · no consistent trend in fertilizer consumption or availability.
Despite the deregulated systems in fertilizer procurement and distribution, in many African countries, there is still a need to address: · high import costs due to complexity and lengthy procedures and limited economy of scale in imports (small quantities); · higher costs due to inefficient fertilizer demand forecasts, implying in many cases considerable stocks; · inadequate supply or severe shortage in remote areas (higher costs for the private sector); · insufficiently trained personnel in the whole marketing channels (new involvement of the private sector). 76 Land degradation in relation to food security with focus on soil fertility management
FIGURE 9 Fertilizer use level in Africa (average 1988-1990) Integrated soil management for sustainable agriculture and food security in Southern and East Africa 77
Pricing and subsidy Among the important fertilizer policy instruments is the subsidy. Usually during the introductory stage, fertilizers are heavily subsidized to promote their adoption and use by farmers. However, with the development of their use and the increasing volume of fertilizer consumption in a given country, the volume of subsidy constitutes a heavy financial burden on the government. This calls for more emphasis of both research and extension on enhancing fertilizer use efficiency in order to achieve the production targets with lesser volume of fertilizer products. Improving fertilizer supply and distribution systems (including reduction in physical losses and costs) are among the areas of intervention (both from the public and the private sector) to reduce the fertilizer farm- gate prices in order to lessen the impact of subsidy removal.
Experience of many countries suggests that if it is socially desirable to phase out subsidies, they should be phased out gradually and with improvements in procurement, marketing and distribution, as well as research and extension. Ad hoc and abrupt changes in pricing/subsidy are counter-productive for steady fertilizer use level. Like the subsidy policy, the privatization of the fertilizer sector's operations should also be gradual and supported with adequate development of skills, infrastructure and institutional development.
Fertilizer donations The supply of fertilizer in many SSA countries has been partly secured through aid-in-kind. It is observed, however, that most of the traditional donors are reducing or suppressing their fertilizer grants, mainly due to the difficulties encountered by many countries to utilize the fertilizer sale proceeds effectively for agricultural development programmes.
In order to sustain at least a modest fertilizer supply in many countries in Africa, to supplement the local sources of plant nutrients, appropriate and effective linkages between agricultural commodities export and fertilizer imports should be envisaged (e.g. financing fertilizer imports from the proceeds of cash crops exports).
Conclusion:
The stagnation of fertilizer use in SSA would imply that, for the intensification of crop production and for soil fertility restoration, more emphasis should be placed on Integrated Plant Nutrition Systems (IPNS), with focus on mobilization of local organic sources of plant nutrients: composting, mixed cropping, green manuring, farmyard manure, agroforestry, etc. Depending on the country's condition, the local sources could be supplemented by external/mineral fertilizers. The use of local phosphate rock should be promoted whenever it is feasible and economically viable.
SOIL MANAGEMENT OPTIONS FOR ADDRESSING SOIL FERTILITY DECLINE Soil fertility depletion in smallholder farms is the fundamental biophysical root cause for declining per capita food production in Africa, and soil fertility restoration/recapitalization should be considered as an investment in natural resource capital. Besides improved soil management practices , accompanying technologies such as soil conservation, and enabling policies are needed to make recapitalization operational. The issue of who should pay for this recapitalization is based on the principle that those who benefit from a course of action should incur the costs of its implementation. On-farm maintenance costs should be borne by farmers, whereas national and 78 Land degradation in relation to food security with focus on soil fertility management
global societies may share the costs of substantial phosphate and other soil amendment applications (Sanchez et al., 1997).
There is no single technology that would lead to soil fertility restoration and soil productivity improvement due to the diversity of the bio-physical, ecological and socio-economic environment of the farmers' community. A lot of technologies have been generated but, in most cases, the bottleneck lies in their adoption and implementation, particularly by the small scale farmers.
Nevertheless, the known technological options for restoration of soil fertility could be grouped as follows (Mokwunye et al., 1996): · increased and more efficient use of mineral fertilizers; · exploitation and use of locally available soil amendments such as phosphate rocks, lime and dolomites; · maximum recycling of organic products, both from within and from outside the farm (crop residues, animal manure, composts, urban waste/refuse, etc.); · improved land use systems, based on both indigenous and improved methods such as appropriate crop rotation, intercropping, agroforestry and related tree-based farming systems, increased use of species that can fix N from the atmosphere, alternatives to slash- and-burn so that fallows can be improved; · effective methods to control wind and water erosion, tailored to indigenous knowledge and emphasizing local biological resources and simple physical structures; · promotion of the Integrated Plant Nutrition Systems (IPNS) which aims at maintenance or adjustment of soil fertility and of plant nutrient supply to an optimal level for sustaining the desired crop productivity, through optimization of the benefits from all possible sources of plant nutrients (organic and inorganic) in an integrated manner.
Constraints and potentials of these alternative technologies are given below: · To restore soil fertility and achieve specific yield targets, technologies that save nutrients from being lost from the agro-ecosystem may not be sufficient; they need to be supplemented by technologies that add nutrients to the agro-ecosystem. When used judiciously, i.e. proper type, amount and timing of application for the specific crop, soil and climatic conditions, use of mineral fertilizers can result in considerable production increases without harming the environment. The two major environmental risks of continuous fertilizer use in Africa are soil acidification and the accelerated depletion of nutrients that are not included in the fertilizer. Farmers buy mineral fertilizers to achieve immediate product increases rather than to increase soil fertility. In some African countries, the use of local phosphate rock is a viable alternative to the use of expensive soluble imported P fertilizers, particularly in areas close to the phosphate deposits (to minimize transport and distribution costs). The use of phosphate rock is particularly attractive in P-deficient areas with relatively high rainfall and on acid soils, for wetland rice and on leguminous species, and in areas where tree crops are common or where afforestation is envisaged. · Organic material serves as an indispensable source of plant nutrients. In addition, organic material improves the soil chemical, physical and biological conditions. Maximum use of organic inputs includes maximum recycling of both on-farm and off-farm supplies. Reported major constraints are labour, transport, and low nutrient concentration. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 79
Technologies that involve low-capital inputs such as crop rotations, green manures, fodder banks, improved fallows, and agroforestry systems have a role to play in the restoration of soil fertility. The extent to which this can be successful is largely determined by soil, climate, farmers' willingness to invest scarce labour into improving their land and crop management practices, and the degree to which the policy environment is "enabling". · Erosion is a very important cause of nutrient depletion. Therefore, soil and water conservation is of prime importance in restoring soil fertility through nutrient-saving rather than nutrient-adding mechanisms. Major constraints to soil and water conservation practices are the labour requirements and the fact that farmers see no immediate economic gain for their efforts. This highlights the need to combine efforts on soil and water conservation and soil fertility restoration. · The philosophy behind IPNS shows that a combination of technologies is better able to redress nutrient imbalance and depletion in African agro-ecosystems. Under an IPNS philosophy, the farmer can optimize the allocation of the different production factors to different parts of his/her land. This may involve both low- and high-external input practices. As mentioned earlier, the stagnation of fertilizer use development in many SSA countries implies that more emphasis should be placed on IPNS and maximum use of organic inputs and local phosphate resources, in order to address soil fertility decline.
Examples of soil and plant nutrition management practices for addressing fertility decline and enhancing soil productivity are discussed below: Maintenance and increase of soil organic matter Options for improvement and maintenance of the soil organic matter in soils are: (a) intensifying biomass production per unit area, within the existing cropping system by improving the soil moisture regime particularly in rainfed areas, balanced fertilization and improving soil conditions through amendments and better husbandry; (b) increasing biomass production through changes in the cropping/farming system such as intercropping, improved rotations and fallows that include grasses and agroforestry systems; (c) reduction of the rate of loss of soil organic matter through maintenance of soil cover to keep soil temperatures down, slowing down of erosion, avoiding/controlling fires, stimulation of soil fauna growth and change to minimum tillage techniques; and (d) application of organic materials (farmyard manure, compost, plant residues, etc.) which would favour accumulation and build up of humus substances in the soil.
Within the above range of options, the application of organic materials would involve a capital for simple and low-cost equipment, know-how for improving the quality of organic materials and an input of labour by the farmer. Each option would be decided upon by the farmer depending on the value of the crop, the expectation for an attractive price, availability of residues and cattle on the farm and availability of farm labour.
Use of soil amendments and fertilizers for addressing specific soil limiting factors For highly acid soils, the application of limestone or dolomite would reduce aluminium toxicity and improve availability of calcium and magnesium. Since liming requirement could be up to 4-5 Mt/ha, transport cost and labour required for application should be assessed.
Experience obtained in Madagascar, however, showed good results with a basal dolomite dose of 1-2.5 Mt/ha (depending on the soil type and pH) followed by a maintenance application of 350 kg/ha, from the third subsequent year. The best results, however, were obtained by 80 Land degradation in relation to food security with focus on soil fertility management
applying about 500 kg/ha of dolomite in combination with fertilizers, mainly phosphate, and organic manures in the first year.
On the other hand, for sodic or saline/sodic soils in arid/semi-arid environment the use of gypsum as soil amendment is essential for restoring the productivity and the reclamation of these problem soils.
Phosphate rock (PR) deposits of potential economic significance occur at more than 100 locations in at least 31 countries in sub-Saharan Africa (e.g. in Togo, Mali, Senegal, Tanzania, Burkina Faso, Niger, Angola, etc.), and often in proximity to P-deficient arable lands. The quantity of resources and the average P205 concentration varies from less than 100 000 tonnes to greater than 800 million tonnes and from 5% to 33% P205 (Appleton, 1995).
Some of these materials of sedimentary origin and reactive have been found to be suitable for direct application, while others are only effective when partially acidulated, compacted or mixed with organic inputs. Igneous PR deposits (Burundi, South Africa, and Zimbabwe) are seldom suitable for direct application and are best used to manufacture superphosphates or partially acidulated PR.
Despite the existence of such resources (Figure 10), few countries have mobilized their resources and their use as direct application is still very limited. There is a need for additional agro-economic evaluation and assessment of the reasons for restricted use (Togo, for example, produces some 2.5 million tonnes of phosphate but only some 300 tonnes are used as direct application in the country). Farmers are still reluctant to use PR because of the dusty character of the finely ground materials, its slow reactivity and perhaps the less visible direct effect on the growing crop as compared to P fertilizers. The choice of P source depends on many factors such as cost differentials between PR and superphosphates, soil acidity and the P-sorption capacity of the soil. Cost differences per kg P can be major; the more acid the soil, the more rapid the dissolution rate of PR. Given these variables as well as logistic, financial and infrastructure consideration, the choice of P fertilizers source and the rate for replenishment is "site" and "situation specific".
The degree of solubility, accessibility and processing and transport costs vary widely. The solubility of phosphate rock can be increased through various processes, including grinding, heating or acidification. Low-cost grinding may be most practical for high rainfall areas with highly acid soils.
The high residual effects of PR has an important bearing on its agro-economic evaluation. This is an area that has often been neglected since economic benefits are made on the basis of one season's agricultural production. Although PRs are most effective in wet soils/high rainfall, they have proved effective also in drier zones of West Africa (Mokwunye et al., 1996).
In this respect it should be noted that long-term benefit (or economic return to farmers) from investment in land improvement (for example, the application of lime, gypsum or rock phosphate) have often not been adequately demonstrated to farmers and, therefore, this should be given due consideration in projects aiming at restoration of soil fertility and land productivity improvement.
Additionally, there is a need for complementary studies to include: Integrated soil management for sustainable agriculture and food security in Southern and East Africa 81
FIGURE 10 Location of phosphate depostis in sub-Saharan Africa excluding South Africa (Appleton, 1995)
· Inventory of resources, synthesis of applied research and experiences on the use of soil amendments such as: lime, dolomite, gypsum, etc. in land improvement schemes in selected countries of Sub-Saharan Africa. · Inventory of resources, synthesis of agronomic and economic benefit from the use of local rock phosphates, as compared to phosphate fertilizers, in some targeted countries of Sub-Saharan Africa. The reasons of the limited use and/or extended use in specific country (countries) could be highlighted by the study for more rational follow-up actions in Soil Fertility Initiative related projects. 82 Land degradation in relation to food security with focus on soil fertility management
Phosphorus-replenishment strategies are mainly fertilizer-based with biological supplementation, while N replenishment strategies are mainly biological with chemical supplementation.
Techniques to replenish soil P, therefore, consist of P fertilization (either from commercial fertilizer or PR, as appropriate), the effective use of available organic sources and therefore the maintenance of activity and biodiversity of key soil organisms such as mycorrhiza. Decomposing organic inputs produce organic acids that help solubilize phosphate rocks. The integration of available organic resources with commercial fertilizers and/or PR - may be the key to increasing and sustaining levels of P capital in tropical soils.
For example, in Western Kenya, an interesting soil fertility recapitalization strategy focused on: · Improved fallow of Sesbania Sesban (6-14 months). The fallow will reduce the Striga infestation and supply some 100 kg N/ha. · Contour bunds, ditches for controlling soil erosion with Tithonia plants. Additional Tithonia are also planted near hedges and along field boundaries. · Application of organic resources such as compost and cattle manure produced on the farm. · Application of PR, incorporated with the Tithonia and other leguminous fallow leafy materials, before planting the maize crop. The on-farm research in Western Kenya with (Minjingu) PR, at the rate of 250 kg P/ha, in combination with 1.8 t/ha of Tithonia diversifolia dry biomass showed substantial increase in maize yields (from 1.8 to 4.2 t/ha). The benefit from Tithonia was also attributed to addition of K, as this plant is also high in K concentration. Subsequent research confirmed higher maize production with sole application of Tithonia biomass than with an equivalent rate of NPK mineral fertilizers ( Sanchez et al., 1997). P replenishment, however, must usually be accompanied by N replenishment (from organic and/or inorganic sources) in order to be effective, because most of P-deficient soils are also deficient in N. Emerging evidence suggests that N demands can be met biologically through Biological Nitrogen Fixation (BNF) for maize crop yields in the order of 4 tonnes/ha. Two-year old Sesbania fallows (in Chipata, Zambia) doubled the maize yields over a 6-year period, in comparison with continuous unfertilized maize production. Agroforestry systems like Sesbania fallows are thus able to substitute fertilizer N application, for profitable maize production. Green manure fallows also provide sufficient N inputs through BNF to meet the needs of one subsequent maize crop. The use of Mucuna, for example (to fix N and smother Imperata weeds) is expanding rapidly in some Western African countries such as Benin and Ghana (IITA, 1995).
Improving soil physical conditions and soil moisture Soil structure is important for all aspects of soil use and management. A well structured soil, which does not crust under rainfall, will provide optimal water conditions if the water inputs are sufficient. Repeated cultivation without any effort to redress structural degradation will result in a decline in productivity. For most soils, maintenance and improvement of existing structure could be achieved through optimization of the organic matter content and of the activity and species' diversity of the soil fauna and other organisms. Conservation tillage, as compared to clean tillage for example, could promote the maintenance of soil structure and aggregates at the surface and Integrated soil management for sustainable agriculture and food security in Southern and East Africa 83
thus reduce wind and water erosion. FIGURE 11 Under specific soil conditions, The central importance of soil structure (after Lal, however, conventional tillage could 1994) promote water infiltration, control weeds, reduce mechanical impedance to root growth and promote the incor- poration of crop residues into the soil. Tests and demonstrations on farmers field in Ethiopia showed that double ploughing, using an improved and locally produced plough (mould- board) at a cost of $30 per unit increased cereal yields by 28% and saved considerably on labour inputs for weeding. Application of the recommended dose of imported fertilizers increased yields by 31% on the same soil type (Nitosols, Combisols). Adopting the combined practices increased yields by 48%. The inter-linkage between different aspects of soil physics and the central role of soil structure are shown in Figure 11. The adoption of simple measures such as water harvesting and more efficient in situ capture of rainfall, improvements of water infiltration and increasing the water holding capacity of soils could yield significant improvements in productivity, especially in drier climates. Examples of measures which could be adopted by farmers to retain water on the surface and thereby increase the time available for infiltration include mulching, contour tillage, tied ridging, contour planting, strip cropping. These and similar measures would also reduce splash erosion and evaporation of water from the surface. Improved infiltration and percolation could be promoted by tillage, sub-soiling to break compact surface and subsurface layers; and measures to increase soil organic matter levels and liming to improve soil structure and promote biological activity.
CONCLUSION The diversified agro-ecological conditions and socio-economic environment of the farmers make it unlikely that a single technology will lead to the goal of soil fertility restoration and crop production intensification. There should be a close linkage between the respective technologies suggested, since land development combined with water control are known to contribute positively to crop production intensification. In this respect an "Integrated Soil, Water and Nutrient Management Approach" for the restoration of soil fertility and productivity is required, since segmented intervention on soil, water or nutrients may not result in a significant or sustainable yield increases. The majority of small-scale/ resource-poor farmers in Africa are faced with constraints which are limiting their ability to adopt improved technological innovations and appropriate management practices. These constraints could include: limited access to credit, lack of timely and availability of agricultural inputs such as fertilizers, seeds, farm implements, soil amendments; inadequate involvement of NGOs and private sector for facilitating input supply 84 Land degradation in relation to food security with focus on soil fertility management
and distribution; limited infrastructure, lack of effective linkage between research and extension, inefficient extension service; institutional weakness and lack of appropriate and enabling mechanisms for farmers' participation and direct involvement in the identification of production constraints, selection and testing of appropriate technological packages; and last but not least the lack of enabling and conducive policies to address the underlying causes of degradation and to enhance farmers adoption of improved technologies. Realistically, farmers are expected to adopt improved technologies for soil fertility restoration where there is: a conducive macro-economic policy; a need for production intensification caused by land scarcity without possibility for expansion; a secure access to land where farmers will benefit from their investment in land improvement; access to credit and markets of agricultural inputs and farm produce. It is obvious that soil fertility restoration in Africa will require significant policy changes/reforms at local level by rural communities and decentralized administrative authorities, at national level by governments, and also at global level by donors and international agencies concerned with agricultural development. These policy reforms would address the prevailing farmers' constraints and promote the implementation of effective measures to ensure, in particular, appropriate land tenure systems, efficient agricultural credit, sound agricultural pricing policies for farm produce and inputs and possibly short-term targeted agricultural subsidies for soil amendments. Moreover, there is a need for appropriate institutional set-up and coordination, efficient farmers’ organizations, important adaptive research and extension education. Technological options for restoration of soil fertility and enhancing productivity are available, but the bottleneck is their wider adoption by the small scale farmers for which enabling policies and conducive measures must be in place.
REFERENCES Appleton, J.D. 1995. Indigenous rock phosphate mobilization, processing and use in Sub-Saharan Africa, British Geological Survey, UK; AGL:FAO/PNP/95/16 E. Brabant, P. et al. 1997. Human-induced land degradation in Togo, Explanatory notes on the land degradation index map (1:500 000). C.N.E. No. 112. ORSTOM. FAO 1976. A framework for land evaluation. FAO Soils Bulletin 32. FAO, Rome. FAO 1990. International Scheme for conservation and rehabilitation of African Land (ISCRAL), ARC/90/4, Rome. FAO, WSRR No. 78. 1994. Land degradation in South Asia, its severity, causes and effects upon the people. (Report compiled by A. Young 1992, UNDP/FAO/UNEP). Goswami, N.N. and Rattan, R.K. 1992. Soil health - key to sustained agricultural productivity. Fertilizer News (India). IITA. 1995. Annual Report of 1994. International Institute of Tropical Agriculture, Ibadan, Nigeria. Lal, R. 1994. Sustainable land use systems and soil resilience. In: Soil Resilience and Sustainable Land Use. D. J. Greenland and I Szabolcs (eds.). CAB International, Wallingforth, UK, pp. 41-67. Mokwunye, A.Z. de Jager, A. and Smaling, E.M.A. 1996. Restoring and maintaining the productivity of West African soils: Key to sustainable development. IFDC, Africa. Oldeman, L.R., Hakkeling, R.T.A., and Sombroek, W.G. 1990. Human-induced soil degradation. Revised 2nd edition. International Soil Reference and Information Centre, Wageningen, The Netherlands. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 85
Oldeman, L.R., Engelen, V.W.P., Van Pulles, J.H.M. 1990. The extent of human induced soil degradation. Annex 5 "World map of the status of human-induced soil degradation, an explanatory note". ISRIC, Wageningen. Pagiola, S. 1997. Draft paper "The global environmental benefits of land degradation control on agricultural land" Sanchez, P.A. and Logan, J.J. 1992. Myths and science about the chemistry and fertility of soils in the tropics. SSSA Special Publication No. 29. Sanchez, P. et al. 1997. Soil fertility replenishment in Africa: an investment in natural resource capital. Paper presented at ICRAF Meeting on Approaches to Replenishing Soil Fertility in Africa - NGO Perspectives, Nairobi, Kenya. Smaling, E.M.A., Stoorvogel, J.J. and Windmeijer 1992. Calculating soil nutrient balances in Africa at different scales. II. District scale. DLO, The Winand Staring Centre, Wageningen. Steiner, K.G. 1996. Causes of soil degradation and development approaches to sustainable soil management. GTZ, Margraf Verlag, Germany. Stoorvogel, J.J. and Smaling 1990. Assessment of soil nutrient depletion in Sub-Saharan Africa: 1983- 2000. Report No. 28. Winand Staring Centre, Wageningen. UNEP 1992b. Desertification, land degradation (definitions). Desertification Control Bulletin 21. Young, A. 1991. Soil monitoring: a basic task for soil survey organizations. Soil Use and Management 7. 86 Land degradation in relation to food security with focus on soil fertility management
Appendix 1
UN/FAO frameworks and initiatives related to land degradation and management
It is evident that land degradation and sustainable land resources management are important issues as underlined in the relevant chapters of Agenda 21 of the Earth Summit, the International Scheme for Conservation and Rehabilitation of African Land (ISCRAL), the Convention to Combat Desertification (CCD), and the Soil Fertility Initiative (SFI). Since such global initiatives have considerable implications on FAO or member countries' programmes, for addressing degradation and for improving land productivity, some are highlighted in Annex 1 and 2.
AGENDA 21 The most prominent outputs of the UN Conference on Environment and Development (UNCED) were the Rio Declaration on Environment and Development and its Agenda 21 Action Programme. Agenda 21 presents a blue-print for action to achieve sustainable development into the 21st century. Of the total 40 chapters of the Agenda, 3 chapters are relevant to land degradation, sustainable land resources management and conservation: Chapter 10: Integrated approach to the planning and management of land resources (for which FAO/AGL is the task manager). Chapter 12: Managing fragile ecosystems: combatting desertification and drought. Chapter 14: Chapter 10: its broad objective is to facilitate allocation of land to the uses that provide the greatest sustainable benefit and to promote the transition to a sustainable and integrated management of land resources. It emphasizes that “expanding human requirement are placing an increasing stress on these land resources and the resulting conflicts and competition are creating inefficient and ineffective patterns of use. Integrated physical, economic and social parameters with land use planning and management is suggested as a practical technique that can help resolve conflicts and move towards an optimal use of land and its natural resources”. Chapter 12: assigns a high priority to combatting desertification (land degradation in arid, semi- arid and dry sub-humid), to the implementation of preventive measures to conserve lands that are not yet degraded, or which are only slightly degraded. It draws the attention to the importance of the participation of local communities, rural organizations, governments, NGOs and regional, national and sub-national organizations, in the process of combatting both desertification and drought. Among the programme areas under this chapter are: combatting land degradation through appropriate management and conservation and reforestation; strengthening the knowledge base and developing information and monitoring systems. Chapter 14: draws attention to policy and agrarian reform, people’s participation and human resource development, income diversification, land conservation and rehabilitation, improved and integrated management of inputs for sustainable food production and rural development. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 87
ISCRAL The purpose of the FAO International Scheme for the Conservation and Rehabilitation of African Lands (ISCRAL) (FAO, 1990) is to provide a framework by which African countries can develop their own programmes to fight degradation and improve land productivity. ISCRAL discusses the extent and implications of land degradation, examines lessons from past projects addressing the issue and suggests a new sustainable approach based upon integrating conservation and production to provide land users with immediate benefits. ISCRAL Framework for Action at national level emphasizes the control of degradation by first determining the reasons for misuse; encouraging participation to allow land users to organize their resources, plan and implement solutions, develop national institutions to provide land users with needed support. At the regional level, the emphasis is upon information networks, advanced training and research. At the international level, long-term financial support, close cooperation of governments, NGOs, technical assistance agencies and financing institutions are emphasized. (Similar schemes are being adopted by several countries in Asia “CLASP” and Latin America “CORTALC”).
CCD The objective of the UN Convention to Combat Desertification and mitigate the effects of drought in countries experiencing serious drought and/or desertification, particularly in Africa, through effective action at all levels, supported by international cooperation and partnership arrangements. Action contributing to the sustainable development of affected areas, is to be carried out within the framework of an integrated approach consistent with Agenda 21. The CCD specifies (i) a series of action programmes, (ii) a framework for scientific and technical cooperation and (iii) supporting measures: · Action Programmes (Articles 10, 11, 12): concerned with elaboration of National Action Programmes (NAP), Sub-Regional Action Programmes and International Cooperation. · Technical and scientific cooperation (Article 16): deals with information collection, analysis and exchange to ensure systematic observation of land degradation in the affected area and to understand better and assess the processes of drought and desertification - an area of prime interest to FAO in general and AGLS in particular. (Article 18) which deals with transfer, adaptation and development of technology. · Supporting measures (Article 19) deals, among others, with capacity building of all types - an area where FAO has a particular strength. Besides the global mechanism for mobilization of resources, the Permanent Secretariat (the location of which was decided by the recently held Conference of the Parties), the Committee on Science and Technology (on which FAO is represented), are already functioning. Through collaboration with other UN agencies (IFAD, UNDP, GEF funding resources), FAO is assisting member countries in the formulation and implementation of National Action Programmes (under CCD) as well as the formulation of pilot projects in land resources use, management and conservation (example Mali, Cuba). FAO/AGLS is also promoting a comprehensive drylands and desertification control programme. 88 Land degradation in relation to food security with focus on soil fertility management
Appendix 2
Soil Fertility Initiative (SFI)
It has been recognized that the key to restoration and enhancement of soil fertility is the collective responsibility of many parties, including governments, inter- and non-governmental organizations and all stakeholders in the food production process. Accordingly, the World Bank has taken the initiative to provide the leadership to assemble and coordinate a global effort that will focus on reversing the detrimental effects that result from soil degradation and nutrient depletion in Sub- Saharan Africa. Other international organizations involved in the initiative are FAO, ICRAF, IFDC, IFA and IFPRI. In support of the larger goals: poverty alleviation, food security and environmental protection; the major objective of the SFI is to improve the productivity of cultivated lands and the revenue of farmers through a combination of technology adaptation and policy reform. The thrust of the SFI will include: · dissemination of appropriate technologies for the restoration and maintenance of soil fertility and intensification of agriculture through an integrated approach using organic and inorganic fertilizers, erosion control, land and water management to enhance food security and farm income; · promotion of enabling policies that would correct market and institutional constraints to improve soil productivity; and · development of programmes that would provide incentives and bring the full participation of individual farmers and communities for the restoration of soil fertility and improved land management. The SFI was officially launched during the World Food Summit, November 1996. After the Summit, consultation took place between FAO and the World Bank (January 1997) in order to design modalities of cooperation in support of the SFI and its linkage with the Special Programme for Food Security (SPFS), particularly in SSA. A workshop was organized in Togo (April 1997) with the participation of 120 delegates representing 22 countries in SSA, sub- regional institutions, NGOs and private sector, international development and research organizations, including FAO. The workshop re-emphasized the need for recapitalization, maintenance, and improvement of soil fertility, as a basis for long-term food security. A draft strategic framework for soil fertility improvement was also outlined. After a series of discussions and refinement, involving FAO, the "Framework of National Action Plan for Soil Fertility Improvement" was developed.
The salient features of the Framework are summarized below: Rationale: A National Action Plan has to promote actions, capital and labour investments for soil fertility improvement and for the supporting sectors (e.g. improved availability and accessibility of soil Integrated soil management for sustainable agriculture and food security in Southern and East Africa 89
amendments and inputs for agricultural intensification), and for alleviating socio-economic and technical constraints, The soil recapitalization and improvement is a prerequisite to improved efficiency of inputs and higher productivity. Improved soil productivity are in the interest of not only the farming community but also the national society and the international community as a whole. It could trigger rural and national economic development, improve farmers' standard of living, while controlling environmental degradation and help in reducing rural migration, etc.
Steps during the preparatory phase for the NAP: · Implementation of a national workshop and working groups: The workshop will permit identifying the needs for Soil Fertility Improvement, create general awareness and establish working groups which include all stakeholders (NGOs, farmers groups' representatives, agricultural input/output producers and distributors, research and extension services, policy makers and multidisciplinary technicians). The groups will assist in: - identification of actions/investments to be promoted; - definition of socio-economic constraints to be alleviated; - indication of ministries and public services to be involved; - institutional arrangements to be made (at public level) and to be promoted (at private level); - preliminary studies to be executed; - strategies for implementation · Identification of ministries, institutions and public services to be involved: The creation of a conducive environment and input & output market development surpasses the competence of the Ministry of Agriculture. As such it is expected that other ministries will have to play a role in the SFI such as: ministries of environment & forestry, finance, planning, science & technology and social affairs. Arrangements have also to be made to identify the responsibilities and operational involvement of various institutions at national, sub-national and local level. · Preliminary data and studies: The data required for the preparation of a National Action Plan for SFI would include: geographical and agro-ecological characteristic data, socio- economic data, agricultural data as well as agricultural policies and strategic data and orientation. Studies and agricultural constraints analysis will also be required during the preparatory phase. The constraints and possible solutions related to soil fertility improvement will depend on the national, sub-national or local socio-economic and agro-ecological conditions in a given country. The strategies to implement the NAP will vary from one country to another, depending on the extent and magnitude of soil degradation and nutrient depletion, local availability of inputs, other soil management technologies, available means and donor commitments. As such, the strategy may, for example, start with "Pilot Project" in selected areas in the country, and gradually expand the scope and area coverage for an investment oriented large-scale national programme. · The implementation of the NAP will involve the participation of all stakeholders and the strategy adopted by the government, donors or lending agencies support. The real executors of the SFI (the farmers) and the private sector may wait until the conducive policy environment and the market development are in place. 90 Land degradation in relation to food security with focus on soil fertility management
Monitoring and evaluation of the NAP performance have also to be established, this would include a core of "Indicators". These indicators are likely to include: · physical indicators such as nutrient balance, land use systems and intensity, land cover, increased use of amendments, organic and inorganic fertilizer, and measurements of soil fertility (pH, CEC, OM, nutrient status); · economic indicators such as trends in crop yield, livestock productivity, output levels, prices and rural income; · social indicators such as rate of adoption of improved soil management practices by farmers and farming communities, increased stability of rural communities (e.g. reduced migration); · environmental indicators such as rate of deforestation, state of rangelands and erosion.
WB/FAO collaboration in formulating and implementing pilot projects in land management and soil fertility improvement
The Plan of Action adopted by the World Food Summit called for concerted efforts at all levels to raise food production and increase access to food, with focus on the Low Income Food Deficit Countries (LIFDCs), particularly in Africa, with the objective of reducing by half the present level of malnourished people in the world by the year 2015. Subsequently a memorandum of understanding between FAO and the WB was signed, in order to strengthen the collaboration of the two institutions within the framework of the Special Programme for Food Security (SPFS), and in particular promote rural development and food security programmes in the Africa Region, through implementation of projects in the fields of: (i) low cost small-scale irrigation, water control; (ii) improved land management and soil fertility enhancement; (iii) crop intensification and diversification; (iv) analysis of policy constraints, policy reform and capacity building. Both institutions would seek, as appropriate, to mobilize supplementary resources to meet the requirements of jointly agreed programmes. After a series of consultations between the two institutions, it has been agreed to launch the preparation of "National Action Plan for Soil Fertility Improvement" and relevant pilot projects in a number of Sub-Saharan African countries, in connection with the ongoing/foreseen SPFS. Initially, the following countries would be included: Guinea, Niger, Malawi, Madagascar, Rwanda, Burkina Faso, Eritrea, Ethiopia, Mali, Ghana, Senegal, Benin, Lesotho. It may be noted that the pilot projects will be conceived to ensure participative land management and fertility improvement schemes, draw upon the experiences of WB/FAO assisted projects: ("Gestion de terroires" - community-based natural resources management), the improved land husbandry methods, the Farmer Field Schools (as extension instrument for promoting site-specific integrated soil, nutrient and pest management) as well as the conservation/minimum tillage; in representative agro-ecological conditions and contrasting socio- economic environment. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 91
Erosion-induced loss in soil productivity and its impacts on agricultural production and food security
Since 1984, the United Nations Food and Agriculture Organization (FAO) has been supporting an international initiative to investigate the impact of soil erosion. The FAO has taken the lead in publicizing the threats to sustainability, developing research designs to quantify the impacts, and encouraging the research and development community of professionals to design ameliorative measures. It has been the lead agency to support the Network on Erosion-Induced Loss in Soil Productivity. This Network provides data for local, national and international agencies on soil and water conservation; establishes norms for economic planners on the costs and benefits of erosion control and soil conservation; identifies the agro-ecologies where concerted action is needed now or in the near future to avert substantial agricultural production loss and the consequent food security threats brought about by soil erosion. With the recent emphasis and priority programme of FAO on food production in support of food security, issues related to land degradation and its negative impacts on food production as well as land improvement for enhanced productivity are receiving special attention. Rectifying soil degradation and sustaining crop production through appropriate soil management and conservation measures are, therefore, important components in the efforts towards food security.
It is timely, therefore, that this Expert Consultation on Integrated Soil Management for Sustainable Agriculture and Food Security in Southern and East Africa should consider the impact of soil erosion on food security. A primary link in the threat to food supplies is the diminution in soil quality and consequent decline in crop yields. A complex set of processes is involved which will be addressed by the Consultation. This contribution from the Soil Resources, Management and Conservation Service (AGLS), Land and Water Development Division of FAO in Rome was commissioned from Michael Stocking and Anna Tengberg of the Overseas Development Group, University of East Anglia in Norwich who have been working with South American members of the Network, and brought together a selection of data sources on erosion- induced loss in soil productivity which have particular applicability to Southern and East African conditions. It is hoped that the scenarios constructed for the region will assist participants of the Consultation in their deliberations on this important subject, and provide a unique data set from which to assess the potential threats to sustainable agriculture and food security.
Michael Stocking, Overseas Development Group, University of East Anglia, Norwich, UK Anna Tengberg, Physical Geography Earth Sciences Centre, Goteborg, Sweden 92 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
SOIL EROSION TO FOOD SECURITY This paper is about soil degradation and its influence on productivity. Productivity, with its emphasis on the long-term ecological sustainability of soil resources, is the key determinant of food security. We focus principally on soil degradation by water erosion1. According to global assessments such as GLASOD (Oldeman et al, 1990), water erosion is the principal cause of the nearly 2 million hectares (22.5% of total land use) of degraded agricultural, pasture and forest land worldwide. Soil erosion by water affects the physical and chemical status of a soil, and in so doing it reduces soil quality, long-term productivity and crop yields. Understanding the process of soil degradation is crucial to addressing the whole problem of erosion-induced loss in soil productivity. It changes the erosion-productivity link from a `black-box’ model where we are unable to intervene because of not knowing why yields decline, to a `grey-box’ where some light is shed and remedial measures can be designed to target the principal processes. So, for example, if soil erosion reduces yields because of nutrient losses, the resource manager will be alerted to measures which may replace nutrients. Some of these relationships between component processes, type of degradation and means of improvement are explored in Table 1. This paper will, therefore, dwell on the best available evidence for the process reasons for decline in productivity.
TABLE 1 Component processes and types of soil degradation Component process Type of soil degradation Improvement measures Physical soil Crusting Live barriers management Compaction Terracing Sealing Revegetation of denuded land Wind erosion Tree protection Water erosion Soil decompaction Devegetation Breaking up pans Overtillage Cover crops Windbreaks Soil deposition Improved tillage methods Soil water Impeded drainage Irrigation management Waterlogging Water harvesting Reduced waterholding capacity Field drainage Reduced infiltration Draining of waterlogged areas Salinization Filter strips Soil nutrient and Alkalinization Fertilization organic matter Acidification Composting management Nutrient leaching Green manuring Removal of organic matter Animal manuring Burning of vegetative residues Flushing of saline/alkaline soils Nutrient depletion Liming acid soils Soil biology Overapplication of agrochemicals Introduction of biotic organisms management Industrial contamination Nitrogen-fixing microorganisms Vegetation Decline in vegetative cover Increased vegetative cover management Decline in biodiversity Increased species diversity Decline in species composition Improved species composition Decline in valued species Improved availability of valued species Source: adapted from Scherr and Yadav, 1996
1 The following sections will also discuss linkages with the Consultation themes on physical and chemical degradation of soils. To separate these degradation processes and treat them independently of water erosion is an abstract distinction. Nevertheless, the differences will prove useful in discussing the process of loss of soil productivity - or how soil degradation affects food security. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 93
Implicit in decline in productivity is the threat to food security. Some authors see soil (or land) degradation as posing the main threat to global food supplies (Brown and Kane, 1994; Pimentel et al, 1995). Others argue that land degradation is overestimated (Crosson, 1994) and that some African populations have been able to adapt, cope and even overcome apparently severe degradation (Tiffen et al., 1994). Concern over whether food security is threatened perhaps disguises that degradation has a significant impact on rural livelihoods, making it inevitable that rural producers find it increasingly difficult to survive (IFAD, 1992). These and related issues were discussed at a workshop on land degradation and its implications for food supply, organized by the International Food Policy Research Institute (IFPRI) in 1995 (Scherr and Yadav, 1996). The conclusion of that meeting was that land degradation could be a potentially serious threat to both food production and rural livelihoods, particularly in densely-populated areas of current rural poverty. The threat, however, is not uniform. It depends upon a variety of environmental, social, economic, demographic and political circumstances. These complex permutations of factors are beyond the scope of this paper, except to highlight the intricate sets of processes which lead to land degradation and to suggest a number of critical “hot spots” where land degradation poses a significant threat to food security for large numbers of poor people - see selected African examples given in Table 2. The IFPRI Workshop felt that future policy interventions should focus on such “hot spots”. This Consultation would, no doubt, derive different areas where interventions are needed. However, the principle is the same: to combat the potential threats to food security and rural livelihoods, targeting of effort is crucially needed. This paper seeks to lay the groundwork of environmental and soil physico-chemical circumstances that contribute to erosion-induced loss in soil productivity. It is impossible to make projections and determine planning priorities and conservation strategies without good quality data on both the rate of decline in productivity with erosion and the biophysical processes responsible. So much of the debate has been marred by lack of data and uninformed speculation, often hugely exaggerated, that developing countries face massive food deficits because of soil degradation. We shall bring together the quantitative experimental evidence, and conduct a number of scenario predictions of future production in a degrading environment, in order to inform the debate.
TABLE 2 “Hot spots” for land degradation in Africa Nutrient Depletion Water & Wind Erosion Vegetation Degradation Constraints to Yield Increase Semi-arid croplands Subhumid SE Nigeria on Arid and semi-arid Unsustainability of of Burkina Faso and sandy soils rangeland devegetation annual crops in humid Senegal (leading to (e.g. Ciskei), particularly lowlands of West outmigration) Wind erosion in Sahel near water sources Africa Large areas under Mechanization in North Devegetation due to Densely-populated transition to short Africa causing water and intensive collection of highlands in Rwanda, fallow or permanent wind erosion wood fuel (around cities) Burundi and Kenya - cropping Devegetation due to no obvious source of overstocking (e.g. production increase Morocco and Tunisia) Lack of suitable Reduction of silt Mechanization with Reduced yields due to technology for crops deposits in Nile Delta inappropriate ploughing Imperata and grown in areas less following construction techniques (e.g. transition Chromalaena infestation than 300 mm rainfall of Aswan High Dam zone of West Africa) in degraded soils in North Africa Source: adapted from Scherr & Yadav, 1996 94 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
DEFINITIONS This paper is specifically about erosion-induced loss in soil productivity; that is, the decline in soil productive potential that can unambiguously be ascribed to soil erosion by water. There are other reasons for production to decline: almost any cropping can, for example, lead to an offtake of nutrients which exceeds natural rates of renewal or resupply. These other reasons are functions of the land use system, and may also be related to erosion. It is hard entirely to separate the portion of yield decline attributable to erosion. For practical purposes, if there are quantities of nutrients and organic matter in the sediment and runoff water, then there is prima facie evidence that erosion-induced loss in soil productivity is occurring because these are losses which would not have happened without erosion. More difficult to identify is where erosion may be causing physical and structural deterioration of the soil and where it induces certain chemical deficiencies and/or toxicities.
The word ‘productivity’ is much used and abused. In the literature it is often confused with ‘production’ or even ‘yield’. From the original FAO review (Stocking, 1984) on erosion- productivity, the following definitions were offered: · Productivity is a measure of the rate of accumulation of energy, or, in the context of soil (or land or agricultural) productivity, it is the productive potential of the soil system that allows the accumulation of energy in the form of vegetation. Soil productivity is, therefore, a function of many factors including individual soil variables, climate, management and slope. It is close to the concept of ‘soil fertility’1, being a real and intrinsic property of the soil. However, it is conceptual and encompasses the whole range of factors that contribute to soil quality. · Production is the total accumulation of energy, without necessary reference to how quickly or over what area or with what assistance it accumulates; and agricultural production is normally measured as crop yield, or the amount of production per unit area over a given time. · Yield is a measure of production. It can also be used as an indicator of productivity. As an indicator it is imperfect because yield is an expression of historical production whereas productivity is an expression of potential (i.e. future) production.
In modern farming systems, then, production includes artificial enhancements such as fertilizer, improved tillage practices and high yielding varieties. Production integrates not only the inherent soil properties but also the technologies applied to the soil system. Productivity, on the other hand, should strictly relate to the inherent soil quality and refer to the productive potential of the soil. It follows that soil productivity can be masked by technology. A decline in soil productive potential could (and usually is, in intensive agricultural systems) compensated by inputs such as irrigation or agro-chemicals. Intensive production systems can use soil merely as a growing medium through which plant requirements are met artificially. In such systems, production can be extremely high, but the soil productivity can be extremely low. One way of looking at erosion-induced loss in soil productivity is to see it as a real loss in the soil’s quality and as a factor which makes agricultural production more costly, risky and tied to the continual provision of inputs.
1 ‘Soil fertility’ is another term commonly misapplied, being often limited to the chemical status of the soil only. In fact, fertility embraces all the soil’s functions that contribute to it supporting vegetative growth - including soil structure, permeability and depth. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 95
If agricultural production becomes divorced from soil qualities, external factors will prevail in assuring continued output. The cycle of continued production while soil quality deteriorates also means that the decline in soil productivity of land goes unnoticed. Hidden loss in soil productivity is a major difficulty for researchers and policy-makers. Not only does it make identification of decline in soil quality problematic, but also it calls into question whether a problem exists at all. Soil productivity1 is, therefore, a key criterion of food security. It relates to future production and describes how far the intrinsic quality of the soil resources may underpin that production. While actual production may be adjusted by access to and application of technology, soil productivity may only be enhanced by careful conservation of soil restorative functions such as nutrient cycles, soil biota and plant-available soil water holding capacity. Additionally, food security holds the notion of empowerment of land users to provide productive output for their areas without continual reliance on externally-sourced inputs. Similarly, the concept of soil productivity embraces a security of future production which utilizes natural soil processes. This is why, we agree with other authors that erosion-induced loss in soil productivity is the major threat to food security.
GENERAL RELATIONSHIPS BETWEEN EROSION AND PRODUCTIVITY There is strong evidence that yield decline with erosion follows a curvilinear, negatively exponential form (Figure 1). In other words there is a sharp initial decline from a status of high productivity, followed by successive stages of decreasing impact. The implication of this general trend is that it is vitally important to define the starting point when making observations on erosion-induced loss in soil productivity. An initially pristine soil will have a very severe decline, whereas an already badly-eroded soil may not suffer much further decrease in yield. A further implication is that, other things being equal, efforts at conservation should be aimed at preventing good soils from eroding rather than trying to save eroded soils from more erosion2. Although remarkably similar, there are some variations in the detail of the curvilinear relationship. The differences are mainly related to initial yield levels, type of soil, cropping system and levels of management. Soil type differences will be the main focus in this paper. Comparisons will be made, whenever possible, between how yields vary for a standard reference crop (rainfed maize) for the principal tropical and subtropical soil types, balancing the fact that some soils erode more easily while others display a much larger yield decline per tonne of soil loss. Nevertheless, in using yield as the indicator of soil productivity, it can make a substantial difference in our view of productivity whether the crop itself is susceptible to the soil factors which may diminish with erosion, and whether our analysis commences on a soil that is already eroded. These last points of detail will not be dwelt upon here but they will be important in specific cases. However, this
1 Some authors differentiate between crop productivity and soil productivity. Crop productivity is determined by the agronomic characteristics of the crop and soil productivity by the inherent properties of the soil. Thus yield alone cannot be used to compare productivity of soils that have been planted with different crops and subject to different management practices. 2 Things are not, however, equal. This utilitarian approach to allocating priorities for conservation efforts on the best soils ignores other good reasons why already-degraded soils should be targeted. For example, the poorest people tend to live on the poorest soils; conversely, it might be seen as socially irresponsible to concentrate conservation resources in areas which are already well endowed and where richer sections of society predominate. Also, marginal and degraded areas usually give rise to huge off-site impacts such as sedimentation of water storages. 96 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
FIGURE 1 General form of the relationship between soil loss and yields compiled from various sources
Cumulative soil loss (t/ha) paper will make a strong conceptual distinction between (1) erosion rate differences and (2) impact differences per unit of erosion for the various reference soils.
In another paper (Tengberg et al., 1998), a conceptual framework for erosion-productivity modelling is presented which may be helpful to this Consultation to show the different data sources and successive steps to construct loss in production scenarios (Figure 2). The first step is to collect site-specific data on soil, slope, rainfall and cover (Block A: Figure 2). Because of the direct link with erosion impact, a farming system characterization is then needed (Block B) which includes crop, management and levels of inputs. Through erosion rate (Block C) and erosion impact (Block D), the overall soil productivity for any land use scenario may be presented as the predicted yield changes over time (Block E), and may be converted into monetary values (Block F). Block A thus incorporates the physical attributes of the site which control erosion over time, while Block B takes in land use and management which both influence the impact of erosion and are in turn affected by erosion. The two blocks (A & B) control very different conceptual properties of the whole erosion system - we term them ‘resilience’ and ‘sensitivity’.
Resilience is the property that enables a land system to absorb and utilize change; it is literally the resistance to a shock such as a soil erosion event. Soil loss-time relationships (Block C: Figure 2) express such an ability: the steeper the line, the less resilient is the soil. A soil which lacks resilience is easy to degrade, and after misuse land management has great difficulty in restoring its productive potential. Sodic soils are the most extreme example of poor resilience; they erode easily when wet through deflocculation of colloids which have more than 15% exchangeable sodium. Furthermore, the severe impact of erosion, including piping, cannot easily be reversed. That is why many sodic soils make up typical ‘badlands’ landscapes: e.g. central Integrated soil management for sustainable agriculture and food security in Southern and East Africa 97
Mashonaland, Zimbabwe in the Ngezi/Mondoro area. Conversely, a resilient soil will not erode easily, but the effect of the erosion is variable. For example, a deep Vertisol is resilient in having low erosion rates, but the consequent degradation may have different impacts.
Sensitivity is the degree to which a land system undergoes change when subjected to an external force. It can also be seen as how readily change occurs with only small differences in external force. In the modelling framework, it is the degree of impact that a unit amount of erosion exacts (Block D). In the general erosion-productivity curve, good soils are far more sensitive than degraded soils. Similarly, many Ferralsols may be subject to high erosion (i.e. they lack resilience), but the effect of that erosion may only be small. A Phaeozem, in contrast, may display a massive impact to a unit quantity of erosion, thereby demonstrating its extreme sensitivity at least initially. For practical purposes, it would be good to identify the possible permutations of resilience and sensitivity of southern and East Africa soils. High sensitivity, low resilience conditions (e.g. some fragile rangeland ecologies; or steep slope environments) should, if they are important contributors to production and supporters of rural livelihoods, be priority areas for targeting intervention. High sensitivity, high resilience conditions (e.g. some clayey humid tropical rainforest soils on low angle slopes) suggest conservation approaches using organic matter as a buffer against their sensitivity. Low resilience, low sensitivity situations (e.g. many Acrisols and Andosols that erode easily but uncover subsoil that is not significantly inferior to the eroded topsoil) will need low-cost agronomic conservation approaches. High resilience, low sensitivity conditions (e.g. perhaps some of the humic Nitisols on low angle slopes) can probably look after themselves.
FIGURE 2 Conceptual framework for modelling erosion-yield-time relationships
A Site- Specific C Data Erosion Rate soil, slope, soil loss-time F cover, relationships E RESILIENCE Potential Yield Loss in Time Reduction or Production Nutrient Losses or D with Time Resource Value B The Impact of Farming Erosion System soil loss-yield/ nutrient loss crop, inputs, relationships management SENSITIVITY 98 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
CHEMICAL DEGRADATION: AN OVERVIEW In the original FAO (1979) Provisional Methodology for Soil Degradation Assessment, chemical degradation was limited to two principal processes: acidification and toxicities. Acidification was defined as the decrease of base saturation (i.e. total exchangeable bases divided by cation exchange capacity, expressed as a percentage change per year). Toxicity was the increase in toxic elements (other than salinization or sodication) in ppm/year. Today, it is perhaps useful to see chemical degradation more widely as the set of processes that lead to a diminution of the chemical status of the soil. This includes the loss of chemical components (nutrients) from the soil by water erosion, and the effects such losses have on other soil functions. In a useful chapter on the ‘myths about the chemistry and fertility of tropical soils’, Sanchez and Logan (1992) challenge the received wisdom and prevailing perceptions that the soils of the tropics are universally acid, infertile and incapable of sustained agricultural production. Manifestly, the evidence of substantial increases in per capita food production in tropical Asia and Latin America belie this prejudiced view of chemical potential of tropical soils. Yet it is inescapable that soil chemical status in the tropics can be very changeable and susceptible to rapid decline. Rather than brand all tropical soils as chemically fragile, it is more reasonable to divide soil chemical fertility into a number of specific soil constraints, each of which is examined for its relationship to erosion - see Sanchez et al, 1987, for specific examples, and Sanchez and Logan (1992) for further details on the following categories taken from their work:
Low nutrient reserves: about 36% of the tropics (1.7 billion ha) have such soils, defined as having less than 10% weatherable minerals in the sand and silt fractions. These are the highly weathered soils with limited capacity to supply P, K, Ca, Mg and S. They are particularly prevalent in the humid tropics. Because the nutrient storage in the soil is so small, so transitory and concentrated in the organic cycling, water erosion may be very effective in impacting these soils and causing substantial productivity decline. However, any usage is also a challenge to sustainable production on these soils and in humid environments where stripping the land of its natural vegetation inevitably deletes the major part of the nutrient cycle.
Aluminium toxicity: one third of tropical soils (about 1.5 billion ha) have sufficiently acid conditions for soluble Al to be toxic for most crop species. This constraint is defined as where more than 60% Al-saturation occurs in the top 50 cm of soil. Erosion can easily tip the balance of acidity by removing the buffering of organic matter and by encouraging leaching and removal of bases. Al-toxicity is one of the most serious chemical degradation processes, which has the potential to cause very sudden and serious declines in yield with only moderate levels of erosion. The humid tropics and acid savannas are most at risk, with Ferralsols and Acrisols most commonly affected.
High phosphorus fixation: many tropical clay soils fix large quantities of added P. Fixation in this context refers to rendering plant-available P (usually soluble) into insoluble forms that cannot be used by most crops in the short term. This affects about 22% or 1 billion ha, being most common in the humid tropics and acid savannas. P-fixation is directly related to clay content, organic matter and acidity - loamy Ferralsols and Acrisols are least affected. As with Al-toxicity, there is a close correspondence of the effects of water erosion with increase in P-fixation on susceptible soils.
Low cation exchange: soils with a critically low level of effective cation exchange capacity -1 (ECEC< 4 cmolc kg ) occupy about 5% of the tropics. Such low values indicate limited ability to Integrated soil management for sustainable agriculture and food security in Southern and East Africa 99
retain nutrient cations against leaching. These would be poor soils anyway even without water erosion.
Salinity and alkalinity: locally, serious salinity (electrical conductivity >4 dS m-1) and alkalinity (> 15% Na saturation) problems occur, mainly in the humid tropics, semiarid tropics and wetlands. Water erosion may exacerbate the problems by transfer of salts and waterlogging.
Table 3 summarizes the extent of the various aspects of chemical degradation for Africa as a whole, and the potential links with water erosion.
TABLE 3 Main chemical soil constraints in Africa and relationship to erosion Soil constraint Extent Extent Relation to water erosion (millions ha) (% Africa) Low nutrient reserves 615 20 Made substantially worse by erosion Aluminium toxicity 479 16 Induced by erosion on susceptible soil High P fixation by Fe oxides 205 7 Induced by erosion on susceptible soil Acidity without Al- toxicity 471 16 Can be made worse by erosion Calcareous reaction 332 11 No direct link Low CEC 397 13 Selective removal of colloids by erosion makes this worse Salinity 75 3 Washing in of additional salts Alkalinity 18 - Cause of some of the worst forms of erosion Source: areal data based on Sanchez and Logan, 1992
PHYSICAL DEGRADATION: AN OVERVIEW Physical degradation refers to adverse changes in soil physical properties, including porosity, permeability, bulk density and structural stability. The FAO (1979) methodology divided it into two primary aspects: increase in bulk density and decrease in permeability, both measured in percentage change per year. As with chemical status, it is now useful to see physical degradation more broadly as encompassing the range of soil physical properties that affect plant growth and crop production. Again, the soils of the tropics are highly variable in their physical properties and their susceptibility to change. Following the categories in Cassell and Lal (1992), the following types of soil physical degradation may be identified. Only a brief account can be given here:
Mechanical impedance: closely related to soil structure, this refers to the mechanical resistance the soil offers to shoot emergence and root growth. Essentially, it is an increase in overall bulk density which reduces the volume of macropores and increases soil strength. The process of mechanical impedance may be generated in a number of ways. First, soil compaction is an outcome of intensive farming methods, usually involving mechanization, where soil structural units (aggregates) disintegrate into soil separates, thereby becoming prone to being packed into denser masses. Fragments are pushed ever more tightly into pore spaces. At the same time, ultradesiccation may occur on tropical soils with low organic matter. Setting hard when subject to extreme drying in the subhumid and semiarid tropics, they develop a hard consistency and extreme compaction, even in their natural state. Soil erosion and runoff may assist the process by removing colloids and water; and the rate of erosion itself may be greatly accelerated on such soils. 100 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
Crusting is perhaps the single most common physical degradation feature of tropical soils, occurring as a function of high intensity rainfall and poor vegetation cover. Crust strength may impede germination of crops and prevent water infiltration. It depends upon factors such as soil texture, soil structure, aggregate stability and water content. Soils with a loamy sand texture are most at risk of crusting. The process of formation of a crust is directly related to the degree of splash erosion on bare soil surfaces, and hence to water erosion. Pans are layers of high bulk density at depth in the soil. They form a barrier to root penetration, limiting soil depth and productivity, especially if the pan is exhumed over time by surface erosion. Plough pans are common on Ferralsols and Acrisols in the tropics when subjected to mouldboard ploughing or discing. Duripans (also known as laterite and plinthite) are generally hard sheets of Fe-Al cemented soil. It is estimated that about 130 million ha of savanna soils in west Africa have such concretions; in Niger and Burkina Faso with mean annual rainfall of 200- 500 mm, iron-rich duripans probably affect half the land surface. Duripans form over long periods of time, possibly in response to devegetation and changed water balances - it is difficult to draw a direct link with water erosion, although the two processes may occur simultaneously. A final mechanical impedance is the occurrence of lag-gravels at depth. These represent old erosion surfaces, now buried, and are often severely compacted and rigid. As with duripans, they become an important threat to productivity as they are exhumed by surface erosion. Changing soil-water relations: as noted by Cassell and Lal (1992), the fate of precipitation, once it has arrived at the soil surface, is intimately linked to soil structure. A changing structure because of physical degradation easily affects the water balance, infiltration, plant-available soil water and soil productivity. There is a good case for suggesting that reduced plant-available water is the single most common cause for reductions in yield consequent upon erosion in the seasonal, semiarid and sub-humid tropics. Even though total annual rainfall may be adequate, plants may undergo severe moisture deficiencies because of excessive runoff. That runoff may be induced by a deteriorating soil structure. The various aspects of soil-water relations identified by Cassell and Lal (1992) are: · Infiltration is a function of soil structure, pore-size distribution, pore-connectivity and antecedent moisture conditions. The infiltration capacity of most tropical soils under natural vegetation exceeds all but the most extreme rainfall intensities. However, once subject to cultivation, surface crusting and reduction in micropores substantially reduce infiltration. It is only if tillage can leave a rough surface with a high surface water storage capacity that total moisture penetration can be maintained. Eroded soils have notoriously low infiltration rates. Once water has infiltrated, its retention in the soil can vary greatly depending on porosity, pore-size distribution, organic matter content, biological activity and soil management. Generally, it can be said that water erosion processes combine to produce far lower water retention characteristics than in non-eroded soils. · Puddling is the surface deterioration of soil structure when wet. Puddling occurs when soil strength is low. There is no direct link to water erosion, except that runoff from areas of puddled soil is greater.
Increased soil erodibility is also an aspect of soil physical degradation, especially in the tropics. Normally, erodibility is considered to be an intrinsic function of static soil properties. However, soil erodibility is intimately bound with water-stable aggregates and organic matter content. Both these properties are affected by water erosion. At the Institute of Agricultural Engineering, Harare, on a high-clay soil, once organic carbon content had decreased below 2%, soil erodibility suddenly increased fivefold (H.A. Elwell, personal communication). Integrated soil management for sustainable agriculture and food security in Southern and East Africa 101
EVIDENCE OF SOIL PRODUCTIVITY CHANGES WITH EROSION Data sources In this section we will mainly draw upon findings from the FAO-sponsored Erosion-Productivity Network, which is using a standardized design to generate comparative data from different soils and agro-ecologies - see list of references relating to the historical development of the Network. This programme was initiated following an inventory of erosion-productivity research in developing countries (Stocking, 1984). It was found that there was a need to quantify the impact of erosion and also to identify soil processes affected by erosion as well as limiting factors for crop growth.
It is not the purpose here to detail the experiment1. The experimental procedure has already been widely disseminated (Stocking, 1986a; da Veiga and Wildner, 1993) and 23 research groups worldwide now constitute the Erosion-Productivity Network. Each group is autonomous, working broadly on the suggested experimental design but with local adaptations according to typical practices and research resources. Briefly, the experiment involves soil loss and runoff plots of about 50 m2. The plots are cleared of vegetation and then allowed to erode naturally by rainfall. Twelve plots are organized in three replicate blocks. Two to three levels of erosion are achieved by covering the plots with varying degrees of artificial mesh, and a fourth treatment is kept as bare soil. The experiment is designed to take four to seven years, depending on the level of prior erosion achieved by natural rainfall. Once sufficiently differentiated levels of erosion are obtained between the treatments, differences in productivity may be assessed in relation to the cumulative erosion since the start of the trials.
Because an important objective of the experiment is to explain yield declines in terms of the specific effects of erosion on soil quality, seven groups of variables are recommended for continuous monitoring: runoff and soil loss; physical and chemical characteristics of in situ soil; chemistry of the eroded sediments, including their enrichment ratios; chemistry of runoff water; biological activity of the soil; climatic factors; and plant parameters to indicate growth stress. This full menu of variables does represent a significant burden on our developing country partners, and hence individual groups have autonomy to choose those variables which are of principal interest and that are within their capacity to Provide reliable data. Due to the long time period needed to finish the two phases of the experiment and thus to get tangible results, not all participating groups have yet reported the final findings. We therefore have to draw, not only on the results reported from Africa, but also from South America, which in many parts has similar agro-ecologies to Africa. An example from Indonesia of the erosion of an Acrisol is also included, as information on the impact of erosion on this soil type is scarce. We also present some findings from associated studies of erosion phase (i.e. topsoil depth) and its relation to soil productivity in order to complement the information base. The progress made so far in quantifying the impact of erosion in terms of changes in yield and soil chemical and physical properties is organized according to country and site where the research was carried out. The impact of erosion on major soil types is subsequently discussed and across site comparisons are made.
Nitosols are very vulnerable to soil productivity decline caused by erosion. But unlike many other soil types, virgin untruncated Nitosols have very deep topsoil so that even though soil loss is
1 See also Olson et a.l (1994) who discuss a variety of other methods. 102 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
relatively high, long periods of erosion are needed before soil productivity changes become pronounced (Boxes 1 & 2).
The situation is quite different for red sub-tropical soils. Evidence from soil erosion- productivity experiments, using the FAO standard design, in southern Brazil indicates that soil erosion has a considerable impact on the productivity of Ferralsols and Cambisols. Decreasing yields, reduction of organic C, increasing soil acidity and free aluminium, and P-fixation are common problems, especially for Ferralsols (Boxes 3 to 5).
The reason that we only include one example of erosion-productivity research from a truly semi-arid area is twofold. First, very few experiments have been carried out in this type of environment and second, it takes a longer time to get good results because of low and highly variable rainfall (Box 6).
BOX 1 - EUTRIC NITOSOL, ETHIOPIA
Slope: 10-20% Rainfall: 1,335 mm Cropping System: haricot beans This experiment was carried out in the Ethiopian Highlands at the Gununo Soil Conservation Research Station, using the FAO standard design. Average annual soil loss for bare soil amounted to 144 t/ha. Seed yield (haricot beans) was closely correlated with erosion. Erosion also induced considerable changes in soil chemical properties. Organic matter and total N content declined with erosion. Among the basic cations on the exchange complex, erosion had its greatest impact on Mg and the Ca/Mg ratio - Mg increased with erosion and consequently the Ca/Mg ratio dropped (after Tegene, 1992).
BOX 2 - HUMIC NITOSOL, KENYA
Slope: 27-34% Rainfall: 1,006 mm Cropping System: maize with fertilizers This experiment took place in the Kenyan Highlands at Kabete Campus Erosion Research Farm outside Nairobi. The FAO standard design was used. Average annual soil loss from bare soil amounted to 124 t/ha. Erosion resulted in a decline in maize yields. Generally, erosion had a more negative effect on soil chemical properties than on physical properties. P was the nutrient most vulnerable to losses through erosion. Changes in in situ soil pH, organic C and N content were significantly correlated with cumulative soil loss (after Gachene, 1995).
BOX 3 - RHODIC FERRALSOL, BRAZIL (SAÕ PAULO STATE)
Slope: 10% Rainfall: 1410 mm Cropping System: maize without fertilizers This experiment was conducted at the Experimental Station, belonging to Instituto Agronômico do Campinas. Annual soil losses for bare soil amounted to 51 t/ha. After seven years of induced erosion there was a 50% decline in yield, amounting to a loss of 4kg/ha of maize per tonne of cumulative soil loss. Losses of nutrients (organic C, P, K, Ca and Mg) in the runoff and eroded sediment were also significant with far higher levels of losses associated with the eroded sediment. Changes in thein situ soil were less clear, but the decrease in organic C and increase in acidity could unambiguously be attributed to soil erosion. Erosion also affected the nutrient content of the crop - mainly N, Ca and B (after Tengberg et al., 1997a). Integrated soil management for sustainable agriculture and food security in Southern and East Africa 103
BOX 4 - RHODIC FERRALSOL, BRAZIL (SANTA CATARINA STATE)
Slope: 16% Rainfall: 1,850 mm Cropping System: maize without fertilizers This study was conducted at EPAGRI’s (Empresa de Pesquisa Agropecuária e de Extensaõ Rural de Santa Catarina) Research Station at Chapecó. Annual soil losses for bare soil amounted to 290 t/ha. After three years of erosion, 60% of the crop yield was lost from treatments with high erosion compared to a treatment with very little erosion. However, due to the extraordinarily high soil losses measured at this site, yield decline per tonne of soil loss was only 0.12 kg. There were also significant changes in the in situ soil content of organic C, P, K and Ca+Mg. Moreover, soil acidity and Al increased (after Tengberg et al., 1997b).
BOX 5 - EUTRIC CAMBISOL, BRAZIL (SANTA CATARINA STATE)
Slope: 24% Rainfall: 1,750 mm Cropping System: maize without fertilizers This study was conducted by EPAGRI at an Agricultural College at Itapiranga. Annual soil losses from bare soil amounted to 23 t/ha. After three years of erosion 25% of the yield was lost, but due to relatively modest soil losses yield decline per tonne of soil loss was higher than for the Ferralsols at Campinas and Chapecó and amounted to nearly 19 kg. Erosion did not give rise to any significant effect on in situ soil properties for this soil (after Tengberg et al., 1997b).
BOX 6 - EUTRIC CAMBISOL, BOTSWANA Slope: 0.5-1% Rainfall: 525 mm Cropping System: sorghum This trial was located at Content Farm, Sebele. The FAO standard design was used. Average annual soil loss from bare soil amounted to 9 t/ha. No erosion-induced losses in productivity are directly discernible. However, a negative logarithmic relationship best fits the soil loss-yield data, but this relationship is not statistically significant. Significantly higher amounts of N, P and K are lost from bare soil plots than from plots under good cover. Absolute nutrient losses are greatest from the runoff losses than soil losses. So runoff loss seems more important at this site than soil loss. Moreover, infiltration was not affected by soil erosion (after Pain, 1992).
Two parallel erosion-productivity experiments are conducted in Tanzania - one based on erosion phase/soil depth, which looks at a number of different soil types and another one on a Ferralsol that uses the FAO experimental design (Boxes 7 & 8).
BOX 7 - EROSION PHASE, TANZANIA
Three locations with different soils and agro-ecological conditions were studied: (1) Nitosols in the humid eco-zone; (2) Ferralsol and Lixisol in the sub-humid zone; and (3) Cambisol, Alisol and Luvisol in the sub-humid/semi-arid zone. For the soils in the sub-humid/semi-arid zone, maize production was influenced by soil depth, soil pH and the sand fraction in the soil. The productivity of the Luvisol was also influenced by available water capacity. For the Alisol, sand and clay fraction as well as available water capacity influenced yields. For the Ferralsol, maize yield was affected by sand and silt fraction and bulk density of the soil. For the Lixisols, organic C and total N had a significant influence on yield (after Kaihura, 1996).
Information on the impact of erosion on the productivity on Luvisols (Box 9) is scarce and now somewhat dated. For associated soils such as Acrisols (Box 10), we have had to refer to Indonesian data, again without yield impact information. 104 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
BOX 8 - FERRALSOL, TANZANIA Slope: 4% Rainfall: 830 mm Cropping System: maize This experiment was instigated in 1994 and conducted at Sokoine University of Agriculture, Morogoro. By the time of writing no yield has yet been reported. Average annual soil losses for bare soil amounted to 5 t/ha. The impact of erosion on soil properties has been described by Mtakwa & Shayo-Ngowi (1997), who conclude that available P is the nutrient most vulnerable to losses through the eroded sediment, while exchangeable Mg suffers least losses.
BOX 9 - LUVISOL, NIGERIA Slope: 5-10% Rainfall: 1,100-1,500 mm Cropping System: maize and cowpeas This study was carried out at the International Institute of Tropical Agriculture in western Nigeria during 1976 and 1977. It was found that a negative exponential relationship best described the fall in yield with cumulative soil loss. The pattern in yield loss for both the grain crop and the legume was similar. The drastic declines in yield were attributed to a decrease in clay and organic matter content with erosion and a reduction in rooting depth with its associated water-holding capacity and poorer water infiltration (after Lal, 1981; Stocking & Peake, 1986).
BOX 10 - ORTHIC ACRISOL, INDONESIA Slope: 13% Rainfall: 3000 mm Cropping System: variety of food crops This study was carried out by the Centre for Soil and Agroclimatic Research, Lebak District, 65 km NW of Bogor. Annual soil losses for bare soil were extraordinarily high and amounted to between 260 t/ha to 425 t/ha. While no information exists on the impact of erosion on productivity, its impact on soil properties was documented. All the macronutrients decreased, except Al. The largest reduction was in organic carbon followed by N. The micronutrients (Fe, Cu and Zn) showed the opposite trend, possibly increasing to near-toxic levels for some crops (after FAO, 1991).
BOX 11 - HAPLIC PHAEOZEM, MOZAMBIQUE Slope: 3-5% Rainfall: 500-800 mm This study is carried out at the Agrometeorological Experimental Centre for the South of Save River at Boane. The installation of the experiment was completed in 1995, so as yet not much data is available. However, there seems to be significantly higher losses of N from the more eroded plots (after Pereira et al., 1996).
BOX 12 - LUVIC PHAEOZEM, ARGENTINA Slope: 1-2% Rainfall: 880 mm Cropping System: maize without fertilizers, and crop rotation of wheat and soybeans This experiment is carried out at the Argentine Agricultural Research Institute’s Experimental Station at Marcos Juarez, in the middle of the Pampas Region. At this site, different depths of soil have been artificially removed (i.e. desurfaced). The different treatments were subsequently planted with wheat and soybeans. Natural erosion rates from different cropping systems have been measured in parallel in large runoff plots. Annual soil losses from bare soil amounted to 13 t/ha. Yields declined significantly with increasing soil removal. However, due to the very low erosion rates at the site, according to the monitoring of soil loss and runoff, it can take up to 50 years before yield reductions become discernible. Desurfacing resulted in a reduction of organic matter, C, N and P. No major changes occurred in texture, moisture equivalent, conductivity, pH or bulk density (after Stocking & Tengberg, 1998; Weir, 1997). Integrated soil management for sustainable agriculture and food security in Southern and East Africa 105
Phaeozems are not common in Africa, but are included here as there is an ongoing experiment in Mozambique on a Phaeozem, and also because they are considered to be one of the very best agricultural soils (Boxes 11 & 12).
EROSION RATES As noted earlier, erosion rates are related to the resilience of the soil to erosion: that is, its ability to withstand erosional processes. We combined this aspect of resilience into a conceptual model (Figure 1) where resilience is the quality that determines the nature of erosion-time relationships. Since food security necessarily must consider to what extent erosion progresses over time, it is important to examine typical soil loss rates for the soils discussed in the previous sections. At the same time, sensitivity helps us to conceptualize the impact of unit amounts of erosion. Table 4 summarizes our best estimates at differential erosion rates based on the evidence of the studies reported in the section “Data sources”. It uses the management levels which will be taken up in the section “Scenarios of Yield Decline Over Time for Southern and East Africa” of this paper in order to construct food security scenarios.
We could have used a soil loss model such as SLEMSA (Soil Loss Estimation Model for Southern Africa), which has been locally validated for the Zimbabwe Highveld. However, since the FAO Erosion-Productivity Network results give us comparative data for actual soils on the slopes for which these soils are typically found, we felt it preferable to use actual measurements for the scenario constructions. Most of the soils in Table 4 are on moderately steep slopes, except the Phaeozem and one of the Cambisols, which occur in nearly flat terrain. The Acrisol and one of the Ferralsols have by far the highest erosion rates, followed by the Nitosols. The Phaeozem has the lowest erosion rate, partly due to the gentle slope of the site, but also the Cambisols seem to be resilient, even on moderately steep slopes. Increasing the degree of soil cover has the least impact on the Acrisol and the largest impact on the Nitosols in reducing erosion and improving soil resilience.
TABLE 4 Estimates of annual soil losses (tonnes/ha) for different soils and treatments. Good Moderately Poor Bare soil Typical cropping cover good cover cover system without conservation Eutric Nitosol (10-20% slope) 1 38 90 144 17 Humic Nitosol (27-34% slope) 0.4 20 86 124 29 Rhodic Ferralsol (10% slope) 16 -- 38 51 -- Rhodic Ferralsol (16% slope) 76 94 187 290 -- Orthic Acrisol (13% slope) 117 157 200 297 113 Eutric Cambisol (24% slope) 1 5 9 23 -- Eutric Cambisol (0.5-1% slope) 2 2 6 9 6 Luvic Phaeozem (1-2% slope) 0.2* 0.6* 5* 13 0.6 Note: *estimates
DISTRIBUTION OF REFERENCE SOIL TYPES IN AFRICA The following discussion is limited to what we call our Reference soil types: i.e. those soils for which we can reasonably confidently either construct erosion-yield-time relationships based on experimental data from Africa and South America or make inferences based on soil characteristics and an understanding of resilience and sensitivity. It serves to give an overview of 106 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
the likely relevance of our constructed scenarios to be presented in Section “Scenarios of Yield Decline Over Time for Southern and East Africa”. The main information source is FAO/Unesco (1977). Acrisols occur most often in the Sudano-Zambezian savanna zone where eco-climatic conditions tend to be unfavourable to agricultural development. Acrisols are found mainly on poor materials (Luvisols of higher base saturation normally develop on richer materials). The soils concerned are therefore mainly poor and are subject to difficult ecological conditions. In Eastern Africa most Ferric Acrisols occur in Tanzania. These soils are covered with Miombo woodland and degraded formations such as Zambezian-type tree savannas. Subsistence agriculture based on cassava, sorghum, eleusine (finger millet), beans and some groundnuts and maize is combined with livestock raising. Cambisols are found in all the ecological zones of Africa from the equator to the edge of the desert. They are characteristic of a recent stage of soil formation and therefore possess a fairly high potential fertility. Their use depends essentially on ecological and topographical conditions as well as management. Ferralsols, which represent the final stage of ferralitic weathering, are widely distributed throughout central Africa. These soils, which have a low adsorbing complex and are often highly desaturated and possess no mineral reserves, have a limited potential fertility. The fertilizing elements of Ferralsols are mostly immobilized in the organic matter of the soil and in the plant cover. The content of clay is also of importance for their fertility. Phaeozems are not widely distributed in Africa. In Morocco they occur in relatively flat terrain under a Mediterranean climate and are generally planted with wheat. In Nigeria they are found in a hot tropical climate and are used for extensive grazing and cereal agriculture. There are also patches of Phaeozems on the Mozambique Plain, which is characterized by aeolian and fluvial deposits. Phaeozems are excellent soils for both traditional and modern agriculture. They have no soil limitations and are very suitable for all crops and for pastures. Seasonal drought is the only limiting factor. Fluvisols are very important in many African valleys. They occupy the best drained parts of these valleys and usually occur in association with Gleysols, Vertisols and Regosols. In the humid tropics they are more fertile than neighbouring soils. A wide variety of Luvisols occur in Africa. Most Luvisols are found under unfavourable eco-climatic conditions, and the irrigation water needed for intensification of agriculture is often lacking. These soils are therefore best suited for extensive livestock raising combined with the cultivation of essential food crops. Nitosols occur under forest or savanna in dissected terrain with a humid tropical climate. They are typical of the intermediate stage of ferralitic weathering of materials of fine or medium texture. They are more fertile than Ferralsols, and in general they still have some mineral reserves. Andosols occur in the volcanic regions of Cameroon, Zaire, Rwanda, Uganda, Kenya, Tanzania and Ethiopia. Highland Andosols show considerable potential fertility, but the degree of saturation depends on rainfall. In Uganda, Tanzania and Kenya, Andosols occur under highland forest. The main crops are bananas, beans, peas, potatoes and vegetables. Livestock raising and cultivation of arabica coffee and tea are also important activities. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 107
FIGURE 3 General erosion-productivity relationships for the major soil types with initial maize grain yield on virgin land set to about 4000 kg/ha
FIGURE 4 Scenario for maize yield decline over time for a Ferralsol with high erosion rate 108 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
In many African valleys there are large areas of Vertisols, especially in regions with a long dry season. In eastern and southern Africa they are particularly well represented in Tanzania and South Africa. Vertisols are sometimes inundated by river floods or submerged by rain water that accumulates in poorly drained depressions. The natural vegetation is generally grass savanna. Vertisols are very heavy and difficult to work and are rarely used for traditional agriculture. They are preferably used for extensive grazing.
THE IMPACT OF EROSION As is clear from the inventory of data sources and soils, information on the impact of erosion is still lacking for some important agricultural soils in the tropics, notably for Acrisols, Fluvisols, Andosols and Vertisols. However, as some of these soils occur in association with soils for which the impact of erosion has been quantified, some extrapolations and comparisons are justified. This is, for example, the case for Acrisols with Luvisols, and for Ferralsols, Nitosols and Cambisols to be considered in relation to each other. For the soils where both soil loss and its impact on production have been measured, there generally seems to be a curvilinear decline in crop yields with cumulative soil loss, as also noted earlier. This relationship most often takes a negative exponential or logarithmic form (Figure 3), with different exponents for different soils. These relationships, which are related to the sensitivity of the soil to erosion, together with typical erosion rates (the resilience) for different soils under different levels of management, can now form the basis for modelling of yield changes with erosion over time.
From Figure 3, Luvisols and Nitosols have the lowest sensitivity to erosion, followed by the Ferallsols and Cambisols, while Phaeozems have the highest sensitivity. However, if we relate these results also to the resilience of the soils to erosion and typical erosion rates for different soils and settings (Table 4), the Phaeozem and the Cambisol appear as the least problematic soils.
Some general conclusions can be drawn as to the impact of erosion on soils in the tropics: · in humid to sub-humid tropical areas, productivity correlates highly with soil loss, generally on negative exponential or logarithmic form, which makes it feasible to use simple soil loss- productivity models. In semi-arid areas the situation is different as water availability becomes a major constraint to crop growth and temporal variability in rainfall is high, · all soils are sensitive to losses in organic C, · soil chemical properties are more influenced by erosion than soil physical properties, particularly for the ferralitic soils, for which high soil acidity, Al toxicity and P-fixation can follow erosion, · in general, legumes are more tolerant to soil erosion than cereals, · a good soil cover is very effective in reducing productivity decline.
SCENARIOS OF YIELD DECLINE OVER TIME FOR SOUTHERN AND EAST AFRICA By using the relationships for yield decline with cumulative soil loss (soil sensitivity) for different soils (Figure 3) and combining these relationships with typical soil losses for different levels of management (soil resilience; Table 4), we can predict yield changes over time. These yield changes are the basic data needed for food security scenarios. For our reference soil types, they enable predictions to be made as to how long soils can continue to produce under any specified Integrated soil management for sustainable agriculture and food security in Southern and East Africa 109
management condition including level of soil conservation. Such predictions are initiated in Section “Erosion-Productivity Issues Important to Food Security”. As in all modelling we have to base our scenarios on a number of assumptions, such as stable climatic conditions, stable erosion rates and general applicability of broad management categories. A further assumption in order to simplify the analysis is that there is only one cropping season per year. For the bimodal growing seasons of East Africa, compensatory adjustments may be needed. However, the most important assumption is that there exists a universally good correlation between soil loss and productivity. Accurate, reliable and rational relationships between cumulative soil loss and yield, and for erosion rates under specified conditions are at the heart of making estimates of food security. Hence, in this section we elaborate scenarios for yield decline over time for the major soil types and discuss the relative importance of soil sensitivity versus soil resilience. The underlying processes, as reflected in changes in soil chemical and physical properties, are also discussed and summarized based on the evidence presented in previous sections.
Overall, the Ferralsols have the second highest erosion rates (Table 4). Ferralsols are deeply weathered, leached, stoneless and clayey. Virtually no weatherable minerals remain in the upper two metres, rendering the soil extremely limited in potential fertility. Its sensitivity to yield decline is, therefore, moderate, but its resilience to erosion is very poor. Ferralsols as a broad group are therefore judged to have low resilience and moderate sensitivity, resulting in high erosion rates but relatively low impact per unit quantity of soil loss. However, due to the very high annual soil losses in our example, maize yield declines dramatically with erosion and is virtually down to nil after ten years with erosion even with a good soil cover (Figure 4). This indicates that physical conservation structures, such as terraces are necessary in hilly areas to sustain the productivity of Ferralsols.
From two earlier studies (Young and Wright, 1979; Stocking, 1986b), the significant characteristics of Ferralsols in relation to degradation processes are: · low supply of available plant nutrients - erosion has little additional impact, · strong acidity, high in free aluminium - erosion may set in train a large impact from Al- toxicity, if it is not already evident, · low levels of available phosphorus - erosion may also cause a critical threshold of P-fixation, · no reserves of weatherable minerals - erosion has little additional impact, · topsoil organic matter easily lost - erosion will assist natural rates of humification..
Conclusion: Ferralsols: low resilience, moderate sensitivity. Addressing erosion rate by combinations of structures and biological measures is indicated.
By the same analysis, Nitosols are considered to be one of the safest and most fertile soils in Africa, but at low input levels a distinction needs to be drawn between Dystric and Eutric Nitosols. The rainforest Eutric Nitosols suffer: · acidity problems and P-fixation - both exacerbated by erosion, · substantial increases in erodibility with losses of organic carbon - strongly related to erosion. 110 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
Nitosols have therefore a moderate resilience and moderate to low sensitivity, which result in stable yield with erosion with a good soil cover or high levels of management, without physical conservation structures, but steadily declining yields for lower levels of management (Figure 5). Good cover and maintenance of organic matter as a buffer against acidity and its associated problems and as a measure to reduce soil erodibility are essential ingredients of a management and conservation strategy for Nitosols. Conclusion: Nitosols: moderate resilience, moderate to low sensitivity. Biological conservation measures effective for both erosion rate and erosion impact.
Luvisols have been described as the ‘mid-point in the spectrum from poor to good tropical soils’. However, they do suffer substantial physical and chemical degradation which is closely related to water erosion: · moderate nutrient levels, concentrated in topsoil - erosion has a substantial initial impact, · low to moderate organic matter content - erosion has some impact, · weak topsoil structure, prone to crusting - erosion has a significant impact on crusting and knock-on effects such as reduced plant-available water.
Luvisols do not, therefore, have the highest erosion rates (moderately resilient), and their sensitivity to erosion is moderate to low, which results in yield scenarios similar to those for the Nitosol (Figure 6). However, many African Luvisols are currently used for smallholder cultivation at low levels of productivity and will not suffer much further decline. Conclusion: Luvisols: moderate resilience, moderate to low sensitivity. Productivity of Luvisols can be maintained only by addressing erosion rate and by conserving nutrients and water-holding capacity on-site. This is most obviously accomplished by tillage practices which maximize surface water infiltration (e.g. contour ridging; tied ridging) and biological measures which maintain cover.
Our database contains little specific information on one of the poorest of tropical soils: Acrisols. It has most of the degradation hazards of Ferralsols but with some additional physical and chemical problems when cultivated: · low supply of plant nutrients and trace elements - both affected by erosion, · strong acidity, low calcium, high free Al - all made worse by erosion, · topsoil organic matter easily lost - assisted by erosion, · weak structure - subject to wind erosion, crusting and compaction, · argillic B-horizon - if compacted and exhumed, an extremely serious impediment to production.
Acrisols have, therefore, a very low resilience and a moderate sensitivity. Erosion impact is likely to be similar to that for Luvisols. However, erosion rates are higher and initial productivity lower (Figure 7). As the poorest of the major soil groups, erosion is unlikely to have much additional impact to what has already occurred within historical times. Conclusion: Acrisols: very low resilience, moderate sensitivity. Having the worst combination of resilience and sensitivity, agricultural production cannot be sustained beyond 1-2 years and only continuous cover (grass or forest) is indicated. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 111
FIGURE 5 Scenario for maize yield decline over time for a Nitosol
FIGURE 6 Scenario for maize yield decline over time for a Luvisol 112 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
FIGURE 7 Maize yield decline over time for an Acrisol
FIGURE 8 Scenario for maize yield decline over time for a Cambisol Integrated soil management for sustainable agriculture and food security in Southern and East Africa 113
Cambisols are the tropical ‘brown earths’ with somewhat higher base status than Luvisols, but otherwise fairly similar limitations. Erosion rates are low in our case examples from South America and Botswana (Table 4) and they are judged to have high resilience. They do have increasing clay with depth, and therefore have moderate sensitivity to erosion. The good resilience and the moderate sensitivity of the Cambisols therefore result in less dramatic yield losses with erosion than for the previously discussed soils (Figure 8). It is noteworthy that even with a very low level of management, there will still be something to harvest after 20 years of erosion. Conclusion: Cambisol: high resilience; moderate sensitivity. The most robust of our reference soils; low-cost, mainly agronomic, measures of conservation such as intercropping or surface residue management may be worthwhile. Phaeozems have a good structure and are generally resistant to erosion (good resilience). The Phaeozem in our example in Table 4 is subject to the lowest soil losses, partly as a result of good structure and partly because of the very gentle slope at the site. However, according to Figure 3, Phaeozems have a very high sensitivity to erosion - i.e. large yield losses per unit of soil loss. But as Phaeozems are often found in flat terrain on aeolian and fluvial plains, which is the case with Phaeozems in both Argentina and Mozambique, we combine very low erosion rates with high sensitivity in the modelling of yield changes with erosion. It appears from Figure 9 that High resilience in combination with high sensitivity result in high and relatively stable yields for good to moderately good management (cover), whereas yields for lower levels of management drop drastically after only a few years. Conclusion: Phaeozems: high resilience, high sensitivity. The key to the sustainable use of Phaeozems is good vegetation cover.
FIGURE 9 Scenario for maize yield decline over time for a Phaeozem
EROSION-PRODUCTIVITY ISSUES IMPORTANT TO FOOD SECURITY Erosion-productivity research issues Having established scenarios for yield decline with erosion over time with different levels of management for some major soils in East and southern Africa, we are now in a position to 114 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
consider the differential impact of erosion on food security. However, the foundation for good predictions is good research. Our ability to construct erosion-yield-time relationships has been hampered by missing data and uncertainties caused often by dubious results. Data on specific agro-ecologies are drawn from in-country research groups who have limited resources and competing demands on their time. Therefore, before constructing the final scenario projections on food security, it is relevant to the issues of this Expert Consultation to report on the findings of the March 1996 Erosion-Productivity Workshop held in Chapecó, Brazil (Stocking and Benites, 1996) - see Box 13. This was a gathering of 28 researchers from 14 countries, representing the combined experience of many of those actively engaged in erosion-productivity research.
BOX 13 – CONCLUSIONS AT THE FAO WORKSHOP, BRAZIL, 1996 Methodological issues: problems remain with the collection and analysis of information. Data base: there is a need for a general data base on erosion-productivity and a standard protocol; information is currently too scattered and difficult to compare. Soil management and rehabilitation: a focus on soil management is indicated, with particular emphasis on organic and inorganic fertilizers and green manures. Evidence of productivity decline: the strong evidence of productivity decline should be related to economic costs of erosion and benefits of conservation. Continuity of research: the experiments should continue, but the reward system for in-country researchers is inadequate. Communication: there has been a lack of communication between researchers; a coordinated effort will require better liaison and learning form others. Farmer participation: farmers are key partners in these research outputs and must be more involved. Economics of soil erosion: the results are not yet in a form suitable for economists and policy makers to appreciate the significance. Contact with planners: the research is isolated from strategic national programmes and policies and should be re-prioritized through planning departments. Source: adapted from Stocking and Benites, 1996
The Chapecó Workshop was concerned mainly with the erosion-productivity experiments, and naturally emphasized the research and the role of the researcher. Several of the highlighted issues (Box 13) are worth elaborating for this Expert Consultation in the context of soil fertility, soil degradation and food security: · methodologies for deriving erosion-productivity relationships necessarily have to simplify complex reality in order to obtain results that are comparable. The report on the Workshop (Stocking and Benites, 1996) listed some of the problems and desirable changes which have yet to be enacted. Recommendation: for southern and East Africa, address the critical need for provision of good quality comparable data through a standard research protocol, clear advice on recommended methodologies and adequate local support, · emphasis to date has been on erosion, rather than conservation and production. For the many degraded conditions in southern and East Africa, it would be more appropriate to examine conservation-induced gain in productivity through practices such as green manuring, live barriers, minimum tillage and crop sequences and rotations. However, the same questions arise: what are the relationships? How can we predict the gain in future production with such improved practices? Standard experimental designs are again indicated in order to provide an adequate data base. Recommendation: a new emphasis on soil rehabilitation should be promoted, using measures that can be employed by farmers to improve eroded soils, but still obtaining the data to construct accurate scenarios, · farmer involvement has been missing from erosion-productivity research to date. Issues of soil fertility and food security intimately involve rural households, their labour, capital and resources, as well as farmers’ own technologies and adaptations. Recommendation: any new Integrated soil management for sustainable agriculture and food security in Southern and East Africa 115
phase of erosion-productivity or conservation-productivity research must be carried out on- farm and with the immediate involvement of land users.
FOOD SECURITY ISSUES What are the implications of unchecked (or partially checked) soil erosion for food security? Food security is itself a balance between supply and demand: the supply is provided by the soil resources, crop management and the farming system; the demand comes from the needs of the populations who depend on the production of the farming system. For simplicity, this analysis takes the rural household’s needs as paramount; that is, demand is derived from the immediate food needs of farmers and their families. Therefore, a farm-level perspective is taken of food security. With the household as the unit for analysis, we assume that each adult household member consumes approximately 200 kg of grain per year, and that children’s consumption is 50 per cent less. A household is taken to comprise two adults and six children. A unimodal rainfall pattern is assumed with one harvest per year. These assumptions lead to a critical yield level of 1000 kg/ha/year to meet household food security. The number of years it takes to reach critical production levels differs greatly between soils and management levels (Table5). For the Ferralsol and the Acrisols, it takes only between one to four years to reach the critical level. The other soils respond more favourably to an increase in the degree of soil cover and thus good management sustains a tolerable production level for longer than a generation. For the moderate cover, which most closely resembles the cover given by conventional cropping of maize, the Phaeozem gives the longest period with tolerable yields. For the lower levels of management, the Cambisol best meets food consumption requirements.
TABLE 5 Years taken for the different soils in the scenarios to reach a critical yield level of 1000 kg/ha/yr with continued erosion Management level Ferralsol Acrisols Luvisol Phaeozem Cambisol Nitosol Good cover 3 4 93 200 210 950 Moderate cover 2 3 23 65 42 19 Poor cover 1 2 9 7 23 4 Bare soil 1 1 5 3 9 3
These estimates of “food-secure productive life” could also be used to ascertain sustainability of production for the different soils. If effective sustainability is taken to be a productive life of at least one generation, say 50 years, then only a few of the conditions in Table 6 are allowable without special precautions.
Ferralsols and Acrisols: any continuous use is unsustainable. If cropping is to be contemplated at least two or more of the following measures must be considered: · mechanical conservation measures such as bench terraces to bring erosion well below the good management” levels of 76 t/ha, · provision of long rest-periods; Young and Wright (1979), based on expert opinion, specify at least 3 years in 4 as the rest-period requirement, · high inputs of nutrients and calcareous amendments to maintain both soil chemical fertility and pH, · cropping systems with high biomass production which can be used for mulch and green manure, irrigation. 116 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
Luvisols and Cambisols: continuous sustainable production is possible under good management with high levels of maintained cover. Productivity problems arise from a mixture of limited nutrient availability to the topsoil, low levels of organic matter and relatively poor water-holding properties: · annual cropping needs to be rotated so that poor cover crops such as cotton alternate with better cover crops such as maize and beans, · intercropping and agroforestry systems are ideal in maintaining cover and retaining nutrients on-site, · tillage practices which retain water and minimize impedance (e.g. crusting) should be encouraged.
Nitosols: with good management, production can be maintained indefinitely without special measures. The rehabilitation of eroded Nitsols (e.g. the Ethiopian Highlands; Lesotho and Swaziland Highvelds) would seem to be a high-priority task with possible substantial gains in production in the short term. Rehabilitation would involve the re-creation of a topsoil which might only take a decade or so of careful cropping and build-up of organic matter. So, for continuous and sustainable production: · attention to possible acidity problems through liming and/or organic buffers, · attention to P-fixation, again by liming and by resupply of soluble P, · maintenance of organic matter levels (organic C > 2%) to keep soil unerodible and resistant to rainsplash and detachment.
Phaeozems: these are the most robust amongst our Reference Soils with highest resilience. However, they are sensitive to yield decline. Although not abundant in Africa, areas of Phaeozems should be carefully protected for food security purposes: · although suitable for most continuous cropping under smallholder agriculture, a minimum level of management standard must be maintained, · good to moderate crop cover needs to be maintained, in which case erosion rates will remain low and productivity unchallenged, · no particular special management practices are indicated, other than a balanced resupply of chemical components and maintenance of water-holding properties.
From the above analysis, it can be deduced that farm management level and type of management are crucial in determining food security. All soils, other than Acrisols and Ferralsols (which would demand special precautions), are capable of meeting the food needs of growing populations provided that overall crop management is good and particular soil-related constraints are addressed. Studies in East and Central Africa have shown that farm management depends on farmers’ access to resources. Richer farmers are likely to have a higher level of management than poorer farmers (cf. Scoones, 1996). Interventions designed to address household food security therefore need to take account of both soil type and the wide range of socio-economic conditions farmers are facing that determine their overall resource level. Our preliminary analysis of food security indicates that, without soil and water conservation structures, all groups of farmers on Ferralsols and Acrisols are likely to reach critical yield levels only after a few years, whereas for the other soil types, poorer farmers are more at risk. Even Ferralsols and Acrisols could continue Integrated soil management for sustainable agriculture and food security in Southern and East Africa 117
to provide a sustainable production under long-cycle shifting cultivation, but that is becoming an impossibility as populations increase and available land per person diminishes. At this stage, it is important to differentiate between ‘food production security’ and ‘food consumption security’ (cf. Reardon et al., 1988). It is well-known that so-called farmers in southern and east Africa have developed highly diversified income-generating opportunities. For richer households (often those with the most highly diversified income base, encompassing, for example, off-farm income), ‘consumption security’ may not be a problem although ‘production security’ may be at risk, as these households generally generate enough cash income for purchasing additional food. For poorer households and households with a low degree of income diversification, ‘production security’ and ‘consumption security’ tend to go hand in hand. Poorer and marginal households tend to live on the poorer soils - Luvisols, for example, which are fairly easy to cultivate but which lose their fertility quickly. So, for effective food security at the household level, policy will need to target these marginal groups subsisting on some of the most difficult soils. Our analysis suggests this may be a daunting task. Without prejudice to the discussions at the Expert Consultation in Harare, the following policy issues and recommendations (to add to those already given at Section “ Erosion-Productivity Research Issues” are relevant from the scenario predictions and associated soil-related constraints: · food security is a useful way of viewing the conceptual term ‘sustainability’: if production can be assured for a reasonable length of time (we have assumed 50 years), then food security is effectively achieved. Recommendation: food security is an indicator of both soil productivity and sustainability - policy makers should establish food security targets at a variety of levels (household, community, national and regional) and researchers could respond by providing recommendations for targeting particular soils, environments and socioeconomic groups. · Secure access to soil resources and the means to achieving “good management” are vital to the protection of the environment and of future production. While a soils-led analysis such as we present provides a baseline for making scenario predictions, the reality is that farmers respond according to their social and economic needs, not to the wishes of society. Recommendation: soil fertility, productivity and sustainability are not politically neutral; they need to be incorporated into policy issues concerning equitable and fair access to resources, advice and subsidies in order to promote the wider benefit to society of the good management that is expected of farmers.
Finally, the analysis of soil erosion and food security indicates that we are dealing with complex situations, where full knowledge of every permutation of soil sensitivity and resilience as well as farmer resource level is an impossibility. An adaptive management and policy approach is needed, where it is essential to allow solutions to emerge from the local level. It is thus time to take the erosion-productivity experiments on-farm and together with farmers identify problems and remedies for different soils and settings. Remedies could, for example, encompass the development of existing indigenous soil and water conservation techniques (Reij et al., 1996). Furthermore, the links between management levels and farmer resource levels also indicates that it is important to support the diversification of the rural income base. However, we leave it to the participants in this Workshop to discuss and identify appropriate policies for coping with erosion induced loss in soil productivity in their respective countries. Our hope is that we have, through the work of our colleagues in the FAO-sponsored Erosion-Productivity Network, set a baseline whereby appropriate policy recommendations can be developed in the knowledge of how the soil productive resources would respond and whether people might gain the food needs that they require. 118 Erosion-induced loss in soil productivity and its impacts of agricultural production and food security
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Soil degradation assessment and soil conservation inventory on a SOTER basis: Asian experience
This paper will present the methodology and some results of a recent soil degradation assessment for South and Southeast Asia (ASSOD), and of an inventory of soil and water conservation activities in Thailand and SE. China (WOCAT) using the same base map units derived from a 1:5 M physiographic map that was compiled following the SOTER methodology. This approach offers a strong framework using standardized and internationally accepted methodologies (SOTER, ASSOD or GLASOD, WOCAT) that can be applied at different scales. Parts of this approach have also been - or will soon be - implemented in Africa (GLASOD: whole continent at 1:7 M; SOTER: Kenya 1:1 M, Benin; WOCAT: Eastern, Southern and Western Africa 1:5 M).
GLOBAL AND NATIONAL SOILS AND TERRAIN DIGITAL DATABASE (SOTER) Background Policy-makers, resource managers and the scientific community at large have repeatedly expressed the need for ready access to soil and terrain resources through geo-referenced databases in order to make assessments of the productive capacity of soils, to have a better understanding about the risks and rates of soil degradation and to better quantify processes of global change. The SOTER programme is a system which can store detailed information on natural resources in such a way that these data can be readily accessed, combined and analysed from the point of view of potential use, in relation to food requirements, environmental impact and conservation.
SOTER characteristics and development SOTER provides an orderly arrangement of natural resource information through the creation of a computerized database containing all available attributes on topography, soils, climate, vegetation and land use, linked to a Geographic Information System, through which each type of information or combination of attributes can be displayed as a separate layer or overlay, or in tabular form. SOTER is an initiative of the ISSS and was adopted at the 13th World Congress of Soil Science in 1986.
Under a UNEP project, ISRIC developed a methodology for a World Soils and Terrain Digital Database (SOTER) for use at a scale of 1:1 M, in close cooperation with the Land Resources Research Centre of Canada, FAO, and ISSS.
G.W.J. van Lynden International Soil Reference and Information Centre, Wageningen, The Netherlands 122 Soil degradation assessment and soil conservation inventory on a SOTER basis: Asian experience
SOTER was tested in three areas, involving five countries (Argentina, Brazil, Uruguay, the USA and Canada), using local data. Results were reported at the 14th World Congress of Soil Science in 1990. Based on the experience obtained in the pilot areas the SOTER methodology was further refined and a training programme and course material were developed by ISRIC. In 1993 the Procedures Manual for Global and National Soils and Terrain Digital Databases was jointly published by UNEP, ISSS, FAO, and ISRIC (in English and Spanish), accompanied by attribute input software. A SOTER based methodology for an assessment of water erosion risk and for Automated Land Evaluation (ALES) was developed. In 1993 the SOTER programme was implemented at national level in four countries (Argentina, Uruguay, Kenya, and Hungary). In Argentina and Uruguay, SOTER windows at scales up to 1:100,000 are also scheduled. These national SOTER programmes were formulated and financed by UNEP with technical support and coordination provided by ISRIC. More recently a 1:500 000 SOTER project started for Hainan Province in China with UNDP funding. The programmes are carried out by the national soil research organizations.
In 1992, an international panel convened by UNEP to evaluate the SOTER programme, recommended not only implementation of SOTER activities at a national level, but also the development of small-scale continental SOTER databases. In 1993, an action plan for the compilation of a Latin American SOTER at a scale of 1:5 M was jointly formulated and financed by UNEP, FAO, and ISRIC, which was finalized this year. Within the framework of the ASSOD project (see below), the SOTER methodology was used to prepare a physiographic map for Asia at a 1:5 M scale in 1995. It is hoped that this map will be complemented with a full SOTER (soil) database in due course. Currently a 1:2.5 M SOTER map is under preparation for Central and Eastern Europe in the context of the project Soil Vulnerability Assessment in Central and Eastern Europe (SOVEUR).
ASSESSMENT OF THE STATUS OF HUMAN-INDUCED SOIL DEGRADATION IN SOUTH AND SOUTHEAST ASIA (ASSOD) Recently a project called Assessment of the Status of Human-Induced Soil Degradation in South and Southeast Asia (ASSOD) was completed by ISRIC in collaboration with FAO and national institutions. The project is a sequel to the UNEP/ISRIC survey of Global Assessment of the Status of Human-Induced Soil Degradation (GLASOD; Oldeman et al. 1991). In 1993 an Expert Consultation in Bangkok of the (FAO) Network on Problem Soils in Asia made a recommendation (RAPA, 1993) for the preparation of a soil degradation assessment covering 17 countries in South and Southeast Asia based on a modified GLASOD methodology. A new physiographic map for Asia at a scale of 1:5 million that was compiled by ISRIC (van Lynden, 1993) following the SOTER methodology was used as the mapping basis for this assessment. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 123
ISRIC was the coordinating institution for ASSOD, while national soils- or agriculture research institutions were providing the data. The project was jointly funded by UNEP, FAO and ISRIC.
Methodology Guidelines for the assessment of human-induced soil degradation in South and Southeast were prepared by ISRIC, based on the GLASOD methodology. Natural resource institutions in the participating countries were requested to provide degradation data following these guidelines. The most important differences with the GLASOD methodology, besides the geographical focus (17 countries in S. and SE Asia) and the larger scale (1:5M), are the assessment of impacts on productivity as a function of management level (rather than the degree of degradation). Like the GLASOD map, ASSOD provides information and increase awareness on soil degradation problems among policy- and decision-makers and the general public in the region. It describes the current status of (human-induced) soil degradation, but with more emphasis on the impacts of degradation on productivity and on trends of degradation (recent past rate). The impact of soil degradation was evaluated on the basis of the expected productivity increase (or decrease) for three levels of management (high, medium, low). More emphasis was also placed on the rate of degradation, the latter being considered an important item in degradation dynamics and in prioritization of conservation areas. Finally, a greater flexibility in data handling and analysis was achieved by storing the information in a digital database linked to a GIS. Unlike GLASOD, the number of identified degradation types and related characteristics is now potentially unlimited. The link with a GIS facilitates the preparation of various outputs and thematic maps on specific items.
This showed a general trend towards a slow or moderate increase in degradation for all major degradation types, although for water erosion in particular some smaller areas show an improving trend. Although the project has recently been terminated, improvement and updating in the future will remain possible. A report is available with two accompanying maps (one showing the dominant degradation types for the entire region, the other showing specific degradation types for four “windows”) and various graphs. Individual maps on specific themes or for specific regions can be produced on request. Information from ASSOD was extensively used in the second (revised) edition of the World Atlas of Desertification, which has been recently published by UNEP.
Results The ASSOD results show a wider variability of degradation types in comparison with the GLASOD map for the same region, with especially more frequent occurrence of fertility decline and salinization. Compared to the GLASOD map, water erosion is much less dominant (Figure 1). This is probably more the result of differences in scale and approach than of real changes in degradation. Water erosion (on and off site) nevertheless still is the most widespread degradation type (398 M.ha or some 22% of the entire land area, see Figure 2) with agriculture and deforestation being reported as the main causative factors. Second in importance is chemical deterioration (mostly fertility decline), covering some 210M.ha or 11 % of the total land area. The main causative factor for this degradation type is agriculture. This type of degradation is largely concentrated in the more humid tropical parts of the region. Wind erosion (on- and off site) is understandably concentrated in the Western and Northern arid and semi-arid parts of the region, covering some 175 M.ha (9% of total land area). Its main causes are overgrazing and to a lesser extent deforestation and over-exploitation of natural vegetation. Physical deterioration was 124 Soil degradation assessment and soil conservation inventory on a SOTER basis: Asian experience
FIGURE 1 ASOD GLASOD comparison
FIGURE 2 Relative distribution of degradation types and non-degraded land (as percentage of total land area)
generally considered less important although locally waterlogging, aridification or urbanization/industrialization are significant.
WORLD OVERVIEW OF CONSERVATION APPROACHES AND TECHNOLOGIES (WOCAT) In 1992 the World Association of Soil and Water Conservation (WASWC) together with the Centre for Development and Environment in Bern initiated a “counterpart” project of GLASOD: Integrated soil management for sustainable agriculture and food security in Southern and East Africa 125
the World Overview of Conservation Approaches and Technologies (WOCAT), to assess what measures are being taken against degradation (in particular soil erosion). Data on extent and impact of soil and water conservation (SWC) are not available at a global level, but are even rather scanty or incomplete at national levels. The project developed a standard methodology to evaluate existing SWC technologies and the approaches to implement these technologies in the field. Rather than considering only technical aspects (as in many SWC handbooks), the “enabling environment” is also evaluated which facilitates the identification of reasons for success or failure. Comprehensive questionnaires have been developed that are filled in during regional workshops. Three such workshops have been organized to date for eastern Africa, southern Africa and western Africa respectively. The results of the questionnaires are stored in a digital database and can be extracted in summarized or full form.
Moreover, specific geo-referenced data are collected for map compilation. For Africa the map units of the GLASOD map (1:15 M) served as a basis for the WOCAT map, enabling linkage to the degradation data. In spite of the global scale of the assessment, the methodology can be used at national and even sub-national level as well: a first national WOCAT workshop was held in Thailand in September 1997 and very recently a sub-national workshop was held in China, initially covering Fujian province in the Southeast. The mapping basis for both of these inventories was the SOTER based physiographic map that was also used for the 1:5 M degradation assessment (ASSOD), thus offering a geographical linkage between physiographic information (SOTER), type, extent, impact and rate of degradation (ASSOD) and land use data, SWC type, effectiveness, extent, etc. (WOCAT). When - at least part of - the Asian SOTER database will be completed with soil data in the near to medium term future, this will result in a comprehensive geo-referenced database on soils, terrain, degradation and conservation, which will be a useful tool for planners and decision makers. More detailed studies and applications could be implemented for certain “hot spots” using the same methodologies. 126 Soil degradation assessment and soil conservation inventory on a SOTER basis: Asian experience Integrated soil management for sustainable agriculture and food security in Southern and East Africa 127
Socio-economic aspects of soil management for sustainable agriculture and food security in Africa with particular reference to Zimbabwe
As in the past decades, the satisfaction of the ever-growing demand for food remains the major challenge to world agriculture. This is particularly true in Africa where tremendous socio- economic transformation renders traditional small scale farming systems incapable of meeting this challenging demand. In fact it is the only continent in the world where per caput food production has constantly been declining over the past decades (Hailuetal 1992). Rapid increases in the African population demand increased production of food from land. To meet this need, vast tracks of land are being brought into production. The total area of cultivable land available to Africa is however limited as is its productive potential. Land must be carefully managed if its productivity is to be maintained or increased. If it is not well managed, or if it is used in a way which is beyond its potential, some form of soil degradation inevitably occurs. At present, as the pressure on small scale farming land increases, large areas are being misused. The results of poorly managed land can be seen in various forms of soil degradation such as desertification, erosion, salinization, toxicity and water logging. The issue of soil degradation has increasingly drawn the attention of many international development and research institutions, planners, policy makers, scholars and donors particularly concerned with the challenge posed on production systems in Africa.
The World Bank (1988) estimated that 100 million people in Africa are food insecure and noted that Africa’s food situation is not only serious, it is deteriorating. Soil degradation, through erosion, has been identified as one of the major causes of declining food production and therefore of the increasing inability of people to feed themselves. Brown (1991) also pointed out that soil degradation has continued in spite of the environmental protection efforts of national governments, the creation of numerous environmental agencies, the thousands of protective laws passed, the activities of tens of thousands grassroots environmental groups and the production of environmental issues. The World Bank (1989) showed that primary forests are disappearing at a rate of 0.6% per annum across sub-Saharan Africa. These rates vary substantially among African countries. For example, the forests of Ivory Coast declined on average by 51% per annum from 1965 to 1984 (Elthel and Hertel 1989) and in arid areas annual rates of up to 25% were reported (Olsson K. 1985). In the context of the close correlation between population growth, soil degradation and food production the following can be derived from the population increases (for various regions) estimated by the United Nations Fund for Population Activities (Table 1).
D. Tawonezvi and P.N. Sithole Senior Agricultural Economist and Senior Socio-economist of Agritex, Harare, Zimbabwe 128 Socio-economic aspects of soil management for sustainable agriculture and food security
The world population is expected to stabilize at about ten and half thousand million by the year 2110, and the African population at 2,193 (about 21% of the world population) (Table 1). In the table the expected population increases are shown in relation to 1980 population together with the number of years over which they will take place to emphasize how great a food production increase will be needed within a short period of time. The world has to more than double its food supplies over the next 130 years. The figure for Africa is significantly higher with over four times more food being required 130 years from 1980 just to maintain the 1980 standard of nutrition. This presents a challenge to Africa as a whole, to put in place mechanisms which facilitate the attainment of the above levels of food production. This may call for continued expansion of land under cultivation or improving of technology which allows higher productivity per unit area. The present outlook in both respects (land expansion and improved productivity) gives a cause for concern. Africa’s soil resources are being destroyed much faster than ever before. The present production base tends to occupy the best land. The remaining areas are more marginal, generally possessing a lower production potential and a more fragile ecological regime. Their cultivation would require the most immense development programme. On the basis of current development, soil management (soil degradation in particular) needs close attention if Africa is to meet its future food requirements.
TABLE 1 Expected population increases Region 1980 Stable Stable population in Year of Period population population relation to 1980 stabilization (years) (millions) (millions) population World 4.434 10,529 +137% 2110 130 Africa 470 2,193 +367% 2110 130 Latin America 364 1,187 +236% 2100 120 North America 248 318 +28% 2060 80 East Asia 1,059 1,725 +63% 2090 110 South Asia 1,405 4,145 +195% 2100 120 Europe 484 540 +78% 2030 90 Oceania 23 41 +120% 2070 80 USSR 265 379 +43% 2100 120 Source: FAO, 1983.
OVERVIEW OF SOIL DEGRADATION IN ZIMBABWE Environmental deterioration accompanied by soil loss and soil depletion pose tremendous implications for agricultural development in Zimbabwe. The potential productivity of the soils is declining steadily on a national scale. Year by year the inherent fertility of Zimbabwean land is being depleted, soil profiles are shallowing and rills and gullies are encroaching into every corner of the catchment areas.
The following is a summary of the state of soil resources in Zimbabwe: · Current rates of soil loss from annual ploughed land are of the order of 50t/ha/yr. About one third of the seasonal rainfall is lost as surface runoff and up to 50% of the applied fertilizers is washed off the land (Elwell and Stocking 1988). · As a by product of soil erosion the country is estimated to be losing $1.5 thousand million worth of nitrogen and phosphorus each year from the arable land and 2.5 million tonnes of organic matter essential for soil stability and fertility (Stocking 1986). Integrated soil management for sustainable agriculture and food security in Southern and East Africa 129
· Thirteen percent of the total area of Zimbabwe and 27% of communal land is classified as severely eroded (Whitlow 1988). · The soil in most agricultural land has been reduced to its minimum agricultural potential through degradation of soil structure, seriously limiting yields and substantially increasing inputs (Elwell 1989). · Virgin soil is being reduced to its minimum yield potential within five to ten years after land has been first opened up and many lands become totally unproductive and non-reclaimable within thirteen years. · Marked changes have occurred to the hydrological balance of our catchment areas such that rainfall amounts and distribution are being adversely affected. Groundwater levels are declining and the nation’s water supplies are jeopardized by siltation and drought.
TYPES OF SOIL DEGRADATION IN ZIMBABWE Soil degradation is a complex process in which several features can be recognized as contributing to a loss of productive capacity. Generally, the processes are many and varied, and in Zimbabwe they include soil erosion by water and wind, soil fertility decline, salinization, water logging, lowering of water table, deforestation, forest degradation and rangeland degradation.
Soil erosion by water In Zimbabwe forms of soil erosion by water include sheet, rill erosion and gullying. Human- induced intensification of land caused by vegetation clearance and construction, etc., is also included. Sheet erosion alone has been found to be causing soil losses of the order of 50 t/ha/year in the communal lands. The major physical factors controlling the rate of erosion by water in Zimbabwe are rainfall, vegetation or soil cover, topography and soil types. Rainfall. The effect of rainfall (erosivity) is directly related to its amount, intensity and distribution. The erosivity of rainfall in Zimbabwe is at its greatest at the beginning of the rain season when the soil is largely unprotected. Research has shown that up to 20 tonnes per hectare of soil can be removed following a heavy storm and up to 100 t/ha over the whole season. Much of the silt being carried in runoff water ends up in dams reducing yields (Elwell, 1990). This is in contrast to the rate of soil formation which is about 1 mm per year (IFAD 1991). Vegetation and Soil Cover. Vegetation cover influences the effect of runoff on the soil surface and this in turn affects its erodibility. Where there is growth of vegetation, the force of rainfall is intercepted by the above ground part. In addition, plant roots protect the soil and improve its structure, infiltration rate and moisture storage capacity and runoff. When sandveld on 4 % slopes denuded of vegetation by overgrazing, annual soil loss increase by 21 times and runoff by 8 times that from veld with 70% total vegetation cover (Elwell and Stocking 1974). Topography. The degree of land slope has a very strong influence on amount of erosion. Soil losses from steep slopes are much greater than from gentle slopes. The undulating topography over most of Zimbabwe coupled with frequent storms make the lands susceptible to sheet erosion. Soil. Soils vary in their resistance to erosion. Heavily textured fertile soils are more resistant to erosion than light infertile soils. 130 Socio-economic aspects of soil management for sustainable agriculture and food security
Soil erosion by wind Wind erosion refers to loss of soil by wind, occurring primarily in other parts of the country and during dry seasons. It has not been possible to obtain quantitative estimates of the extent and severity of wind erosion. There is no doubt however, that the problem is wide spread in most parts of the country. Generally, wind erosion in Zimbabwe is pronounced :
In Natural Regions 111, 1V, and V, where rainfall is low, poorly distributed and variable, thereby making the soil dry, dusty and easily blown away. Wind erosion is also a problem in all areas during the drier months of August to October. · In marginal areas of the country where vegetation cover is poor or heavily grazed, wind erosion is also enhanced by human practices of cultivation and burning. · In smallholder areas where there is a high proportion of fine silt in the soil.
Soil fertility decline Soil fertility decline refers to the deterioration in soil physical, chemical and biological properties. The process involves lowering of organic matter, degradation of soil physical properties (structure, aeration, water holding capacity), as brought by reduced organic matter and adverse changes in soil nutrient resources (phosphorus, nitrogen potassium). Most soils in Zimbabwe are low in organic matter and inherently infertile. Nitrogen is the most limiting nutrient as it is rapidly depleted in cultivated soils (without replacement). Many soils are also deficient in phosphorus, potassium and sulphur (particularly in soils that have been heavily cropped without nutrient replacement). Population pressure has reduced the fallow period and contributed to a decline in soil fertility. Erosion from such infertile soils is quite pronounced because of their poor physical properties.
Waterlogging Waterlogging is the lowering in the land productivity through the rise in ground water close to the soil surface. Also included under this heading is the severe form, termed ponding, where the water table rises above the surface. Water logging is common in poorly managed smallholder irrigation schemes.
Salinization Salinization refers broadly to all types of soil degradation brought about by increases of salts in the soil. It thus covers salinization (build up of salts) and sodification (the development of dominance of the exchange complex by sodium). In Zimbabwe, there are very areas of naturally occurring saline and sodic soils. Saline soils have been found in Matibi II communal area, along the Mwenezi river, at Malipati and on alluvial soils along the Save river below Birchenough Bridge. There are also some few irrigation schemes on which soil salinity has developed as a result of poor management. Examples are: · Mutema irrigation scheme in the Save Valley which is based on the use of groundwater. Salinity occurs because of insufficient application of water to leach salts from soil profile. · Ingwezi irrigation scheme where patches of saline soils developed due to inadequate leaching of salts from soil profile. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 131
It was not possible to get information on the extent of sodicity on Zimbabwean soils. However, it is known that the development of sodic soils under irrigation have not been extensive, mainly because of strict standards of soil and water testing for irrigation.
Lowering of the water table This is brought about through pumping of groundwater for irrigation exceeding the natural recharge capacity. This has the effect of lowering land productivity. This has occurred in the Nyamandlovu aquifer in Matabeleland North province during the 1992/93 drought season.
Deforestation Deforestation is a widespread and extremely serious type of land degradation in the country. At the same time, it is a major cause of other types of degradation, particularly water and wind erosion. According to forestry Commission over 70,000 hectares of land are deforested every year. According to Whitlow (1980) reserves of timber in Zimbabwe are shrinking rapidly. Trees are being cut down at an unprecedented rate to supply the basic needs of shelter and fuel for the expanding population. Quoting Zvimba communal land as an example of the effect of population pressure on deforestation, Whitlow pointed out that it had taken only 20 years for the region to have been transformed from a predominantly woodland landscape to one almost devoid of trees, to the extent that the rural population was having to resort to burning crop residues and dung for fuel.
Rangeland degradation This is the lowering of the productive capacity of grazing lands to support livestock. It occurs as a result of excessive livestock populations, inadequate pasture management, or both. Currently, the smallholder livestock population stands at a stocking rate of 5.5 hectares per Livestock unit (including cattle, goats, sheep and donkeys). The recommended stocking rates vary from 4 hectares per Livestock Unit (LSU) in Natural Region II to 10 hectares per LSU in Natural Region IV, but higher for degraded land. It is quite clear from these figures that the grazing lands are overstocked by several times the recommended rates.
SOCIO-ECONOMIC CAUSES OF SOIL DEGRADATION In Zimbabwe, farmers are rapidly destroying the soil which they depend on for existence (as already indicated), though some knowledge is available on the causes and processes of soil formation, degradation and erosion and on the methods and techniques of conservation and reclamation. Land use pattern is affected by socio-economic factors such as land tenure, population pressure, economic conditions, social structure and educational standards. Only when these controlling factors are identified and their linkages and interactions recognized and taken into account is it possible to formulate a programme which has any possibility of producing optimum production potential and at the same time preserve or even increases resources of soil and vegetation. This section assesses the social, economic, political and institutional policy environments in the context of soil degradation in Zimbabwe. It then examines the fundamental relationships between the above factors in the context of cause and effect relationship or causal nexus. 132 Socio-economic aspects of soil management for sustainable agriculture and food security
Land distribution Zimbabwe has a relatively large agricultural base. Approximately 82% of the total land area of 39 million hectares (i.e. 32 million hectares) is classified as agricultural land. The rest is mountains and National Parks. The distribution of this agricultural land is the result of historical events which saw the peasant population being pushed off the better land into areas that are unproductive. There are about 4,500 large-scale commercial farmers on 11 million hectares of land, who use capital intensive, high cost technologies to produce over 70% of the value of agricultural output in most years. The smallholder sector is largely traditional (i.e. uses low cost and inefficient technology) with nearly 6 million households living on about 22 million hectares of land that has the lowest agricultural potential. Table 2 shows land distribution by farming sector and by Natural Regions. The five regions commonly referred to as Natural Regions or Agro- ecological regions are based on moisture availability for agriculture.
TABLE 2 Major features of farm sub-sectors in Zimbabwe Small-scale farms Large-scale farms Communal Resettlement Small-scale Large-scale Parastatal area area commercial commercial Government Number of farms 1,000,000 56.794 8,500 4,832 55 Total area (million ha) 16.34 3.29 1.38 10.74 0.42 Share of total agricultural 50.8 10.2 4.3 33.4 1.3 land (%) Average farm size (ha) 18 58 162 2,223 7,644 Of which is arable (ha) 3-5 3-5 10-40 highly varied highly varied % of land in: NR I 0.86 0.9 0.7 1.8 2 NR II 7.8 17.9 17.4 32.9 2 NR III 17.2 37.7 38.4 21.5 32 NR IV 44.9 24.6 36.2 21.7 12 NR V 29.2 18.8 7.2 22.2 52 Irrigated area (000 ha)5 7.2 3.6 126 13.5 Share of national 21 44 35 woodland area (%) Estimated population 5.327 421 166 1,160 38 (000)7 Pop. density (P./sq km) 32.6 12.8 12.0 10.8 9.0 Cropping intensity 14.0 5.8 4.3 4.2 2.3 (Planted area/Total area)(%)8 Livestock stocking rates 5.5 8.2 6.4 (Ha/LSU)9 Notes. Community cited estimate; A. As for April 30, 1994; B. CSO, 1994; C. CSO (1993); D. FAO (1993); E. Bradley and McNamara; F. Census (1992); G. Masters (1991); H. Cattle = 0.7 LSU : Sheep/goats= 0.15 LSU; I. For 1989/90 from Masters (1991)
Most of the land suitable for intensive farming, in regions I, II and III, was allocated to commercial farmers and the less productive regions IV and V were allocated to small-scale farmers. In fact over 70% of the smallholder farmers occupy the marginal regions IV and V.
The misallocation resulted in efficient use of land and low per caput income for the smallholder farmers. Because of the relatively small areas of land allocated and consequent population pressure in smallholder areas, the poor quality of the land and poor agricultural support services resulting in relatively unimproved traditional farming practices, the productivity of the land progressively declined over the years. This situation, coupled with the discrimination Integrated soil management for sustainable agriculture and food security in Southern and East Africa 133
in the provision of infrastructure, combined to restrain production and increase land degradation in the smallholder sector. With 70% of the rural people residing on land mostly of poor to marginal potential, population densities have long exceeded the land’s carrying capacity, resulting in serious degradation of land and land resources. The bulk of Zimbabwe’s population is exerting pressure on land that is naturally fragile and prone to soil erosion, fertility depletion and deforestation.
Land tenure Land tenure is important to soil management because it governs the size and quality of land available to agriculture and hence the scale of its economic potential and capacity for resource investment. The type of land tenure may be important in determining the availability of bank or other funds for financing of agricultural inputs. Land tenure may affect the scale of soil conservation investment. Confidence in ownership may tend to promote soil management whilst lack of assurance may not.
With regard to Zimbabwe, land tenure coupled with distribution have been the dominant factors in the pattern of agricultural production and the most important cause of soil mismanagement. Four main types of land tenure systems prevail as defined by who has the rights over the land. These are : · Communal, where a defined group of smallholder farmers has the right but no title to the land (found in the communal areas). · Private, where an individual legal entity has the rights (common in large -scale farms). · State, where the public sector has the right. · Resettlement, where tenants have the permit to live and cultivate but have no legal rights over the land.
The communal tenure system is composed of traditional villages comprising a defined group of households with defined village boundaries. In each traditional village land falls into two categories: · Traditional Freehold Land: for arable and residential land allocated to a family, which will have the right to bequeath and subdivide amongst family. · Village Communal Land: includes grazing, forests and sacred areas administered through traditional heads.
The traditional heads also administer any changes on traditional freehold land. The communal area freehold system is ideal for investment and any form of development as evidenced by the existence of orchards, boreholes, fences, modern tile or brick houses, etch in the homesteads. The issue of land degradation emanates mainly from the management of village communal properties (grazing, forests, rivers and dams). These resources are utilized as “commons”, and this approach does not lend itself to effective management of these resources. Over-exploitation and poor land husbandry are common practices in such areas leading to problems such as overgrazing and siltation of dams. Local heads lack the powers to legally administer the use of the common resources. A person can cut down trees at will without any punishment. There is no limit to the number of cattle a household can own and in most cases livestock numbers exceed the carrying capacity, thus putting pressure on the land. The tenure system in the resettlement areas is such 134 Socio-economic aspects of soil management for sustainable agriculture and food security
that participants enjoy precarious tenure at the pleasure of the state. Households have the permit to cultivate, but there is no right to bequeath and subdivide amongst family members. The settlers are viewed as Zimbabwe’s first tenants, growing cash crops under public supervision on state land. The farmers are directly supervised by a resident Resettlement Officer, who has the right to cancel off the permit at any time if the settler does not comply with the rules and regulations of resettlement farming. Grazing lands, forests and water resources are communally owned by the settlers and usually over-exploited, just like in the communal areas. Most of the resettlement schemes have experienced indiscriminate cutting of trees, overgrazing of rangelands and siltation of dams and weirs.
Although there is little evidence that farmers would rather leave the resettlement schemes than submit to the climate of over-regulation that prevails there, there is a disturbing tendency among some settlers to sit back and wait for the state to deliver services rather than provide for themselves through entrepreneurship or collective action. The system discourages farmers to invest in land conservation measures since their future rights to use the resources are not secure. Land tenure is also an issue affecting soil management in smallholder irrigation schemes. Irrigation schemes by their nature require huge investments in implements (e.g. tractors, water meters, conservation, labour and inputs). This investment can only be possible if farmers have confidence in security over the land. Furthermore most of these investments need financial support from banks, who demand collateral or security of tenure. The prevailing system in the smallholder schemes (i.e. direct control by the government) does inhibits farmers from committing themselves into huge investments and disqualifies farmers from getting bank loans. Private ownership facilitates private investment in technologies which prevent or address the effects of soil degradation, as evidenced by high levels of management and productivity in the commercial farms.
Land shortage It has always been recognized that land is a finite resource, but only recently (at the turn of the 20th century) has the full impact of this fact occurred. Food shortage or poverty by smallholders could be combated by taking new, unused land into cultivation (a system called shifting cultivation). As soon as the fertility of the soil was exhausted a new piece of land was opened up and the old one was left fallow to regenerate. The extent and type of agriculture was thus in harmony with nature. By about 1920 - 1930, this situation was no longer possible as a general practice in Zimbabwe and is virtually unknown today. The rapid increase in population over the years (at a rate of 2.5 - 3% per annum) coupled with the colonial government’s confiscation of larger proportions of available land area for large-scale commercial farming, created land shortages in the smallholder sector, thus making shifting cultivation impossible. The smallholder farmers were forced to continually cultivate the same piece of land as a way of contending with land shortage problems. With this system soil erosion began to increase and by the mid nineteen seventies, overgrazing, deforestation, soil erosion, declining soil quality, siltation of rivers declining groundwater reserves and general signs of desertification had reached alarming proportions (Elwell, 1974, 1983).
Today there is almost no unused but usable land in the smallholder sector. All of the best land is already taken up and that which is not cannot be used agriculturally on a sustainable basis. Farm sizes range from an average of 18 hectares for communal areas, 58 hectares for resettlement areas and 162 hectares for small-scale commercial farms. (These figures contrast with an average of 2,550 hectares possessed by large-scale commercial farmers). With regard to arable lands, average farm sizes for communal lands and resettlement areas are 3-5 hectares and Integrated soil management for sustainable agriculture and food security in Southern and East Africa 135
10-40 hectares for small-scale commercial farmers. These small land holdings lead to severe economic pressures on farms (especially in the communal areas)to obtain sufficient needs. Because of such pressure in the short term, labour, land and capital resources can not be spared to care for the land, for example soil conservation structures.
A 1991 survey of households in three communal lands in the Mashonaland West Province reveals the land degradation impact of increasing population density (land shortage) in communal lands (Mehretu and Mudima, 1991). The findings from three communal lands : Zvimba in Natural Region I, Mhondoro in Natural Region II and Mupfure in Natural Region IV are given in Table 3. Households were interviewed to get their views on the changing land quality. A majority of households in all three communal lands reported that their lands were undergoing severe stress from over cultivation (Table 3). Over 50% of the households reported a decline on maize yields over the last ten years. 30% of the households reported that grasslands have become poor and depleted. Forest land depletion is high in communal lands with high population densities as experienced by Zvimba in Natural Region II. Mupfure, located in Natural Region IV (NR IV) suffers the least amount of deforestation because of low population density. Ten years ago, about a third of households in Zvimba (NR II) met their domestic fuel requirements from collected wood as compared to only 16% today. In Mupfure (NR IV), which has the lowest population density of the three communal lands, all households still collect domestic fuel wood from forested areas.
Table 3 reveals that one third to half of the households in a communal land cut down standing forests to meet their fuel requirements. Most households in high density Zvimba have begun buying wood for domestic needs, The overall pattern is one of continuing degradation of the land resources, including soil, under increasing population density. The last 5 rows of Table 3 clearly demonstrate how forest depletion is a direct function of population density (refer to Table 4 for density figures). High population densities are accompanied by a high degree of forest depletion, reduced availability of collected wood, high incidence of chopping down of forests and increasing need to buy wood for domestic use.
TABLE 3 Household views on changes in land potential in communal lands (percentage of household reporting) Communal Lands Zvimba Mhondoro Mupfure Natural region II III IV Reduced land capacity 86.4 70 75.0 Farm land over cultivated 56.6 66.7 60.0 Experiencing land deficit 37.7 28.5 32.5 Land under pressure 70.8 52.3 55.0 Decline in maize yields 59.7 42.0 57.5 Poor (over-grazed) pasture 77.3 65.4 82.5 Poor (depleted woodlands) 77.4 64.6 10.0 Fuel wood used to be collected 10 years ago 58.8 96.9 100.0 Fuel wood still collected at present 16.2 61.1 100.0 Wood fuel obtained from tree cutting 28.6 55.3 40.0 Wood fuel purchased 53.2 10.0 00 Source: Mehretu and Mudimu (1991). 136 Socio-economic aspects of soil management for sustainable agriculture and food security
TABLE 4 Household profile in three Communal Lands, 1991 Communal Lands Zvimba Mhondoro Mupfure Natural Region 11 111 1V Population density 56.1 50.5 11.3 Land holding per household (has) 2.4 2.0 2.3 Changes in acreage over last 5-10 years % reporting no change 89.6 87.7 82.5 % reporting increase 5.8 6.2 12.5 % reporting decrease 4.5 5.4 5.0 Average household size, all members Resident members 4.6 4.2 4.2 Non resident members 2.5 2.2 2.9 Average age of residence 19.2 16.4 27.5 Average age of resident females in years 24.1 21.0 22.5 No of years of schooling 6.5 6.4 6.6 % households in agriculture 95.5 93.1 87.5 % households with small enterprises 12.3 25.2 7.5 % households with other non-farming 53.9 64.1 75.0 activities % households experiencing food deficit 9.7 24.4 42.5 % households reporting : Resettlement as immediate solution 42.9 23.7 17.5 Occasional or no use of extension 68.2 83.1 82.5 Extension inputs not affordable 42.9 39.2 42.5 Mean annual household income (Z $) 4,365 3,020 2,052 Source: Mehretu and Mudimi (1991) ; CSO (1990).
Poverty Smallholder areas have few economic opportunities due to low agricultural production and poor infrastructure. Most of these farmers are resource poor and cannot afford to purchase the necessary inputs to increase production. The low levels of agro-industrial development and non agricultural activities result in few alternative forms of employment and income generation in rural areas. Farmers are therefore caught in a cycle of poverty, defined as access to basic necessities of life. Poverty leads to soil degradation. It can be shown that richer farmers maintain their soils in better state than poor farmers. The 1994 enormous survey of the state of arable lands in the commercial sector, where management is generally high, showed that the cropping potential of 12% of the available arable land has been damaged (Elwell 1988). This is lower than 23,2% recorded for the poverty stricken smallholder farmers.
Population According to the 1992 population census, the estimated total population for Zimbabwe at the end of the year was 10,4 million. This implies a total population of 12 million in 1997 (at a growth rate of 3%) and 293,5 million in 2110 when the population is expected to stabilize. The total population density for the country, according to 1992 census results, measured in persons per square kilometer is 26. For communal areas farms, it is fairly high, more than 32 while in commercial farms it is only 9. With the above rate of population growth, Zimbabwe will have to increase its food supplies 28 times over the next 113 years just to maintain the 1992 standard of nutrition.
This can be achieved through increase in land under cultivation and/or increase in average productivity of land. The present state of affairs for both strategies looks impossible for Integrated soil management for sustainable agriculture and food security in Southern and East Africa 137
Zimbabwe. A research by Whitlow (1988) seems to justify this point. He found a correlation between erosion damage and population density with high density of settlement almost invariably associated with widespread soil erosion. He found 57% of communal lands to be overpopulated, some grossly so, and pointed out that this inevitability resulted in a cycle of ecological degradation having adverse effects on living standards, which in turn, limits the ability of people to reverse the downward trend. It can be assumed therefore that the increase in degradation per head of population is not linear but probably exponential in form. In view of Zimbabwe’s population growth rate, future prospects are grim.
Changes in attitudes This is a contributory factor not always appreciated by outsiders. Prior to independence in 1980, most smallholder farmers accepted the situation into which they were born (i.e. subsistence cultivation of annual crops) even if it was one of relative poverty. With the improvement of rural infrastructure (roads, communication etc.) smallholder farmers were influenced to have greater aspirations (e.g. expansion of maize production), thus increasing area under cultivation. This was a transformation in line with changing economic environment. This had an effect of exerting more pressure on the already cultivated land, thus leading to degradation.
Lack of resources Smallholder farmers lack almost all basic factors of production (i.e. land, labour, capital and entreprenuership). Lack of land resources result in excessive local population pressure which puts the ecosystem beyond its carrying capacity at the level of inputs and technology currently being practiced.
Capital. This is a major constraint in that smallholders have very low incomes to allow purchasing of farm inputs. This lack of capital prevents smallholders from carrying out work to deal with the problem of soil degradation. Lack of adequate financial resources also prevents the government from practicing methods which would solve soil degradation problems.
Labour. Smallholder farmers usually experience labour shortages for intensive activities such as contour ridging, reclamation of gullies, etc.
Entrepreneurship Lack of adequate technical knowledge and extension support limit farmers from practicing methods which would solve the soil degradation problem.
Defective organization or policy In the period following Independence, (1980-1988) the new government adopted a reconstruction policy for the agricultural sector with the emphasis placed on providing agricultural services and support for the smallholders. These services and support policies covered marketing and pricing programmes including the provision of marketing infrastructure such as depots at various districts to cater for the smallholders. In response to the favourable conditions, smallholders increased their agricultural output (particularly maize and cotton.) This growth in output was achieved through expansion of planted area. Because of the relatively small areas of arable land available, the smallholders expanded into marginal areas thus initiating destruction of land resources. 138 Socio-economic aspects of soil management for sustainable agriculture and food security
Defective planning of agricultural projects Over the past decades, to date, all agricultural projects (e.g. smallholder irrigation schemes), were primarily predicated on financial, economic or social grounds, with most of the development aimed at achieving self sufficiency, production of export crops and raw materials for the industrial sector. There was no legal requirement for some form of environmental impact assessment in the feasibility studies of these projects. Environmental considerations were purely at the discretion of the planners involved. As agricultural development proceeded in the country, new areas of development began to encroach areas that are marginal for agricultural development and where risk of environmental damage is great. Examples of such areas are those with soils that are marginally suited for irrigation, areas of poor water quality, or areas that are marginal in both respect (see under Salinization).
LAND SHORTAGE, POPULATION, POVERTY AND SOIL DEGRADATION: THE CAUSAL NEXUS The socio-economic causes of soil degradation are linked by a chain of cause and effect or causal nexus (Figure 1). The two exogenous driving forces are limited land resources and increase in population in the smallholder areas. This means there are no longer substandard areas of usable, unused land in the smallholder areas, but the number of people supported from this finite land is increasing every year (at a rate of 3%). These two primary forces combine to produce land shortage. This refers to increasing pressure of population on land (marginal lands for most smallholders), resulting in small farms, low production per person and increasing landlessness. A consequence of land shortage is poverty. Land shortage and poverty, taken together, lead to non sustainable soil management practices, meaning the cause of degradation. For reasons outlined above, poor smallholder farmers are led to clear the forest, cultivate steep slopes without conservation, over graze range lands and make unbalanced fertilizer application. The non sustainable management practices lead to degradation. This leads to reduced land productivity; a lower response to some inputs or, where farmers possess the resources, a need for higher inputs to maintain crop yields and farm incomes. This has the effect of increasing land shortage, thus completing the cycle.
Other causes Under this heading are the direct causes of soil degradation (unsuitable land use and inappropriate land management practices), which include: deforestation of unsuitable land, over cutting of vegetation and overgrazing.
Deforestation of unsuitable land. Deforestation becomes a cause of degradation when the land that is cleared is steeply sloping, or has shallow or easily erodible soils and where the clearance is not followed by good management. The extent of deforestation as a type is given in Section 3. It is the leading cause of water erosion in steeply sloping environments and also a contributory cause of wind erosion, soil fertility decline and salinization.
Over cutting of vegetation. Communal and resettlement people cut natural forests, woodlands and shrublands to obtain timber, fuelwood and other forest products. Such cutting becomes unsustainable where it exceeds the rate of natural regrowth. This has happened widely in densely populated areas, where fuel wood shortages are severe (see section on land shortage). Impoverishment of the woody cover of trees is a major factor causing both water and wind erosions. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 139
FIGURE1 Cause and effect of land degradation
Causal nexus between land, population, poverty and soil degradation
Increase in smallholder population
Land shortage
Poverty Limited land Soil degradation resources
Non-sustainable soil management practices
Source: FAP (1994). Land degradation in South Asia: Its severity, causes and effects (Rome, Italy)
Overgrazing. Overgrazing is the grazing of natural pastures at stocking rates above the livestock carrying capacity. It leads directly to decrease in the quantity and quality of vegetation cover. This is a leading cause of wind erosion and also water erosion in dry lands. Both degradation of the vegetation cover and erosion lead to a decline in soil organic matter and physical properties, and hence in resistance to erosion. The stocking rates for the communal areas are given in Table 2 under Rangeland degradation.
CONSEQUENCES OF SOIL DEGRADATION The consequences of soil degradation are many and varied. Some are quantifiable and some are not. The effects can be considered at two stages; effects upon production and consequences for the people.
Effects upon production Soil degradation affects crop, livestock and forest production. The effects depend on type and extent of degradation. The effects in Zimbabwe are as follows:
Land abandonment. The exact area which has been abandoned for cropping because of declining fertility or any other form of soil degradation is not known. However, there is no doubt that it forms a significant proportion of what was once the potential arable areas. Abandoned arable lands can be seen in all parts of Zimbabwe and some very extensive stretches occur in Mutoko and Sabi Valley areas (Elwell 1990). These areas are characterized by very gravelly surface or by compact partially weathered sub-soil (Elwell, 1990). 140 Socio-economic aspects of soil management for sustainable agriculture and food security
Reduced productivity. Declining soil fertility in smallholder areas is leading to unsustainable production levels. (e.g. maize yields in Zvimba, Mupfure and Mhondoro area). There is a closer relationship between the depth and humus content of the soil and crop yields. When the rich top soil is removed or degraded, productive capability falls rapidly. Some other factors contributing to lower yields are: · Leaching and washing out of plant nutrients and fertilizer particularly potassium and nitrogen. · Deterioration of soil structure and texture due to reduction in organic matter, the washing down of finer particles and exposure of sub-soil. · Reduction of soil depth so that there is less soil available to plant roots, greater loss of water due to runoff and decreased moisture availability during dry periods. · Poor aeration of soil during rainy season because of poor structure and reduced depth. · Chemical imbalance such as increasing salinity.
Livestock production levels are also affected by soil degradation since the quality of range lands is a function of how well the land is managed.
Greater need for agricultural inputs. The level of poverty of many smallholder farmers in Zimbabwe is such that they cannot accept the consequences of reduced crop yields or lower livestock production. Instead, they try to maintain their crop production levels by means of increased inputs (soil from anthills and manure from forests) and in the case of livestock they attempt to maintain livestock numbers despite a reduced carrying capacity of pastures, thus leading to a vicious circle of further degradation. The other reasons for wanting increased inputs are: · Less favourable soil texture and structure increases energy requirements for cultivation and decrease the range of moisture content within which the soil can be worked. · Increase in the number of rocks and stones on the surface impedes cultivation and leads to wear and breakage of implements.
Reduction in the value of land, loss of land. As soon as erosion or any form of soil degradation begins, the productive capability of the land starts to fall, and with it the value of the land. If degradation continues the area loses all capacity to produce and becomes a desert, having almost no value. This is a financial loss to the owner and a permanent loss of resources to the community and the nation.
Reduced responses to inputs. It is conventionally accepted that fertilizers are best utilized by application of low to moderate amounts, whilst seeking to obtain high responses. Land degradation, particularly lowering of soil organic matter, has the opposite effect, that of lowering fertilizer responses.
Loss of flexibility in cropping pattern. Reduced crop yields force smallholder farmers to grow only staple food crops (e.g. maize, sorghum, and millet). Again this has an impact on soil management, since continuous grain production causes further decline in soil fertility.
Greater risk. Smallholder farmers are risk averse when it comes to agricultural production (especially in dry areas such as natural regions IV and V). The recurrence of drought in these Integrated soil management for sustainable agriculture and food security in Southern and East Africa 141
regions make crop production a risky business and because of this, farmers tend to be reluctant to use scarce capital or fertilizers.
Reduced productivity on irrigated land. A specific case of lower crop yields and reduced responses to inputs occurs on smallholder irrigation schemes which are widespread in the country. These irrigation schemes have been established at high cost, whether capital, as in surface and sprinkler systems, or labour, as in the case of hand-dug small earth dams. Lowered productivity as a result of soil fertility decline and waterlogging reduces output from smallholder irrigation schemes, leading to inefficient utilization of scarce capital and labour resources.
Siltation. Vast quantities of soil eroded from fields and hills are washed into rivers dams or weirs. Deposition of such large quantities of soil in rivers and dams has adverse effects. Storage capacity is reduced far more quickly than expected, and dams designed to last 100 years or more become almost useless in twenty or thirty years. If there is an irrigation scheme associated with the dam, this means there is less water for irrigated crops, incomes fall and they must eventually be abandoned. Figures from measurement of siltation in 1974 revealed that silt load in the Mazowe river is causing a loss equivalent to 6-7 hectares of top soil each day the river was in flood. A random survey of 16 important dams contacted in 1983 in Masvingo and TABLE 5 Matabeleland Provinces showed five of Details of sheet dam and its catchment 2 them to be more than 100% silted and 8 to Catchment Area 464.75 km Impounded Date 13/9/46 be more than 50% silted. A more detailed Mean Annual Rainfall 500 mm survey of 132 small to medium size dams Original Capacity 1.49 * 106 km2 in Masvingo province (1983) showed 16 to Present Capacity 0.658 * 106m3 be fully silted and more than half to be Decrease in Capacity 0.491 * 106 or 42.7% 6 over 50% silted. Thus, these figures would Annual Rate of Siltation 0.0109 * 10 or 0.95% indicate that by 1983 some 12-13% of dams in this region were totally useless and 50% of structures had less than half their capacity (Elwell, 1985). A silt survey of Sheet Dam (in Matabeleland South Province) carried out in July/August 1990 also gives some striking results about the state of reservoirs in Zimbabwe. The results of the survey are given in Table 5.
The original full capacity of the dam was 1.149 * 106m3 and the present capacity is 0.658 * 106m3. There has been 42.75 reduction in capacity due to siltation over a period of 45 years. Both human activities and natural factors had a significant effect on this high rate siltation. The results of these surveys are by no means a complete reflection of the state of siltation in Zimbabwean dams. They only represent merely the foreboding tip of the iceberg. Large numbers of dams and weirs throughout the country in both commercial and communal areas are already full of silt. There is no practical way of reclaiming them. Alternative sites being second choices, are bound to be more expensive and less effective than the first choices: and they too will inevitably fill with sediment. The only feasible solution is to remedy the cause of the problem (i.e. control the erosion).
Effects for the people The effects of land degradation have impacts on the living conditions of the smallholder population and these include: 142 Socio-economic aspects of soil management for sustainable agriculture and food security
· Food insecurity. As the soils deteriorate in quality, food security becomes more and more difficult to ensure; in fact no longer guaranteed (Elwell 1992). Lowering of crop yields means reduced production of food crops and subsequent food insecurity. · Increased labour requirements. Reduced crop yields means low returns to labour. Labour used in reclaiming or rehabilitating the soil environment is labour lost from production. · Lower incomes. Lower incomes is the most serious consequence of soil degradation in the smallholder areas. These result from either increased inputs or reduced output or both. With soil degradation all the factors of production, of capital and labour are inefficiently applied and productivity and subsequent incomes are lowered.
CONSTRAINTS AFFECTING SMALLHOLDER TECHNOLOGY ADOPTION Adoption of modern technology for soil management by smallholder farmers is influenced by personal attributes of the farmer, farming systems and resource characteristics, institutional and infrastructural and environmental factors. Personal attributes of the farmer include age, level of education and sex. Farming systems and resource characteristics comprise cultivated area, family size, and availability of appropriate inputs such as fertilizer, seed, machinery, equipment and the liquidity position of the farmer. Institutional and infrastructural factors cover laws and regulations governing the supply and accessibility of credit, extension advice, training and input markets. Environmental factors, basically agro-ecological potential and capacities, give farmers and input suppliers incentives to participate subject to extended gains.
Personal attributes Older farmers and the less educated are less likely to adopt new technology. This could be due to inability to fully understanding the technology and the associated risk. Sex has also been found to be a factor in technology adoption with women being less likely to adopt than men. None or late adoption by women is related to tendency to consult absentee husbands as well as lack of control of the little available household income. Personal attributes were found to be pertinent in adoption of technologies for soil fertility management in Resource Integration Research undertaken in Zimbabwe, Kenya and Zambia and funded by EU and Danida (TSBF, 1996).
Awareness, perceptions and interpretation of land degradation Soil degradation is a very slow process and almost invisible, e.g., sheet erosion. Therefore it may not be perceived as an immediate problem. According to observations from many African countries, farmers attribute deterioration of crop yields to declining rains (TOIT 1995). There is clear evidence that during the past 20 years droughts occurred more often than the decades before. However, soil degradation may also have affected the water holding capacity and thereby reduced the soil’s ability to overcome situations of stress. Very likely, this process may also have contributed to the decline of yields. As long as farmers do not perceive soil degradation as a major determinant of decreasing yields this trend will certainly not be reversed (Shaxson, 1985).
Farming system and resource characteristics Small-scale farmers usually control limited quantities of land. Because of small land size, they are not able to take advantage of improved technology, new managerial practices and adopt the use of more profitable enterprise combinations. Communal area farms, because of small arable land holdings, do not have adequate land to set aside for two to three years under legume tree Integrated soil management for sustainable agriculture and food security in Southern and East Africa 143
improved fallows which has been shown to increase maize yields. Size of family has an impact on labour availability. Where the household comprises mainly school going children this negatively affects adoption of soil management practices. Application of top dressing fertilizer, manure and ant hills are all labour intensive. In research carried out in Northeastern Zimbabwe, resource endowment was found to influence farmers’ choice of soil fertility management techniques. Farmers with many cattle were found to use termitarium soil. Farmers who had scotchcarts and were on rich soils were found to use compost (TSBF, 1996). The liquidity position of the farmer affects his ability to invest in soil improving technology. A substantial proportion of available income is invested in non-production activities i.e. education (in the form of school fees, text books and uniforms) and household consumption. Education is the largest investment expenditure. There is little cash income to meet adequately the investment required in agricultural production. As a result farm households are not able to purchase sufficient yield increasing inputs needed to improve crop productivity.
Institutional factors Lack of coordination among implementing agencies: The management of natural resources in Zimbabwe is the responsibility of several government departments, parastatals and non- governmental organizations (NGOs). Government departments include the Department of Natural Resources, through the Natural Resources Board (NRB), with the responsibility of policing and advising government on the implementation of natural resources management strategies, Agritex (which provide technical knowledge on soil conservation and management) and the Department of Water Resources (responsible for catchment management).
The Forestry Commission through the Rural Afforestation Division plays a crucial role in afforestation activities including the establishment of village nurseries and woodlots. The District Development Fund (DDF) implements water related projects (including boreholes, dams, irrigation schemes) in the smallholder areas. NGOs are quite numerous and they include CAMPFIRE, SAFIRE, and ENDA Zimbabwe among others. This multiplicity of institutions creates problems in that priorities in terms of resource allocation between agencies are not coordinated. For example construction of an irrigation project by a NGO is not accompanied with the allocation of funds for conservation works. There is a number of smallholder irrigation projects which were developed by NGOs without conservation works, due to the fact that they consider conservation to be Agritex’s responsibility. But in most cases Agritex is not informed about the need for conservation works and in some instances, even if they are informed, they lack financial resources to undertake the works.
Another shortfall in agricultural project development is the lack of coordination between the implementing agencies and the beneficiaries. Farmers are usually not involved in the overall planning and management of projects, yet they are expected to produce on a sustainable basis. As long as the proposed project or improvement is not demonstrated to serve farmers’ interests they will not participate in proper resource management.
Agricultural research and extension: Up to 1980, the national research system focused on generating technologies for the large scale commercial farms located mainly in high rainfall areas. The thrust after 1980 was to develop sustainable crop and livestock production systems suited to the low rainfall areas. But to this day, the recommendations on soil fertility improvement are general. There is no close contact between the researchers and smallholder farmers in terms of specific recommendations. The soil testing facility that is available to farmers is inaccessible to a 144 Socio-economic aspects of soil management for sustainable agriculture and food security
communal farmer in the remote areas with poor access to information and communication facilities. Another area which needs attention is the identification of research areas. Generally research work is done in areas which are accessible to researchers and in many cases far away from the beneficiaries. Results obtained from such research can not by any means address the problems of smallholder farmers. Their direction and contents tend to reflect the interests and professional goals of the researchers. In most cases, the results are published in the form which is unusable by the extension worker at grassroots level. It is helpful to have farmer based research, which involves the identification of problems together with the farmers and the collective implementation of the research work.
In Zimbabwe, delivery of technology was improved by adopting alternative extension strategies with emphasis on farmer groups. Mobility of extension staff was also improved through provision of motor cycles (AEWs) and cars (Officers) through World Bank loan in 1990. More staff, particularly farm level AEWs were hired to reduce the AEW: farmer ratio from 1: 2,000 before 1980 to 1: 500 - 800 after independence. These were posted to ward and village levels. Of late, with the pressure to reduce public spending, the extension services is no longer well provided for. Salaries are low compared to the private sector. The budget for field duty allowances is very small virtually grounding extension staff for weeks if not months. Courses designed to train extension staff and keep them up to date with the latest technology are often times canceled due to lack of funds. The pool of vehicles and motorcycles given to Agritex through World Bank in 1990 have already surpassed their economic lives, therefore need replacement. Extension officials sometimes have to use buses or bicycles to go to work. This is not an ideal situation for sound agricultural development.
All these factors negatively affect extension delivery and therefore limit smallholder farmers’ ability to adopt improved technological innovations.
Local Traders. There are inadequate inputs at the local level. Farmers are forced to source inputs from urban based suppliers. Local traders fail to stock adequate levels of agricultural inputs due to cashflow problems, lack of transport facilities as well as lack of storage. This lack of inputs locally is problematic because farmers have to pay a lot to transport inputs from far away centres. When farmers organize themselves and purchase in bulk inputs are never delivered in time. Large input suppliers do not give priority to low income farmers. They deliver last and only when high volumes of inputs have been ordered.
Credit. The Zimbabwean experience after independence shows a direct relationship between availability of credit to smallholder farmers and increase in agricultural input use. With the extension of the AFC’s mandate in 1979 to cover the smallholder sector, the number of loans to communal farmers rose from 18 000 (valued at Z$4.2 million) in 1979/80 to 76 000 loans with a nominal value of Z$40 million in 1985/86. This stimulated quantity of purchased inputs such as fertilizer and improved seed. The quantity of fertilizer purchased increased from 25-30 thousand tonnes in 1978/79 to 130,000 tonnes in 1985/86. Delivery of improved seed to the small farm sector rose from 4,250 tonnes in 1978/79 to 22,000 tonnes in 1985/86. Thus the expansion in credit facilities in the communal lands enabled more farmers to have access to yield augmenting resources. The 1985/86 season was the peak in terms of credit extension to the smallholder sector. By 1992/9 season the number of loans was down to 15,221. The major reason for the fall in loan extension to the smallholder sector was high default rate. The AFC would generally not lend to farmers in default. Reasons given by farmers for having failed to repay as scheduled included drought and low repayment capacity. Farmers complained that in cases where they Integrated soil management for sustainable agriculture and food security in Southern and East Africa 145
decided to honour their debts, they remained broke and could not pay for their other commitments like school fees, clothing and other household costs. While the majority of non current borrowers stopped borrowing because AFC would not lend to farmers in default, there are some who paid up and yet did not want to borrow again because of what they term poor service from the AFC. This poor service included failure by the institution to give farmers correct loan statements. Some smallholder farmers have limited information about available sources of credit, terms of loans and correct structuring of farm debt. Some farmers observed neighbours or relatives who were financially stressed from borrowing lose their farms and /or equipment because they were not able to repay the debt. This has resulted in the farmers wanting to remain debt free because of fear of farm closures. Without adequate credit, the farmers cannot invest in productivity enhancing technologies such as fertilizers. Credit finance is important in the purchase of capital equipment such as tractors and scotchcarts. Other sources of finance include crop sales, livestock sales, remittances and other non form activities. But these sources are not significant enough for the purchase of capital equipment. Low outputs due to low inputs means that there is little left for investment once the living expenses of the farmer have been deducted from farm income. Low investment in livestock, machinery, buildings, conservation, and so on will keep the farm’s incomes low, and so the cycle conditions. In a study of smallholder credit situation in Zimbabwe carried out in 1993 by Vudzijena, non borrowers ranked their sources of money for inputs purchase as follows : Crop sales 80% Livestock sales 28% Remittances 15% Local job 4% Personal savings 28%
This means that in the event of a drought, the average non borrower needs credit to finance the next season’s inputs to maintain his usual productivity.
Marketing. Smallholder farmers are generally long distances away from markets. Because of this they suffer from poor market information. The situation is aggravated by the lack of marketing intelligence system and storage and packaging facilities. With the opening of the economy, marketing has become central in production economics, especially on the aspects of what to produce, how to produce and how much to produce. Without markets there is no point producing and even managing the factors of production (e.g. soil resources).
Transport. Shortage of transport in communal lands where the majority of smallholders are, restricts the operation of private market, raises marketing costs and diminishes farmer access to outlets. Improved transport systems and in particular the development of a comprehensive and flexible private network of medium and small trucks is likely to be a pre-requisite for effective expansion of private sector marketing systems for both agricultural inputs and outputs.
Infrastructure. While the Zimbabwe rural road system is generally well developed, the feeder road system in most communal, resettlement and small scale commercial farming areas is in a deplorable state with most of the roads impassable during the wet season. The inadequate rural road system is one of the main factors affecting the growth of the rural transportation system and has given rise to inefficient input supply and produce marketing systems. Smallholder farmers in a majority of cases, do not receive inputs at the right time and in the required quantities. Inputs such as fertilizer and seed are often delivered as late as 146 Socio-economic aspects of soil management for sustainable agriculture and food security
November/December. In addition, because crops cannot be transported to the market on time, high post harvest losses are incurred. The inefficient input distribution system and produce transportation systems severely affects the competitiveness of the smallholder farmers as marketing costs represent at least 25% of total costs per tonne produced in the smallholder sector as compared to 12% for commercial farms (Vudzijena, 1993).
Rural areas are characterized by poor postal and telecommunication systems. Survival in the new economic environment requires farmers to be constantly in touch with the market in order to make timely decisions on what inputs to use, at what levels compared to value of outputs. Smallholder farmers are constrained in their decision making on profitability of enterprises due to poor telecommunication system in rural areas.
Unfavourable trading position Maize is the major crop in communal areas both in terms of numbers of farmers who grow the crop and the proportion of land allocated to the crop. Generally, looking at data from 1986 to 1996 (Table 6), prices of fertilizer have been rising faster than prices of crops produced by farmers. The net result is that farmers have been facing a price squeeze. The price squeeze adversely affects the communal farmers’ income position and their ability to invest in agricultural inputs the following season.
TABLE 6 Fertilizer to maize price ratios in Zimbabwe (1986-1996) Harvest year Compound D Ammonium nitrate Maize (Grade A ) Fertilizer/Maize price ratio 1986 355.6 406.0 180.0 2.1 1987 355.6 406.0 180.0 2.1 1988 416.6 415.4 195.0 2.1 1989 416.6 415.4 215.0 1.9 1990 463.8 416.0 225.0 2.0 1991 655.0 613.0 270.0 2.3 1992 1,048.0 981.0 550.0 1.8 1993 1,048.0 981.0 900.0 1.1 1994 1,296.0 1,222.0 900.0 2.8 1995 1,296.0 1,222.0 950.0 2.7 1996 1,604.0 1,970.0 1,200 1.5 Source: Oni 1997. Note: Fertilizer price changes occur at various times of the year. Prices quoted are generally those ruling at the end of the planting period. The fertilizers/maize price ratio refers to a 50:50 blend of Compound D and Ammonium nitrate.
Technology constraints Available machinery technology for working in the soil is not adequately scaled down to meet the needs of the small farmers. The available machinery requires substantial capital outlay. This results in over-investment and increase in fixed costs of production. The alternative for smallholder farmers has been buying used equipment. However, this means high repair and maintenance costs and increased down time. The machinery technology appropriate for the small farmer should be easy to maintain and free of some luxury gadgets. The equipment should be sized to suit the small farmers’ production systems as well as managerial and technical skills. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 147
CONCLUSION We are living in a challenging period which may even become more and more challenging in the history of agricultural development in Zimbabwe, Africa and the world. If we continue along our present pattern, ignoring the warning signs, the environment is constantly signaling to us, we are doomed for a certain disaster.
From the analysis it is clear that land degradation has reached serious levels in Zimbabwe. It has taken place within the context of a high population density in relation to available land, lack of resources in the small-scale sector, poverty and defective policies.
At this moment, erosion is costing the farmers and the nation vast amounts of money in terms of reduced yields, higher inputs and loss of moisture, nutrients and fertilizer, not to mention the cost of food damage, the siltation of dams and the growing area of barren land.
Radical changes are inevitably needed in our attitudes and practices. The problem should no longer be regarded as one for the future generations.
Attempts to combat land degradation directly by conservation measures have been undertaken in Zimbabwe but with limited success. In fact, this strategy has had provided short term effects. It is clear that the problem will continue unabated unless technical measures are accompanied by efforts to tackle the underlying causes of degradation. These lie in the causal nexus between population increase, limited land resources, land shortage, poverty, non- sustainable management and land degradation. In the prevailing situation in Zimbabwe, in which there is no spare land in the smallholder sector, population increases will largely or entirely counteract the effects of measures for improvement.
A prerequisite for effective action is recognition by the government of land degradation and its effects upon the people, the agricultural sector and the natural economy. It is necessary but not sufficient to pay service to environment or to write reports. There must be allocation of staff, budget and resources.
RECOMMENDATIONS Protection of natural environment is as important to the government as defense of its borders for sustainable socio-economic development. Because of this, the government should ensure that it creates an enabling environment in which the soil user can employ production and management systems which do not lead to degradation of soil resources. In addition the government should put in place an appropriate institutional framework for enhancing farmers’ capacity towards adoption of improved technologies for soil improvement, conservation and sustainable land use and production.
Institutions for environmental management exist in Zimbabwe, but there is need for re orientation and strengthening of their current capacities. In this context, the organizational and institutional framework should enhance linkages between different participating agencies, provide resources and where need be, create new organizations. 148 Socio-economic aspects of soil management for sustainable agriculture and food security
Some of the important aspects which need special attention in the process of transforming soil management include appropriate land tenure systems, efficient credit facilities, research, extension and training, etc.
This section of the paper proposes a conducive socio-economic and policy measures (including the above). as they relate to the limitations and problems previously illustrated.
Guarantee security of tenure The farm productive potential of smallholder lands will be realized only when farmers feel it is truly theirs (an aspect that is lacking in the present system). Farm operators make long term investments to optimize land productivity only when they own the property or have security of tenure. Security of tenure is associated with four main sets of rights: rights to use, transfer rights, exclusive rights and enforcement rights. Tenure security to safeguard communal resources of grazing forests etch in communal areas can be improved through strengthening the powers of traditional leaders and the administering of village communal lands through the traditional village court system. It is recommended to have individuation of rights on a community basis where each community has a well defined territorial boundary over which it has monopoly rights over resource utilization under its control. The grazing land and the common resources should be managed by a local board whose membership would include the local chiefs, headmen, kraal heads, councilors and Village Committee chairperson. Any one found cutting trees or doing any activity which causes degradation should be punished accordingly.
Tenure security on resettlement can be secured by replacing the permit system with two options: · Leases with option to purchase. · Long leases of up to 99 years.
These options can encourage farmers to undertake long term investments suitable for sustainable agricultural production and natural resource management. For new resettlement schemes it is recommended to have individual tenure system, whereby each individual is allocated 60 or so hectares which are demarcated into grazing, arable and residential areas. The individual will have the right over the land under any of the two options given above. This systems can encourage investment and proper management of resources.
Improving the extension service The declining real operational budget for Agritex is a major policy issue requiring urgent attention. Budgeting provisions should be aimed at progressively improving operating exercises. This improvement is necessary to prevent extension officials from becoming office bound because of shortage of funds. The extension service should also have access to reliable vehicles and motorcycles. It is unsustainable to have staff travelling by bicycle, bus service or by old and worn out vehicles liable to frequent breakdowns. The extension service should go beyond production advise and focus on other important elements such as marketing, financial management and leadership. Farmers have realized it’s quite important to have marketing included in the extension thrust. The marketing system of smallholders can be enhanced through the setting up of a marketing intelligence system or marketing information system. The private sector can also participate towards the establishment of such systems if a workable environment is created for them. This system can facilitate the farmers decision making process and even allow them to take risks in their day to day management practices, including managing of soils. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 149
Creation of enabling environment for private traders A key strategy in soil management is to provide incentives which enable private sector participation in the small-scale agricultural sector. This could be done in several ways and these include : · AFC extending loans (at concessionaire rates) to rural traders to allow the purchasing of trucks for transporting inputs and outputs. · Short term loans for restocking are particularly important in alleviating the trader’s cashflow problems.
With a reliable input supply and output delivery system farmers will be motivated to embark on full-scale sustainable production.
Rural infrastructure The government should improve rural infrastructure i.e. road (for input and output delivery), communication (for marketing information and ordering) to help the farmer make rational decisions on what to produce, when to produce, how much to produce.
Mobilization Farmers as a group can do a lot themselves if a conducive atmosphere is put in place. For instance, if farmers are trained and some initial capital is injected by say government or donor agency, farmers can get motivated to take the lead. They can build warehouses for inputs/outputs, can get discounts through bulk purchasing and can enjoy other economies associated with large- scale production. A strategy like this was implemented in the Wedza district of Mashonaland East Province. Farmers were given a revolving fund by a donor to buy stocks for inputs. A lot of training, related to general and financial management was given to the participants to allow smooth running of the business. The farmers operated as traders, buying and selling inputs at a profit. The scheme proved to be successful and until now the farmers are enjoying its benefits which include no transport costs, timeliness of inputs, among others.
Research improvement Zimbabwe has a well developed research system which however, needs some reorientation in a number of aspects. There is need to strengthen research/extension/ farmer linkages to facilitate the flow of information to the farmer. Furthermore the research should be farmer based and not be conducted in areas which suit the researcher. To facilitate the implementation of this strategy, research and extension officials should be thoroughly trained in Participating Rural Appraisal (PRA). This approach is important in fostering communication between the government agencies and the community.
Training Problem solving requires both the will and the intention and capability or expertise. Many of the relationships and processes which result in soil degradation are more or less technical in nature, and may even be difficult for a lay-person to recognize. It is impossible to devise and apply solutions to the soil degradation problem unless both the farmer and technical officials have sufficient knowledge about the subject. It is only through environmental education that communities and staff can acquire knowledge, skills and commitment to adapt to pursue 150 Socio-economic aspects of soil management for sustainable agriculture and food security
development activities in harmony with the environment. Environmental education should also be included in the schools curricula and environmental magazines, and other publications for both children and adults. It should also be broadcast on radios and television. Regular workshops and seminars with school teachers and farmers can also help to address the problem of land degradation. It is also important to suggest alternatives when it is felt that one resource is being overused. For instance, instead of firewood farmers can be advised to use other sources of fuel such as biogas and “tsotso” stoves which use little wood.
It is also encouraged to carry out environmental impact assessment before embarking on major developmental projects (e.g. irrigation projects) to reduce negative impacts on the land and soils. The main purpose of carrying out environmental impact assessment is to ensure that environment, socio-economic costs and benefits of developmental projects are properly accounted for and that unwarranted negative impacts (e.g. salinity in irrigation projects) are avoided. The following is a summary of recommendations for remedying the situation: · Study of the causes of land degradation. · Study of the economic and social effects upon the people. · Translation of the problem into policy objectives and national programmes. · Research into measures to combat degradation. · Research into cropping systems, soil and water management, husbandry and techniques that can be affordable and accepted by the farmer. · Improved educational and training opportunities for farmers to enable small farmers to adopt practices which improve and maintain soil fertility. · Financial support for necessary inputs to stop fertility decline and improve yields. · Infrastructure development to facilitate the ordering and delivering of inputs and outputs. · Improved institutional, economic, environmental and social conditions associated with small holder farmers.
When the above strategies and proposals are achieved, a balance will have been achieved in land use development. Man and environment will have seized fire in their perpetual struggle and will be working in harmony
REFERENCES
Elwell. H.A. 1980. Soil, The Basis of Life. Harare: Institute of Agricultural Engineering. Elwell. H. A. 1983. The degrading soil and water resources of the communal areas Harare: The Zimbabwe Science News. Vol. 17. Nos 9/10. Elwell, H. A. 1990. Soil Erosion in Post Production activities and marketing in small-scale farming areas of Zimbabe. Harare. FAO. 1983. Guidelines for the control of soil degradation. Rome. FAO/Government Cooperative Programme. 1986. Regional Soil Conservation Project for Africa, Phase 1. Rome. FAO. 1994. Land Degradation in South Asia: Its Severity, Causes, and Effects upon People. Rome. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 151
Mehretu. A. and Mudimu. G. 1991. Dimensions of Cognitive Behaviour on Conservation of Land Resources in Selected Communal Areas: Preliminary Survey Findings. Harare: University of Zimbabwe. Ministry of Agriculture. 1995. Zimbabwe’s Agricultural Policy Framework: 1995-2020. Harare. Oni. S. A. 1997. Impact of ESAP on the Communal Areas of Zimbabwe. Harare: University of Zimbabwe. Rukuni. M. and Eicher. K. 1994. Zimbabwe’s Agricultural Revolution. Harare: University of Zimbabwe Publications. Sithole. G. 1995. The Food, Agriculture and Natural Resource Policies of Zimbabwe Harare. TSBF. 1996. The Biology of fertility of Tropical soils: Report of the Tropical Soil Biology and Fertility Programme. Vudzijena. 1993. Study, Analysis and Recommendations of the credit situation for smallholder farmers in Zimbabwe. Harare. Whitlow, J.R. 1988. Deforestation in Zimbabwe: Some Problems and Projects. Harare: Natural Resource Board. Whitlow, J.R. 1979. The Household Use of Woodlands Resources in Rural Areas. Harare: Natural Resources Board. Whitlow, R.J. 1980. Agricultural Potential in Zimbabwe: A Factorized Survey Zimbabwe Agricultural Journal, 77 (3):97-105. Zegeye, H. and Runge-Metzger, A. 1992. Sustainability of Land Use Systems. Verlag Josef Margraf Scientific Books. 152 Socio-economic aspects of soil management for sustainable agriculture and food security Integrated soil management for sustainable agriculture and food security in Southern and East Africa 153
Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe
GENERAL DESCRIPTION OF ZIMBABWE Zimbabwe is a tropical country which lies between 15° 30' and 22° 30' South latitude and between 24° and 33° East longitude. The country stretches over a total surface area of 390 000 km2 sharing common borders with Botswana to the West, Zambia to the North, Mozambique to the East and South Africa to the South. The land mass is apportioned into the following categories; communal lands (163 600 km2), resettlement farming lands (26 400 km2), commercial farming land (142 400 km2), national parks (47 000 km2) state forests land (9 000 km2), urban and state land (22 000 km2). The population of Zimbabwe is approximately 11.9 million people, of which approximately 75% reside in the communal areas. The physical features of Zimbabwe are characterized by three broad relief regions namely; the lowveld (300-900 m) the middleveld (900–1 200 m) and the Highveld (1 200 – 2 000 m). In addition, a narrow belt of mountains known as the Eastern Highlands, stretches some 250 km, running from north to south along the eastern boarder with Mozambique. The greater part of Zimbabwe experiences a tropical climate with the exception of the Highveld and Eastern Highlands which experience a sub-humid to temperature climate owing to the modifying effect of altitude. Rainfall is highly variable, with mean annual rainfall ranging from below 400 mm in the extreme south of the Lowveld to above 2 000 mm on isolated mountain peaks in the Eastern districts. Rainfall reliability generally increases with elevation and from the south of the country to the north. Coefficients of variability range from more than 40% south of Bulawayo at the boarder with Botswana, to less than 20% in the highveld and parts of the Eastern Highlands. Rainfall distribution and reliability are generally of more importance to dryland cropping than the annual average (Anderson et al., 1993). In the driest parts of the country, where mean annual rainfall is less than 400 mm, even if well distributed, the rainfall is insufficient to support crop production other than the most drought tolerant crops such as some millet varieties.
Agro-ecological zones and their characteristics In Zimbabwe, rainfall has been used as the single most important parameter in defining agro-ecological zones and their suitability for agricultural production (Vincent and Thomas, 1960). A description of the agro-ecological zones or Natural Regions (NR) as they are known in Zimbabwe, and their distribution is given in Table 1.
Godfrey Nehanda Institute of Agricultural Engineering, Harare, Zimbabwe 154 Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe
TABLE 1 Land distribution by agro-ecological zones Region Land area Percent of Description (km2) total area I 7,000 1.8 Specialized and diversified farming. Very high rainfall, often in excess of 1000 mm with comparatively low temperatures (under 150C). Region is suitable for afforestation, dairying, tea, coffee, fruits and intensive livestock production. II 58,600 15.1 Divided into two sub-regions (sub-region IIa and Sub-region IIb) Sub-region IIa - suitable for intensive farming based on crops and/or livestock production. Experiences moderately high rainfall (750-1,000 mm) confined to the summer season. Normally enjoys reliable rainfall conditions with low chances of severe dry spells in summer. Sub-region IIb-experiences the same amount of rainfall as IIa, but characterized by severe dry spells during the rainy season. Suitable for intensive farming based on cropping and/or livestock. III 72,900 18.7 Semi-intensive farming region. Annual rainfall is 650 - 800 mm. Region is subject to fairly severe mid-season dry spells which renders it marginal for enterprises based on crop production alone. Farming systems should therefore be based on both crops and livestock. IV 147,800 37.8 Semi-extensive farming region. Annual rainfall is 450 - 650 mm. Region is subject to periodic seasonal droughts and severe dry spells during the rainy season. Farming systems should be based on livestock production. V 103,700 26.6 Extensive farming region located in the very hot low lying areas suitable for extensive animal production with crops under irrigation. Rainfall is generally under 450 mm, which is too low for rainfed agriculture.
National rainfall trends over the last three decades Natural Regions become increasingly marginal for dryland crop production as one moves from Natural Region III to Natural Region V and the risk of getting poor yields also increases accordingly. Hussein (1987) gives the probabilities of normal seasons occurring in Natural Regions III, IV and V as 60%, 40% and 35% respectively. A normal season has been defined as the season when rainfall (in terms of both quantity and distribution) is adequate to sustain plant growth over the entire growing season without any adverse mid-season droughts. On a national scale, seasonal quality has tended to decline in recent years, with the frequency of agricultural droughts being significantly higher over the last 20 years when compared to the long term (1910 - 1997) period (Vhurumuka and Eilerts, 1997). Dryland crop production is strongly influenced by rainfall trends and seasonal quality as shown in Figure 1.
THE STATE OF SOIL AND WATER CONSERVATION IN ZIMBABWE The main source of soil and water conservation problems in the LSCFS are related to intensive use of agricultural machinery for annual ploughing; which pulverize the soil and renders it prone to erosion. Ridging up and down the slope in tobacco growing areas is also a major problem which accelerates sheet erosion. Rill and gully erosion on many farms have been checked by installation of efficient mechanical conservation systems (Table 2). Most communal areas on the other hand, are situated in marginal regions, where rainfall is erratic rendering the areas susceptible to periodic droughts. The soils are predominantly granitic sands, which have low inherent fertility, low cation Integrated soil management for sustainable agriculture and food security in Southern and East Africa 155
FIGURE 1 Rainfall and communal area maize production trends for the 1969/70 season
TABLE 2 Conservation tillage techniques under evaluation Tillage Description Location Responsible technique Institution Residue or - Requires 30% residues to be left on the soil Art Farm (NRII) Agricultural mulch surface. Research farming - Soil may be ripped (Mr) or not (zero tillage) Trust Ripping Similar in many ways to mulch farming. Domboshawa Farm (NRII) Agritex/GTZ between Involves ripping between previous year rows Makoholi Experimental rows into to open planting lines (NRIV) Station residues Institute of Agricultural (mulch Engineering (NR II) Agritex ripping) No-till-tied Involves deep ploughing and making ridges Domboshawa Farm (NRII) Agritex/GTZ Ridging with cross ties across the slope at approx. Makoholi Experimental " 1% grade. No tillage will be required in Station (NRIV) subsequent years except for maintenance of Institute of Agricultural Agritex the ridges. This system harvests water in dry Engineering (NRII) years and facilitates drainage in wet year. Cotton Research Institute CRI/SRI Planting is normally on top of the ridge. No-Till Involves planting narrow strips of row crops Institute of Agricultural Agritex Strip alternating with dense cover crops to Engineering (NRII) Cropping minimize soil loss and run off. The land is not tilled and only compost manure is used Domboshawa Farm (NRII) as a fertilizer. The strips of crops (70% maize, 20% legume, 10% rapoko) are Makoholi Experimental rotated every year Station (NRIV) Agritex/GTZ No-Till Tied Land is planed into a series of shallow vee Chiredzi Research Station DR&SS Furrow shapes drawn across the slope. During (NRV) intense storms, rainfall runs down the sides of the vees into the furrow where the crop is planted. Ties are built across the vees to store excess water 156 Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe
exchange capacity and low water holding capacity. They therefore require a very high level of management to sustain crop production.
The LSCFS is made up of farms which are owned and operated on freehold title basis. These farms occupy approximately one third (1/3) of Zimbabwe's land area, and are dominated by about 4 500 highly skilled mainly white commercial farmers. Thirty-two percent of these farms are in agro- ecological zones I and II, which constitute the most productive zones in Zimbabwe, with good soils and high natural rainfall. Individual holdings in this sector are generally large (1,000 - 4,000 ha on average) and this has in some instances led to the under utilization of land. The sizes of farms become increasingly bigger as one moves from the high potential areas in Natural Regions I and II, to the more marginal areas in Natural Regions III to V. This state of affairs, in addition to a wide resource pool and a reasonable knowledge base, offers opportunities for good land management systems to be applied, thereby protecting the land and minimizing erosion related problems. In fact 48.7% of commercial farming areas have been described as having negligible erosion and only 2% of the land has been described as being severely eroded (Whitlow, 1988). This data however relates to gully and rill erosion and does not reflect on the extend of sheet erosion in the LSCFS, which may be quite considerable.
Low levels of agricultural productivity and poor access to essential resources (e.g. draught animals, finance, etc.), compounded by inadequate socio-economic infrastructure to support agricultural development, have led to exploitative land use and extensive cultivation to meet basic food requirements. This situation is worsened by an ever-increasing population in the communal areas. Of the 11.9 million people in Zimbabwe, 75% derive their livelihoods in the communal areas. Total area of land cultivated has been expanding over the years in response to population pressure, and therefore corresponding demand for land to grow more food crops. Since land is a static resource, previously uncultivated non arable lands have been opened up for cropping purposes, and land cultivated per capita has declined in response to population growth. The overall land per household within the communal areas declined to 4.1 ha in 1982, Compared to 6.0 ha in 1979 and 18.9 ha in 1931 (Zinyama, 1986). More recent studies show that total area cropped to maize, millet and cash crops in the 1980s stood at 1.97 ha per household. This dropped further to 1.63 ha per household in the 1990's (Vhurumuku and Eilerts, 1997). This decline in per capita land holdings has a strong bearing on the increased vulnerability of communal areas to soil erosion and land degradation as continuous ploughing and cropping with little or no rotations becomes the norm. Elwell (1992 and 1993) reported that all land that has been annually ploughed in Zimbabwe for more than 5 - 10 years can be expected to be structurally degraded. In sandy soils, which are predominant in the communal areas, soil degradation is reflected in almost total loss of organic matter, increase in acidity, decline in fertility, decline in water holding capacity; and increased runoff and soil loss (Norton, 1995).
The environmental factors, and the socio-economic circumstances prevailing in the communal areas, have created a vicious cycle of poverty which makes it difficult for the farmers to uplift land management standards, based on currently available technologies. Most of the technologies available today, were developed for the large-scale commercial farmers. Inspite of their lack of reference to the smallholder sector, they are still being recommended for adoption by smallholder farmers. Farmers have responded by largely ignoring these technologies because of their inappropriateness to their natural and socio-economic environments. In most communal areas, where these technologies have been partially adopted, the result has been widespread land degradation, increased surface runoff and consequently massive soil erosion. Annual soil and runoff losses from conventionally tilled lands in the communal areas have been estimated at 50t/ha and 30% of seasonal rainfall respectively (Elwell and Stocking, 1988). In an erosion study in Southern Zimbabwe carried out in the 1992/93 season, Hagmann measured soil loss rates in rills of 59t/ha (Hagmann, 1996). He also concluded that years Integrated soil management for sustainable agriculture and food security in Southern and East Africa 157
following severe droughts, during which communal grazing eliminates litter and vegetation cover, provide the most favourable conditions for soil erosion and land degradation in general. Whitlow, (1988) estimated that up to 27% of the land in communal areas is severely, to very severely eroded on the basis of visible erosion.
The above scenario therefore calls for investment in the development of land management systems that are effective at reducing soil losses and runoff, improving soil conditions for crop production; which in turn will stabilize yields and productivity. The technologies must be developed with the full participation of the end users, with the objective of adapting them to suit the farmers prevailing socio- economic circumstances. Conservation tillage techniques are one such group of technologies which can have major impacts in checking soil and water loss problems, and alleviate the effects of recurrent droughts on crop yields.
TILLAGE, CONSERVATION TILLAGE AND MOISTURE MANAGEMENT The history of the western type of tillage in Zimbabwe dates back to the early twentieth century when agricultural machinery and implements were introduced from Europe by the white settlers following the controversial, but successful land appropriation of the late nineteenth century. The tillage system introduced, which is now commonly termed conventional tillage, involves annual ploughing, turning soils using a disc or mouldboard plough to perform primary operations of preparing a desirable seedbed which is weed free using tractor or animal draught power. Application of the conventional tillage system, in conjunction with the use of hybrid seed, fertilizers and agro-chemicals to control pests and diseases, assisted the country to achieve high economic growth during the green revolution period. This practice was extended to the smallholder sector in the 1920s when the ox-drawn mouldboard plough was introduced in the communal areas. The extensive extension drive that ensued, resulted in widespread adoption of the plough in the smallholder sector. To date, over 90% of households in the smallholder sector own a mouldboard plough. Continuous use of the plough, and poor agronomic practices are now generally believed to have contributed significantly to the land degradation dilemma currently prevailing in the communal areas. Although the recommended ploughing depth is 23 to 30 cm for a good cropping environment to be created, most smallholder farmers have never been able to achieve these depths. This is due to a variety of problems which include among other things, lack of proper knowledge on the use of the plough and general poor draught animal condition which limit the ability of the animals to pull the plough. Plough pans have therefore developed at shallow depths creating impeding layers which limit water infiltration, root development, aeration and nutrient uptake, consequently contributing to poor yields. Conventional tillage which has been widely practised in Zimbabwe, is therefore now increasingly being recognized to have deleterious effects on soil conditions and is regarded as unsustainable (Elwell, 1991). After several years of continued conventional cultivation, soils become depleted in organic matter; soil structure deteriorates and losses of soil and nutrients by erosion and runoff start to spiral. The soil profile then holds less nutrients and moisture (Elwell, 1989, 1991; Norton, 1987). Conservation tillage techniques which have now gained considerable ground in the large scale commercial farming sector, are now being promoted as viable alternatives to conventional tillage (McClymont and Winkfield, 1989).
Development of conservation tillage systems Conservation tillage systems in Zimbabwe are generally defined as any tillage practice that leaves a large proportion of crop residues on the soil surface after planting (McClymont and Winkfield, 1989). There is however another group of conservation tillage techniques such as the no-till tied ridging system (Elwell and Norton, 1988) and the no-till tied furrow system (Nyamudeza and Nyakatawa, 1995) 158 Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe
which do not conform to the definition above, as surface mulching is not necessarily a requirement. These two systems are better adapted to the smallholder sector, where residues are scarce, as they are normally fed to livestock during the dry season. Conservation tillage systems were first introduced into Zimbabwe during the 1960's in response to escalating fuel, machinery, repair and maintenance costs (Smith, 1988; Winkfield, 1992) Since then, experiences at the Agricultural Research Trust (ART) Farm, the Institute of Agricultural Engineering (IAE), Chiredzi Research Station, Cotton Research Institute (CRI), Makoholi Research Station and Hinton Estates, have demonstrated that conservation tillage systems have a marked influence on soil properties, moisture conservation and yield parameters. The specific benefits attributed to conservation tillage are as follows (McClymont and Winkfield, 1989): · reduced soil erosion and surface sealing, · increased water resources for plant growth, · moderation of extreme temperatures, · increased water infiltration, · increased soil fauna activity, · reduction in crusting and compaction, · a better developed rooting system.
History of conservation tillage research The conservation tillage research programme reported on by Smith (1988) began in the 1970's following concerns over machinery costs and the need for increased output per tractor and reduced operation costs per ha to sustain production at previous levels. The trials were mostly conducted using tractor draught as they were designed to meet the needs of Large Scale Commercial farmers. The programme compared the effects of reduced tillage techniques such as rough ploughing, wheel track planting, rip and disc, harrowing, "badza" holing out and tine planting on yield parameters to the standard conventional tillage practice. Some of the interesting results that came out of this programme are summarized below:
Mulch effects from type of tillage trials. Planting into crop residues at Henderson and IAE resulted in increased water infiltration than on conventional tillage treatments. The increased water infiltration tended to produce higher yields in mulch treatments than ploughed treatments in drier years. In wet seasons, when moisture was not a limiting factor, the increased infiltration resulted in lower yields under mulch tillage. This effect was attributed to higher leaching losses, and water-logging for susceptible crops. Run-off losses and soil losses were also lower under reduced tillage treatments than under conventional tillage systems.
Frequency of tillage trials. These trials involved a system of alternating ploughing in one season with reduced tillage on a three year rotational basis. Generally, yields were gradually reduced during the reduced tillage phase, possibly due to the reduced soil rooting volume and increased pest and disease incidence. However, the "bonus" effect experienced in the ploughing season of the rotation compensated for the losses during the reduced tillage seasons, making the mean yield over several seasons comparable to continuous ploughing. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 159
Current Conservation Tillage Research Programmes This section reviews research work which was initiated after 1980 and is still in progress. Following independence in 1980, research focus by government institutions and donor organization was turned to the smallholder sector. A number of programmes to develop conservation tillage techniques based on animal traction and designed to suit smallholder farmers were initiated. The research programmes were related to dryland cropping to cover the needs of farmers in marginal areas (Natural Regions III to V) as well as those in the wetter areas (Natural Region II). The responsibility for developing conservation tillage trials pertaining to large scale commercial agriculture has largely been taken over by the Agricultural Research Trust (ART), which is a non-governmental organization set up to service the needs of commercial producers. Table 2 summarizes the tillage techniques being evaluated by different institutions under the current research programme.
Agritex/GTZ Conservation Tillage for Sustainable Crop Production Project (Contill) The Contill project began in the 1988/89 season as a collaborative research project between Agritex and GTZ (Germany Technical Agency). Although GTZ support has now been withdrawn, the trials have continued to run with government resources. The trials are being conducted at the Domboshawa site (NRII) and the Makoholi site (NR IV). The main objective of these trials is to test several alternative conservation tillage systems by comparing their yield, soil loss and runoff merits to conventional tillage. The most important conservation tillage techniques that are being compared to conventional mouldboard ploughing are ripping between rows into residues and no-till tied ridging (Table 2). The results from Domboshawa presented in Table 3 show that both mulch ripping and no till tied ridging were effective at controlling soil loss and runoff as compared to convention tillage. Similar results were obtained for the drier region, at Makoholi (Table 4). The Annual soil loss figures recorded for the two conservation tillage treatments at Domboshawa and Makoholi were below the maximum acceptable level of 5t/ha/year (Elwell, 1980). Soil loss from sheet erosion at Domboshawa was consistently below 1.0 t/ha with the exception of one odd situation in the 1989/90 season, when losses went up to 2.2 t/ha. On the other hand, soil loss from conventional tillage was as high as 11.8 t/ha in the 1992/93 which followed a severe drought in the 1991/92 season. No till tied ridging treatments consistently yielded better than conventional tillage at the Domboshawa site, except for the 1991/92 season, which was a very dry year. Yields on mulch ripping plots tended to fluctuate, but show signs of stabilization as mulch continued to accumulate over the seasons.
Conservation tillage trials at the Institute of Agricultural Engineering (IAE) From the 1993/94 season to the 1995/96 season, mulch ripping treatments performed better than conventional tillage treatments. This shows the positive long term effects of conservation tillage systems on the production base. In the semi-arid south (Makoholi) mulch ripping showed great potential when compared to no-till tied ridging and conventional tillage. For the first six years of the trials, average yields of maize were highest for mulch ripping (3.6 t/ha) and lowest for no-till tied ridging (2.5 t/ha). Yields of conventional tillage (2.9 t/ha) were marginally better than no till tied ridging. Profile moisture contents on sandy soils have shown that no till tied ridging, despite its outstanding water harvesting benefits through effective runoff reduction, does not overally increase the soil water content within the rooting zone (Vogel, 1993). This has been attributed to low water holding capacity of the sands, which results in water losses through deep percolation. The plant available water of the Domboshawa sands is only about 10% by volume. 160 Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe
TABLE 3 Grain yield, surface runoff and soil loss over an eight-year trial period (1988/89 to 1995/96) at Domboshawa 1988/89 3.82 62.9 1.7 1989/90 2.76 274.3 9.5 1990/91 3.06 15.0 1.1 Convent tillage 1991/92 1.16 9.4 1.0 1992/93 5.10 105.0 11.8 1993/94 4.59 13.0 1.5 1994/95 2.38 99.5 10.3 1995/96 3.10 * * 1988/89 5.03 2.3 0.2 1989/90 4.56 116.5 2.2 1990/91 4.56 1.4 0.3 Tied ridging 1991/92 0.75 0.1 0.1 1992/93 6.57 13.0 0.9 1993/93 5.95 0.7 0.2 1994/95 2.39 5.9 0.7 1995/96 3.37 * * 1988/89 3.81 86.2 2.0 1989/90 2.07 109.1 2.6 1990/91 3.96 4.8 0.6 Mulch ripping 1991/92 0.34 1.0 0.3 1992/93 4.25 15.2 1.1 1993/94 5.69 1.7 0.6 1994/95 3.46 4.4 0.6 1995/96 3.86 * *
TABLE 4 Grain yield, surface runoff and soil loss over seven years of trials (1988/89 to 1994/95) at Makoholi Tillage treatment Season Grain yield Surface runoff Soil loss (t/ha) (t/ha) (mm) 1988/89 2.8 7 0.7 1989/90 6.6 93 1.3 1990/91 1.9 41 5.8 Conventional tillage 1991/92 0.0 1 0.7 1992/93 5.8 92 11.8 1993/94 2.4 95 40.2 1994/95 0.9 49 6.8 1988/89 3.2 5 0.5 1989/90 7.1 28 1.0 1990/91 3.0 2 0.6 Mulch ripping 1991/92 0.0 1 0.3 1992/93 7.0 35 3.7 1993/94 2.6 5 0.2 1994/95 2.2 4 0.1 1988/89 2.1 0.3 0.02 1989/90 3.0 26 0.09 No-till tied ridging 1990/91 1.5 0.2 0.12 1991/92 0.0 0.1 0.11 1992/93 4.8 34 2.68 1993/94 3.0 16 3.00 1994/95 1.1 4 0.14
The Institute of Agricultural Engineering (IAE) site is on deep well drained fersiallitic red clays in natural region II. The on-going tillage trials at IAE were first established in the 1991/92 season. The main objective of the trials is to establish the sustainability of ripping into residues, no till tied ridging and no-till-strip cropping by comparing rates of soil loss, runoff and soil structural changes to conventional tillage. The test crop used on all treatments is a medium season maize variety called Integrated soil management for sustainable agriculture and food security in Southern and East Africa 161
R215. The results in Table 5 confirm the superiority of conservation tillage systems in reducing soil loss and runoff over conventional tillage.
TABLE 5 Maize grain yield, surface runoff and soil losses over a five year trial period (1991/92 to 1995/96 seasons) at the Institute of Agricultural Engineering (IAE) Tillage treatment Season Grain yield Surface runoff Soil loss (t/ha) (t/ha) (mm) 1991/92 1.53 36.6 4.73 Conventional tillage 1992/93 7.49 86.6 3.81 1994/95 4.42 66.9 3.20 1995/96 6.54 238.3 6.86 Mulch ripping 1991/92 1.67 10.8 0.48 1992/93 8.74 8.8 0.52 1993/94 9.90 3.4 0.20 1994/95 4.47 2.3 0.32 1995/96 6.77 5.9 0.39 No-till strip cropping 1991/92 1.89 8.8 0.40 1992/93 9.29 2.3 0.11 1993/94 9.44 1.4 0.25 1994/95 2.95 1.5 0.10 1995/96 6.86 4.6 1.42 No-till tied ridging 1991/92 2.63 0.0 0.00 1992/93 9.84 9.7 0.53 1993/94 9.51 1.2 0.25 1994/95 2.40 18.8 1.48 1995/96 7.32 12.3 1.08
Improved soil conditions, and better infiltration allow soils on mulch ripped plots to capture early rains and wet up their profiles much faster than conventionally tilled plots. This gives the crop on mulch ripped plots the advantage of early crop establishment as compared to conventional tillage, particularly when erratic rains are experienced at the beginning of the season. The yield results for the 1991/92 to 1995/96 seasons (Table 5) show that there are no clear trends, and no significant differences in terms of crop yield responses to tillage treatments. When averaged over the five seasons, however, No till tied ridging gave the highest yield (6.34 t/ha), followed by mulch ripping (6.31 t/ha). No-till strip cropping gave the third highest yield (6.09 t/ha) and conventional tillage gave the lowest yield (6.01 t/ha). What is more important, however, is that conservation tillage treatments do not adversely affect yields, and they exhibit tremendous potential to stabilize yields through their positive impact on soil structure, increased infiltration and reduced soil loss and runoff.
No-till tied furrows technique - Department of Research and Specialist Services (DR&SS) Research on the no-till tied furrow technique was initiated by DR&SS at its Chiredzi Research Station and Chisumbanje Experiment station in the 1982/83 season (Nyamudeza and Nyakatawa, 1995). These two stations are located in natural region V, in the South east lowveld of Zimbabwe. The soils at Chiredzi Research station and Chisumbanje Experiment station are sandy paragneiss and vertisoils (heavy clays) respectively. The objective of the research programme is to determine the effects of reducing run-off on soil water and crop yields. Tables 6, 7, 8 and 9 show the effectiveness of tied furrows in conserving moisture down to a depth of 0.75 m when compared to the flat. At the Chiredzi site soil, water content in the furrows of tied furrows was up to 33% more than on the flat. 162 Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe
TABLE 6 Total soil water (mm) to a depth of 0.75 m under tied ridges and on flat land from 8 to 21 days after sowing during 1985/86 season. Days after sowing 8 22 36 50 53 64 79 93 107 121 Rainfall 89 0 34 33 45 80 85 8 27 0 Treatment Tied Ridges 175 148 152 141 185 175 163 130 120 120 Flat 175 147 145 135 162 141 123 115 117 111 Difference 0 +1 +7 +6 +23 +33 +40 +15 +23 +9 S.E Difference 6.6 6.6 7.2 4.7 6.9 6.4 6.0 4.9 5.8 4.9 Significance N.S N.S N.S N.S ** ** ** ** ** N.S CV (%) 14 15 18 12 15 15 15 15 17 16 Source: Nyamudeza and Nyakatawa,1995 Note: N.S. not significant, ** P< 0.01
TABLE 7 Total soil water (mm) to a depth of 0.75 m under tied ridges and on flat land form 20 days before sowing to 99 days after sowing during 1986/87 season Days after sowing -12 15 29 43 57 71 85 99 Rainfall (mm) 431 67 0 47 23 26 2 21 Treatment Tied Ridges 214 212 184 186 171 142 130 122 Flat 197 189 164 162 155 132 121 113 Difference +17 +23 +20 +24 +16 +10 +9 +11 S.E difference 7.2 8.8 6.9 6.4 6.2 5.7 5.4 4.2 Significance ** ** ** ** ** ** N.S N.S CV (%) 14 16 15 13 14 15 16 16 Notes: N.S not significant, * P < 0.05, ** P < 0.01 1158 mm of rainfall fell in eight days in April 1989 on bare soil and the soil was kept bare through the winter; 43 mm fell from 1st October to 20 days before sowing.
TABLE 8 Total soil water (mm) to a depth of 0.75 m under tied ridges and on flat land from 11 to 104 days after sowing during 1986/87 season Days after sowing 11 17 25 39 53 67 81 95 104 Rainfall (mm) 95 56 1 24 56 56 25 32 Treatment Tied Ridges 133 166 141 163 158 137 111 108 104 Flat 119 127 117 133 131 122 103 110 103 Difference +14 +39 +24 +30 +28 +15 +8 -2 +1
S.E. 4.2 4.7 4.4 4.4 4.4 4.2 3.4 3.5 3.5 Difference N.S ** ** ** ** ** N.S N.S N.S Significance 14 9 16 15 13 14 15 16 16 CV (%) Source: Nyamudeza and Nyakatawa, 1995 (Tables 9 & 10) Note: N.S. not significant, ** P < 0.01.
Tied furrows also increased maize and cotton yields by 27% and 35% respectively over six years and sorghum yields by 44% over seven years. (Table 9). Integrated soil management for sustainable agriculture and food security in Southern and East Africa 163
TABLE 9 The effect of growing sorghum, maize and cotton in tied furrows and on flat land on grain yield (kg/ha) of the crops at Chiredzi Research Station from 1983/84 to 1990/91 Crops Season Mean a) Sorghum 83/84 84/85 85/86 86/87 87/88 89/90 90/91 Treatment Tied furrows 631 2,892 2,630 755 687 2,771 1050 1,631 Flat 413 2,771 2,018 465 50 1,865 369 1,136 S.E. difference 42 131 91 131 - 80 100 Significance * N.S * * - ** ** C.V. (%) 36 14 12 30 - 18 29 b) Maize Tied Furrows 0 3,634 3,100 162 0 2,741 - 1,606 Flat 0 3,537 2,302 0 0 1,745 - 1,264 S.E. Difference - 217 333 - - 168 - Significance - N.S * - - ** - C.V. (%) - 6 9 - - 26 - c) Cotton Tied furrows 487 2,850 1,433 862 899 1,565 - 1,349 Flat 301 2,427 1,320 564 672 704 - 998 S.E. Difference 54 188 200 77 53 38 - Significance ** * N.S * * ** - C.V. (%) 15 7 14 10 24 13 - Note: N.S., Not significant, * P < 0.05, ** P < 0.01 Source: Nyamudeza and Nyakatawa, 1995
FEASIBILITY OF IMPLEMENTING CONSERVATION TILLAGE SYSTEMS IN THE SMALLHOLDER SECTOR Minimum tillage systems involving shifting cultivation and use of the hand hoe to open up planting stations were commonly practiced in Zimbabwe during the pre-colonial period. The western style of agriculture, which emphasized ploughing as a necessary technology for good seedbed preparation and weed control was introduced and vigorously promoted in the smallholder sector during the colonial era. Promotion of the ox-drawn mouldboard plough as a tool for good land preparation, which was part of the ploughing campaign, was highly successful and resulted in widespread adoption of the western style of tillage. To date more than 90% of smallholder farmers own an ox-drawn mouldboard plough in various states of repair. Minimum tillage systems were therefore depopularized and regarded as backward technologies which could only be practiced by the poor who did not own draught animals and could not afford to purchase a plough. The concept of minimum tillage literally disappeared from smallholder agriculture over the years with the exception of areas where livestock development was hampered by the impacts of severe droughts and animal diseases in areas such as the Zambezi Valley where tsetse flies are rampantly present. Conservation tillage has therefore become a relatively new concept to most of the present generation smallholder farmers which needs to be reintroduced as a practice that offers the best alternative to conventional tillage in a scenario where: · Farmers are losing draught animals due to more frequent and severe droughts, · Draught animals are much smaller than they were a few decades ago due to inbreeding and declining grazing, · Poor animal condition at the beginning of the season resulting in delayed land preparation and planting, · Soil fertility and yields are declining, · Soil loss and runoff have increased resulting in man induced droughts. 164 Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe
Development and promotion of conservation tillage systems for the smallholder sector was only intensified recently in the late 1980's into the 1990's following realization that there was a need to urgently deal with the rampant soil degradation problems in the smallholder sector. The programme is still in its infancy and although the concept has been enthusiastically received in some areas, it would be too early to expect widespread adoption of the technologies at this stage. As was the case with large scale commercial farmers, a slow change process would be expected at the beginning and then accelerate as more information becomes available and the farmers develop confidence with the systems. An important development in the programme however, has been the recognition of the farmer as an important partner in the development, evaluation and dissemination process of all technologies. All current conservation tillage programmes have therefore either adopted a two pronged approach involving complementary on-station and adaptive on-farm research or they have gone whole sale on- farm.
The collaborative Agritex/GTZ Contill project initiated complementary adaptive on-farm trials in the 1990/91 season as a way of ensuring that generated technologies would be relevant to the socio- economic circumstances of the end users, the smallholder farmers. The approach was further adapted to embrace participatory approaches in the experimentation process (Hagmann, 1993). The current approach is based on the hypothesis that only farmers themselves can develop and/or adapt technologies to their specific needs and requirements. The new approach which focuses on research and participatory development of agricultural innovations seeks to empower farmers and enable them to analyze their problems, to define and to develop appropriate interventions and to express their demands for support in-order to achieve self reliant development (Hagmann et al, 1995). From the on-farm research programme, it has so far been concluded that mulch ripping is the only conservation tillage technique that can be considered to be ecologically sustainable for the semi-arid environments (Natural Region IV). No-till tied ridging has excellent soil and water conservation and drainage properties, and has performed much better in the higher rainfall areas.
Performance of the different tillage techniques in the semi-arid region (NR IV) and the sub-humid environment (NR II) has proved to be highly variable depending on soil, site and farmer specific conditions. To address the problem of high variability of conditions, it was concluded that different techniques and systems should be promoted as options rather than blanket recommendations and that farmers should be encouraged to select, test and experiment with options in order to adapt techniques to their specific needs and conditions (Chuma and Hagmann, 1995). The success of participatory approaches in technology generation and dissemination will rely on the ability of scientists to adopt and accept farmers as research partners; and the ability of extension organisations to transform their role from that of teachers to facilitators. Change of attitudes, particularly in organisations that have built their reputation on the basis of top - down approaches, can only be expected to be a process rather than an event. It is important however to underline that participatory approaches appear to be taking research and extension in the right direction, being based at the level of the farmer himself.
Opportunities for practicing conservation farming The most important component of residue farming is the availability of residues to give surface cover of at least 30% when the crop is planted. The problem with the communal area situation is that residues are normally fed to livestock and there is not much left at the beginning of the season to allow for conservation farming to be practiced. The best opportunities for practicing residue farming do exist in the resettlement and small scale commercial farming areas, where per capita land holdings are much bigger than in the communal areas. The government is currently in the process of acquiring 5 million hectares of land from the LSCFS for resettlement purposes under the land acquisition act of 1990. Whilst it is not clear how the land is going to be redistributed, subdivision of land into smaller units, Integrated soil management for sustainable agriculture and food security in Southern and East Africa 165
but offering people bigger land parcels than those currently prevailing in the communal areas in certain. Bigger land parcels in both resettlement areas and small scale commercial farming areas offer better opportunities for implementing effective grazing management systems, hence offering better chances for preserving stover on arable lands which is a pre-requisite for conservation farming to succeed. Conservation farming is also possible in the communal areas where large numbers of livestock have been lost due to severe droughts, such as the one that was experienced in the 1991/92 season.
Development of conservation tillage technologies must also run concurrently with development of appropriate tillage equipment. The most commonly available implement in the smallholder sector is the ox-drawn mouldboard plough. Conservation tillage equipment development must be based on the main frame of the plough so that additional attachments for specific operations can easily be attached and removed from the beam of the mouldboard plough. This will ensure minimum investment on the part of the farmers thereby making the technologies attractive and more easily adoptable. Feasible solutions also need to be found to weed control problems if the technologies are to be attractive. Overall, however, there is great scope for implementing conservation tillage technologies in the smallholder sector, with appropriate steps being taken to create a favourable environment for such technologies to be adopted.
CONCLUSIONS The research data from different agro-ecological zones show that conservation tillage techniques effectively reduce soil loss and runoff. The systems also offer opportunities for improving available water in the soil profile to support crop growth under dryland cropping, especially on medium to heavy textured soils. This property becomes even more important during drought years and during mid- season drought periods where they provide a buffer, and reduce the chances of crop failure.
Conservation tillage technologies would therefore make substantial contributions in addressing the problems of widespread land degradation and soil erosion that are destroying the agricultural base, particularly in the communal areas.
It is important to ensure that the technological and socio-economic constraints that hinder the adoption of conservation tillage techniques are addressed. One way of doing this, would be to employ participatory approaches in the technology developmental process as well as at the dissemination phase. Adoption of participatory development approaches can only succeed with full commitment from research organizations, extension organizations and farmers.
REFERENCES Anderson, I.P., Brinn, P.J., Moyo, M., and Nyamwanza. B. (1993) Physical Resources Inventory of the Communal Lands of Zimbabwe. An Overview. NRI Bulletin. No. 60 O.D.A. Chuma, E. (1994) The contribution of different evaluation methods to the understanding of farmer decisions and adoption and adaptations of innovations. Experiences from the department of a conservation tillage systems in Southern Zimbabwe. Project Research Report No. 12. Agritex/GTZ, Harare. Ellis-Jones, J., and Mudhara, M. (1995) Factors Affecting the Adoption of Soil and Water Conservation in semi-arid Zimbabwe: In: Soil and Water Conservation for smallholder farmers in semi-arid Zimbabwe. transfers between research and extension. Proc. of a Tech. Workshop, April, 1995. Masvingo: 106 - 117. Elwell, H.A. (1980) Design of safe rotational systems Agritex Handbook, Harare. 166 Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe
Elwell, H.A. (1989) Soil Structure under conservation tillage. In: Conservation Tillage. Communal Grain Producers Association Handbook, Harare. Cannon Press, Harare: 33-39. Elwell, H.A. (1991) A need for low-input sustainable farming. The Zimbabwe Science News. 25: 31 - 36. Elwell, H.A. (1992) Cropland Management options for the future. Proc. of the 3rd Ann. Sci. Conf. SADC - Land and Water Management Research Programme, October 1992, Harare: 278 - 289. Elwell, H.A. (1993a) Report on the measurement of soil erodibility indices 978 - 1990. Report of the I.A.E. Agritex - Harare. Elwell, H.A. and Norton, A.J. (1988) No-Till Tied Ridging: A recommended sustainable crop production systems. I.A.E handbook, Harare. Elwell, H.A. and Stocking, M.A. (1988) Loss of Soil nutrient by Sheet erosion is a major hidden cost. The Zimbabwe Sci. News, 22(7/8),: 79 - 82. Hagmann, J. (1993) Farmer Participatory Research In Conservation Tillage and Approach, Methods and Experiences from an Adaptive On-Farm trial programme in Zimbabwe. Project Research Report, No. 8. Agritex/GTZ Hagman, J. (1996) Mechanical Soil Conservation with contour Ridges: Cure for, or cause of, Rill Erosion? Land Degradation and Development. Vol 7 (2): John Wiley and Sons, Ltd.: 145 - 160. Hagmann, J., Chuma, E., Murwira, K., and Moyo, E. (1995). Transformation of Agricultural Extension and Research Towards Farmer Participatory; Approach and Experiences in Masvingo Province, Zimbabwe. In: Soil and Water Conservation for Smallholder farmers in semi-arid Zimbabwe. transfers between research an extension. Proc. of a Tech. Workshop, April, 1995. Masvingo, GTZ - ARDA/PPU: 135 - 145. Lineham. S. (1978) the onset and end of the rains in Rhodesia. Notes on Agricultural Meteorology No. 24. Department of Meteorological Services. Mashavira, T.T., Hynes, P, Thomlow, S. and Willcocks, T. (1995) Lesson learned from 12 years of Conservation Tillage Research by CRI under semi-arid smallholder conditions. In: Soil and Water Conservation for smallholder farmers in semi-arid Zimbabwe. transfers between research and extension. Proc. of a Tech. workshop, April, 1995. Masvingo GTZ - ARDA/PPU 22 - 31. McClymont, D. and Winkfield, R. (Eds) (1989) Conservation Tillage, Commercial Grain Producers Association Handbook Cannon Press, Harare. Nehanda. G. (1996) A comparison of the effects of two tillage systems on maize crop growth and performance on a red clay soil at IAE. Paper presented at the Rockefeller Foundation Second Forum Grantees Meeting. Nairobi, August 1996. Norton, A.J. (1987) Improvement in Tillage Practices. Paper for FAO/SIDA sponsored seminar on Increased Food Production. Through Low-cost Food Crops Technology, Harare, Zimbabwe, March, 1987. Norton, A.J. (1995) Soil and Water Conservation for smallholder farmers in Zimbabwe. Past, present and future: In: Soil and Water Conservation for smallholder farmers in semi-arid Zimbabwe. transfers between research and extension. Proc. of a Tech. workshop, April, 1995. Masvingo. GTZ -ARDA/PPU. 5 - 21 Nyagumbo, I. (1993) Farmer participatory research in conservation tillage. Experiences with no-till tied ridging in communal areas lying in the sub-humid north of Zimbabwe. Project Research Report No. 8. Agritex/GTZ Harare: 17 - 30. Nyamudeza, P. and Nyakatawa, E.Z. (1995). The effect of sowing crops in furrow of tied ridges on soil water and crop yields in NRV of Zimbabwe: In: Soil and Water Conservation for smallholder farmers in semi- arid Zimbabwe. transfers between research and extension. Proc. of a Tech. Workshop, April, 1995. Masvingo GTZ - ARDA/PPU 32-40. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 167
Sarupinda, C.D. (1992) Preliminary study of the adoption of no-till tied riding systems in Musana, Chinamhora, Mutoko and Chiweshe communal Lands. Agritex M & E Section, Harare. Smith, R.D. (1988) Tillage Trials in Zimbabwe 1957 to 1988. Institute of Agricultural Engineering Report. November 1988. Vincent, V. and Thomas, R.G. (1960). An Agricultural Survey of Southern Rhodesia. Part 1. The Agro- Ecological Survey. Salisbury: Government Printers. Vhurumuku, E., and Eilerts, G. (1997). Zimbabwe Food Security Reference Manual for Early Warning. 1996/97. USAID (Fews) Project - 698 - 0491 - 5615903. Whitlow, R. (1988) Land Degradation in Zimbabwe. A geographical study. Geography Department, University of Zimbabwe. Natural Resources Board Publication. Winkfield, R. (1992) Minimum and zero tillage versus conventional tillage. In: Improved Land management - The lessons learned. Proc. from a two day conference. April, 1992. Zinyama, L.M. (1986) Rural Household Structure, Absenteeism and Agricultural labour: a case study of two subsistence farming areas in Zimbabwe. Singapore, J. Trop. Agric. Vol 7 (2). 168 Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe Integrated soil management for sustainable agriculture and food security in Southern and East Africa 169
Summary analysis of the country papers
Out of the 21 countries covered by the FAO Subregional Office for Southern and East Africa, 11 were given the opportunity to participate in this important Expert Consultative Workshop on Integrated Soil Management for sustainable agriculture and food security. The main objectives for organising this workshop were: · Discuss the status of land degradation under contrasting agro-ecological and socio-economic conditions. · Exchange experiences on constraints for controlling land degradation and examine possible solutions to overcome these constraints. · Develop national and sub-regional programmes in support of land development schemes to enhance productivity in support of food security in the region.
Reversing the process of soil degradation and sustaining crop productivity through soil management and biodiversity conservation are important aspects of food security. Although cost effective options are available, there is a need to increase the awareness campaign at high policy- making level as well as maintain the determination of agriculturalists to achieve their goals. It is, therefore, important to document the information on the extent of soil degradation, its bio- physical, economic and social impacts as well as successful examples of soil improvement programmes within the region.
FOOD (OR CEREAL) PRODUCTION AND REQUIREMENTS Most of the rural community in Eritrea live on subsistence agricultural (mainly on crop and livestock production), the majority of whom are in a low socio-economic status and vulnerable to food shortages. In general, there are constant crop production deficits, and for the last three decades, basic food requirements have not been met. The emphasis should be to improve the management aspect of agricultural production, water use efficiency, agricultural inputs, high yielding varieties and cultural practices.
In Ethiopia, the performance of the agriculture sector in the last few decades has been poor. The total area under crops and the total production has remained stagnant for several years. As a result, the country became a net importer of food grain since 1981. For generations, Ethiopian farmers have been producing at subsistence level, mainly because of limited access to modern research-led agricultural technologies, including inputs such as commercial fertilizers and organic matter. Even though extensive areas of land are cultivated each year and the size of the population engaged in the farming activities is very large, the total annual food production is always substantially much below the national requirement.
C.F. Mushambi Chemistry and Soil Research Institute, Harare, Zimbabwe 170 Summary analysis of the country papers
Between 1987 and 1997, the food production in Uganda increased by 18.8 percent whilst the population increased by 42.9 percent. Hence the population is increasing much faster than the food production. Therefore, the food requirements versus food production situation in Uganda are likely to become alarming in the near future. The population growth rate of Malawi is currently estimated at 3.3 percent per annum, and about 90 percent derive their livelihood from Small Land Holdings. High population densities and growth rates limit available land for agricultural expansion. Most small holder farmers lack basic needs such as adequate food. The future prospects in meeting the national basic food demands for a growing population are bleak and worrisome. Zambia has faced food deficits in the past, mainly due to droughts and unfavourable agricultural policies. The growth in agricultural production has not kept pace with the population growth rate (estimated at 3.2 percent per annum) in recent years. Accordingly, Zambia faces serious and chronic food deficits in the coming years, unless measures are taken to reverse the adverse trends. Crop production in Zimbabwe has a tendency to vary with agro-ecological zones and also with seasonal variations in weather patterns. Rainfall has been used as the single most important parameter in defining agro-ecological zones and their potential for agricultural activities. Other factors involved in the levels of crop production, particularly in the smallholder sector, are levels of agronomic management, access to inputs, availability of credit, and marketing facilities. Given a good rainy season, Zimbabwe produces surplus food in relation to its requirements. The cereal production in Namibia varies significantly according to rainfall. National cereal production has varied in recent years from low yields (33 100 t per year) in drought years to medium yields (118 900 t per year) in good years. With an estimated national demand for cereal of 201 900 t per year, Namibia has to import a significant amount of its cereal requirements. South Africa produces a wide variety of food crops which take full cogniscence of the people's nutritional needs. In terms of value and quality, South Africa does not only meet its own food requirements, but is also a major exporter of cereals and other agricultural products. Tables 1 and 2 show the summary of food production and requirements as well as deficits and surpluses for the ten (10) countries represented at this Consultative Workshop.
TABLE 1 Summary of food (cereal) production and requirements Annual Production Annual Requirements Eritrea 220 000 - 250 000 MT About 384 600 MT Ethiopia 8 000 000 MT 9 000 000 MT Uganda 13 219 000 tons in 1987 Not Available 15 703 000 tons in 1997 Tanzania 7 500 000 tons in 1988/89 Not Available Zambia 1 020 749 tons in 1994 1 220 935 tons in 1994 Zimbabwe 70's 1 814 481 tons Not Available 80's 2 176 012 tons 90's 1 807 004 tons South Africa 11 086 800 tons per year Not Available during 1975/76 - 1994/95 MT-Metric ton Integrated soil management for sustainable agriculture and food security in Southern and East Africa 171
TABLE 2 Summary of food (or cereal) deficits or surpluses for ten African countries Country Deficit in Domestic Sufficient in Domestic Surplus in Food Requirement Food Requirement Domestic Food Requirement Eritrea * Ethiopia * Kenya * Uganda * Tanzania * Malawi * Zambia * Zimbabwe * Namibia * South Africa * * Sourced from country papers Note: Surplus figure are dependant on the impacts of weather patterns and/or drought.
Given the size of agricultural land resources available in these African countries, the food deficit scenario is not a healthy one. It is the responsibility of each government to reverse this situation and be able to efficiently utilise the agricultural production sectors.
EVALUATION OF PER CAPUT CULTIVATED LAND AND TRENDS IN CEREAL CROP Africa's food crisis can be defined as the steady decline in agricultural production per person. Between 1965 and 1982, Africa's food production per person fell by 12 percent in 33 of the sub- Saharan African countries. During the same period, Southern Africa's per caput food production fell by 19 percent.
There are several factors contributing to this decline, such as the high population growth rate which, on average, is approximately 3 percent per annum, and the continued land over-utilisation which leads to low agricultural productivity.
Over the past two to three decades, the increase in food supply in most regions of the world was gained through increasing yields per hectare, but in sub-Saharan Africa, the increase in food supply has occurred through expansion of cultivated land and/or shifting cultivation. Because Africa is facing a high population growth rate and the arable land per caput is constantly being reduced, emphasis must be placed on increasing yield particularly through maintenance of soil productivity, rather than concentrate on the expansion of cultivated land areas.
Although there is a potential for increasing food productivity in Ethiopia, while, the expansion growth for the same period in the area of cultivated land is small compared to population growth. Available data indicates that the increase in the area of cultivated land from 1961 to 1991 was about 20 percent, however, that of population growth for the same period was about 150 percent. As a result, the per caput land area decreased by more than half. Furthermore, yield per unit area also decreased, due to excessive soil degradation and nutrient depletion.
The same scenario is also experienced in Eritrea, Uganda, Kenya, Tanzania, Malawi, Zambia Zimbabwe and Namibia, where the cultivated land per caput is decreasing fast, and is not being compensated with an increase in crop yields. Therefore, corrective measures are long overdue. 172 Summary analysis of the country papers
In South Africa , the annual population growth rate is 2.7 percent. Land per caput ratios are worsening, and it is estimated that the area of arable land per caput will drop well below the accepted minimum of 4 ha before the year 2010. At present, food production per caput is sufficient but agricultural output has to be expanded to maintain and conserve the natural resource base. Over the last two decades, South Africa has more or less maintained its agricultural production under the harsh population pressure, scarcity of land, and unfavourable climatic conditions.
Per Caput Cultivated Land Eritrea: The per caput arable land declined from 4.3 ha in 1943 to 1.10 ha in 1996.
Ethiopia: The per caput cultivated land decreased from 0.574 ha in 1961 to 0.279 ha in 1991.
Uganda: The per caput cultivated land decreased from 0.27 ha in 1990 to 0.25 ha in 1997.
Kenya: Population increase has led to a big land pressure. This implies that the per caput cultivated land is decreasing (figures are not available).
Tanzania: Population increase has led to pressure on land. Therefore, per caput cultivated land is decreasing (figures are not available).
Malawi: As a result of increasing population on limited land area, the per caput cultivated land is decreasing (figures are not available).
Zambia: The declines in per caput cultivated land are a result of high population growth rates (figures not available).
Zimbabwe: The per caput cultivated land in the 1980's was 0,393ha, but in the 1990s this figure dropped to 0.325 ha.
South Africa: Person-to-land ratios are worsening fast. It is estimated that cultivated land per caput will drop well below the accepted minimum of 4 ha before the year 2010.
In summary, the per caput cultivated land is decreasing fast for all the countries represented on this Workshop. Therefore, emphasis must be put on increasing yield as opposed to land expansion or shifting cultivation.
EXTENT OF SOIL DEGRADATION AND ITS BIOPHYSICAL AND SOCIO-ECONOMIC IMPACTS The basic challenge facing agriculture and food security in many developing countries today is the steady loss of plant nutrients leading to decline in plant biomass, organic matter, microbial activity, and finally crop yields. These processes in combination with bad soil management practices, overgrazing and deforestation, cause large scale soil degradation. Soil degradation can be described as a loss of soil productivity brought on by various physical and chemical depletions. Soil degradation is the end result of a combination of factors, which damage the soil and vegetation resources, and restrict their use or productive capacity. Major forms of land degradations include soil organic matter depletion, acidification, salinization and high population Integrated soil management for sustainable agriculture and food security in Southern and East Africa 173
pressure (human and livestock). The processes of soil degradation are more prevalent and more intense in the smallholder and resource poor farming sectors of the community, which are characterised by fragile environments and have the highest population densities.
Research indicates that soils in sub-Saharan Africa are low in organic matter due to less plant residue materials recycling back to the ecosystem. At the beginning of this century, the vegetation cover in Eritrea was estimated at 30 per cent. Presently it is less than 1 percent. Similarly, in all the African countries, the area covered by forests has drastically been reduced since the turn of the century. This situation has created agricultural soils that have very low fertility status and are subjected to accelerated erosion. One of the serious crop yield limiting factors to the majority of farmers in sub-Saharan Africa is lack of inputs either through residue incorporation in the form of organic matter or through the addition of inorganic fertilizers. In places, which have been settled for decades, the soils have been continuously "mined" of nutrients through harvests and soil erosion resulting a decline in the crop yield.
The over exploitation of land resources by man, through inadequate soil and water conservation and, at times, inappropriate farming practices, are the underlying causes of land degradation in Africa. Dissemination of research information in the areas of soil, water and biodiversity conservation by researchers to the extension workers and farmers is also limited. It is important to have a multi-disciplinary approach that involves everybody in the definition of the problem and the identification of possible solutions regarding soil degradation. Similarly the causes and types of degradation processes are very much related between these countries. It is not surprising, therefore, to note that these soil degradation types are the same among the countries of the region.
Table 3 highlights the major types of soil degradation in each country and also indicating close similarities between them. It should be mentioned here that wind erosion is more prominent in Eritrea, Ethiopia and Namibia; whereas, water erosion is prominent in Malawi, Zambia, Zimbabwe, and South Africa.
TABLE 3 Major types of soil degradation by country Type of Eritrea Ethiopia Kenya Uganda Tanzania Malawi Zambia Zimbabwe Namibia South degradation Africa Erosion (wind **** **** **** **** **** **** **** **** **** *** & water) Fertility *** *** *** *** *** *** *** *** *** *** decline Acidification * * * * * ** - ** * **** Sodicity/ ** ** ** ** ** ** ** * **** * Salinity Compaction * * * * * * * * * * Crusting * * * * * * * * * * Key : **** Very high (major) *** High (2nd major) ** Medium * Low 174 Summary analysis of the country papers
AVAILABLE TECHNOLOGICAL OPTIONS FOR CONTROLLING SOIL DEGRADATION AND ENHANCING PRODUCTIVITY The challenge facing scientists at the moment is to develop and test more technologies that will control soil degradation and enhance crop productivity. These technologies should be affordable and easily sustainable to the ordinary smallholder farmer.
Summary information based on country papers Types of Degradation Causes of Degradation
· Wind /Water erosion: - Lack of vegetation cover, due to deforestation and overgrazing · Soil fertility decline: - Exhaustion of nutrients through continuous cropping without inputs. - Leaching of plant nutrients - Poor farming practices · Acidification: - A combination of factors which include - depletion of soil pH - availability of toxic elements such as Al, Mg and Fe. - deficiencies in P, Ca, Mg and K - low water holding capacities resulting in excessive leaching in bases · Sodicity/Salinity: - Accumulation of dissolved salts.
Some of the technologies currently being applied to control soil degradation (and indeed many others not listed here) are highlighted in Table 4 and have a role to play in the overall search for good management options for improving soil fertility in Africa. Due to the new soil and water conservation programmes in Eritrea, the vegetation is regenerating well and earth dams and ponds have made significant contributions to water harvesting. Other success stories about various technologies that are being carried out are mentioned in the country papers.
TABLE 4 Technologies Utilized to Control Soil Degradation. Programmes in Eritrea Ethiopia Kenya Uganda Tanzania Malawi Zambia Zimbabwe Namibia South Place Africa Soil and Water + + + + + + + + + + Conservation Minimum Tillage + + + + + + + Inorganic + + + + + Fertilizers Lime and Liming + + + + + Materials Manures and + + + + + + + + + Other Organic Fertilizers Biological + + + + + + Nitrogen Fixation Agroforestry + + + + + + Technology Based on country papers (see this issue) Integrated soil management for sustainable agriculture and food security in Southern and East Africa 175
In the future, it is hoped that all researchers will take the participatory type of approach, where farmers and extensionists are fully involved throughout the duration of the programme.
CONCLUSION Sub-Saharan Africa can no longer sit back and watch its natural resources (soil, water, vegetation) disappear through mismanagement and unfavourable policies. Strategies and conservation programmes must be formulated and action plans drawn up in order to overcome problems of soil degradation.
This workshop is being held at an opportune moment. It is hoped that each country will revisit its activities on the natural resource conservation and then concentrate on those areas that require strengthening; then work on the practical solutions concerning land degradation. The ultimate goal being to sustainable increase the yields of food crops whilst at the same time conserving the natural resource base.
REFERENCES Country Papers from: Eritrea, Ethiopia, Kenya, Uganda, Tanzania, Malawi, Zambia, Zimbabwe, Namibia and South Africa (see this issue). 176 Summary analysis of the country papers Integrated soil management for sustainable agriculture and food security in Southern and East Africa 177
Country reports 178 Integrated soil management for sustainable agriculture and food security in Southern and East Africa 179
Eritrea
COUNTRY FOOD PRODUCTION AND REQUIREMENT Food balance The total national area is around 125 020 square kilometres. It is part of the Sahelian belt of Africa and has an estimated population of about 3 million. Eritrea is divided into six agro- ecological zones namely the Central Highland Zone (CHZ) with sub-zones SML, NML and H, Escarpment Zone (WEZ), North-Western Lowland Zone (NWLZ), South-Western Zone (SWLZ Western), Green Belt Zone (GBZ) and the Coastal Plain Zone (CPZ).
The agricultural sector occupies about 80% of the labour force. It contributes about 26% of the GDP (World Bank, 1994). Most of the rural community live on subsistence agriculture (mainly on crop and livestock production) out of which 78% (Cliffe, 1991) are in low socio- economic status and are vulnerable to food shortage. Besides, few of the population depend on fisheries. Agricultural production in Eritrea ranges from nomadic pastoral systems to small scale irrigated horticultural production. Cliffe (1991) recognizes three major systems: pastoral (11%), agro-pastoral (22%) and agricultural (67%). Survey studies in the highlands of Eritrea (Haile et al., 1995, Azbaha et al., 1996), show that the population is predominantly agro-pastoral. Pure crop cultivators without livestock are of a rare occurrence, since crop production is dependent on animal traction. Owing to its ecological diversity, Eritrea produces a wide range of cereals, vegetables, pulses, fibber crops are grown (Mesghina and Bissrat, 1997; Araia et al., 1994). Subsistence farmers in the highlands grow taff, barley wheat oil seeds and legume. In the lowlands the main crops grown are pearl millet, sesame, groundnuts, cotton, sorghum, fruits and vegetable. Sorghum is the most important crop and accounts for about 46% of annual yield in the country (Cliffe, 1988; World Bank, 1994). Next to sorghum, are pearl millet (16%) and barley (15%) (Araia et al., 1994). Commercial agriculture also played a significant role before the war. It included rain-fed cereal and cotton production as well as large scale irrigated agriculture for the production of fruits and vegetables mainly for export. The potential for expansion of small and large-scale agriculture is still there. It is estimated that the area under horticulture is about 7 000 ha (World Bank, 1994). This figure appears to be on the low side.
The food requirement of a person per year is 0.145 Mt (World Bank, 1994). Table 1 and Figure 1 show that the basic food requirement was not met during the last three decades. However, the south mid altitude and the coastal areas do produce enough food to support the local population as well as export it to other regions of the country. Food deficit periods in the highlands and lowlands differ. In the green belt and eastern coastal areas, there is food deficit from October-January. In the highlands and the western lowlands, it is between May and September, which is the time of land preparation, sowing and the beginning of crop maturity.
Woldeslassie Ogbazghi and Anwar ul-Haq College of Agriculture and Aquatic Science, University of Asmara 180 Eritrea
TABLE 1 Food production and annual deficits in percentage (1976-1996) Year Production Self-sufficiency Deficit Sources 000 tonnes % % 1975-76 188 42 58 Araia et al., 1994 1988 100 N/A. N/A. World Bank, 1994 1990 170 N/A. N/A. World Bank, 1994 1991 70 16 84 Tesfay, 1992 1992 278 64 36 Appleton et al., 1992 1993 90 16 84 UNICEF, 1994 1994 265 60 40 FNSP, 1996 1995 142 32 68 IGAD, 1996 1996 97 20-25 75-80 MOA, 1996
Some coping strategies during food shortage periods FIGURE 1 Food production 1986-96 (000 Mt) include sale of livestock and livestock product, collection of 300 wild fruits like Cactus, Balanites 250 spp. doum palm and Zizyphus fruits. Under such circumtances, 200 wild plants constitute almost the 150 Production major dietary part during these 100 months. Although the national 50 picture seems to be deficient in 0 food production the southwestern 1986 1988 1990 1991 1992 1993 1994 1995 1996 lowlands, southern midlands and coastal areas with spate Years irrigation are self sufficient in terns of their grain requirement.
Historic records reveal that there is constant crop production deficit in Eritrea. Cliffe (1991) estimates a normal harvest under non-disastrous situations to be between 220-250 thousand metric tons covering between 55-65% of the annual need only. Consequently, during the struggle for liberation, and immediately after, most of its people were dependent on food aid. It was estimated that 72% of the Eritrean population during 1992, was food-aid dependent (Appleton et al., 1992). Since liberation(1991), government focus was to shift from food-aid dependency to food security. Pre-liberation statistics regarding food production are scarce and unreliable. Recent sources, however, indicate that food production follows a similar pattern as before (Figure 1).
Food requirements projections (1996 -2010) Food requirement projections are made based on 1992 food production estimated to be 278,000 metric tons which covered about 64% annual food demand for that year. The population size of Eritrea in 1996 is taken 3 million with per caput food requirement of 0.145 tonnes per annum. The annual growth rate has been taken as 2.9% per year. The yield of cereals is estimated to be 0.74 MT/ha (World Bank, 1994). Integrated soil management for sustainable agriculture and food security in Southern and East Africa 181
FIGURE 2 Projected food demand and food crops required area
1000
800 600
400
000 Mt and ha 200
0 1996 1998 2000 2002 2004 2006 2008 2010
Years
Food demand Required area
By the year 2010, the population of Eritrea is expected to be about 4.5 million and the annual food requirement by that year is estimated about 649 089 metric tons. If the 1992 grain production figures (278 000 tonnes) are taken as base, then production will have to increase by about 133%; the required crop area would be 877 147 ha (Figure 2).
If the additional requirement in grain of 371 089 tonnes were to be achieved by putting more land under cultivation, an additional 501 471 ha of land would have to come under production. This would require 1.3 times more than the area under production in 1992. If average yield were to increase by 50%, an additional 337 353 ha of land would be required. NEMP-E, (1995), estimates, about 2 million ha of land are available for rainfed agriculture mainly in the southwestern lowlands of Eritrea. By looking at the potential arable land, it is tempting to say that Eritrea would satisfy its annual food requirement by putting more land under cultivation. In spite of Eritrea’s arid and semi-arid climate, the challenges of achieving this objective is not beyond the reach of the country’s capacity.
It is estimated that about 600 000 ha is potentially suitable for irrigated agriculture. World Bank (1994) estimated that 22 000 ha were already under irrigation and suggested to expand this to 60 000 ha. Attaining the objective would be feasible if the yield of rainfed agriculture for 1992 is maintained and at the same time the yield in irrigated agriculture is increased to 1.2 tons per ha. Although the potential for expansion of arable land is there, it should be done at slower pace. The emphasis should be to improve the management aspect including irrigation, water use efficiency, agricultural inputs, high yielding varieties and improved cultural practices. This is particularly important in protecting the environment and adopting sustainable agricultural production strategy.
EVOLUTION OF PER CAPUT CULTIVATED LAND AND TRENDS IN CEREAL CROP YIELDS Eritrea has a total area of 12 167 697 ha (Table 2) out of which 1 084 821 is cropped land which is 8.9%. The unproductive and currently unutilized land is 2.0% and 33.1% respectively. A total of 3.2 million hectares is suitable for production which could allow expansion by 17%. 182 Eritrea
Land use and land cover The population of Eritrea has quadrupled during the last six decades. The per caput total area has decreased from 16.3 ha in 1943 to only 3.4 ha in 1996. The per caput potential arable land has also declined from 4.3 ha in 1943 to 1.10 ha in 1996. The expected yield from per caput of arable land is shown in Table 2. By the 2010, the population of Eritrea will grow by 49.2% using the 1996 as a base line. As a consequence, the per caput cultivated area and potential arable land will be decreased by 34.5% as shown in Table 2.
TABLE 2 Per caput total area, current arable land and potential arable land of Eritrea Land per caput Year Population Total area Potential arable Expected Current Expected land yield arable land Yield (000) (ha) (ha) (tonnes) (ha) (tonnes) 1943 (a) 750 16.3 4.30 3.18 1.50 1.10 1952 (b) 1,031 11.8 3.10 2.30 1.10 0.81 1964 (c) 1,500 8.10 2.10 1.60 0.72 0.53 1996 (d) 3,000 3.40 1.10 0.81 0.36 0.27 2010 (e) 4,476 2.70 0.71 0.53 0.24 0.18 Sources: a) Longridge, 1943 b) Trevaskis, 1975 c) Aradom, 1964 d) World Bank, 1994, e) projection
CONSTRAINTS TO FOOD PRODUCTION Drought. Most parts of Eritrea are affected by drought and the erratic nature of the rainfall pattern. The climate of Eritrea ranges from sub-humid in the green belt agro-ecological zone to arid in the coastal areas. In the highlands and the western lowlands, the rainy season is from June-September. In the eastern escarpment, however, it is from October to March (winter rains). Owing to diverse topography and altitude, annual precipitation varies between 100 mm in the lowlands to more than 1000 in localized areas in the green belt that benefit from bi-modal rainfall regimes. The temperature in the lowlands is very hot and cool in the highlands. In the lowland, the climate is hot or very hot with annual mean temperature between 26.5 and 29.0 °C. Areas located between 1 000 and 1 500 m of altitude are warm to mild and their temperature ranges between 19 and 22 °C. The highlands (above 2 000 m) are cool, with mean annual temperature of 19 °C (FAO, 1994).
Impact of war. The gap in food production was widened due to the protracted war of liberation where the country lost a great proportion of its labour force. During the war, draught animals were killed, irrigation canals and dams were destroyed together with farm tools and implements (Araia et al. 1994). As a consequence, the ability of farmers to save seed from stock has became impossible. The war also caused food deficit because villages were abandoned and burned and the area under production was limited (Cliffe, 1988).
Lack of agricultural infrastructure. The Government of Eritrea has invested to build roads and agricultural infrastructure. However, due to the topography of Eritrea, it is still very difficult to communicate between the major production areas and the market centres of the country. Most of the productive areas are located a long distance from the major roads
Land degradation. Low food production in Eritrea is the result of progressive loss of fertility and erosion. Although land degradation is widespread throughout the country, the areas of great concern are located in the highlands where majority of the population live. In most cases, the Integrated soil management for sustainable agriculture and food security in Southern and East Africa 183
topsoil is removed and the soil fertility is very poor to support cultivation without significant intervention to improve its quality. Under the present situation, increase in crop productivity is likely to be difficult without extensive rehabilitation efforts. In the highlands, soil degradation is associated with the removal of the vegetative cover (Jones, 1991; Azbaha et al., 1996). Deforestation in Eritrea is the result of removal of the vegetative cover for grazing, cultivation, construction and fuelwood. Land degradation was also worsened due farming on steep slopes as well as the shortening of the fallowing period due to population pressure. This resulted in accelerated soil erosion that washes away topsoil almost within a season.
Land tenure. The major constraints of food production in Eritrea include the counter productive land tenure system. The land tenure varies from place to place (Nadel, 1946; Zekaria, 1964; Jordan, 1989). The Diessa land tenure system does not guarantee tenure right and farmers are reluctant to make efforts in terracing, planting trees or invest in improved cultural practices.
Lack of research outputs. Although agricultural research stations were established as early as 1901 (Yemane, 1988), their contribution to the enhancement of agricultural productivity in the country is limited. This is because research activities failed to address relevant production problems in the country. During the war, research activities were confined to limited areas and research finding did not reach the farmers. This gap between research findings and their dissemination to the farmers is still wide
Lack of marketing and storage facilities. The cost of food in Eritrea is high because farmers consume little less than three quarters of their produce and the rest is sold in the market (Araia et al., 1994). Most farmers produce what they consume and consume what they produce (Tesfay, 1992). Insufficient storage capacity on the farm and marketing facilities discourage farmers from producing surplus. In addition, it is estimated that lack of storage facilities causes substantial loss of agricultural produce. Moreover, farmers are also discouraged from producing perishable horticultural crops primarily due to lack of marketing and storage facilities.
EXTENT OF SOIL DEGRADATION AND ITS BIO-PHYSICAL & SOCIO-ECONOMIC IMPACTS Types of land degradation Water erosion. Reliable data on the extent and impact of soil erosion in the country are not available. Limited research findings conducted in Afdeyu (Central Zone) of Eritrea shows that soil loss is on the average 15 tonnes/ha/year equivalent to over 50 years to remove 4.5 cm top soil. This is estimated to result in annual crop failure of 0.2 - 0.4% and a decline in the livestock of about 0.05 - 0.1% annually (World Bank, 1994). During few rains occurring in the Eritrean highlands runoff is extremely high, flooding whole fields (Grunder and Karl, 1997).
Wind erosion. To date, there are no quantitative data on the magnitude of wind erosion in Eritrea. However, wind erosion is frequently observed particularly in the southwestern, northwestern and coastal areas of the country. This is because of lack of vegetative cover during dry season. Wind blows fine soil particles and organic matter from the surface soil. Moreover, wind erosion causes continuous movement of sand dunes in the coastal areas accelerating the process of land degradation. The lowlands are subject to strong winds and it is common to find aeolian deposits (Murphy, 1959). 184 Eritrea
Salinity and alkalinity. In the western and coastal areas of Eritrea, the soils are deeper compared to those the highlands. The surface texture is mostly sandy, loamy sand and sandy loam. The soil reaction generally varies from slightly alkaline to strongly alkaline. In some places, the soil reaction is reported as high as 9.5. The organic matter content extends from 0.6-2.5. Under arid conditions, there is accumulation of salts on the surface, and there is high potential for the development of saline alkaline, and calcareous soils (Maskey, 1985). This problem is particularly serious in the coastal areas where the annual rainfall is less than 200 mm with evapotranspiration exceeding 2,000 mm/year. In the highlands, there are indications on the development of saline soils in irrigated areas using water from deep wells.
Physical degradation. The extent of physical degradation in Eritrea is not well documented. However, (Jones, 1991) pointed out that livestock causes physical soil degradation in Rora Habab area. In the highlands, during rainy season, livestock are confined to limited grazing areas. This exerts tremendous pressure on the soil through trampling that reduces infiltration. Consequently, it is common to observe the creation of gullies caused by runoff. Besides, the removal of organic matter (animal dung and crop residues) from agricultural fields as well as over tillage contribute to physical degradation of soils. In the highlands, land preparation is done five times per year (Azbaha et al., 1996).
Extent of land degradation Eritrean farmers equate soil degradation to land degradation. It is perceived as the reduction in the productivity of land by biological, chemical, or physical processes (NEMP-E,1995). Land degradation is a process and phenomena (Azbaha et al., 1996). As a process it is continuous and incremental. It is an increasing weakening of the physical, biological, and economic potential of land thereby reducing the overall capacity of the productivity of the land. Land degradation is a process that lowers the productivity of land assuming all other factors such as technology, management and weather held constant (Bojo, 1995). As a phenomenon, land degradation is the end product of a long process that is manifested by decrease in cultivable land per peasant household, decrease productivity of a unit land per specified in-put, decline in livestock population, loss of vegetative cover and shortage of fuelwood, wood materials, loss of top soil, and generalized ecological disturbances (Biswas and Biswas, 1980, Azbaha et al., 1996). The soils of most parts in Eritrea are very poor in organic matter content (Murphy, 1959; Azbaha et al., 1996; Haile et al., 1995, Jones, 1991). A general picture of some soils in Eritrea is given below.
Central Highland Agro-ecological Zone, Debubawi Anseba. Debubawi Anseba is located in the central highland of Eritrea. The area is mountainous and densely populated with little potential for expansion of rainfed agriculture. The altitude of the highest peak is about 2300 m above sea level. It has a cool semi-arid climate (FAO, 1994) with mean annual temperature of 18 °C and mean annual rainfall of 400 mm per annum. During the past three decades, rainfall has shown great fluctuation in terms of distribution and amount. The soil are angular to subangular in structure. The consistence of dry moist and wet soils is soft, slightly hard and wet friable respectively. The mean soil depth is about 62 cm and ranges from 30 to 160 cm. The deeper soils were from valleys and agricultural areas. Out of a sample of 32 surface soils, 18.77%, 62.50%, 9.38%, 9.38% were loamy sand, sandy loam, loam, and silt loam respectively. The soil colour is light yellowish brown to yellowish brown. In many places soils are shallow or very shallow due to erosion (Murphy, 1959; Maskey, 1985). In some areas, especially in depressions, the soils are relatively deeper The soils are coarser in texture due to slow weathering process and parent material i.e. schist. However, in depressions with colluvial materials the soils are of medium Integrated soil management for sustainable agriculture and food security in Southern and East Africa 185
texture and are deep. The soil reaction is mostly neutral and organic matter (1.07%) and phosphorous (2,76%) content is low, whilst no particular salinity problems is recorded.
South Mid Altitude Zone, Egela Hatsin. Egela-Hatsin is located in the southern midland agro- ecological zone of Eritrea. The topography of the area has gentle slope, steep and almost flat at the upper, middle and lower parts of the catchment respectively. The elevation of the area ranges between 1400- 2000 m above sea level. Annual rainfall ranges between 400 mm/annum. The mean annual temperature is 270 C. The soils in the area are angular to subangular in structure. Dry soils are soft to slightly hard; moist soils are friable to firm and wet soils non-sticky to sticky consistence. Out of a sample of 37 surface soils, 54.05%, 40.54%, 2.70%, 2.70% were sandy loam, loam, silt loam and clay loam respectively. The mean soil depth is about 54 cm ranging from 40 to 150 cm. The soil colour is light yellowish brown to yellowish brown. The soil reaction is slightly acid and organic matter (1.00%) and available phosphorous (2.23%) content is low, whit no salinity.
Coastal Plains Agro-ecological Zone, Ghatelay. Ghatelay area is located in the coastal plains of Eritrea. The altitude of the area ranges between 200-400 m above sea level. It is a flat area with some hills here and there. The area is hot and dry with mean annual rainfall of 200 mm and temperature 350C with maximum range of 45 °C. The soil structure is angular to sub-angular. The consistence of dry, moist and wet soils is soft, friable to firm and slightly sticky respectively. The soil depth ranges between 15 - 100 cm with mean value of 75 cm. The soil texture is sandy loam or silt loam and has brown colour. In the coastal areas of Eritrea, there are sand dunes and aeolian deposits and in many places these are very deep. Alluvial materials brought up from the highlands are good for many of the spate irrigation systems. Analyses of soils from these areas indicate that the soils collected from areas which don't receive seasonal floods are affected by salinity problems. However, the salinity levels of the soils in fields under spate irrigation are low. These soils are characterized by low organic matter (1.10%) and phosphorus (2.10%) that limit agricultural productivity in the area. The soils are alkaline in reaction. Owing to the dry climate in the area, there is a very high possibility for the development of saline and alkaline soils.
Northern Mid Altitude Agro-ecological Zone, Rora Habab. Roral Habab is an area located in the northern mid land agro-ecological zone of Eritrea. The elevation of the area ranges between 1,900 - 2,200 m above sea level. Annual rainfall ranges between 300-400 mm and temperature ranging from 15 - 23 °C. Previously the area was covered with dense forest and deforestation is closely associated with erosion and nutrient impoverishment. Land clearing resulted in decline of organic matter and essential plant nutrients due to decreased litter returning to the soil (Jones, 1991). The area comprises of hills and mountains and erosion due to water remains a very serious problem. Most of these places are left devoid of the topsoil. Surface soils are clay loam, loam, or sandy looms with clay content ranging 9-48% (Jones, 1991). Valleys have deeper soils owing to sedimentation from the hills. The soil reaction is ranges from neutral to moderately alkaline. The organic matter content varies from 0.80 - 4.0% in which the higher values were reported from non-cultivated areas. The soils in cultivated areas have less N, organic carbon, exchangeable Ca, clay, CEC and sum of bases than soils in grazed areas and woodlands. The total nitrogen and organic carbon in cultivated areas have on the average 22 - 31% less total nitrogen, organic carbon, exchangeable Ca, CEC and sum of bases than grazing and woodlands (Jones, 1991). 186 Eritrea
Causes of soil degradation Soil degradation is the result of prolonged combined effects of intricately related factors. These factors could be categorized as biophysical and socio-economic factors (Azbaha et al., 1996). The biophysical factors include the inherent topography of the country, climate, drought. Socio- economic factors are essentially related with the traditional land tenure, population growth and legacy of war. Given Eritrea's topography, geological instability and steep slopes, some levels of natural soil erosion are inevitable. Erosion in the highlands results in few depositions and sedimentation opportunities in the lowlands. However, the natural erosion has been substantially accelerated by human interaction. The intensive bombardment during the thirty years war of liberation, the demand for fuelwood, construction materials and clearing of land for timber, fuelwood, and cultivation have contributed the widespread destruction of forests and of vegetation cover (Azbaha et al., 1996; World Bank, 1994). This in turn has affected the structural stability of the soils. The loss of tress and hence foliage also meant that less nitrogen returned to the system. With the declining availability of fuelwood, many rural communities use animal dung as source of domestic energy.
Deforestation. Studies on the natural vegetation of Eritrea are scarce. Most of the literature on this topic are in Italian and generally are descriptions of broad vegetation types and formations. Nevertheless, it is now known that vegetation cover of the country has been greatly reduced during the last century. The forest cover at the beginning of the century was estimated to be about 30%. In 1952, it had declined to 11% (NEMP-E, 1995) and in 1960, to 5% (MOA, 1994). Recent estimates by FAO (1994), and the MOA (1994) show that this is now reduced to 0.4%. The major causes of the disappearances of the vegetation include land clearing to extract firewood, agricultural implements and construction materials. In addition, over-grazing, improper land use, lack of improved agricultural practices, shifting cultivation and burning of grasslands have substantially accelerated the process. The widespread destruction of vegetative cover has affected the structural stability of the soils. The loss of trees results in the loss of nitrogen returning back to the system. With the decline of fuelwood, many rural communities resort to use animal dung and biomass residues for household energy requirement thus, depriving the land of nutrients. This loss is not in all cases replaced by either the addition of fertilizers or the planting of leguminous plants. Overgrazing. Livestock is an important component of the agricultural sector (FAO, 1994). The indigenous livestock population is estimated about 1.65 million Tropical Livestock Unit (1 TLU = 250 kg). These comprise of 1,258,000 cattle, 4,153,000 goats, 851,000 sheep, 268,000 equine, 185,000 camels and 2.5 million backyard chickens (Azbaha et al., 1996). FAO estimates about 40% of the livestock are found in the highlands. These comprise mainly of oxen used to plough the land and the rest are kept in the lowlands. The overall livestock size expressed by TLU is not markedly different from the estimated FAO carrying capacity. The issue of overgrazing among pastoral herd remains debatable. Azbaha et al. (1996) argues that using carrying capacity and stocking rate used to determine the number of animals that theoretically can be supported on rangelands. This useful only in providing a generalized description of the ecosystem, averaged over space and time. In the Eritrean context, space and time are important indicators rather than the number of animals that determines the sustainable carrying capacity of the system. In the highlands sedentary agriculture, livestock have contributed substantially to land degradation primarily because of lack of mobility and lack of feed during the dry season. During the rainy season, most of the southern and central highlands are cultivated and animals do not get enough grazing areas. Consequently, in localized areas (water holes, routes etc.), trampling the soil during the wet season results in localized compaction. The same is also reported by Jones (1991) Integrated soil management for sustainable agriculture and food security in Southern and East Africa 187
in the northern midlands agro-ecological zones of Eritrea. Compaction results in poor infiltration and causes accelerated runoff. The net result is creation of gullies and poor regeneration of vegetation. Soil mismanagement. In Eritrea, the traditional land tenure varies from place to place (Nadel, 1946; Ambaye, 1964; Jordan 1989; Kidane, 1992). Until recently, there were three main systems: Resti (family ownership), the Diessa (village or collective ownership) and Demaniale (state ownership). In Resti system, land is acquired by occupation, purchase or grant by rulers and could be individual or institutional such as the church. The ultimate ownership resides on extended family who have pioneered the earliest settlement in an area. An individual landholder can cultivate the land and arrange share cropping but cannot sell to an outsider without the consent of his extended family (Azbaha et al., 1996). In this land tenure system, unlike agricultural land, pasture land is communally owned. Diessa land tenure system is village-wide ownership of land (Azbaha et al., 1996) and prevails mainly in the highlands of Eritrea. Land belongs to the village community and is managed by a committee of village elders that establish criteria for eligibility for the full share of crop fields. The crop fields are subject to redistribution every 5-7 years. To ensure equitable distribution of land, the various land categories are classified into very fertile, fertile and poor soils. A household is entitled for a field in each group which could be located in different sites. These have resulted into an increasingly fragmented parcels of land that are difficult to manage. The increasingly small sized parcels, also force farmers to plough against the contour exacerbating the risk of soil erosion. Moreover, it has also diminished the willingness of the farmers to practice effective soil and water conservation. In the current situation, it is difficult to share water channels. Village ownership of land does not favour the integration of multi-purpose perennial trees and crops. Besides, integration of livestock into the system is difficult essentially because the grazing resources are communally managed. This hinders the potential benefit of the livestock to soil fertility. These happen because the community members are aware that their land would be given to another farmer in the following land redistribution. Demaniale refers to state ownership of land. Italians introduced Demaniale by confiscating holdings of the indigenous population. In the lowlands, all areas were declared as Demaniale. During the British rule, confiscation of land was in favour of demobilized Italian soldiers (Mesghina, 1988). The Demaniale lands have been open to access to every body. Open access and unregulated land use system is believed to have subjected land to abuse. While Demaniale opens land to abuse Diessa and Resti lead to land mismanagement. In addition, land in Resti and Diessa suffers from poor maintenance, lack or shortening of the fallowing period and has a negative impact on the agricultural productivity of the soil. Furthermore, the rapid population pressure has led to successive fragmentation of arable land and the unscrupulous cutting of trees which are typical evidences of land mismanagement. Population pressure. Above sixty percent of the Eritrean population live in the highlands that accounts only to about 5-10% of the total land mass of the country. This area was once very suitable for the production. However, steady increase in human population over the past decades has led to the fragmentation of holdings and the pressure to move into marginal land. Period of fallowing have been reduced while the continued use of low level of technology and inputs have compounded the depletion of soil fertility in most parts of the highlands.
Biophysical impacts The biophysical impacts of land degradation are reduction in the organic content of the soil and loose soil structure. Moreover, erosion by water creates huge gullies and results in the reduction 188 Eritrea
of agricultural lands. Poor organic matter in the soil accelerates leaching of the essential elements that is essential nutrient to crop and thus results in decline of productivity. Losses of vegetative cover and grazing areas have also equally important consequences on the overall production.
Economic impacts Reliable data on the economic impact of land degradation in Eritrea are scanty. However, There is a decline in agricultural production in all parts of the country owing to loss of fertility. Yield has dramatically declined by 1/3 during the past three decades. Consequently, farmers depend largely on sale of animals, animal products and other off-farm activities. Currently the trend is most families are not self sufficient with their domestic grain demands. The constant food deficit is exerting more pressure to the resource base of the country. The average yields of the major crops in the Central Zone are shown in Table 3. The data presented in this table show also that the there is a gradual decline in yield of all the cereals grown in the highlands. This could be corrected in the short term by applying commercial fertilizers.
TABLE 3 Yield of crops on farmers’ fields without fertilizers in Central Zone (quintals/ha) Crop 1992-93 1994 1995 Average Barley 11.70 9.40 8.96 10.10 Wheat 9.63 7.11 7.28 8.00 Maize 8.45 10.00 5.88 8.11 Sorghum 4.90 7.97 1.32 4.72 Taff 2.89 4.80 1.72 3.17 Pearl Millet 5.90 10.70 0.68 5.76 Finger Millet 8.24 4.80 2.00 5.01 Source: Azbana et al., 1996
The data in Table 4 show that there is a potential to enhance production by adding commercial fertilizers. Yield has increased by 40.7%, 42.2% and 45% in barley, wheat and sorghum thanks to the application of 50 kg of DAP.
TABLE 4 Yield increase of fertilized wheat, barley and sorghum in two locations (quintals/ha) Crop Yield without Yield with Difference Increase fertilizers fertilizer quintals/ha quintals/ha quintals/ha % Barley 14.46 20.35 5.89 40.73 Wheat 13.50 19.20 5.70 42.20 Sorghum 23.18 33.75 10.57 45.59 Source : Azbana et al., 1996
AVAILABLE TECHNOLOGICAL OPTIONS FOR CONTROLLING SOIL DEGRADATION AND ENHANCING PRODUCTIVITY National activities The technological options so far are limited. Since independence, the Government of the State of Eritrea has taken top priority activities related to soil and water conservation as shown in Table 5. Most land rehabilitation and the soil and water conservation activities are on hillsides. Local farmers do the work in turn of Food for Work (FOP) and Cash for Work Programmes (CFW). At the moment, there are no scientific evidences on the impact of these activities on the agricultural productivity. In spite of this however, the vegetation in enclosures is regenerating Integrated soil management for sustainable agriculture and food security in Southern and East Africa 189
well. Earth dams and ponds have made significant contribution to alleviate the shortage of potable water. However, many of the earth dams in the country are not fully exploited for irrigation purposes. In recent years, terracing, earth bounds and soil conservation measures have also been expanded to agricultural fields. The success of such initiatives will depend eventually on the land tenure reform. Personal observation indicates that fields with earth bounds, check dams and terraces have improved yield owing to better moisture holding capacity. However, this requires to be substantiated with quantitative data and hence a detailed study.
TABLE 5 Soil and water conservation activities so far undertaken in Eritrea Activities Year 1992 1993 1994 1995 1996 Total Hillside terraces 55 891 25 276 11 678 12 010 4 223.5 109 078.5 (km) Check dam (km) 1 183 606 174 347 72.5 2 382.5 Microbasins 145 174 208 888 241 757 177 821 7 000 780 640 Seedling produced 18 918 622 18 966 312 10 021 137 13 577 096 8 621 373 70 104 540 Planting & replanting 17 644 893 17 166 642 7 790 116 11 870 528 4 164 165 58 636 344 nurseries Nurseries 10 19 11 4 2 46 established Closures (km) 49 942 22 589 4 503 34 966 9 805 121 805 Earth dams 51 24 11 30 15 131 Ponds 19 54 18 17 5 113 Wells 33 34 22 13 3 105 Embankments (km) 171 119 103 105 2 500 Canals (km) 0 7 3 2 28.6 40.6 Diversions (km) 0 1 3 4 - 8 Source: MOA, 1997
Research station activities There are attempts to measure runoff and rate of erosion at experimental station in Afdeyu, Eritrea. Assessment was made to study the impact of different land use systems on the rate of erosion. Some results of these experiments are shown in Table 6. These show that the traditional test plot 2 was able to adequately control soil erosion and runoff, since the erosion level remained at tolerable rate. Test plots 1, and 4 experienced significant differences mainly due to slope. All were similar to vegetative cover (Gunder and Karl, 1987).
TABLE 6 Test plot (2m x 15 m) runoff and soil loss results, Afdeyu Slope Test Plot Cover Soil Loss Runoff Runoff (%) (No) (T/ha) (mm) (%) 2 2 maize 8.30 34.10 8.9 10 3 grass 23.7 165.80 43.1 31 1 grass 44.50 188.90 49.1 65 4 grass 33.2 150.90 39.2 Source: Gunder and Karl, 1987
Traditional activities In Eritrea, the different groups have adopted methods to combat soil erosion. These methods include stone bounds, earth bounds, stone walled diversions, structure across slopes, ridging along contour and leaving stand trees in agricultural fields. However, the level of application of 190 Eritrea
the technique or group of techniques varies from one socio-economic groups to another as shown in Table 7. In addition to combating the adverse effects of erosion, farmers in Eritrea have also developed various methods to tackle decline in soil fertility. Gaim (1996) indicated that none of the socio-economic groups in Eritrea use forest fallow. Except for the Maria, none of the groups used commercial fertilizers. The different coping strategies across the different groups are shown in Table 8. In some areas in Eritrea, where land was periodically redistributed, most people lived within the margins of subsistence. In order to catch up the annual subsistence, every farmer had to increase its labour.
TABLE 7 Common methods applied to counter soil erosion by socio-economic groups of Eritrea Methods II III IV V VI VII VIII IX Stone walled terraces ++++ +++ - ++ + ++++ - +++ Earth bunds ++++ ++ - + + +++ + +++ Stone walled diversions ++++ ++ - + - ++++ - ++ Structures across slopes ++++ ++ - + ++ +++ - + Ridging along the contour ++++ + - - - ++ - + Stand of trees ++++ + - + ++ +++ - ++ Barriers of bushed to ++ ++ - + + +++ + + accumulate debris in gullies Source: Gaim Kebreab, 1996 Notes: II = Tigringya, III = Saho, IV = Benamer, V= Maria, VI = Nara, VII= Bilen, VIII= Hedareb, IX= Beitjuk; ++++ = used by all respondents, +++= used by 75% of respondents, ++= used by 50% of the respondents, += used by 25% of respondents and - = not used or 0 -25%.
TABLE 8 Traditional knowledge techniques applied to counter fertility decline in Eritrea Methods II III IV V VI VII VIII IX Forest fallow ------Bush fallow - - +++ ++ ++++ - ++++ - Short fallow + ++ ++ ++ ++ + ++ + Organic manure ++++ ++ - + ++ +++ + +++ Fertilizer - - - + - - - - Crop Rotation ++++ ++ - - - +++ - ++ Inter-cropping ++++ + - - - +++ - +++ Vegetation burning + + + - ++ ++ + - Source: Gaim Kebreab, 1996
SUCCESSFUL CASES OF IMPROVED SOIL MANAGEMENT Large scale improved soil management schemes are not common in the country. Since 1995, however, there are some efforts aimed at introducing soil management packages. These include distribution of fertilizers to farmers, Vertisol and spate irrigation management.
Vertisol management The sub-zone of Adiquala is one of the agricultural potential areas in Eritrea. It is located in the south mid-altitude agro-ecological zone of the country. The main soil types in this area are vertisols that are characterized by poor drainage particularly during the wet season. Poor drainage hampers early seedling growth and development of crops grown in the area. Recently, to tackle this problem, Vertisols management programmes were introduced on a small scale. In addition, commercial fertilizers are distributed to farmers on credit through SASAKAWA global 2000. Although the programme is new, it is gaining wide acceptance by the farmers. In 1996, it Integrated soil management for sustainable agriculture and food security in Southern and East Africa 191
was launched at a pilot level and in the following year it was expanded to include a large number of farmers interested in the scheme. The results from the last two concurrent years indicate that yield of major cereal crops have almost tripled (Table 9).
TABLE 9 Yield in Quintals/ha of Treated and Non-treated Fields in Sub-Zone, Adiquala Crop Yield (Quintals/ha) Fertilizer + Vertisol No Treatment Yield Difference Management (%) Taff 17 4 76.5 Wheat 26 6 76.9 Sorghum 30 7 76.7 Maize 34 8 76.5 Source: Ministry of Agriculture, Sub zone Adiquala, Eritrea.
Vertisol management and application of fertilizers is now integrated at a pilot project encompassing few farmers. In the future, there are plans to expand to other areas with similar problem (Yemane, Head ministry of agriculture, Sub-zone Adiquala, personal communication). Having seen the extraordinary increase in yield, farmers are requesting for the technology. This is because application of fertilizer to the field improved the fertility status of their land. The result is significant improvement on yield of cereals such as wheat, maize and taff as shown in Table 4. Higher yields are expected from combination of fertilizers with vertisol management. The possible reasons for the success of these activities are the: · Use of simple and relatively cheap equipment to prepare drainage canals, · Use of farmers’ experience and local knowledge and their involvement on voluntary basis in the diagnosis and implementation of the programme, · Conducting of on-farm demonstration and training and · Access to credit for fertilizers and pesticides.
Management of spate irrigation World Bank (1994) estimated the total irrigated area in Eritrea to be about 20 000 ha of which about 10 000 ha is under spate irrigation in the coastal plains agro-ecological zone of Eritrea. The major areas under spate irrigation are Sheeb, Wokiro, Shebah, Figret, Zula and Wadilo. In this system, the seasonal floods are diverted to grow sorghum, maize, pearl millet and various vegetables. The major problems in this area include sedimentation of diversion canals and uncontrolled flow of floods. Occasionally field canals and diversion canals are destroyed and cause damage to agricultural fields. Farmers maintain the canals using branches of Acacia trees. For this purpose, a large area of the woodland is cleared resulting in land degradation. Efforts are underway to improve the diversion canals and to construct reinforced concrete structures. In some areas, like Sheeb the diversion canal is already completed and in others it is in process. The objectives of these activities are to ensure a sustainable distribution of water to the agricultural areas and environmental restoration.
INSTITUTIONAL FRAMEWORK AND POLICIES FOR LAND RESOURCES MANAGEMENT Traditional Institutions According to Gaim (1996) institutions influence human choices by influencing the availability of information and resources, shaping incentives and establishing the rules and social transactions. 192 Eritrea
In Eritrea, there were eight customary laws (Gaim, 1996). These laws included land tenure, land management, civil law, family law, and penal laws. Today, these institutions are gradually being replaced by new laws. These institutions were created in response to severe competition for land among the users group. The main functions of these laws were to regulate access to and use of land, arbitration and conciliation forceful sanctions such as group morality and public opinion (Nadel, 1946b). The codes of customary laws contain a wealth of information regarding the traditional resource management systems. Eritrea represents a wealth of mosaic tradition and culture originating from varied socio-economic background of the population. The diversity of the country in terms of ecology and topography is also considerable. It is therefore difficult to make generalized statements about the land tenure and land management practices. Nevertheless in all cases, decisions were made by consensus i.e. collective agreement on the utilization of scarce land and water resources. The Diessa land tenure system is which the land distribution is made periodically by the village council has been questioned by Gaim (1996). The author raised the issue of incentives to the farmers, investment on the land, over-use and under-investment because of the possibility of transfer to the next allocate”.
Government Institutions The Government of the State of Eritrea is in the process of coordinating its activities. At the moment, soil management is dealt within two ministries namely the Ministry of Agriculture and the Ministry of Land Water and Environment. The Government has fully recognized the economic importance of agriculture and the following objectives are set by the Ministry of Agriculture (MOA, 1997): · Food security through the promotion of improved technology, · Employment generation through the establishment of labour intensive activities, · Improve the supply of raw materials to domestic industries by encouraging the farmers to produce industrial raw materials, · Increased foreign exchange earnings through direct and indirect export promotion strategies, · Environmental protection and restoration and · Sustainable satisfaction on the demand for fuel wood and construction materials.
To date, there are no formulated comprehensive soil management policies. In the future, there is a need to set soil management objectives with clear institutional responsibilities. Soil management activities should be integrated with forestry, soil, water conservation and irrigation. Soil management should include both water resource management and rehabilitation of degraded lands. Hence, activities carried out by the Ministry of Agriculture and Land Water and Environment need to be coordinated. The Government of the State of Eritrea has promulgated a new land law (Government of The State of Eritrea, Proclamation 58/1994). The new law will eventually replace the traditional land tenure system. The proclamation guarantees all Eritreans above 18 years of age irrespective of marital status or ethnic affinity usufruct right. The Ministry of land, Water and Environment is responsible for the allocation of land on equitable basis. This new land law would confirm security of tenure and thus increase inputs environmental protection such as planting of trees, building of terraces and application of fertilizers and manure. The new land law provides farmers with lifetime right of usufruct over currently held land thereby doing away with periodic redistribution of land. The life time usufruct is expected to substantially improve incentives favourable to sustainable use of land. Currently, soil management falls broadly under the Ministry of Agriculture and the Land Water and Environment. Both ministries Integrated soil management for sustainable agriculture and food security in Southern and East Africa 193
have baseline information and carry out field activities. The department of Environment has a supervisory role. The current situation in these ministries have limited effectiveness to soil management. It is, therefore, imperative to introduce integrated soil management to boost agricultural production. The issue of soil management needs to be given due consideration. It is also important that law is required to protect investment on land management (commercial investment or management infrastructure) as investors are rarely prepared in the absence of law. The present lack of law, policy and strategy on soil management in Eritrea is a severe constraint to the development of agricultural production. The present laws, proclamations and strategies are only in draft forms and that the constitution is promulgated and gazetted for further gazettement of all legislation, policies and strategies should not be far.
Allocating soil management responsibilities. During the transition period, care should be taken to avoid confusion on land management responsibilities. Allocation of responsibilities should be set in short and long-term perspectives. In the short-term, responsibilities could rest with the central government with grass root participation at village level. In the long-term, however, responsibilities may be transferred to the regional institutions. In the highland, land has been subjected to heavy human and animal pressure over many centuries (Gaim, 1996). That it has been able to support the growing population in the context of available technologies might be due to our failure to understand the copping strategies adopted by the farmers. Gaim (1996) believes that the rules were enforced and conventions methods have evolved over time in response to the need to derive resources of livelihood from fixed or diminishing resources in the context of unstable environment.
Legislation. There is a need for clarification and co-ordination of legislation related to soil management. The need for effective and coherent legislation on soil management is immediate with clear mandate to implement soil management. Other significant social factors like food security and land tenure need to be considered seriously. Integrated soil management legislation could be implemented by the Ministry of Agriculture. In this regard, the role of the central government would be to provide skilled personnel, funds, technical assistance and equipment if necessary. At the same time, it could issue policies, legislation and working guidelines in co- operation with the local government. The role of the zones and sub-zones would be to implement the national action plan in co-operation with local communities. Initiatives, however, would have to be generated from the communities. At grass root level, the villages being the direct beneficiaries of soil management activities, implementation should be done with full participation of the villagers. The technical skills of personnel at the zones, sub zone and the villages levels should upgraded through on job training.
PROPOSALS OF PROGRAMMES FOR IMPROVED SOIL MANAGEMENT AND PRODUCTIVITY ENHANCING Most parts of Eritrea suffer from serious soil erosion and depletion of soil fertility. Integrated soil management strategies should be adopted to eliminate the causes of land degradation. The current situation of food production trends in Eritrea could be improved if a combination of the following improved soil management enhancement programmes would be adopted. · The new land law should be implemented so as to promote investment on land, trees, soil, water conservation structures and fertilizers. In addition, soil management and maintenance strategies of soil and water conservation structures should be enforced at a village level. 194 Eritrea
· Alternative sources of energy should be explored to alleviate the chronic shortage of domestic energy. The use animal dung has detrimental effect on soil fertility and hence production. · Introduction of multipurpose perennial trees and grasses to restore fertility status and reduce soil erosion. · Reclamation of degraded lands (sand dunes, gullies and marginal lands) through construction of mechanical structures and planting trees. In the coastal areas, drought and salinity tolerant multipurpose trees should be identified and tested in multi-locational trials. · Tree planting should be promoted at individual household levels. Appropriate tree selection could be done in collaboration with local farmers. These trees should include exotic and indigenous browse and fodder species. · Studies on the indigenous soil and water conservation practices and soil fertility maintenance strategies should be undertaken. This would provide baseline information for further studies and action. Introduction of soil management practices should be based on the existing socio- economic and ecological setting of Eritrea. This would require a multidisciplinary research team and participatory research approach. · There is an urgent need to assess the erodability of soils in catchment areas as well measure the sedimentation process in down streams and reservoirs. · Dissemination of improved soil management practices at farm level. Preferably, this could be an action-oriented research to address immediate farmers' problems. · There is a dire need to undertake on-farm training and education particularly to farmers and extension workers. The training would include issues related to the importance of integrated soil management practices in boosting agricultural production and environmental rehabilitation. The effect of narrow grass strips, and conservation tillage on soil erosion and yield of crops should be assessed. · In Eritrea, the conservation and rangeland management is usually overlooked while considering soil management options. It is time to reconsider possible techniques to improve grazing areas and reduce land degradation. Studies should be conducted to investigate the effect of overgrazing on soil degradation. · Under the arid situation in Eritrea, emphasis should be given to the conservation and efficient utilization of water resources. Focus should be given to spate irrigation and runoff harvesting not only for crop production but also to improve the quality of browse to the pastoral communities. · Provision of soft loans to needy farmers and reward to exemplary farmers who practice sustainable soil management in their fields.
REFERENCES Appleton, J. A., M. S. Bellmans and Reynolds 1992. Observations on food Security nutrition and demand for fish in Eritrea. Department of Marine resources and Inland Fisheries, Asmara, Eritrea. Araia, W., M. K. Omer, A. Haile and W. Ogbazghi 1994. Resource-Base, Food Policies and Food Security. In 'Inducing Food Insecurity Perspectives on Food Policies in Eastern and Southern Africa,' Ed. M.A. Mohammed Saleh, The Nordic African Institute, Uppsala, Sweden. Awalom, H. 1996. A research proposal on food security in Eritrea: an overview. Unpublished MOA Eritrea. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 195
Azbaha et.al., G. Iyassu, W. Ogbazghi, K. O. Mohammed, W. Araia, Tesfaselassi and Ghiday 1996. Rehabilitation of Degraded Lands in Eritrea. University of Asmara, MOA and IDRC. Asmara, Eritrea. Biswas, Asit K. And Biswas M.R. eds. 1980. United nations Conference on Desertification. Oxford, Pergamon Bojo 1995. Rehabilitation of Degraded Lands In Eritrea. World Bank Report. Cliffe, L. 1988. Food and agricultural production assessment study: an independent evaluation of the food situation Eritrea. Agriculture and rural development studies, University of Leeds. Cook R. L. And Boyd G. E 1992. Soil Management, A World View of Conservation and Production. Krieger Publishing Company, Malabar, Florida. FAO 1994. Agricultural Sector Review and Project Identification. FAO, Rome. FAO/MOA 1996. Formulation of a national Food security and Nutrition Programme. A report on Working sessions, Keren, Eritrea. Fisseha, A. 1995. The role of Eritrean rural women in the fight against desertification. A paper presented at the IGADD sub-regional workshop in Asmara, 1-3 August 1995. Gaim, K. 1996. People on the edge of the horn. Red Sea Press. Ghebru, B. and Asefaw Tekeste, 1995. A case of disaster Profile: The Eritrean Experience. UN Disaster Management Training Programme for Africa. Eritrea-National Work shop 20-24 Feb. 1995. GOE 1994. Proclamation of the State of Eritrea No 58/1994 on changes on land holding and use procedures. Government of the State of Eritrea 1994. Macro-Policy. Grunder. M. and Karl H. 1997. Soil Conservation Research Project. Vol. 8. Seventh progress Report. University of Berne, Switherlanl. GTZ 1991. Integrated Food Security Programmes. Agricultural services and food security, OE 421. Haile, A., W. Araia, M. K. Omer, W. Ogbazghi and M. Tewolde 1995. Diagnostic Farming Systems Survey in South Western Hamasien Eritrea. CAAS, University of Asmara, Eritrea. IGADD 1996. Food Situation Report, No. 1/96, IGADD, Early warning and food information System, Djibouti. Jones, P. S 1991. Restoration of Juniperus exelsa and Olea europaea sub sp africana in woodland in Eritrea. A Ph.D. Thesis, Department of Biological and Molecular Sciences, University of Stirling, Scotland. Leach M. and James Fairhed 1994. Natural Resource Management: The Reproduction and Use of Environmental Mismanagement in Guinea's Forest-Savannah Transition Zone. ids bulletin 25 no 2 1994. Maskey R. B. 1985. Soils their Fertility and management in Eritrea. University of Asmara. Unpublished. MOA 1997. The State of Eritrea's experience on the implementation of UN-CCD MOA 1992. Annual Report. Asmara, Eritrea. Murphy H.F.1959. A report on the Fertility Status of Some Soils Of Ethiopia. Experimental Station Bulletin No 1. Imperial Ethiopian College of Agriculture and Mechanical Arts. Nadel. F. S. 1946b. Land Tenure in the Eritrean Plateau. Journal of International African Institute VOl. XII No1. Nyborg, I. and R. Haug 1994. Food security indicators for development activities by Norwegian NGO'S in Mali, Ethiopia and Eritrea. The SSE program, NORAGRIC. Riley, Frank 1995. Addressing Food Insecurity in Eritrea. A report prepared for World Food Programme/ Eritrea Draft. 196 Eritrea
Tecleab M. and B. Ghebru. 1997. Analytical Review of the National Agricultural Research System NARS in Eritrea. Tesfay G. 1992. Agricultural Development in Eritrea. A Paper Presented at the Economic Policy Conference 15-19, July 1991, Asmara, Eritrea. Thomas D. B. E. K. Biamah, A. M. Kilewe, L. Lundgren and B. O. Mochge 1986. Soil Conservation in Kenya. Department of Agricultural Engineering, University of Nairobi and SIDA. UNICEF 1994. Children and Women in Eritrea. World Bank 1994. Eritrea options and Strategies for Growth Vol I-II reports No 12930-ER, Washington D.C. world Bank. Yemane M. 1988. Italian Colonialism, the case Study of Eritrea 1869- 1934. Lund, Sweden. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 197
Ethiopia
COUNTRY FOOD PRODUCTION AND REQUIREMENT The total area of the country is 1.1 million square kilometres out of which about 79 million hectares are suitable for agriculture, although only approximately 7 million hectares are used for crop production in any one year (FAO, 1986). Economically, the highland zone is important as most of the economic activities are concentrated in this zone. Although large portions of the highlands are put under continuous cultivation, the total amount of grain produced every year is very low. It is estimated that yields on the overall are about 10 q/ha for cereals, which is considered very low as compared to the potential yield of these crops. This is mainly due to the extremely low level of plant nutrients in the soil that does not allow the crops to express their potential yields, even in areas where there are no moisture limitations. In the majority of the highlands that have been settled for several centuries, the soils have been continuously mined for nutrients through harvests and soil erosion. The yield of crops in most areas has continuously declined and in some cases has reached a point where the soils can no longer support plant growth. Except in some alluvial plains, where the soils are recharged every year with top soils carried away from over-lying areas, the productivity of the majority of the highland soils have reached the lowest level. Ethiopia is the second most populous country in sub-Saharan Africa, with a population of more than 55 million and a growth rate of 2.4% per annum, of which 89% lives in the rural areas. The country's social indicators are among the lowest in the world, with over half the population suffering from chronic food insecurity. Out of the total potentially arable land, only 14.8% are currently under production of annual and perennial crops. In general, cereals are the most important crops occupying about 76.3% of the total cropped area and 70% of the caloric intake of the population. The remaining is occupied by pulse and oil crops (2.1%), coffee (5.1%), fruits and vegetables (1%), and cotton (0.8%). Out of the estimated total annual cereal crops output (average of 9-10 million metric tons) the contribution of the small holder farmers is about 96%. Recurrent draught and consequent depletion of assets of peasant farmers have made the agricultural sector weak and vulnerable (World Bank, 1995). Despite the enormous agricultural resource base, the country has been facing reduced crop production and food insecurity during the last two decades, since 1970. Recurring draught periods had significant effect on crop yields. By 1990, the balance between food production and population growth had worsened. The per caput calorie intake per day had decreased dramatically from around 1 740 in 1983 to 1 550 in subsequent years. Considering the cereals contribution to the national diet (70-80%), it was estimated that additional gross production of 5 million tons per year were needed to meet the populations food requirement and avoid famine in the nineties (Bateno, 1997). For generations, Ethiopian farmers have been producing at subsistence level. This is mainly due to limited access to modern research-led agricultural technologies, including inputs such as fertilizers and organic matter.
Sahlemedhin Sertsu National Soil Research Laboratory, Ministry of Agriculture, Addis Ababa 198 Ethiopia
Traditional farming systems are low yielding due to excessive depletion of plant nutrient, and as a result farmers are continuously forced to expand their territory of cultivation to marginal lands that are prone to excessive erosion. All these and other factors have resulted in low cereal crops yield, hence, excessively lowering the total grain production of the country (Table 1). The possibility of expanding the areas under crops in the central highlands is severely limited, due to the growing population pressure and the large number of livestock herds. Land scarcity has led to increasing the cropped area at the expense of both fallow and grazing, with crops being grown on more marginal, steep and poorly drained lands that are more susceptible to erosion. Moving to the sparsely populated lowland areas (expansion to virgin areas) is restricted due to human and livestock diseases, and unavailability of public service facilities, etc. Estimated food production and requirement balances for the country from two sources are shown in Tables 2 and 3.
TABLE 1 Major cereal crops grown in Ethiopia: average area, total production and yield, 1990-92 Crops Area (hectares) Production (Mt.) Average yield (quintals) Teff 1,318 1,028 7,8 Maize 1,000 1,605 16.1 Sorghum 813 899 11.1 Barley 950 914 9.9 Wheat 687 886 12.9 Source: FAO computer files AGROSTAT/PC (quoted by Belay, 1997)
TABLE 2 Food production and requirement balance up to the end of the century Items Unit Years 94 95 96 97 98 99 Population Projection @ Million 54.43 55.90 57.41 58.96 60.55 62.19 2.7%/year Per caput food grain requirement kg/year 134.00 136.00 138.00 142.00 146.00 150.00 (cereals + pulses) Total net food grain requirement million 7.29 7.60 7.92 8.37 8.84 9.33 (row 1x2)1,000 tons Gross food grain requirement million 8.38 8.74 9.11 9.63 10.17 10.73 including wastes & seed (@ 15%) tons Domestic output with incremental fertilizer use I) assumed growth rate % 3.00 3.00 3.10 3.20 3.30 3.40 II) estimated production million 7.60 7.83 8.07 8.33 8.60 8.89 tons Estimated food sap (Row 4- 5 (II) million 0.78 0.91 1.04 1.30 1.57 1.84 tons Source: World Development Report, 1993 (quoted by World Bank, 1995)
Even though an extensive area of land is cultivated each year and the size of the population engaged in the farming business is very large, the total annual food production is always much below the national requirement. Although a number of natural, socio-economical and political reasons could be attributed to the low crop productivity, the major ones are: · Extreme exhaustion of nutrients and degradation of the soils as a result of several centuries of continuous cultivation, particularly on the highlands, with little to no external inputs and very low level of soil management thus exposing the land to extreme soil erosion and degradation, · The total dependence of crop production on rainfall, which is very erratic from year to year in both amount and distribution, Integrated soil management for sustainable agriculture and food security in Southern and East Africa 199
· Fast population growth as compared to the stagnant level of crop production, which also increased the stress on agricultural land and decreased yield per unit area, · Excessive land fragmentation, redistribution and tenure system which made farmers indifferent in utilization of improved land management techniques, · Inability of the majority of farmers to purchase and use essential inputs like fertilizers and utilization of every farm residue for household purposes rather than adding to the soil. There are a number of reasons for the low level of chemical fertilizer used by farmers, the major one being the high fertilizer price. The data in Table 4 show the results of a socio-economic survey conducted in one region which indicated the reasons given by farmers for the limited use of fertilizers.
TABLE 3 Food requirement and balance for the period between 1979-80 and 1988-89 Period Population Food production Food production per Calories per (tonnes) caput per year (kg) caput per day 1978-80 37 758 000 7 495 580 199 1 854 1980-81 38 966 000 6 560 523 163 1 518 1981-82 40 213 000 6 296 217 157 1 463 1982-83 41 500 000 7 805 370 188 1 751 1983-84 42 828 000 6 336 604 148 1 379 1984-85 44 255 000 4 855 301 110 1 025 1985-86 45 737 000 5 403 657 118 1 099 1986-87 47 189 000 6 261 697 133 1 239 1987-88 48 587 000 6 769 778 139 1 295 1988-89 50 167 000 6 375 812 127 1 183 Average 6 416 054 148 1 380 Sources: C.S.A. 1991. The 1984 population and housing census of Ethiopia, Analytical Report at National level, pp 307, Addis Ababa; Wheat equivalent 340 calories/100g, ENI. Gunnor Agren and Rosaline Gibson, Food composition Table for use in Ethiopia
TABLE 4 Farmers view on fertilizer consumption Reason for low use of fertilizers No. of households % Expensive 1 532 61.3 Unavailable 284 11.4 No difference in production 69 2.8 Lack of knowledge about fertilizers 524 21.0 Others 89 3.5 Total 2 489 100.0 Source: UNDP, SAERP/WARDIS PROJECT in Tigray Region, January, 1997.
EVOLUTION OF PER CAPUT CULTIVATED LAND AND TRENDS IN CEREAL CROP YIELDS Cultivated land against population growth The agriculture sector of Ethiopia accounts for 41% of the GDP, 90% of the foreign exchange earnings and 85% of the employment. Although the total area of the potentially arable land is estimated to be about 79 million hectares, only about 14.8% of it is cultivated at present. Out of the estimated 3.5 million hectares of potentially irrigable areas, no more than 0.1 million hectares are currently under irrigation (Berhe, 1995). In spite of such high potentials for increasing productivity, the expansion in the area of cultivated land is very little as compared to population growth. As a result of excessive soil degradation and nutrient exhaustion, yield per unit area is 200 Ethiopia
also decreasing rather than increasing. The size of the population, however, seems to increase steadily at the rate of 2.7% per annum. Under such circumstances, recurrent famine and hunger are inevitable. In order to meet the food requirement of the growing population, crop production has to be increased through improved management technologies, appropriate land tenure, and agricultural policies. Evolution of land use and the change in cultivated land compared to population growth from 1961 to 1991 is shown in Table 5. These data indicate that the increase in the area of cultivated land is about 20% during the 30 years, while the population growth is about 150% during the same period. Irrigated land increased from 150 000 ha in 1961 to 162 000 ha in 1991, which is still very low compared to the potentially irrigable area of 3.5 million ha. The increase in cultivated land area does not keep pace with the population growth. As a result, the per caput land decreased by more than half. The data also show that the 20% increase in the cultivated land area was at the expense of the pasture and the forestland. The other significant shift as a result of population growth is the increase by about 10% of the land in the "others" category, which is the wasteland that increased as a result of degradation of the cultivated land.
TABLE 5 Population growth, and of land use and cultivated land (ha) per caput evolution, 1961-91 Year Population Cultivated Pasture Forest Others Cultivated land land per-caput 1961 20 000 11 486 46 350 30 000 22 264 0.574 a) 486 b) 11 000 1991 50 000 13 930 44 850 27 000 24 320 0.279 a)730 b)13 200 Variation + 3 000 + 2 444 - 1 500 - 3 000 +2 056 - 0.295 Sources: FAO 1993 (Jassen and Willekens, 1994); 1991. Population and housing census of Ethiopia. Notes : (a) permanent land, (b) annual + irrigated
Major causes of low productivity The majority of the farmers land holdings are too small to be economically viable through the use of inputs, mechanization and efficient utilization of time and labour. This affects highly the productivity of farmland. The fact that the land belongs to the Government and continuous reallocations and redistribution of land have been taking place in the past and is still occurring at present, has taken away the sense of ownership from the farmers. Such lack of ownership results in less commitment for the conservation and better management of soils and other land resources that are essential for improving agricultural productivity, hence, bringing about excessive land degradation and continuously declining productivity. The lack of ownership to the land has a multiple effect on soil and land management and agricultural productivity. The fact that a farmer never feels sure of maintaining his land to be able to pass it to his children or to sell it any time he wants, prevents him from investing on his land for long-term rewards. Because, he always thinks that the part or whole of his land could be passed to another person, if officials feel to do so. This means, farmers have the tendency to make the land less attractive to others, i.e. less productive and degraded. In other words, they try to use the land for a longer time with little investment and effort, before the land is fragmented and passed to another person, without compensation for permanent crops, if they at all have established one. The major land improvement incentives to the farmers in Ethiopia, particularly for soil conservation works, are the grain and oil rations that are issued as part of the food for work programme. Such programme, although, has run for a long time, was not found to be successful. The lack of success was mainly because most of the farmers consider the grain and oil incentives as a source of rations rather than soil management Integrated soil management for sustainable agriculture and food security in Southern and East Africa 201
incentives, resulting in piling and unpiling of stone-bund terraces on the same piece of land every year. Research outcomes have shown that the majority of the cereal cultivated land on the highlands are highly responsive to N and P fertilizers because of the high exhaustion of these nutrients from the soils as a result of several decades of continuous cultivation. Although improved seeds and N and P fertilizers are known to increase the yields of the majority of the cereal crops highly, the consumption of fertilizer in the country is still very low (not more than an average of 7 kg of nutrients per ha of cultivated land). The major reasons for the use of low level of fertilizer are believed to be: (i) limited availability of fertilizers (all imported), ii) limitations of road infrastructure for timely supply of fertilizers to all corners of the country, iii) the lack of know-how from the farmers side, iv) limited extension services, and v) the high price of fertilizers as a result of elimination of fertilizer subsidy in recent years. Traditionally, most farmers are aware about the importance of the common cultural practices like crop rotation and fallowing for the maintenance of soil productivity. With the increase of population that decreased the per caput land holdings, the practice of fallowing has been gradually abandoned and the majority of the land is put under continuous cultivation. Moreover, the tradition of rotation of cereals with pulse and oil crops have also become less and less popular. This is because of the high demand for certain cereals on the market which force the farmers to grow specific cereal crop year after year in order to get high market price and be able to survive on their small piece of land. The result of elimination of fallow system, complete utilization of crop residues and the lack of rotation of cereals with pulses have caused excessive soil nutrient exhaustion and the ultimate low yield. Unchecked population growth and overstocking have resulted in encroachment to steep slopes and ecologically precarious areas to meet the need for food and grazing. Such encroachment followed by removal of natural vegetation and improper land use practices has resulted in the degradation of the cultivated land, eventually converting it to bad land. Such degradation poses the greatest long-term threat to human survival in Ethiopia and remains to be one of the greatest challenges facing the people and the Government today. Under the traditional tenure system, land has been continuously sub- divided among farming members through generation inheritance claims. Reallocation of land by peasant associations earlier and by Regional Government Officials lately, has also resulted in an ever-decreased holding of parcels of land by the farmers. Traditionally, the grain-livestock mixed agriculture is mainly on the highlands, that are relatively free of human and livestock diseases. Although extensive area of land with sufficient rainfall are available in the warm and humid areas, because of the high infestation of human diseases like malaria and livestock diseases through the vector, tsetse fly, expansion of cultivated land to such areas are very much restricted.
EXTENT OF SOIL DEGRADATION AND ITS BIO-PHYSICAL AND SOCIO-ECONOMIC IMPACTS Types of soil degradation and causes of low agricultural productivity Excessive exhaustion of nutrients from the soil through continuous cropping with little or no input through residue incorporation or other external inputs in the form of organic and inorganic fertilizers has become a serious yield limiting factor to the majority of the highland farmers. The results of soil fertility and fertilizer studies in the past have indicated that the majority of the areas under cereal crops are highly responsive to nitrogen, about 25% of the areas, particularly the red soils, are responsive to phosphorus and only few areas are responsive to potassium fertilizers. The general landscape, unique topography, heavy deforestation, intensive rainfall and low level of land management have resulted in heavy soil erosion, particularly in the northern and central highlands. The consequences being low content of mineral nutrients and low moisture 202 Ethiopia
holding capacity of soils, hence low productivity. TABLE 6 The majority of the soils occurring in the warm and Major soil fertility limitations in humid areas of the country are acidic in reaction as a Ethiopian agriculture result of excessive leaching of bases. The Limitations Area productivity of such soils is low because of high P % Steep slopes (8-30%) 32 requirements, Al toxicity and deficiency of the base Erosion prone soils 30 elements. The extent of the moderate to strongly Shallow soils 29 acidic soils (pH <5.5) in the country is around 13%. Very steep slopes (>30%) 26 Most of the soils in the arid and semi-arid areas of Dry 18 Basic reaction 17 the eastern and south-eastern parts of the country, Acidic 11 particularly the irrigated and potentially irrigable Low K reserve 9 lands are saline/alkaline and are prone to this Vertisols 9 problem. Approximately, about 4.5% of the total Aluminium toxicity 5 Salinity 5 land area of the country is believed to be salt Low moisture holding capacity 3 affected. As a result of poor irrigation and drainage Low CEC 1 water management, about 7% of the 70 000 ha of Source : Janssen and Willekens, 1994 irrigated cotton farmland in the Awash valley (within the Rift Valley) is believed to be already salinized. A large portion of the area on the highlands and the alluvial plains are covered with Vertisol or soils with vertic characteristics (10% of the total land area of the country). Such lands are not normally utilized for crop production, due to the excessive waterlogging problem during the main rain season. The water logged soils on level plains are usually used as grazing grounds or for growing crops at the end of the rainy season, particularly crops such as durum wheat and chick- pea that can strive on reserve moisture. High yields are not obtained from these crops due to insufficiency of moisture and low soil fertility. The major soil fertility limitations under Ethiopian agriculture are outlined in Table 6. Among the arrays of yield limiting factors, soil erosion and problems associated with the slope of cultivated lands seem to be the major problems on the highlands.
Extent of soil degradation through erosion Among the complex environmental problems the country faces today, soil erosion and deforestation are the most serious ones that are believed to be the root causes of the recurring food shortage and famine. Out of the estimated 60 million ha of agriculturally productive land (with more than 120 days of growing period), about 27 million ha are significantly eroded, 14 million ha are seriously eroded and 2 million hectares have reached the point of no return; with an estimated total loss of 2 billion cubic metres of top soil per year (Fikru, 1990). Another report also indicates that as a result of such degradation, about 20,000 square kilometres of farm land are thought to have lost their fertility and productivity base (FAO, 1986). Although the magnitude of erosion and soil loss varies from place to place depending on the climatic condition, soil type, land use land cover, etc., the average annual soil loss from cultivated lands are estimated to be about 100 tons/ha (FAO, 1986). Results from experimental plot tests (SCRP, 1985) have indicated that the rate of soil loss in extreme cases range from 0 to 300 metric tons/ha/year. An average soil loss observed from SCRP experiments conducted in six different agro-climatic regions was 70 tons/ha/year, which is beyond the concept of any permissible soil loss. The Ethiopian highland reclamation study (FAO, 1986) predicts that, even if erosion rates stay at their current level, it is projected that the area of farm lands on the highlands with a soil depth of less than 10 cm, which is estimated to be 20 000 km2 at the time of the study, is expected to increase five-fold in the year 2010 and will cover an area of 10 000 km2 arable land. This Integrated soil management for sustainable agriculture and food security in Southern and East Africa 203
means all the essential soil properties and constituents will be lost and the land becomes unproductive.
Estimated nutrient loss through erosion Soil fertility is intricately and insidiously related to soil erosion. High amount of plant nutrients and organic matter are lost along the removal of topsoil by erosion. The magnitude of such losses vary from place to place depending on the degree of erosion and the nutrient content of the soil in question. The calculated range of nutrient losses per ha from the highlands of Ethiopia through soil erosion is given in Table 7. The bases for the calculations of these values are the actually measured soil loss figures and the commonly reported nutrient content values for an average shallow soil in the highlands of Ethiopia.
TABLE 7 Calculated range of nutrient losses through erosion from the highlands of Ethiopia (kg/yr per ha) Plant nutrient Nutrient content Soil-loss range Total amount of nutrient lost of soil lowest highest lowest highest Organic Matter (%) 2.0 18.0 214.4 360 4,288 Total N (%) 0.2 “ “ 36 429 Available P (ppm) 22.9 “ “ 0.412 5 Exchangeable K (%) 0.0078 “ “ 1.40 17 Exchangeable Ca (%) 0.16 “ “ 28.8 343 Exchangeable Mg (%) 0.048 “ “ 8.64 103
Economic impact of soil degradation The estimated range of losses in terms of maize and wheat yields as a result of soil erosion (nutrient loss) is shown in Table 8. The bases of the calculation in estimating these yield losses are the loss in nutrient (N) through erosion at two extreme locations (Table 7) and the crop yield/fertilizer response ratio for wheat and maize (Bateno, 1997). The value of N lost through erosion is considered as fertilizer nutrient, because it is the most limiting nutrient to which crops respond highly in most areas on the highlands.
TABLE 8 Calculated loss in grain yield due to losses in nitrogen through erosion Crop Yield lost (kg) Range of nutrient loss Total yield lost (mg/ha) per kg N lost N (kg/ha) due to N lost (Crop response ratio) low High low high Maize 9.6 36 429 0.345 4.12 Wheat 6.9 36 429 0.248 2.96
The calculated economic impact of nutrient losses from the highest and lowest soil loss areas, in terms of monetary values of crop yield losses and in terms of replacement fertilizer equivalent values of the lost nutrients are shown in Tables 9 and 10, respectively. The data in Table 7 show that the loss of major nutrients through erosion, including soil organic matter, is very high, particularly in the high soil loss areas. The values of nutrients and soil organic matter lost through erosion, in the low and high soil erosion areas, respectively, are: organic matter (360 and 4288 kg/ha/yr), total nitrogen (36 and 429 kg/ha/yr), available phosphorus (0.412 and 4.9 kg/ha/yr), exch. potassium (1.4 and 16.72 kg/ha/yr), exch. calcium (28.8 and 343.0 kg/ha/yr) and exch. magnesium (8.64 and 102.91 kg/ha/yr). 204 Ethiopia
TABLE 9 Monetary values of crop yield losses as a result of soil degradation Crop Yield lost Grain price Total loss (Mg/ha) (Birr/kg) (Birr) Lowest Highest Lowest highest Wheat 0.248 2.960 1.60 396.8 4,736 maize 0.345 4.118 0.80 276.0 3,294
TABLE 10 Loss in terms of replacement fertilizer (N, P and K) equivalent values as a result of soil degradation Nutrient Nutrient loss Price as fertilizer Total loss in terms of cash (kg/ha) (Birr/kg) (Birr) Lowest Highest Lowest highest N 36 429 1.90 68.4 815.10 P 0.412 4.9 2.00 0.82 9.80 K 1.4 16.72 2.00 2.80 33.44
The magnitude of losses of nutrients in the rest of the areas is believed to be in between this ranges. Considering the low level of soil fertility and the extremely low crop yields obtained in most of the highlands of the country, and where very little to no fertilizer is applied to the soils, the above estimated nutrients losses through soil erosion is considered very high. The impact of such soil and nutrient losses, in northern Shoa, where soil loss values are the highest, is clearly reflected in the real situation through the extremely low crop yields and the absolute poverty of the farmers in the area. Most of the sloping lands in this high erosion areas are completely devoid of soils and the bare rocks are exposed on the surface. The reclamation cost in order to bring these soils back to normal production, if there is going to be any attempt at all, is going to be very high in terms of physical management and the supply of nutrients.
AVAILABLE TECHNOLOGICAL OPTIONS FOR CONTROLLING SOIL DEGRADATION AND ENHANCING PRODUCTIVITY Through national and international efforts during the last twenty years, agricultural research has attempted to overcome the basic agricultural productivity constraints, giving more attention to crop improvement programmes. Side by side with the crop improvement programme, though not intensively, research on soil conservation and soil fertility improvement have also been undertaken. In terms of the research findings and development of technology packages, the achievement in agricultural research could be rated successful. The problem is the lack of transfer of technology to the farmers to show significant impact in improving agricultural productivity at national level. Some important and promising research findings and available technology packages are summarized below.
Soil conservation techniques Results of soil conservation research conducted on erosion susceptible farmers’ fields representing the major agro-ecological zones, have indicated that any of the common techniques could highly influence soil loss, if used by farmers. There are, however, high differences among the different types of conservation techniques in controlling erosion. Conservation techniques tested on farmers’ fields and their soil loss reduction effects are shown in Table 11. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 205
Fertilizers (NP) and improved seeds TABLE 11 Since the inception of the fertilizer trials in the Effect of different soil conservation techniques in reducing soil loss at country some forty years ago, the high response of different locations most of the cereals to N and P fertilizers has been Treatment Soil loss reduction realized. The majority of the crops and areas gave (%) high response to N and about 25% to P, particularly Control 0 on red soils, while little or no response has been Graded bunds 32 Graded fanya-juu 54 observed to K. Because of this reason, the extension Grass Strip 66 activities are focusing mainly on N and P fertilizers. Level bunds 80 Although there are good responses to NP fertilizers, Level fanya-juu 89 the farmers in most places did not realize the benefits Source : Berhe, 1993 very well. This is mainly because of lack of know- how on the usage, lack of proper cultural practices like weeding etc., lack of improved seeds, the high price of fertilizer and shortage of moisture. It has been proved to the farmer, however, that crop yields could be increased several fold if packages of technologies like fertilizers along with improved seed and proper cultural practices are used. A number of technical reports and references on research findings could be cited as to the positive effects of technology packages like fertilizers and improved seeds in increasing crop yields. The data on Table 12 show the difference in grain yield of different cereals grown under the traditional practice and those grown according to the recent extension of fertilizers (NP) and improved seeds package in different regions. It could be noted from these results that yield could be increased in several folds with the use of the improved package if moisture is not a limiting factors.
TABLE 12 Yield achievement by farmers 1994-95 Traditional average (Mg/ha) EMIP average (Mg/ha) Region maize wheat Teff sorghum maize wheat Teff sorghu m Tigray 1.0 0.7 0. 4 0.9 3.0 2.0 1.0 2.5 Amhara 1.5 0.7 0.6 1.4 5.0 3.5 1.5 3.0 Oromiya 1.6 1.1 0.6 1.1 4.5 3.4 1.35 3.1 South 1.6 1.2 0.6 - 4.1 2.7 1.3 - Harari 1.2 - - - 2.5 - - 2.0 Region 12 1.2 - - - 3.0 - - - Source : Evaluation report NEIP/EMIP
Improved drainage With an extensive area of poorly drained soils in the country, where the Vertisols (dark clay soils) alone represent over 10% of the total land area, drainage is an important soil management technique for increasing agricultural productivity. Although most Vertisols on the highlands receive sufficient moisture during the rainy seasons, traditionally they are used mainly for free grazing and very little for crop production. This is mainly because of their drainage problem which makes it impossible to grow crops during the rainy seasons. To a limited extent, these soils are used for the production of chickpeas and durum wheat that are planted at the end of the rainy season utilizing the reserve moisture in the soils. At experimental level, it has been demonstrated that with the use of improved land preparation methods like camber-beds to reduce water logging problems and with the application of N and P fertilizers, cereals could be planted on Vertisols and other water-logged soils at the onset of the main rain season. Following such cultural practices that are followed on the upland soils, higher yields could be obtained on Vertisols. However, the preparation of camber beds for draining excess moisture from Vertisols requires mechanization 206 Ethiopia
and could not be easily done with traditional local plow which is pulled by a pair of oxen. Some technology packages on improved land preparation methods that are within the capacity of the farmers, however, have been also tested and demonstrated to the farmers. These are the broad- beds and furrows (BBF) land preparation method with specially designed tools to fit the local plow system and be pulled by a pair of oxen. With the use of this drainage technique and the application of fertilizers (NP) along with improved seeds, crop yields on Vertisols could be highly increased at the peasant farmers’ level. Some tested technology package for improving the productivity of waterlogged soils and are available for use by farmers are cited below.
Organic fertilizers and improved cultural practices Experimental results have repeatedly shown that the application of fertilizers (organic or inorganic (N and P) in most cases increase yield at least where there is sufficient moisture. Some result of experiments conducted with organic fertilizers, improved cultural practices, and with soil amendment materials which could be disseminated to farmers, where situations permit.
SUCCESSFUL CASES OF IMPROVED SOIL MANAGEMENT The national agricultural research and extension systems have made a lot of effort in the past two scores to overcome the major agricultural production limiting problems through different approaches. Although a number of promising research results have been obtained under controlled experimental conditions, the impact of these findings at farmers field level were very limited due to numerous reasons, mainly related to cultural, socio-economic and policy factors. Out of the many agricultural research findings and recommendations taken to the farmers through the extension system the package that reached relatively a large number of farmers and showed a measurable effect is the NP fertilizer. Particularly, through the recently started National Extension Intervention Programme (NEIP), it has been possible to cover large number of farmers through the fertilizer and improved seeds technology package, which also involves other improved cultural practices. Although a number of research based effective recommendation packages could be cited, two cases were selected for presentation in this paper. The first case is the National Extension Intervention Programme (NEIP) which involves Extension Management Training Plots (EMTP) based on the experience of Sasakawa Global 2000 programme. This programme involves the promotion of a technology package consisting NP fertilizers, improved seeds and other cultural practices on selected farmers’ fields with the involvement of the farmers in the actual operations. The other successful case chosen is the outcome of a package of farming system tested through an NGO (World Vision) project in a given degraded and famine stricken locality. As a result of the intervention through the project, the degraded and low productivity area, comprising a large number of farmers, has been completely rehabilitated. Both cases are discussed below (Case I and Case II).
Case I: National Extension Intervention Programme (NEIP) The NEIP, which is considered a successful extension intervention programme, has been launched by the government in 1994/95 through special programme which intensified the existing extension programme. The NEIP is mainly geared towards assisting small scale farmers to improve the productivity of their landholdings through the dissemination of research generated information and technologies for major food crops, including teff, maize, wheat, sorghum, as well as potato and leguminous forage crops. The programme which was limited only to seven regions and 35 000 farmers in the initial year (1994/95) has expanded to ten regions and 350 000 farmers Integrated soil management for sustainable agriculture and food security in Southern and East Africa 207
in the 1995/96 crop season. During the 1996/97 cropping season, the programme covered all the regions and the number of participating farmers reached 600 000. Considering the trickling effect of these Extension Management Training Plots (EMTP) in educating other farmers around each demonstration site, the numbers of benefiting farmers is expected to reach a couple of millions. The productivity improvement effects of the NEIP carried out on farmers’ fields in the different regions during the crop season 1994/95 are shown on Table 12.
Case II: Lessons From Antsokia Valley : Natural Resources Management Project for Sustainable Agriculture The Antsokia project area is located 350 km northeast of Addis Ababa. The size of the project area is about 16 235 ha and is part of a big river basin, where the portion of the area is on steep slopes and uplands, lying at altitudes between 1 600 and 2 600 m a.s.l.. The 45 000 people living in this area earn their living from mixed Agriculture, crop and livestock production on this land, where about 1% of the population are urban dwellers. The Antsokia area has been taken as a project area by the World Vision during the 1984/85 famine period in the country, where numerous lives were also lost in this area. The emergency relief aid programme in this degraded valley was gradually changed to a resource management project for sustainable agriculture and changed the productivity of the valley and the life of the inhabitants successfully in ten years time. The situation of the area before the project, the interventions made and the impacts observed are briefly summarized below. Although the climatic condition at Antsokia is conducive and moisture is adequate, due to deforestation and unwise land management, the area has been excessively degraded. The sloppy mountains and hills have lost their top soils and have become bare rocks. The swamps and water-logged wet lands have become the deposition site of eroded soil. The gentle slopes have lost their fertility as a result of repeated cultivation without fertilizer or rest. As a result of deforestation and increased runoff, springs dried up and rivers became seasonal and flooding. Farmlands were reduced to the bottom of the hills where mountain tops are eroded to bed rock and the valley plains were water-logged. As a result of these phenomena, land carrying capacity showed deficit for both humans and livestock. The agricultural interventions made in Antsokia through the project are the following: swampland management, wet land management, crop land management, forest garden/ homestead management, and forest land management. The overall impact of the project is that total production of cereal crops increased from 5 093 tonnes in 1990 to 8 372 tonnes in 1996, which is an increase of 56%. This is an equivalent to an average yield increase from 0.8 tons/ha to 1.2 tons/ha. This increase in yield indicated a change in total productivity from deficit by 2 106 tonnes to surplus by 372 tonnes, despite the increase in population and a little change in the area of cultivated land. The production of vegetables, fruits and root crops, which was virtually unknown in the area, attained an level where it is exported to the surrounding areas. Similarly, surplus in livestock feed was also observed. As a result of the intervention through the project which changed the overall productivity, there was also an increase in per caput productivity from 141 kg/year to 186 kg/year. As a result of the intervention through afforestation, soil and water conservation, agro-forestry, forest gardens, farm-foresting and inter cropping, the following are the improved life support systems attained in the area: rehabilitated springs, plant growing seasons increased, erosion retarded, rains attracted, land carrying capacity increased, increased farm bio-diversity through the introduction of new crop species and varieties as well as additional livestock that are new to the farm. 208 Ethiopia
INSTITUTIONAL FRAMEWORK AND POLICIES FOR LAND RESOURCES MANAGEMENT The absence of a conducive national policy environment has probably been the single most important factor which depressed agricultural performance in the last two decades. The inappropriate agricultural policies include inter alia: (a) nationalization of privately owned commercial farms without compensation; (b) banning of private investment in commercial farms; (c) arbitrary redistribution of land: (d) insecurity of land tenure; (e) forced settlement and villagization; and (f) rigidly controlled grain market and agricultural prices, etc. The policy environment is also not conducive for the implementation of resource conserving technologies which could encourage the use of indigenous and locally available resources for gradually substituting imported chemical fertilizers and develop self reliance for sustainable agricultural productivity. The present extension policy gives too much emphasis to increased utilization of chemical fertilizers that are less effective on degraded soils and lack sustainability, particularly with the ever-increasing price of fertilizers and unreliability of rainfall. The absence of a conducive agricultural policy has been cited as the probable single most important factor which depressed agricultural productivity and was the cause for excessive deforestation and land degradation during the last three decades, particularly during the socialist Government era. Since the fall of the socialist Government, some policy environments have positively changed in many aspects, except the land tenure policy, which still maintains the ownership of land under the Government. The land tenure issue, which is believed to be very decisive in changing the farmers attitudes for accepting and implementing improved land management technology packages still requires a policy change, if increased and sustainable agricultural productivity are expected to be attained. The current agricultural policy, with the weaknesses it has with respect to land tenure aspects, focuses on strategies for agricultural development led industrialization. The main contents of the post 1991 agricultural policies are: · Giving special emphasis to private small holder model to agrarian socialism, · Promoting modern farming particularly in the low lands by encouraging national and foreign investors with the necessary capital and know how, · Fostering conservation based development in order to restore ecological balance. Due emphasis is given to solving the problem of soil degradation, deforestation and declining wild life resources, · Steps have already been taken to enhance normal or competitive functioning of agricultural input and output markets. Among the major actions worth noting are the National Fertilizer and Seed Policies that are put in place. Prior to 1993, there was not also a national agricultural research policy and strategy to guide and support proper agricultural development. Since 1993, however, a new national research policy and strategy has been formulated and proclaimed in order to shape up agricultural research in the direction of the country's need. The recent Agricultural research policy clearly prioritize the need for technology generation through research relevant to peasant agriculture for the purpose of increased agricultural productivity through conservation based and sustained utilization of land resources. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 209
PROPOSALS OF PROGRAMMES FOR IMPROVED SOIL MANAGEMENT AND PRODUCTIVITY ENHANCING Bio-physical issues Improved land and soil management. The soil is a non replenishable natural resource if improperly managed and once got lost. On the contrary and unlike the other natural resources, if properly managed and protected from degradation, it is inexhaustible resource which could be used to sustain life indefinitely. Therefore, in order to retard physical and chemical degradation of soils and ensure sustainable utilization of these vital resources, it is necessary to promote and encourage soil conservation based agricultural development. Integrated nutrient management. As soil degradation, draught and excessive nutrient exhaustion are the major reasons for low yields in the majority of the Ethiopian peasant agriculture, it is evident that nutrients in the form of fertilizers have to be applied for increasing crop yields. The excessive degradation of soil organic matter as a result of repeated cropping and very little to no incorporation of residues to the soil have gradually lowered crop yields under the no external input system of the peasant farming. Although such conditions could be improved through the use of chemical fertilizers, it lacks sustainability because of the high price, low efficiency and logistic problems for timely availability and distribution of these industrial products that are mainly imported from abroad. A lasting solution to this problem could be popularization and promotion of integrated nutrient management (use of both organic and inorganic fertilizers) for wider use by the farmers. Proper utilization of integrated nutrient management with increased utilization of locally available organic resources along with soil and water conservation could be the means for attaining sustainable agricultural productivity with highly developed self reliance and little dependence on imported chemical fertilizers for improving soil fertility. Policy and socio-economic issues Reform in land tenure policy. The problem of land ownership on land resource management has been very well known during the socialist government era where land ownership was communal. The commitment and devotion for sustainable management of land resources is directly associated with ownership right on the land. Farmers can not involve themselves confidently in any type of land rehabilitation and soil conservation programmes that are relatively costly and time consuming, when they are not sure that the piece of land they are working on really belongs to them or could be shared and redistributed to other farmers at any time. Changing the development approach. Since land and soil degradation are influenced at a catchment or watershed level the development approach should be through the direct intervention of conservation based development packages for a set of catchment or watershed involving a community farmers. If necessary, with sufficient investment to rehabilitate degraded and fragile environment with the direct participation of the whole community in an area in the form of a project. The development approach through the present system which deals on management of farm plots with the supply of seeds and fertilizers will not have a sustainable effect and does not help to retard land degradation. Policies to protect the farmers from low grain prices. The farmers are mostly reluctant to use some better technologies like fertilizers and improved seeds on credit bases because of the fear of not being able to pay the loan, in case crops fail or if harvests are excess and prices of grain fall. If government protects farmers from unexpected price fall in localized areas by establishing floor prices, it may help farmers to take risks in accepting essential inputs even on credit basis. Encouraging private investors to go into farming business. The low agricultural productivity in the Ethiopian subsistence farming, where farmers work on small piece of land, is mainly because 210 Ethiopia
of the difficulty to come out of the vicious cycle of exhausted nutrient reserves in the soil and low bio-mass productivity. Even where the problems are identified and solutions are available to increase productivity, excessive poverty of the farmers prohibits them from adopting any kind of improved technology. Everything on the farm is consumed and no input of internal or external source goes to the soil. If policies permit farmers to rent their lands on individual basis or in groups to private investors in terms of concession for a given period, high investment inputs could tremendously change land productivity. The farmers would also be absorbed as labourers on the commercial farms and at the same time getting the rent for their land without actually losing their ownership rights.
REFERENCES Agricultural Research Task Force 1996. Review of the agricultural research system and recommend future directions. Eth. Agr. Res. and Training Project. Addis Ababa. Bateno, K. 1997. Agricultural development aspects in soil fertility maintenance. a paper presented on a workshop on IPNS, NFIA, Addis Ababa. Belay, E. 1997. Agricultural extension aspects on soil fertility maintenance. Paper presented on a workshop on IPNS, NFIA, Addis Ababa. Berhe, W. A. 1993. Twenty years of soil conservation in Ethiopia. A personal overview. Regional Soil Conservation Unit / SIDA / Nairobi. FAO 1984. Assistance to Land Use Planning, (AG: DP/ETH/82/010). Field document 3. Geomorphology and Soils of Ethiopia. Ministry of Agriculture, Addis Ababa. FAO 1986. Highland reclamation study, Ethiopia. Vol. 1 and 2. (AG:VTF/ETH/037). FAO, Rome. Fikru A. 1990. The role of land use planning in the improvement of natural resources management: In National Conservation Strategy Conference. vol. 3. Janssen, M. and A. Willkens 1994. Interpretation of crop response data, Ethiopia. Consultancy Report, Project GCPF / ETH / 039/ITA, FAO, Rome. Kelsa Kena, Tadesse Yohannes and Tesfa Bogale 1993. Influence of fertilizer and its related management practices on maize grain yield. In Proceedings of the First National Maize Workshop of Ethiopia, 5 - 7 May, 1992. Addis Ababa. Mesfin A. 1980. State of soil science development for agriculture in Ethiopia. EJAS 2(2). Addis Ababa. Mohr, P.A. 1971. The geology of Ethiopia. SSI University Press, Addis Ababa. Murphy, H. F. 1963. Fertility and other data on some Ethiopian soils. Expt. Stat. Bull. No. 11. Ethiopian College of Agri. and Mech. Arts. Dire Dawa, Ethiopia. 511.pp. Odenyo, V. A. O. 1984. Assistance to Land Use Planning, Ethiopia: Land use, Production Regions and Farming Systems Inventory. FAO. Rome. SCRP 1985. Soil loss and runoff assessment findings. Soil Conservation Research Project, Addis Ababa. Taye B. and W. Hofner 1993. Effect of different phosphate fertilizers on the yield of barley and rape seed on reddish-brown soils of Ethiopian Highlands. Fertilizer Research, 34: 243-250. Tekalegn Mamo, et al. (edit.)1993. Improved management of Vertisols for sustainable crop-livestock production in the Ethiopian Highlands. Synthesis Report. Technical Committee of the Joint Vertisol Project. ILCA, Addis Ababa. World Bank 1995. Staff Appraisal Report. National Fertilizer Project., Addis Ababa. Yilma Getachew 1996. Lessons from Antsokia Valley. Natural resource management and sustainable agriculture. World Vision. Addis Ababa. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 211
Kenya
COUNTRY FOOD PRODUCTION AND REQUIREMENT Maize is the most important food crop in Kenya and constitutes the staple food for over 95% of the people with an average consumption rate of 128 kg/person/year according to the Workplan 1997, Ministry of Agriculture, Livestock Development and Marketing. It is grown in almost all agro ecological zones of the country and predominantly on smallholder farms of less than 5 ha. About 80% of all land under cereal production are planted with maize. The crop is grown mainly for human consumption, livestock feed and industrial processing. In 1996, a total of 1.49 million hectares planted under maize produced 23 million bags giving a low national yield of 1.4 tonnes/ha. The 1995 crop was much better producing about 30 million bags, probably due to more reliable rainfall. Among the food crops grown in Kenya, maize receives the bulk of the fertilizer used. It is estimated that about 25-30% fertilizer used in the country goes to maize production while a mere 2-3% goes to the other food crops. Much agricultural research has also gone into maize especially in the area of breeding to produce high yielding varieties suited to the various agro-ecological zones. This has yielded positive results as about 60% of the maize planted is hybrid maize (MDB, 1995). The main constraints related to maize production vary from rainfall unreliability, low use of farm inputs e.g. machinery for large scale farms, fertilizers and pesticides, unavailability of seeds and correct types of seeds; lack of credit facilities; poor dissemination of improved technology; poor producer prices due to market restructuring in 1992; high cost of inputs and high post-harvest losses of up to 20%. Several interventions have been put in place by the Kenya Government to assist the farmers e.g. setting up strategies of improving the provision of machinery and inputs; improve credit facilities at appropriate institutions, disseminate improved technologies through extension workers as well as improved liaison with agricultural research organizations.
EVOLUTION OF PER CAPUT CULTIVATED LAND AND TRENDS IN CEREAL CROP YIELDS Agricultural production requires proper management of the inputs and outputs through proper planning and control. To do this a proper record or inventory of the various components is required. It is unfortunate that in Kenya, the inventory of agricultural land use has not been updated since 1979. However, this exercise has recently started through a new initiative of the Ministry of Agriculture where localized data in 7 random districts in the country has been collected and assessed. These data show that numerous sub-divisions have occurred since 1979, new lands have been brought into cultivation while ownership status has frequently changed. These factors have impacted negatively on the food production situation in the country as land fragmentation/subdivision automatically lead into loss of agricultural land due to roads, footpaths fences, homesteads and public utility sites. Subdivision also leads to uneconomically viable parcels of agricultural land. Population pressure has led to a big land pressure leading people into fragile lands with resultant negative environmental issues. The consequence of these circumstances is the deterioration of agricultural production efficiencies, decline in agricultural output, land degradation and land use conflicts.
S.M. Nandwa, P.T. Gicheru, J.N. Qureshi, C. Kibunja and S. Makokha Kenya Agricultural Research Institute and National Agricultural Research Laboratories, Nairobi 212 Kenya
EXTENT OF SOIL DEGRADATION AND ITS BIO-PHYSICAL AND SOCIO-ECONOMIC IMPACTS Kenya is an agricultural country and depends almost entirely on land productivity for subsistence and socio-economic development from one third of the country as two thirds of Kenya is semi-arid to arid. The pressure exerted on the fragile ecosystems that characterize the semi-arid and arid lands by the large and rapidly increasing human population is at the heart of the land degradation processes. It is nevertheless important to recognize that although land degradation is more of a problem of semi-arid and arid lands, it is also becoming a serious problem in the semi-humid and humid environments (also referred to in Kenya as medium and high potential lands respectively), especially where cultivation has been extended to steep hill slopes without adequate soil conservation measures. Chemical and physical forms of soil degradation occurring in the country are reviewed in terms of their causes and resultant effects.
CAUSES AND EFFECTS OF SOIL CHEMICAL DEGRADATION Evolution of farming systems in Kenya shows a rapid shift from shifting cultivation or natural fallow systems to continuous cultivation. The productivity and sustainability of fallowing systems are dependent on adequate restoration of fertility during the fallow phase to replace and build stocks lost during the cropping phase (Padwick, 1983; Nye and Greenland 1960). This practice has become obsolete in parts of Kenya, as per caput arable land declines. In parts of the continent (including Kenya), abandonment of fallowing systems has been ascribed to pressures of population (Allen, 1965). In systems where fallowing is still practised, the arable phase is often extended beyond nutrients restored or accumulated during fallowing phase, which eventually renders the system unproductive due to depletion of nutrients and carbon accumulated during fallowing. Jones (1972) found that 15 950 769 and 85 kg/ha of carbon, nitrogen and phosphorus, respectively were accumulated in three years of resting phase. However, when measurements were made after three years of cropping the elements were found depleted to negative values of 19 700, 968 and 88 kg/ ha, respectively. High nutrient depletion rates are commonly reported in farming systems in Kenya, where more nutrients are removed than those replenished.
In many crop and livestock farming systems, major nutrient losses are via crop residues, runoff and erosion, denitrification, leaching and through removal in faeces deposited in deep pit latrines or sewage where it can no longer be recycled in agro-eco-systems. In assessing nutrient depletion in SSA, Stoorvogel and Smaling (1990) reported that of the total nutrients removed in harvested products and residues, of cereal crops in the continent (wheat, rice, maize, barley, millet and sorghum), 43.1%, 41.0% and 87.8% of N, P205 and K20 was removed in residues, respectively. This shows the significant negative contribution non-restitution of cereal residues can have on nutrient depletion. In a long-term field trial investigating the effect of organic and inorganic inputs on yields of maize and beans and nutrients removed, Qureshi (1987) reported substantial nutrient removal by maize and beans residues (Table 1). Runoff and erosion occurrences in agro-eco-systems have also been reported to contribute to nutrient depletion. From a study on a Nitisol at Kabete, Kenya, Tefera (1983) reported annual soil losses of 35 and 18 t/ha from plots with 0.5 and 1.5 m wide grass strips, respectively; while cumulative soil loss under bare conditions were reported by Gachene (1995b) to be 247 t/ha with between 247% to 936% richer in P than in the original soil (Gachene, 1995a). The author found that changes in soil pH, organic carbon and total N were significantly correlated with cumulative soil loss (r2 values of 0.59 0.35 and 0.50, respectively; n=20).
A number of studies have been conducted in Kenya on the subject of solute leaching (Smaling and Bouma, 1992; Mochoge and Beese, 1986). In studying N leaching and by pass- flow in Vertisols in lake Victoria basin, Smaling and Bouma (1992) found that N leaching in tilled cropland was less than Integrated soil management for sustainable agriculture and food security in Southern and East Africa 213
5% of applied fertilizer (50 kg/ N/ha) compared to 40% fertilizer N leaching in grassland, unless the soil was pre-wetted which reduced the losses to 12%. Mochoge and Beese (1986) found that leaching was influenced by the amount and quality of applied cations and accompanying anions, which were slightly higher when (NH4)2SO4 was applied than Ca(NO3)2. Hartemink et al. (1996) studied leaching in western Kenya, and estimated that some 100 kg/ N/ha/yr was leached as nitrates and got accumulated at 50-200 cm soil depths. It may be concluded from these studies that the observed leachable quantity of nitrogen could suffice a 4 t/ha maize grain crops if recycled or prevented from leaching.
Nutrient balances are increasingly being recognized as important sustainability indicators of agro- eco-systems. Nutrients stocks are derived from inorganic and/or organic sources as well as from weathering of minerals (feldspars, micas). They are subject to continuous changes as a result of natural and man-induced processes, hence the static concept of nutrient stocks and dynamic concept of nutrient flows. At each spatial scale, the flows can be described in terms of the summation of inputs minus outputs which may be higher or equal or lower than the value zero, hereby termed the nutrient balance. Based on nutrient balances, agro-eco-systems may be experiencing nutrient accumulation (S INPUTS >S OUTPUTS), or in equilibrium (S INPUTS = S OUTPUTS) or nutrient mining (S INPUTS
TABLE 1 Nutrient removal by a harvested maize ad bean Plant component N P K Ca Mg Cu Zn Mn Fe Maize kg/ ha g/ha Stover 40 4 130 19 10 73 30 675 2,712 Grains 51 12 9 4 1 10 11 30 105 Total 91 16 139 23 11 83 41 705 2,817 Bean Grains 35.5 5.6 20.3 1.7 2.9 10 52 24 78 Hulled pods 9.9 1.1 17.1 4.8 2.8 6 25 76 260 Leaves/stems 6.5 0.6 10.9 3.5 1.0 44 44 75 563 Roots 0.68 0.06 0.76 0.70 0.18 1 3 7 55 Total 52.6 7.4 49.1 10.7 7.0 61 124 182 956 Note : maize yield is 4t/ha, bean yield is 1.3 t/ha
Salinization results from natural cycles or from soil and water mismanagement, including irrigation with low quality water. In Kenya it has often been observed that due to poor drainage, high ground water tables develop and hence capillary salinization, leading to the abandonment of irrigation schemes. Excess exchangeable sodium and high pH also strongly influence the availability and transformation of essential plant nutrients. The amounts of potassium in these soils are small compared to sodium, calcium and magnesium, which indicates that there is a likelihood of interference in nutrient uptake and plant metabolism. Toxic levels of sodium in some of these soils may restrict penetration of plant roots. Plant growth in saline soils is adversely affected by low soil-water availability because of the soil solution's high osmotic pressure. Toxic concentration of specific ions may also affect plant growth. Therefore, strongly saline soils have little vegetative cover and are subsequently susceptible to water erosion. 214 Kenya
Excess exchangeable sodium and high pH strongly influence the soil physical properties of saline- sodic soils. As the exchangeable sodium increases, soils become more dispersed and less permeable to air and water. Dispersion causes dense impermeable surface crusts that greatly reduce seedling emergence and water penetration. The reduced infiltration of water enhances soil erosion. In those cases where sodicity occurs in the deeper subsoil, wetting of the soil may lead to structural collapse due to dispersion and subsequent caving in. This may lead to the formation of tunnels which upon widening form deep and wide gullies. Agricultural soils polluted with heavy metals especially cadmium, from different sources (sewage sludge, inorganic additions, mines etc.) is major concern in high external input agro-eco-systems as well as urban agriculture. Little research has been carried out to establish the relationship between soil available labile pools, sources and uptake in crops. This is a major research gap for future research.
Causes and effects of physical land degradation Soil erosion is by far the most important land degradation process in Kenya. The severity of soil erosion problems in the cultivated parts of the Highlands of Kenya was realized as early as in the late 1920s. Maher (1937) described the causes of this soil erosion as due to wrong use of land. In an attempt to arrest land degradation, enforced soil conservation measures were introduced during the period 1930-1940. During this period an inventory of the state of soil erosion and land utilization in the African reserves was carried out (Maher 1937 a, b, c, d). As a follow up, appropriate soil conservation measures were recommended. These included terracing, strip cropping, use of crop residues, plant cover etc. Major emphasis was however laid on terracing. Unfortunately, during the early 1960s there was considerable laxity in soil conservation efforts; the soil conservation measures which were being carried out were not maintained and terracing started to disappear at a faster rate that they were being constructed. However, from 1972, a country-wide soil conservation programme was launched to increase the awareness of the importance of protecting the soil resource from erosion and degradation. The one which are commonly practised are physical or biological, such as strip cropping, contour farming, ridging, mulching and rotation. Physical structures include terracing, cut of drains etc.
At the national level, afforestation is now encouraged as a measure to control erosion. In 1980, the Permanent Presidential Commission on Soil Conservation and Afforestation was established to co- ordinate soil conservation and afforestation activities. In addition, the Soil and Water Conservation Branch of the Ministry of Agriculture, in collaboration with a large number of government departments, non-governmental organizations and community development groups, has been directly or indirectly involved in promoting activities related to soil conservation. It can be concluded that considerable extension work has been done in the field of soil and water conservation. However, little attention has been paid in researching on soil and water management and this is probably due to the little attention paid to this field. The degradation problem feared before the awareness of soil conservation has been reversed in some districts and the long history of conservation interventions in some regions of Kenya has created a favourable environment for attaining sustainable agriculture (Tiffen, 1992). There has been a long term political, social, economic and technical commitment to soil and water conservation. The results of this commitment include an impressive increase in conserved land according to several indicators. Some of them include increased awareness of soil and water conservation techniques.
From previous experiences, wind erosion is expected to be a problem during the dry season and only in the drylands receiving up to 600 mm of annual rainfall and with sparse vegetation. The areas of the country below 600 mm isohyet have been demarcated and eight climatological stations (Voi, Makindu, Garissa, Marsabit, Wajir, Moyale, Lodwar, and Mandera) with the longest and most reliable data within these areas were selected to help determine land degradation indicators for these areas. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 215
Synoptic wind measurements at 10 meter height were used to derive the mean wind speeds at 2 m above the ground. Wind erosivity indices were then calculated using the Fournier equation. Aridity indices (Ratio of precipitation to potential evapotranspiration) were also calculated for the same stations. By combining wind erosivity indices, estimates of soil erodibility, aridity indices and vegetation cover, an assessment of the wind erosion hazard was made for the areas considered susceptible. A second and independent assessment was made by estimating the sand load in the atmosphere from observations of horizontal visibility made at the same sites (Wangati and Said, in press).
The abundance, productivity, species composition and canopy structure of natural vegetation are valuable indicators of land quality and hence the extent and severity of land degradation. Undesirable chemical changes in the soil (acidity, salinity or alkalinity) are often indicated by disappearance of unadapted plant species and build up of species that are more tolerant to such conditions. Replacement of shallow rooted grasses and shrubs by deep rooted drought tolerant trees and shrubs would indicate loss of fertile top soil or serious loss of water holding capacity due to severe loss of soil depth as a result of erosion. Overgrazing and charcoal burning may also result in predominance of unpalatable or otherwise undesirable plant species. The features just described are however often difficult to map since they usually affect relatively small patches of land and may look different in dry and wet seasons. Remote sensing either through aerial photography or high resolution satellite imageries has proved useful but even such pictures require intensive ground truthing for accurate interpretation.
Indicators of land degradation A continental assessment of the nutrient balances of 38 sub-Saharan African countries showed that countries of Eastern, Central and Southern Africa experience high negative nutrient balances, e.g. -42, -3 and -29 kg/ha/yr for N, P and K, respectively (Steervogel and Smaling, 1990). A district level study of nutrient balances in Kisii, Kenya showed much higher nutrient depletion e.g. -112, -3 and -70 kg/ ha/yr of N, P and K, respectively (Smaling, 1993; Smaling et al., 1993). These results are close to those obtained from a NUTrient MONitoring (NUTMON) project in Kisii, Kakamega and Embu districts of Kenya as shown in Table 2 (Bosch et al., 1998).
TABLE 2 Average nutrient stocks, nutrient balance and relative gains and losses for 3 districts in Kenya Kisii Kakamega Embu Stock Balance Change Stock Balance Change Stock Balance Change kg/ ha kg/ ha/y % kg/ ha kg/ ha/y % kg/ ha kg/ ha/y % 11 116 -102 -1.0 8 021 -72 -0.9 8 056 -55 -0.2 3 597 -2 -0.0 2 556 -4 -0.2 3 329 9 +0.3 10 800 -34 -0.3 7 200 18 +0.3 12 800 -15 -0.1
The results indicate that all agricultural land uses in the mixed small-holder farming systems of Kisii District monitored cause high depletion of nitrogen (between -46 to 94 kg/ ha/ yr) followed by potassium especially in tea and coffee farms (between -2 to 26 kg/ ha/ yr). Incorporation of the livestock dairy enterprise was found to mitigate N and K depletion to some extent. These results thus suggested that land use and soil management practices adopted in Kisii, render the agro-ecosystems non-sustainable in the long-run. Results from Kakamega District showed a somewhat unique nutrient balance trend to that observed in Kisii district. The most depleted nutrients were nitrogen (between -30 to -80 kg/ ha/yr, except in livestock incorporated farms) and phosphorus (-kg/ ha/yr especially in non- contracted sugarcane and maize-based farms). The study also suggested that commercial enterprises tend to contribute more to gross margin at the detriment of soil fertility depletion, such that if current management practices are not changed with appropriate interventions, agro-eco-systems in Kakamega 216 Kenya
District will also be rendered non-sustainable fairly soon. Both studies from Kisii and Kakamega Districts are in agreement with results obtained from a study in Vihiga District (part of old Kakamega District e.g. at assessing the economic and ecological impacts of soil management options using a dynamic simulation model (Shepherd and Soule, 1997). The authors reported higher negative balances (-44 kg/ /ha/ yr N and -3.6 kg/ ha/yr P) in low resource endowments farms (0.2 ha, lack of livestock and earning less than $ 455 per year) compared to -37 kg/ ha/ yr P and -1.5 kg/ ha/ yr P in medium resource endowments farms (0.8 ha, with one or two heads of cattle and earning $ 1036) as shown in Table 3. The depletion was attributed to soil losses of 5.6 and 5.5 t ha/yr and N leaching of 21 and 30 kg/ ha/ yr N in low and medium resource endowments farms respectively.
TABLE 3 Simulated soil indicators for low, medium and high resource endowment farms, Vihiga District, Western Kenya Indicator Units Farm resource endowment Soil C balance Kg/ ha/yr -400 -318 190 Soil N balance Kg/ ha/yr -44 -37 50 Soil P balance Kg/ ha/yr - -1.5 32.7 Mineral N net inflow Kg/ ha/yr 54 67 137 -natural a) 10 10 10 - fertilizer 0 0 47 -active b) -8 5 47 - slow 52 52 58 Soil erosion Tons/ha/yr 5.6 5.5 2.1 N leasing Kg/ ha/yr 21 30 5 Notes : Values for year 5 of the 20 years simulation. a) natural inputs from atmospheric deposition and asymbiotic N fixation, b) mineralization of active N
Nutrient balances reported above are based on subtraction of OUT 1-6 from IN 1-6 termed "full balance" and nearly all cases and elements they fall in the nutrient mining class e.g. SIN - SOUT <<0. Average "partial farm balances" SIN 1+2 - S OUT 1+2 were positive at levels of 34, 12 and 27 kg/ ha/yr for N, P and K, respectively; suggesting that farmers used enough external inputs to offset the nutrient loss in harvestable products and residue removal. However, calculation of full balances OUT 1-6 from IN 1-6 resulted in negative values of N (-71 kg/ ) and K (-9 kg/ ) per ha per year while average P balance was still positive (3 kg/ ha/yr P). Negative balances in the NUTMON project were high which was attributed to estimates of leaching (50 kg/ ha/yr N) and gaseous losses (24 kg/ ha/yr N). Depending on the accuracy of the regression analysis data and assumptions, full balances can be either under or over-calculated. This suggests that the application of the nutrient balance concept should be used in combination with soil total and/or available nutrients stocks.
A recent study of the past research on the maintenance and improvement of soil productivity in Kenya identified five soil productivity indicators (besides nutrient balances). These were organic C content; phosphorus stocks, availability and fixation; nitrogen (stocks, leaching potential gaseous); P/N potential supply and soil acidity. At the onset of the long term fertility maintenance trial at NARL (Qureshi, 1987) experiment, the soil contained 36.5 t C/ha in the top 15 cm while after 18 years of continuous maize bean rotation, soil organic carbon contents ranged between 32.6 t C/ha and 26.8 t C/ha in the best and worst conserved treatments (Kapkiyai et al., 1996) or an annual loss of 0.22 and 0.50 t C/ha/yr, respectively.
Soil organic matter losses were intensified by fertilization and stover removal. The most soil carbon was lost from the treatment where only N-P fertilizers were applied with stover removal and the least soil carbon was lost from the treatment receiving the greatest external inputs while retaining stover (16%). In the long term trial one observation of concern is that all land management practices even Integrated soil management for sustainable agriculture and food security in Southern and East Africa 217
where there were large applications of organic matter resulted in a loss of soil organic matter over time. After 18 years of continuous maize bean rotation, soil organic carbon contents in a depth of 15 cm ranged between 25.9 t/ha (stover removed, fertilizer applied) to 31.3 t/ha (chemical fertilizer and manure applied and stover retained). This corresponds to losses of soil organic carbon at the rate of 0.22 and 0.54 t/ha/yr, respectively.
Climatological influences on land degradation may be direct (as in the case of extended droughts which may result in destruction of ground cover and exposure of the soil to severe wind erosion) or indirect. Although the Kenya Meteorological Department has for many years established and maintained a relatively large network of climatological observation stations, these stations are not evenly distributed and coverage of the arid and semi-arid lands is very sparse. The number of observation stations has also declined from over 1 000 to around 800 in 1995. The rainfall indicators considered fall roughly into two categories: those related to frequency and probability of drought, and those related to rainfall erosivity. Climatological records show that in Kenya, recurrences of above and below normal rainfall anomalies and other extreme rainfall events are common in all rainfall time series. Some of the anomalies are relatively small while others are very severe, persistent and affect large areas. The mean maximum, minimum and range of air temperatures close to the ground influence the rate of desiccation of the soil and vegetation. The same parameters are also influenced by the energy balance of the land surface and will therefore respond to changes in land characteristics. These parameters have been investigated in Kenya as possible indicators of existing hazard of land degradation (Wangati and Said, 1997).
Soil erosion resulting from surface water runoff is one of the important and easily recognizable indicators of land degradation. There are three major parameters that influence soil erosion: rainfall erosivity, soil erodibility, slope of the land and soil cover. Quantitative assessment of soil erosion is however problematic as soil erosion rarely takes place uniformly even on a small field. The most widely accepted method is the application of the Universal Soil Loss Equation (USLE) which expresses the annual soil loss (tons per hectare) from a plot as a simple product of rainfall erosivity, soil erodibility, slope length, slope gradient, land cover and land management. The USLE model is however empirical and its application in a given environment requires determination of the relative weighting of the factors. This is done using standard replicated runoff plots on which most of the parameters and the actual soil loss from each plot can be measured. Very few runoff plot experiments have been conducted in Kenya and they do not even cover the major soil and land use types. The USLE model therefore provides at most an approximation to actual soil loss and has been adopted in this assessment as the best means of comparing or ranking degrees of severity of soil erosion hazard. An initial assessment of soil erosion hazard based on the USLE has been done for the whole country at a scale of 1:1 million by the Kenya Soil Survey. The manual integration of the many factors in the model is however a tedious process which does not provide for easy revision as the density of measurements improves with time.
From previous experiences, wind erosion is expected to be a problem during the dry season and only in the drylands receiving up to 600 mm of annual rainfall and with sparse vegetation. The areas of the country below 600 mm isohyet have been demarcated and eight climatological stations ( Voi, Makindu, Garissa, Marsabit, Wajir, Moyale, Lodwar, and Mandera) with the longest and most reliable data within these areas were selected to help determine land degradation indicators for these areas. Synoptic wind measurements at 10 metre height were used to derive the mean wind speeds at 2 m above the ground. Wind erosivity indices were then calculated using the Fournier equation. Aridity indices (Ratio of precipitation to potential evapotranspiration) were also calculated for the same stations. By combining wind erosivity indices, estimates of soil erodibility, aridity indices and vegetation cover, an assessment of the wind erosion hazard was made for the areas considered 218 Kenya
susceptible. A second and independent assessment was made by estimating the sand load in the atmosphere from observations of horizontal visibility made at the same sites (Wangati and Said, 1997).
The abundance, productivity, species composition and canopy structure of natural vegetation are valuable indicators of land quality and hence the extent and severity of land degradation. Undesirable chemical changes in the soil (acidity, salinity or alkalinity) are often indicated by disappearance of unadapted plant species and build up of species that are more tolerant to such conditions. Replacement of shallow rooted grasses and shrubs by deep rooted drought tolerant trees and shrubs would indicate loss of fertile top soil or serious loss of water holding capacity due to severe loss of soil depth as a result of erosion. Overgrazing and charcoal burning may also result in predominance of unpalatable or otherwise undesirable plant species. The features just described are however often difficult to map since they usually affect relatively small patches of land and may look different in dry and wet seasons. Remote sensing either through aerial photography or high resolution satellite imageries has proved useful but even such pictures require intensive ground truthing for accurate interpretation.
It is estimated that the majority of the population ( over 70%) in Kenya live in the rural areas and are entirely dependent on fuelwood, mainly in form of wood fuel, as the source of energy for cooking and keeping their houses warm at night. At least one half of the urban population is also dependent on fuelwood, mainly in form of charcoal, as source of energy for cooking. Since supply of fuelwood from designated forests is minimal, demand for fuelwood places tremendous pressure on the natural vegetation especially close to human settlements. This is more so in the arid and semi-arid areas since most households in the high potential areas can meet their fuelwood requirements from on-farm wood- lots, hedges and multipurpose trees. The arid and semi-arid lands (ASALs) are also the main source of the large quantities of charcoal used in the urban areas. The impact of commercial charcoal burning on the vegetation structure is already evident in the ASALs even hundreds of kilometres from the major cities and townships. Since cooking fuel is a necessity in all households, fuelwood deficit (difference between supply and demand) is an important indicator of pressure on the vegetation and hence land degradation hazard in Kenya. Assessment of this indicator has been made by compiling estimates of demand from previous surveys, projecting growth of that demand in terms of population growth and distribution of human settlements, and transferring where appropriate, demand in cities and major urban areas to the known and projected sources of supply. Fuelwood supply was estimated from an assessment of the structure and distribution of vegetation units considered accessible for fuelwood harvesting.
The state of water resources is a valuable indicator of land quality. Thus, presence of large quantities of sediment in river water is usually the first visible indicator of soil erosion within a watershed while increase in frequency and height of flood peaks in stream flow is an indicator that the water infiltration rate is decreasing as a result of soil compaction and/or loss of ground cover. Deposition of large quantities of silt on flood plains may also adversely affect land productivity through destruction of soil physical and chemical characteristics. In the absence of major and long term changes in rainfall pattern, variations in groundwater characteristics such as depth of water table may be attributed to either excessive water abstraction or land degradation resulting in reduced infiltration and hence groundwater recharge. Poor water and land management in irrigation schemes may also lead to impeded drainage and rise in water table. Land then becomes degraded either through water logging or build up of salinity especially in the dry regions where the rate of evaporation is high. The use of these indicators to identify extent and severity of land degradation has been investigated for each of the main drainage basins, using the data already compiled under the Water Resources Assessment Project (WRAP) in the Water Development Department and the irrigation schemes have been mapped out as potential areas of land degradation. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 219
Socio-economic impacts of soil chemical degradation A comparative study of 22 agricultural soils cultivated for 18-30 years in Western Kenya showed that average carbon stocks were 40 t C/ha while the average loss rate was 690 kg/C/ha/yr (Wissen, 1997). Existence of long-term field experiments provides opportunity to investigate the effects of different land management practices on soil fertility and carbon stocks decline over time (Qureshi, 1987; Swift et al., 1994). For example in a long-term field trial at Kabete, Kenya, on maintenance of soil fertility with organic and inorganic inputs, shows that in 21 years of maize production, yields of no-inputs and NP treatment (120 kg/N and 52 kg/P per ha per yr) declined by 70% and 50%, respectively; which was equivalent to loss in maize production yields of 3 and 2 t/ha/yr, respectively (Nandwa, 1997). The nutrient balances after 21 years for the no-input treatment were -77 kg/N, -9 kg/P and -87 kg/K per ha per yr; while that for NP treatment were -86 kg/N, +10 kg/P and -144 kg/K per ha per yr, respectively (Nandwa, 1997). Results from the experiment showed that there was decline in SOM over time in all treatments with the greatest loss of 608 kg/ C per ha per yr (Kapkiyai et al., 1996). However, the losses were lower by 49% when FYM was continually applied and maize stover restituted. The authors interpreted a loss of one tonne of carbon per hectare to be equivalent to a loss of 243 kg/ ha/yr of maize and 50 kg/ ha/yr of beans.
A crude extrapolation from these changes in the Kabete long-term trial resulting from different inputs suggests that it would require 35 t livestock manure/ha/year alone to maintain the SOM at its initial level or 17 t manure/ha/year with 16 t stover/ha/year to do so when mineral fertilizers are applied. These high rates of manure and crop residues necessary to stabilize soil C in the soils of small- holder farmers are therefore, very high and fall beyond those which provide the most efficient crop returns. Kipkiyai (1996) also compared SOM under various treatments against some soil parameters. Total N, Nitrogen mineralization, extractable K, and Ca, and CEC co-varied with SOM contents resulting from different treatments. The covariance was greatest between N and SOM. Carbon balances suggested that manuring restocks the particulate organic matter fraction more efficiently than do addition of maize stover and that fertilization without organic inputs hasten SOM loss.
A set of recently concluded fertilizer trials throughout Kenya provides additional information on soil C changes during continuous cropping between 4 and 7 years with and without fertilizers. The initial stocks at the sites ranged between 30.2 and 44.1 t C/ha in the surface layer (FURP, 1994; Weemer et al., 1997). Across 24 fertilizer trial sites the overall annual loss from unamended cultivated soils was 0.69 t C/ha/yr. A small positive influence on SOM changes was observed with N fertilization when compared to changes in soils receiving no fertilizers and SOM increases were most pronounced in the soils that were most N-responsive. Besides decline in crop productivity decline, nutrient depletion has other negative consequences for farm livelihoods such as less fodder for cattle and hence less manure, less crop and other plant residues to restitute and less fuelwood for cooking. Recent studies indicate that 14% of the area covered by medium and high potential of Kenya has soils with less than 0-10 kg/ of carbon which is interpreted to mean up 25% the area with less than one gram per kilogram of nitrogen stocks in the top soil (Braun et al, 1996). The study also indicates that over 24% of Kenya's medium potential area has less that 0-15 kg/ of potentially suppliable phosphorus in the top soil (not withstanding absence of data in 40% of the area). This may be attributed to long history of cropping and nutrient mining. To put back the agro-eco-systems to their original productivity potential requires investment and replacement of the nutrients lost.
Nutrient balance studies in Kenya indicate that nitrogen and phosphorus is being depleted at a rate of 40-100 and 2-3 kg/ ha/yr, respectively. However, in spite of the negative balances, some agro- ecosystems are still productive. This is because soil fertility decline may not be noticed because of the 220 Kenya
soils high nutrient stocks and availability or unbalanced nutrient stocks and availability (N/P ratios). Soil fertility decline starts to be noticed in systems with low nutrient stocks and availability (crop yields gradually going down). These studies show that the unsustainability of agricultural production at national level correspond with the observations at farm household level. Thus, from the full balances calculations, the average N-balance at farm level is -71 kg/ ha/yr with large variations between farms ranging from -240 kg/ ha/yr to +135 kg/ ha/yr, while the average K-balance is slightly negative in contrast to the P-balance found to be slightly positive (Jager et al., in press). The authors concluded that both N and K were mined, implying that 32% of the net farm income is based upon nutrient mining. The authors further reported that over 54% of the farms in the study sample realize income levels from farm activities which are below the estimated poverty line. From the foregoing it may be concluded that a large portion of the farm households are producing in an economic unsustainable situation and that off-farm income is essential for large groups of small scale farm households to achieve economic viability.
AVAILABLE TECHNOLOGICAL OPTIONS FOR CONTROLLING SOIL DEGRADATION AND ENHANCING PRODUCTIVITY Productivity of major cereals (maize, wheat, rice, barley and sorghum) is primarily limited by nitrogen or phosphorus or both (FURP, 1987). It was found K to be adequate for most soils in the country and attributed it to parent materials which are high in feldspars and micas; although an early survey of K - deficient soils in East Africa and responses to different crops (bananas, potatoes, etc.) is still valid. Analysis by Esilaba and Ssali (1987) of 13 major agricultural soils in Kenya indicated that most of the soils have a low C reserves (up to 406 mg kg/ -1). Chamberlain (1959) and Chamberlain and Searle (1963) studied trace elements in some East African soils, and found that Cu was deficient in most wheat (Triticum aestivum) fields which resulted in the adoption of soil dressing of CuSO4 over and above NPK fertilizer recommendations. Nevertheless, very few studies have been carried out in Kenya on soil status of trace elements.
Soil fertility restoration and replenishment technologies Fertilizer recommendations in Kenya for wheat, barley and rice are regularly adjusted to address changing soil biophysical conditions. This is possible because for a long time research on these crops has been funded by the industry, e.g. Wheat Board, Kenya Breweries and National Irrigation Board, respectively. Blanket fertilizer recommendations for maize have remained in operation for a long time (KARI, 1992). In economic terms blanket fertilizer recommendations in the long run are considered a waste of resources to the state and to individual farmers. Recent studies suggest that fertilizer recommendations based on limiting nutrients have much higher nutrient use efficiency than those of blanket recommendations (FURP, 1994). To overcome the constraint of low nutrient recovery and optimize fertilizer use there is need to replace such general and over-simplistic fertilizer recommendations with types that are rationally differentiated according to agro-ecological zones (soils and climate), crop types, nutrient uptake requirements and socio-economic circumstances of farmers (FURP, 1994; Jones and Wendt, 1995). Zone-specific and crop-specific fertilizer recommendations, if adopted judiciously can mitigate nutrient depletion in four ways. First, substantial increase achieved in harvestable products is often in similar ratio to increases in crop residues and roots, both which help recycle nutrients and build and increase soil organic matter (SOM). Secondly, targeted yields can be achieved over a relatively smaller proportion of land and thereby result in increased area of land left to recuperate in fertility through fallowing, improved fallows. Thirdly, relatively immobile nutrients such as P, are built up to high levels in the soil, and can be made available for subsequent crops. Fourthly, application of fertilizer according to limiting nutrients, results in savings in fertilizer materials (avoiding Integrated soil management for sustainable agriculture and food security in Southern and East Africa 221
wastage) which can be used to combat depletion elsewhere in appropriate plots, fields, farms or sold to earn the much needed cash.
Long-term (more than three seasons) monitoring of the fertilizer use recommendations (FURP, 1994) on three soil (Smaling et al., 1992) revealed that the same amount of fertilizer gave entirely different yield response at the three sites due to very different climatic and soil conditions (Table 4). On a Nitisol, Phaeozem and Arenosol or Alisol (FAO/UNESCO, 1990), maize grain yields were increased by 133% (on Nitisol), 40% (on Vertisol) and 48% (on Alisol) through application of P only, of N only, and N+P together, respectively. This demonstrated the merits of zone specific and crop-specific fertilizer recommendations over blanket recommendations.
TABLE 4 Yields and NPK uptake of maize on three Kenyan soils as a function of soil type and fertilizer treatment, 1990 Soil Treatment Yield Nutrient uptake ton/ha kg/ ha N P K Nitisol (red, clayey) N50 P0 2.1 42 5 30 N50 P0 2.3 50 6 36 N0 P22 4.9 79 12 58 N50 P22 5.1 82 14 65 Vertisol (black, clayey) N0 P0 4.5 63 24 95 N50 P0 6.3 109 35 126 N0 P22 4.7 70 23 106 N50 P22 6.7 113 46 111 Arenosol (brown, sandy) N0 P0 2.5 38 7 42 N50 P0 2.2 45 7 47 N0 P22 2.3 38 11 68 N50 P22 3.7 66 16 77
A major limitation of zone-specific and crop specific fertilizer recommendations based on short- duration studies (less than three seasons), is that related to the development of soil degradation in form of nutrient imbalances. For example in FURP (1994), continuous application of P containing fertilizer on Nitisols increased N and K uptake by 88% and 93%, respectively, while application of N containing fertilizer on Vertisols increased P and K uptake by 46% and 33%, respectively. These findings rendered the fertilizer use recommendations inappropriate after a short period and thus suggested that there was need to supplement the NP zone specific fertilizer recommendations with these additionally uptake nutrients.
In FURP trials reviewed (FURP, 1994), continuous application of N and/or P also resulted in scenarios where Ca also started limiting production of maize, indicating that there was need to supplement the recommended NP fertilizer recommendations with Ca containing materials. Jones et al.,(1960) showed that the supply of excess K from mulch was the primary cause of nutrient imbalance e.g. in form of Mg deficiency observed in coffee and that this problem was particularly observed with mulch from napier grass (Pennisetum purpureum), which is a known luxury consumer of K. In studying the effect of fertilizer and crop rotation, Wapakala (1976) reported that continued use of (NH4)2SO4 as a source of N on a kaolinitic red clay soil in central Kenya depressed soil pH and available Ca, Mg and K; while a build up in Ca, a rise in pH and an increase in Ca-P in the inorganic P fraction and a depression in occluded AI-P and Fe-P in the inorganic P fraction were observed when CAN was the N source. Furthermore application of DSP was found to decrease available P (Mehlich) but raised the levels of AL-P, Fe-P and occluded Al-P in the organic fraction. After 3 years of 222 Kenya
continuous application of CAN, some soils of Fertilizer use trials also showed clear symptoms of acidification (FURP, 1994; Smaling and Braun, 1996).
In parts of the country, prior to FURP trials, some farmers complained that yield increments as a result of application of DAP were no longer economical (Kenya Times, 1989). An experiment set up to investigate DAP reaction with soil and consequences on yields showed decline in SOM and total N (probably attributed to removal and burning of crops residues). Compaction of subsoil (and inhibition of water infiltration and root development) were major causes of uneconomical crop yields and not DAP per se. These results highlight the limitations of blanket as well as zone-specific and crop-specific recommendations and thus mitigates for the need for balanced nutrition-based fertilizer recommendations. The latter are also termed maintenance fertilizer recommendations. Only recently were the results of fertilizer use trial sites (FURP, 1987) based on the concept of agro-ecological units (Smaling and Van de Weg, 1990) published in district reports (FURP, 1994), journal papers (Smaling et al., 1993, 1992; Smaling and Janssen, 1993; Smaling and Braun, 1996), and doctoral theses (Smaling, 1993; Rotter, 1993; Wokabi, 1994; Nandwa, 1995). Available technologies that can be derived from the FURP district booklets (FURP, 1994) includes responses of maize and other 17 annual crops to different combinations of N, P and K fertilizer, and FYM. Fertilizer response to annual crops were earlier reported by Allan and Stroebel (1987), Okalebo (1977) and more recently by Okalebo and Nandwa (1997). A number of scientists are also preoccupied with studies aimed at extending the agro-ecological extrapolation of the above results, and hence add value to earlier research funding investment. Rotter (1993) investigated the use of a dynamic crop growth model, the WOFOST model (WOrld FOod STudies), on maize growth using FURP data. Wokabi (1994) also used the Automated Land Evaluation System (ALES) to predict maize yield gaps between different production systems. In most cases, these models gave good prediction indicators.
Full adoption of recommended fertilizers rates amongst smallholder is likely to be constrained by poor return to fertilizer application because of (i) poor or low producer price to cereals; (ii) sub-optimal uptake attributed to low plant available water especially in the arid and semi-arid areas of the country. To solve the first problem, there is need for imaginative agriculturists fully involved in participatory technology development on the judicious use of mineral fertilizers, or other less costly inorganic materials such as rock phosphate, or application of the mineral fertilizers on high value crops. Phosphate rock-based technologies in Kenya include direct application, acidulation to produce phosphoric acid of finished products, including partially acidulated phosphate rock (PAPR), and the production of thermally altered phosphates (e.g. fused Mg phosphate, Rhenania phosphate and deflourinated phosphate).
The major challenge in the use of rock phosphates to combat nutrient depletion, is how to solve the problem of ore types (low reactivity quality). This requires development of technology (which is not there yet) adapted to varied ore characteristics (Mclellan and Notholt, 1986). Although Kenya’s rock phosphates (Rangwe carbonatite) have not been exploited (Gachiri, 1991), probably because of its low quality e.g. 1.7-2.1% P (Idman, 1985; Van Kauwenbergh, 1986), nevertheless considerable deposits exist in Tanzania (Minjingu) and Uganda (Busumba and Suku) which could be accessed (Mclellana and Notholt, 1986). In Kenya, several studies have been conducted on the effectiveness and efficiency of rock phosphate in comparison to processed P fertilizers (Woomer and Muchena, 1996; Okelebo and Nandwa, 1997).
The first overall conclusion derived from past studies is that amongst East African rocks, Minjingu deposits on average reaches 65% of the effectiveness of processed P fertilizers (TSP), but only costs about 50 % of it on a P basis (Woomer et al., 1997). The second conclusion is that Integrated soil management for sustainable agriculture and food security in Southern and East Africa 223
application of rock phosphates with organic helps to hasten its solubilization. For example application of 400 kg/ ha-1 MRP (Minjingu Rock Phosphate) was shown to improve maize yield by 1-3 t/ha when applied in combination with organic sources of nitrogen. The third conclusion is that the benefits of phosphate rock application are greater and much more likely only on low pH and P limiting soils (Okalebo and Nandwa, 1997). These encouraging results have provided an impetus and triggered the formulation of a number of projects and proposals in Kenya on large scale soil fertility recapitalization or replenishment of phosphorus with rock phosphates (Okalebo et al., 1996; Weemer and Muchena, 1996; Woomer et al., 1997). Lime and liming materials are often applied to reduce soil acidity, so as to enhance availability of nutrients. Soil acidity may also be ameliorated through better organic matter management practices. The comparative advantages and disadvantages in the use of lime and dolomites to correct soil acidity has been reported by several researchers (FURP, 1994). However, the widespread adoption of liming technology is hampered by (i) its bulkiness (like phosphate rocks) and hence difficult to transport and apply, (ii) high leaching, especially under high rainfall conditions and in sandy soils, and (iii) general unavailability to the resource-poor farmers. These constraints may be overcome by application of comparatively small dressings at a time, well mixed into the soil which has been reported to be a more efficient way of lime application (FURP, 1994; Grant, 1970).
In Zimbabwe, liming-induced Zn deficiency has been reported, but this has been attributed to application of high rates of lime and P fertilizers (Tagwira and Mugwira, 1992, 1993). In general liming technology tends to be adopted mostly by high-external input farmers rather than small-scale farmers. A number of studies in Kenya have shown that liming contributed to higher pH values and better crop yields (up to pH 6), especially with wheat (Nyachiro and Briggs, 1987), tea (Wanyoko, 1989), maize and beans (Nuwamannya, 1984) and beans (Ssali, 1981). The latter author found that liming increased nodule weight and dry matter yield in soils with low organic C and substantial contents of Al or Mn, but in soils with relatively high organic C contents, high lime rates depressed dry matter yields. In Kenya, the third problem (low soil available water) is being tackled through integrated fertilizer and water harvesting techniques field trials in the arid and semi-arid lands (KARI, 1997).
The use of termite soil in situ or through biomass transfer is commonly practised in parts of Kenya. Hesse (1958) studied termites and indicated that Cubitermers did not affect the pH of soil and that termite mound soils contained more C and N than surrounding soil, probably due to higher numbers of cellulose decomposers, denitrifiers and nitrifiers (mainly Nitrobacter and Nitrosomonas spp.) found in termite modified soil than in surrounding topsoil (Mureira, 1980).
In many agro-eco-systems in Kenya organic inputs existing in farms are sometimes not fully exploited as nutrient inputs due to complex trade-offs between costs (labour, land), and perceived benefits on a short and long-term basis. Nevertheless organic inputs may include biomass transfer, agro-industrial by-products and wastes and cropping systems based on nitrogen fixation.
Sustainable agricultural production based on nutrient cycling operates only in systems where enough nutrient biomass is generated on-farm. With declining per caput arable land in sub-Saharan Africa, such systems are decreasing fast. Consequently, many smallholders try to increase their nutrient quantities through materials carried to the site as biomass transfer and count as actual addition of nutrients to the system. This may be in form of manure, leaf litter, pruning, plant residues etc. Biomass transfer-based technologies are not common in the region except where there is abundant animal manure available. A recent survey carried out in central Kenya highlands on biomass transfer indicated that 10-100% of the farmers surveyed imported animal manure from outside the dairy production zone, within the district or from other districts; at prices of between $ 5-100 per tonne, which in some cases is much more costly than inorganic fertilizers (AHI, 1996). A parallel study to inventorize the 224 Kenya
composition, biomass production and transfer and nutrient cycling potentials existing in hedges on smallholder farms in Western Kenya revealed that over 28 species of hedge plants were ubiquitously distributed in the area, which were currently under-utilized in terms of biomass transfer or plant residue restitution for soil fertility improvement. In Zimbabwe, biomass transfer of miombo woodland leaf litter used as a source of plant nutrients, has been reported as a common practice amongst smallholders (Musa et al, 1997).
The use of urban and agro-industrial wastes could help reverse the flow nutrients from crop harvest back to the farm (in form of nutrients cycling if the flows went back to the same farms), but wide adoption may not be justified in economic terms. The by-products and wastes of processed crops e.g. coffee husks and filter mud/bagasse from coffee and sugarcane, respectively, are important source of nutrients. One tonne of these products may contain about 5-20 kg/ N, 7 kg/P and 25 kg/ of K. However, because of their bulkiness, the use of these products tends to be limited to areas in close proximity to their source. Further more, a recent study in Kenya showed that 1 kg/ of N and P from city composts costs 0.5 and 1.2 US $, respectively, compared to 0.42 and 0.18 US $ of N and P in purchased fertilizers e.g. 20:9:0 a elemental N, P, K (Palm et al., 1997). In Kenya, an organic fertilizer humus made from coffee husks named "cofuna" was reported to enhance fertilizer utilization by maize crop. Its application at 400 - 800 kg/ ha gave yields of maize comparable to farmyard manure applied at 4.2 t/ha, but its cost could only be recovered on high value crops.
Nitrogen contribution of legumes and other N-fixing plants has been widely exploited in enhancing productivity of agro-ecosystems, in terms of species for intercropping, relay cropping, agroforestry, rotational species or as species for use in improved fallow technology. Recent studies in East and central Africa highlands on screening of species for improved six months fallows ( Calopogonium mucunoides, C. agatiflora and C. mucronata) and twelve months fallows (Tephrosia candida, Desmodium viscosa and Macroptillium atropurpurem) indicate that in 6-12 months the species produced 6 - 11 t/ha dry matter, 150 - 300 kg/N/ha and 20 - 30 kg/P/ha (AHI 1997). But many past experiments on legume intercropping, have shown that many legumes hardly fix any nitrogen under low soil available P conditions unless inoculated. Moreover, competition for water, light and nutrients between food crops and perennial legumes, makes the intercrops of the latter for soil fertility restoration, as an inappropriate technology, except for soil conservation purposes (Place et al., 1995). Similar competition has been observed in systems where food legumes have been intercropped with maize as a risk aversion or minimization strategy, in case of drought.
Nevertheless, deep rooted legumes species planted as improved fallows contribute to soil fertility restoration through biological nitrogen fixation (BNF) as well as from nutrient capture from subsoil. In a recent study in Western Kenya, on screening soil improving legumes for low P conditions (P stress), results indicated that some species like Dolichos lablabbronga, M. atropurpurem and Canavalia ensiformis responded negatively to P application, an indication that they can do well in P deficient soil conditions. Elsewhere, studies have shown that two tonnes of leaves of some non-leguminous trees and shrubs (Tithonia divesiforlia, Chromoleana ordorata, etc.) produce enough N and K for a 2 t/ha maize grain crop but six times more biomass would be required to supply adequate P. In systems with limited per caput arable land, legume species likely to be adopted are those that are grown for food (grain) or forage purposes, but also yield high above ground (leaf biomass) and below ground biomass e.g. Arachis, Cajanus etc or leguminous cover crops such as Crotalaria, Dolichos Mucuna etc.
Nutrient saving and conservation technologies Recent rising costs of chemical fertilizers has focused researchers attention on recycling of crop and other plant residues (restitution) and weeds as a strategy to buffer the level of soil fertility and maintain Integrated soil management for sustainable agriculture and food security in Southern and East Africa 225
soil organic matter (SOM). Poulain (1980) reported that organic residues may contain appreciable amounts of nutrients, commonly under-utilized in African farming systems. For example a 2 t/ha maize grain crop (4 t/ha stover), on average contains 25, 7.2 and 65 kg/ ha of N, P and K, respectively, in the stover, which is 4 - 5 times that applied from mineral fertilizers by most farmers in SSSA (Steervegel and Smaling 1990). The development of appropriate technologies for efficient nutrient utilization of crop residues requires an understanding of the merits and trade-offs of residues restitution (Prasad and Power, 1991), and factors regulating their decomposition and mineralization and nutrient release patterns (Whitmore and Handayante, 1997). The technologies so formulated need to identify optimum quality, rates, placement and time of restitution of the residue in the context of cropping systems targeted. A number of studies are presently undertaken to determine the short-term and long-term effects of crop residue restitution on crop response (TSBF, 1995). Most of the studies in the region are conducted within the framework of the Tropical Soil Biology and Fertility (TSBF) African Network (AfNet) which uses standard methodology (Anderson and Ingram, 1993), to gain insights of the processes which regulate the release of nutrients.
Emerging results from the AfNet work indicates that (i) about 5 - 10 tonnes dry matter per hectare of crop residues may supply enough nitrogen for a two tonne maize grain crop (80 kg/ N/ha) but cannot meet P requirements (18 kg/ P/ha) and hence P must be supplemented by inorganic P (Palm, 1995), (ii) the availability and supply of 5 - 10 tonnes of crop residues directly as nutrient sources may be a problem especially on resource poor farms where there are competing uses as livestock feed or source of fuel; (iii) and even if availability and restitution of low quality crop residues was possible, in most cases materials with <2% N, >15% lignin, and >3% polyphenol (Palm, 1995) and <0.25% P (Blair and Bennet, 1986), will initially immobilize N and P, respectively, and exacerbate nutrient deficiency, unless this is offset by combination with inorganics or high quality organics. In Zimbabwe, one mango tree has been reported to supply 22 kg/ of leaf litter (on average each farm has 11 mango trees) which when applied was reported to immobilize 10.9 kg/ N/ha (TSBF, 1995). The major constraint to the adoption of or sourcing nutrients from plant residues, is that no field trials have been conducted in the region which allow establishment and recommendation of fertilizer equivalency values of the residues especially for circumstances where organics and inorganics have to be combined (Palm et al., 1997).
Nitrogen recovery in the tropical cropping systems is often reported to be in the range of 30 - 50% which is largely attributed to leaching (Nielsen et al.; 1982; Birch, 1960; Smaling, 1993). In shallow rooted annual crops nutrients leached below the rhizosphere is as good as lost. Split application of nitrogen dressing is one strategy aimed at minimizing such losses. Another strategy is through utilization of untapped subsoil nitrates (Farrel et al. 1996). Such nitrates (at 50 - 200 cm soil depth) are estimated to be in the order <100 kg/ N/ha/yr in Western Kenya. Research on soil and water conservation practices in Kenya dates as far back as 40 years. However little information exists which relates biological methods of control to amounts of nutrients saved from loss (Braun et al, 1997). Most of the work has been concentrated on tillage and tied ridges, minimum tillage versus conventional tillage versus contour farming, mulching and crop residues and crop cover. Kilewe and Mbuvi (1988) reported that minimum tillage had a reduction of 70.8 and 39.2% in runoff, and 53.0 and 58.7% in soil loss in the long and short-rainy seasons, respectively. This is in contrast with conventional tillage which reduced runoff by 25.1 and 20.1%, and soil loss by 8.1% and 39.5%, respectively. The authors found application of maize residues to reduce runoff by 58.7 and 78.6% and soil loss by 94.4 and 64.4% respectively, during the same periods. Similarly, maize intercropped with beans (compared to pure stand maize) reduced runoff by 29.2 and 42.0%, and soil loss by 22.3 and 47.5%, respectively, during the some period. Technologies based on these results have proved fruitful in saving nutrients liable to losses. 226 Kenya
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Malawi
COUNTRY FOOD PRODUCTION AND REQUIREMENT Malawi has a total land area of 11.8 million hectares, of which over 20% is covered by Lake Malawi and other small lakes and rivers. Malawi exhibits great diversity in terms of relief units, soils and climate for a country of its size. There are four major relief units: (i) The High Altitude Plateaus (1,350 to 3,000 m a.s.l.) dominated by Lithosols and some weathered Latosols, (ii) The Medium Altitude Plain (750 and 1,350 m a.s.l.) with deep, well drained Latosols on upland sites and poorly drained hydromorphic soils in dambos, (ii) The Lakeshore Plain (450 and 600 m a.s.l.) characterized by calcimorphic alluvial soils, and (iv) The Lower Shire Valley (35 to 105 m a.s.l.) dominated by calcimorphic alluvial soils, Vertisols and hydromorphic soils in dambos. The climate is semi-arid in the Lower Shire Valley and some parts of the Lakeshore Plain, semi-arid to sub-humid on the Medium Altitude Plateau, and sub-humid to humid on the High Altitude Plateaus. Although most parts of Malawi receive adequate total rainfall for rain-fed agriculture in most years, its distribution is often poor, uneven, and erratic leading to crop failure. The distinctive feature about the rainfall pattern in Malawi is its concentration in a single crop rainy season starting in November/December and ending in April/May. The population of Malawi is currently estimated at 12 million people and growing at the rate of 3.3% per year. About 90% of the population are rural and derive its livelihood from small land holdings of between 1.0 and 2.0 ha per farm family of five people. The population density is estimated at 85 persons per square kilometre, a figure that is too high by African standards. The average population density increases from the north to the centre and then to the south as follows: 44, 113 and 162 persons per square kilometre, respectively.
Agriculture dominates economic activities in Malawi. It contributes well over 40% of the Gross Domestic Product (GDP) and accounts for about 90% of the foreign exchange earnings. Smallholder farmers contribute about 85% of total agricultural production and 30% of the export trade, with the balance coming from the estate sub-sector. The major food crops are maize, groundnuts, cassava, sorghum, millet, beans and other various pulses. The main cash crops are tobacco, tea, sugar, coffee, groundnuts, cotton, macadamia nuts and maize. Maize is the major staple food crop grown by all smallholder farmers on about 65% of the total cultivated land area (estimated at 1.8 million hectares). About 94% of this is grown in association with legumes, whereas 6% is planted in pure stands. The smallholder sub-sector consists of about 1.8 million farm families. Women comprise about 70% of the total full-time farmers and play a vital and indispensable role in agricultural production in Malawi (World Bank, 1995; UNICEF, 1993).
A.R. Saka, W.T. Bunderson, M.W. Lowole and J.D.T. Kumwenda Chitedze Agricultural Research Station, Lilongwe; Malawi Agroforestry Extension Project, Lilongwe; Soil Survey Commodity Team, Lilongwe 232 Malawi
High population densities and growth rates limit available land for agricultural expansion. In 1987/88 56% of all smallholders in Malawi cultivated less than one hectare of land, 31% had 1.0 to 2.0 ha, whereas an estimated 13% had more than 2 ha. The average landholding size among these categories of landholders was 0.55, 1.40 and 2.91 ha, respectively. Most smallholder farmers lack basic needs such as adequate food, water, energy, shelter, health and education. It is estimated that over 60% of the smallholders live below the poverty line, whereas in urban areas, average wage earnings are infrequently sufficient to purchase food and other basic necessities of life. Chronic food shortage is manifested though malnutrition and high mortality, especially among children. The future prospects in meeting basic food demands for a growing population are bleak and worrisome. Most households lack resources and support to undertake sound agronomic and animal husbandry practices to properly manage the natural resource base. Family labour is also decreasing as household members engage in off-farm employment (ganyu) in urban areas at a time when they are supposed to be cultivating in their fields. This has led to increasing poverty and chronic food shortages (Bunderson and Hayes, 1995).
With existing population pressure trends, Malawi is facing enormous problems of natural resource degradation, deforestation and loss of biological diversity. Recurrent droughts, reduced export earnings and declining terms of trade, have magnified the social, economic and environmental problems facing Malawi today. Increasing population pressures on a limited land resource base has direct impact on employment, marketing, food security, health and education (Bunderson and Hayes, 1995). As of now, land degradation is a serious problem in Malawi. The World Bank (1992) estimates that 20 t/ha/year are lost through soil erosion in Malawi. In slopping hilly areas, and where the soils are more erodible, soil erosion rates of up 50 t/ha/year have been reported; whereas in areas with flat terrain and where good crop husbandry practices are followed, soil erosion is negligibly small. The main causes of soil erosion include: poor agronomic practices, poor soil management practices, deforestation resulting from agricultural expansion and increasing demands for firewood, and over-grazing. Malawi's high and growing population has led to chronic land shortages, declining incomes, and stagnating levels of crop production leading to food insecurity at both household and national levels. An examination of national cereal food production in Malawi over the last 10 years (1985/86 - 1994/95) indicate that the per caput cereal requirements have not been met in all years, except during the 1992/93 season which had a notably good rainy season (Table 1).
TABLE 1 Population, cereal production (tonnes) and requirements (kg/ per caput ) 1985/86-1994/95 1985-86 1988-89 1989-90 1991-92 1992-93 1994-95 Population (000) 7 733 8 524 8 806 9 397 9 707 10 358 Production: Maize 1 424 1 660 1 477 723 901 1 568 Rice 37 46 43 24 65 48 Sorghum 21 20 15 4 22 23 Millet 10 11 10 3 15 11 Wheat 1 1 2 1 1 2 Total cereals (000) 1 493 1 739 1 548 754 2 341 1 651 per caput production kg/ 193 204 202 80 241 159 per caput requirement kg/ 232 232 232 232 232 232 Deficit/surplus kg/ -39 -28 -56 -152 9 -73 Sources: Bunderson and Hayes (1995), as extracted from the 1987 NSO Population Census; Crop production estimates from the Ministry of Agriculture (1988); Cereal requirements from UNICEF (1993) Integrated soil management for sustainable agriculture and food security in Southern and East Africa 233
Using 1980 as the base, total food requirements rose by 171% in 1993 and are projected to rise to 249% in the year 2010. The national maize demand in 1996/97 was estimated at 1 351 842 tonnes; whereas the national demand was estimated at 1 800 000 tonnes (Bodzalekani, personal communication). This indicates a shortfall of 448 158 tonnes that must be imported into Malawi. This has serious implications on foreign exchange reserves for Malawi. The actual cereal production (1985/86-1994/95) is given in Table 1; whereas projected national cereal consumption requirements are given in Table 2. The predicted outcomes, or model forecasts, indicate an urgent need to increase cereal production to meet the demands of an increasing population, against a background of declining land holdings. The declining trend in smallholder crop production (food and cash crops) over the last decade (1985/86-1994/95) in relation to land area is depicted in Table 3.
TABLE 2 Projected national cereal consumption requirements (tonnes) in Malawi, 1995/96-2014/15 Years 1995-96 1997-98 2001-02 2007-08 2011-12 2014-15 Population ('000) 10 694 11 384 12 826 15 115 16 700 17 905 Cereal requirements: Maize 2 363 2 516 2 834 3 340 3 691 3 957 Rice 72 76 86 101 112 120 Sorghum 28 30 33 39 43 47 Millet 16 17 19 23 25 27 Wheat 2 2 2 3 3 3 Total cereals (000) 2 481 2 641 2 976 5 507 3 874 4 154 per caput production kg/ 232 232 232 232 232 232 per caput requirement kg 232 232 232 232 232 232 Source: Bunderson and Hayes (1995) as extracted from the 1987 NSO Population Census; Crop production estimates from the Ministry of Agriculture (1988); Cereal requirements from UNICEF (1993) Notes: 1. Estimated annual growth rate of 3.3% from 1986/87 until 1994/95, this rate is assumed to fall by 0.05% from 1995/96 until 2014/15 because of efforts to reduce population growth (e.g., birth control; declining fertility rates; and the possibility of a rising death rate due to diseases) 2. Based on Malawi's current demographic structure, an average intake of 2,200 calories per day is needed to meet minimum calorific requirements. To provide 80% of this requirement, about 190 kg/ of milled maize grain (mgaiwa) needs to be consumed per year. This is equivalent to maize production of 232 kg/person/year assuming a wastage of 18%. Other cereals (rice, wheat, sorghum and millet) have been included for the purposes of this year analysis on the same nutritional basis 3. Assumed that the estate sub-sector produces an annual 10% increment to smallholder maize production.
TABLE 3 Smallholder crop hectarage (ha) and production (tonnes) in Malawi, 1985/86 - 1994/95 Years 1985-86 1991-92 1994-95 Food crops Hectarage Production Hectarage Production Hectarage Production Maize 1,193,275 1,294,564 1,368,093 657,000 1,222,147 1,425,176 Rice 22,874 37,407 18,241 23,798 33,038 47,577 Groundnuts 176,293 88,937 64,386 12,060 89,373 37,182 Sorghum 32,059 20,761 27,668 3,957 61,551 22,574 Millet 17,424 9,526 14,767 3,418 24,882 11,311 Cassava 72,904 218,282 63,965 128,827 94,616 321,362 Sweet potatoes 22,477 80,003 19,886 43,074 56,113 342,003 Irish potatoes - - 5,855 49,194 7,752 70,025 total food crops 1,537,306 1,582,861 1,589,472 Cash crops 247,254 369,648 505,125 234 Malawi
As alluded to earlier, maize is the major staple food crop in Malawi that is grown on an estimated 1.2 million ha under smallholder farm conditions. Hence, maize production needs to rise almost threefold from 1.4 million tonnes in 1994/95 to 3.9 million tonnes in the year 2014/15 to meet the demands of a growing population estimated at 20 million people. This will require significant advances in productivity per unit area, and a commitment from Government, non- Governmental Organizations (NGOs), the donor community and the smallholder farmer themselves. There is an urgent need to increase the current national average yield of 1.1 t/ha to 4 t/ha in the year 2014/15 if Malawi is to satisfy its food requirements at the national level. National food security does not necessarily mean food security at the household level. This is primarily due to the fact that national food security requirements do not take into account the problems of the location where the food is available and its distribution. An average family of 5 persons require a minimum food requirement of 1,058 kg/ at 232 kg/ maize per ha (Ministry of Agriculture, 1988). Hence, landholding size is an important factor in attaining food self- sufficiency. Among the smallest farms, yields must average 1,924 kg/ ha if the whole 0.55 ha is devoted to maize production (Bunderson and Hayes, 1995). This is 65% higher than the mean yield of 1,166 kg/ ha in 1994/95. Under current trends, these households will experience regular food deficits on a year round basis unless they procure food by other means other than through production. These include ganyu labour or other off-farm activities. The challenge facing the Malawi Government today is to produce enough food to feed the rapidly increasing population that is exerting enormous pressures on land and the natural resource base, on the nation's food self sufficiency and food security, the labour markets and the provision of social welfare services such as health and education. In retrospect, concerted efforts are required by Government and the donor community to harness Malawi's natural resources so that the rate of food production should outstrip the rate of population growth.
EVOLUTION OF PER CAPUT CULTIVATED LAND AND TRENDS IN CEREAL CROP YIELDS Land use and land tenure It is currently estimated that 60% (5.7 million ha) of the total land area (9.4 million ha) is considered suitable for agriculture under improved traditional management practices. Under traditional practices, only 32% (3 million ha) can be classified as suitable for cultivation. As a result of increasing population pressures on limited land area (Tables 1, 2 and 3), cultivated land (including land under short fallow) has almost doubled to 4.6 million ha over the last three decades. Of the remaining 1.1 million ha of suitable land, 600 000 ha comprise national parks, game and forest reserves. Land is a resource of pressing importance in Malawi since all the land that is suitable for cultivation under traditional systems of management, and much which is unsuitable for cultivation, is already under rain-fed cultivation (Green and Nanthambwe, 1992). Cultivated land area in Malawi has been unequal among the three regions, a scenario that reflects the longer-term land-use and availability over a longer period of time. The greatest increases in land-use over the last two decades have occurred in the Central and Northern Regions (50 and 57%, respectively), where land for agricultural expansion is still available. The least expansion has taken place in the Southern Region (3%) where the limits of agricultural expansion were reached in the 1960s (Table 4). There are three major categories of land tenure in Malawi: (i) public land, (ii) private land, and (iii) customary land. Land under customary tenure represents about 87% of the total land area. Land in the Northern Region and some parts of the Southern Region, is under the patrilineal system of inheritance; whereas that in the Central Region and some parts of the Southern Region, follows the matrilineal system of inheritance. Despite these differences, in either system, land Integrated soil management for sustainable agriculture and food security in Southern and East Africa 235
which is in use can be held indefinitely and can be inherited. Land that is not under any form of use is considered to belong to the community rather than individuals. All unused customary land is under the jurisdiction of the chief or his headman. This customary land may be declared public land, or a lease (of up to 99 years) maybe granted to a private party or individual.
TABLE 4 Expansion of cultivated area (hectares and %) in Malawi, 1966/67 - 1990/91 Years Area under cultivation by Region Northern Region Central Region Southern Region Total country has has has Has 1967 577 300 1 478 300 1 477 200 3 532 800 1990 902 900 2 171 850 1 505 500 4 580 250 increase % 56.4 46.9 1.9 29.6 Source: Green and Nanthambwe, 1992
Trends in cereal crop production With increasing population pressure on a limited land resource base, and continuous cultivation with little or no added external inputs, most of the intensively cultivated soils in Malawi are heavily depleted of essential nutrient elements. There has also been an increasing trend in the cutting down of trees (deforestation) as a result of increasing population, expansion of the agricultural sub-sector, and increasing demands for fuelwood and wood products. These have interacted over space and time to increase the soil erosion hazard, with catastrophic consequences on soil fertility. Increasing soil erosion, soil nutrient depletion, increasing soil acidity, accelerated deforestation, over-grazing and the depletion of groundwater resources are all signs of Malawi's land degradation, and deterioration of the natural resource base. All these factors have combined over space and time to tremendously reduce crop yields in Malawi (Tables 1 and 3), hence food insecurity, especially among smallholders, and female headed households. Despite the increased use of fertilizer in Malawi over the past few decades, crop yields have either declined or stagnated (Tables 5 and 6). The main reasons for poor crop performance, despite the use of improved technologies, can be attributed to several factors including poor crop husbandry practices (e.g., late planting, inappropriate plant population densities and untimely weeding), poor fertilizer management practices, low soil fertility.
TABLE 5 Three year running average yields of maize and groundnuts (kg/ ha), 1985/86 - 1992/93 Crop season 1985-86 1986-87 1988-89 1989-90 1990-91 1991-92 1992-93 All maize 1.17 1.15 1.13 1.12 1.11 0.87 1.05 Local 1.01 0.98 1.03 0.99 0.91 0.67 0.74 Hybrid 2.94 2.92 2.74 2.69 2.77 2.26 2.42 Groundnuts 0.45 0.46 0.37 0.36 0.36 0.34 0.38 Source: World Bank, 1995
Results from continuous cultivation of maize and cotton have indicated reduced maize and cotton yields, and deteriorating soil chemical conditions at Chitala (Table 7), whereas continuous cultivation under tea in Mulanje clearly illustrate the declining trends in soil chemical fertility, hence crop yields (Table 8). All these are indicative of crop yield decline owing to land degradation under continuous cultivation. The situation is even worse under smallholder farm conditions. 236 Malawi
TABLE 6 Maize and cotton yields (kg/ ha) and soil chemical changes under continuous cultivation with and without fertilizer application, 1962/63 Fertilizer treatment Variables Cropping sequence Continuous maize Continuous cotton No fertilizer applied pH 5.9 5.8 OM% 1.81 1.81 total N% 0.07 0.06 P ppm trace trace K me% 0.26 0.18 yield kg/ ha 918 224 5 t/ha FYM + 200 kg/ ha pH 6.5 5.8 sulphate of ammonia OM% 1.76 1.40 total N% 0.07 0.05 P ppm trace trace K me% 0.44 0.32 yield kg/ ha 3562 941 Source: DAR, 1965
TABLE 7 Soil changes under continuous tea cultivation over a 25-year period, Nsuwadzi, Mulanje Soil variable Treatment N0P0K0 N1P1K1 N2P2K2 Virgin soil OM (t/ha) 140 82.5 (41%) 102.5 97.5 (30%) (27%) N (t/ha) 8 5.0 (38%) 5.0 (38%) 4.5 (44%) P (t/ha) 2.2 2.1 (5%) 2.3 (-5%) 2.8 (-27%) pH (CaCl2) 5.4 4.6 4.3 4.1 K (t/ha) 606 137 (77%) 186 (69%) 205 (66%) Mg (t/ha) 420 152 (64%) 152 (81%) 30 (73%) Ca (t/ha) 1668 175 (90%) 140 (92%) 120 (93%) Source: Maida and Chilima, 1976 Note: Figures in brackets indicate % increase or decrease % decrease = (V - Tp) /v 100, where V = virgin soil; p= cultivated plot -1 -1 -1 N - 45 kg/ N ha ; P - 0 kg/ P205ha ; K - 0 kg/ K20 ha 0 -1 0 -1 0 -1 N - 135 kg/ N ha ; P - 15 kg/ P205 ha ; K - 28 kg/ K20 ha 1 -1 1 -1 1 -1 N2 - 225 kg/ N ha ; P2 - 30 kg/ P205 ha ; K2 - 56 kg/ K20 ha
Effect of liberalization The advent of multiparty politics in the 1990s has brought with it the liberalization of the Malawi economy. The selling and buying of crops, except maize, and farm inputs, including fertilizers, has been liberalized. Liberalization of the market has already shown both interesting and disturbing trends. Estimates of areas grown to different crops indicate considerable changes in response to fluctuating prices. There is generally an increase in the area grown to legumes, little changes to the area grown to maize (although there is a decrease in the area grown to hybrid maize but an increase to the area grown to open pollinated varieties), an increase in the area grown to tobacco (a high value cash crop), and a significant drop in the area grown to soybeans (in response to low farm gate prices for this legume). With the declining land area under food crops, and the low levels of food production under smallholder farm conditions, Malawi is not able to feed itself as a nation.
For Malawi to be self sufficient in food production, there is an urgent need to raise average crop yields per unit area. Blackie and Canroy (1994) have estimated maize growth production levels to increase to 4 t/ha from the present 1.1 t/ha if Malawi is to achieve food self-sufficiency Integrated soil management for sustainable agriculture and food security in Southern and East Africa 237
and security at household level. World Bank (1989) has indicated that for sub-Saharan Africa to achieve food self sufficiency and security at household level, improve nutrition, eliminate food imports and register modest improvements in the living standards of its peoples, then the economics of these nations must expand by 4 to 5% per year between 1990 and the year 2020. This is the challenge that lies a head for Malawi.
TABLE 8 Estimated land area (000 ha) grown to various crops by smallholder in Malawi, 1995/96 and 1996/97 Crop Year Varieties 1996-97 1995-96 Total maize 1,230 1,243 -1% Hybrid 299 369 -19% OPV 20 17 18% Local 911 856 6% Sorghum 79 76 4% Total cereals 1,386 1,398 0% Soybeans 39 54 -28% Groundnuts 97 72 35% Pulses 395 359 10% Cassava 108 116 -0.7% Sweet potatoes 71 69 0.3% Tobacco 98 79 24% Source: MOALD, 1997
EXTENT OF SOIL DEGRADATION AND ITS BIO-PHYSICAL & SOCIO-ECONOMIC IMPACTS Land degradation has become an acute problem in Malawi. This is mainly as a result of increasing human population pressures on limited land area and increasing deforestation caused by agricultural expansion and increasing demands for fuelwood. Soil erosion is currently estimated at 20 t/ha/year (World Bank, 1992), with rates more than 50 t/ha/year in some parts of Malawi. However, Saka, Green and Ng'ong'ola (1995) using data from Zimbabwe estimated that Malawi is losing an average of 35 t/ha/year. In terms of nutrient loss per year, this translates into 74.0 kg/N/ha, 539.0 kg/Organic carbon (OC)/ha and 5.5 kg/P ha. Hence, based on the above assumptions, it can be estimated that the whole of Malawi is losing some 160 million tons of top soil each year from cultivated land that contains approximately 339 000 tonnes of N, 2.5 million tonnes of OC, and 25,000 tonnes of P. Thus, the cost of replacing the lost N, P and OC is enormous considering the fact that fertilizer is an expensive farm input in Malawi owing to high transport costs. The cost of N and P is estimated at over US $ 300 million each year (Saka, Green and Ng'ong'ola, 1995).
Types of land degradation Water erosion is the major form of land degradation in Malawi. Soil erosion by water is quite widespread and manifests itself in the form of rill and sheet erosion, and gullies on cultivated land. It is estimated that 4.5 million ha are annually cultivated or are in recent fallow (Green and Nanthambwe, 1992). Other forms of land degradation include: (i) wind erosion, (ii) rapid mass movement, (iii) salinity, and (iv) chemical, physical and biological degradation. Wind erosion is not much of a serious problem because the ground maintains some of its cover in the form of weeds or crop residues during the dry season. Ridges, which form a rough ground surface, have the effect of reducing wind erosion. However, where the land is bare, this could be a problem, especially in August or September when there is severe wind blow as most trees species shade off 238 Malawi
their leaves. Over-grazed areas, such as in the Shire Valley or along the Karonga Lakeshore Plain, pose a special problem to wind erosion, and so too are some large estates which are not planted with trees on their boundaries.
Heavy and continuous rains have been reported to induce large movements of soil. For example, in 1946, too much rain fell in Zomba which caused massive amounts of soil to creep down the Zomba mountain. In 1992, when too much and continuous rains fell around Mulanje mountain, the flush floods at Phalombe transported large quantities of soil, debris, rocks and tree branches that caused death to many people, destruction to property and untold misery to thousands others.
Salinity is another factor that contribute to land degradation, especially where saline irrigation water is used. This could be a problem in some of our irrigation schemes along Lake Malawi, the Shire Valley and some big river valleys, such as the Limphasa dambo. So far, there are no reported records of salinity. This is perhaps a reflection that the water in Lake Malawi, and other rivers, is not saline, except maybe for Lake Chilwa that does not have an outlet to the sea via the Shire River.
Land degradation is manifested in the depletion of nutrient elements in the soil, the physical breakdown of soil structure and reduction in micro-biological activity in the soil. Since most Malawi soils are old, they are highly weathered and leached of all essential nutrient elements. The soils are deficient in the major nutrients N, P and K, the secondary nutrients Ca, Mg and S, and the micronutrients B and Zn, along with reduced levels of soil organic matter, hence increasing levels of acidity. Reduced soil organic matter content has serious implications on soil structural stability and soil-water holding and transmission characteristics. All these factors have interacted sequentially and simultaneously over time and space to reduce the productive capacity of Malawi's soils.
Main causes of land degradation The main causes of land degradation include the following: (i) rainfall, (ii) soil, (iii) topography, and (iv) cultivation methods. These have been exacerbated by increasing human and livestock population pressures, deforestation and over-grazing. The total seasonal rainfall pattern, which varies from 600 to over 3,000 mm, is generally of very high erositivity. High intensity storms are a major characteristic, especially during the beginning of the rainy season, with intensities of up to 75 mm per hour for several minutes. The highest intensities have been recorded for the south and east of Mulanje mountain in the Southern Region, and along some parts of Lake Malawi. At higher altitudes (>1,700 m a.s.l.), intensities are usually lower, but apart from these areas, over 40% of the total rainfall in Malawi falls at intensities that are greater than 25 mm per hour (Pape, 1971).
Soils of Malawi are very variable. Erodibility too, varies considerably, although it can generally be said that most of the cultivated soils are moderately resistant to erosion under good land and crop husbandry management practices. In the High Altitude Hill Areas, where the soils are deep, well structured and highly permeable, run-off is very low despite the steep slopes in these areas. The length of the slope and its steepness have an important influence on the soil erosion process. There are extensive areas in Malawi that are flat to gently undulating (slopes of less than 6%). These mostly occur in the Shire Valley, the Phalombe Plain, and a large part of the Middle Altitude Plateau. The erosion hazard due to topography in these areas is slight to moderate. The Rift Valley Scarp Zone and the High Altitude Hills areas have steep slopes and are Integrated soil management for sustainable agriculture and food security in Southern and East Africa 239
dissected, although some moderate slopes are found. From the point of view of topography, these areas have an erosion hazard that is high. Poor cultivation and crop husbandry practices have significantly contributed to soil the erosion problem on cultivated land. The main method of land preparation in Malawi involves the making of fresh ridges every year; except in the Shire Valley where farmers have consistently planted on flat land, and some areas along the Lakeshore Plain where cassava is the dominant staple food crop. More often than not, ridges have not been aligned on the contour, inducing a serious avenue for surface run-off; hence massive losses of the valuable top soil. Over-all, when all the factors influencing soil erosion are combined, a situation of high erosion hazard for Malawi emerges (Paris, 1990).
Forms of land degradation A physically degraded soil exhibits several soil problems that greatly limit crop growth and establishment. Some of the major forms of physical degradation include: crusting, water logging, compaction, reduced infiltration rates and soil organic matter contents. These are all signs of soil structural deterioration. Soils exhibiting these characteristics have low soil organic matter contents which is the binding agent for all well aggregated soil types. As alluded to earlier, these generally will come about due to poor soil management practices, and inappropriate crop husbandry practices that do not allow quick vegetative ground cover after the commencement of the rains. In Malawi, most soil types which have been heavily cultivated, or are course-textured, on the Middle Altitude Plateau are showing clear signs of soil physical degradation.
Most of the fertile Ferruginous Latosols on the fertile Lilongwe-Mchinji Plain, are now exhausted and are showing signs of structural instability. So too are the over cultivated sandy soils characterizing the Kasungu and the south-west Mzimba Plains. Increasing acidity, salinization, nutrient depletion and/or excessive nutrient leaching, pollution from industrial wastes, and from the application of agrochemicals, are the major forms of land degradation. Some of these are at an advanced stages in Malawi. For example, the use of sulphate of ammonia is not recommended on upland soils where it has been reported to increase soil pH. On the other hand, this type of fertilizer is perfectly suitable for saline calcimorphic alluvial soils occurring along the Lakeshore Plain or in the Shire Valley. Most soil types in Malawi are heavily depleted in essential nutrient elements as a result of continuous cropping without added external inputs. On the Middle Altitude Plateau many farmers do not return crop residues to their farms to improve soil fertility. This is because of unfavourable dry weather condition that is not conducive to leaf biomass decomposition soon after harvest. However, farmers in the wetter agro-ecologies, e.g., Shire Highlands, have developed cultivation methods whereby crop residues are incorporated into the soil soon after crop harvest. Due to the generally wetter climatic conditions in the subsequent months following crop harvest, crop residues are able to decompose and contribute to the soil organic matter pool. The cation exchange capacity of the soil is increased as the major nutrients, including secondary nutrient elements Ca and Mg, are released from the soil organic matter pool. What is equally significant is the improvement in soil structure. The soil becomes well aggregated leading to improved soil-water holding and transmission characteristics.
Extent and severity of soil degradation Land degradation, as measured though soil loss due to wind and water erosion, physical and chemical degradation is widely spread in Malawi. All cultivated land, apart from a few well managed estates, is prone to land degradation. It is only forest land or bush land, covered with trees and grasses, that is well protected. The economic losses resulting from land degradation are enormous although they are difficult to quantify in exact economic terms. This is because no 240 Malawi
studies have been conducted on coordinated systems of management for soil erosion that quantifies soil loss under different farming conditions in Malawi. However, as alluded to earlier, studies conducted in Zimbabwe, and extrapolated to Malawi, indicate that Malawi maybe loosing in excess of US $300 million due to N and P losses through soil erosion. Concerted efforts are required to reverse the trend of soil degradation in Malawi. Improved land management and crop husbandry practices are urgently required if Malawi is to improve soil fertility and reduce soil erosion, hence attain food self sufficiency at both national and household levels. Strategies that utilize organic fertilizers, augmented with modest levels of inorganic fertilizers, will ensure sustainable crop production and food security for Malawi’s growing population.
AVAILABLE TECHNOLOGICAL OPTIONS FOR CONTROLLING SOIL DEGRADATION AND ENHANCING PRODUCTIVITY Low and/or declining soil fertility is one of the major problems constraining crop production in Malawi. Farmers in Malawi have for time immemorial recognized this problem and have, consequently, responded appropriately. There are currently many options for addressing soil fertility decline and rampant soil erosion hazards, with varying degrees of acceptability, success and adoption rates. What follows is a brief outline of the currently available technologies designed to mitigate the undesirable effects of low soil fertility and soil erosion. The traditional soil fertility improving technologies include: i) shifting cultivation (or bush fallowing), ii) isolated trees on farm land, and iii) use of leaf litter, anthill soil and ashes. Shifting cultivation, which was a stable form of land use system for many decades in Malawi, is now less common, except maybe in a few isolated areas where finger millet is still commonly grown (e.g., Chitipa). The system was able to restore essential nutrient elements under conditions of low population pressures (<15 persons/square km), and long fallow periods (>15 years). With increasing population pressures on limited land area, fallow periods have become shorter rendering the system ineffective to restore declining soil fertility. Along with shifting cultivation, farmers also learned that leaves of some tree species have the capacity to release nutrients and therefore improve soil fertility. Likewise, some farmers have utilized anthill soil and ashes to improve soil fertility.
With the continuing trends in soil fertility decline, against a background of increasing population pressures and the depletion of the natural resource base, other soil fertility enhancing technologies have been developed. These include: i) crop rotations, ii) green manure, iii) tobacco remains, iv) homestead refuse, v) cattle, goat, sheep, pig and chicken manure, and vi) agroforestry technologies. Of the agroforestry technologies, the following have shown potential to improve soil fertility: (i) alley cropping, (ii) relay and strip cropping, (iii) interplanting cereals with Faihderbia albida, (iv) intercropping cereals with legumes, (v) undersowing cereals with Tephrosia vegelii, and (vi) the use of improved fallows using various leguminous tree species (e.g. Sesbania sesban, pigeon peas and Tephrosia vogelii).
These basically include the use of inorganic fertilizers and improved agroforestry technologies. Tremendous increases in crop yields have resulted from the use of inorganic fertilizers over the past few decades. However, despite increases in fertilizer use in Malawi, yields of various crops have declined or stagnated (Table 2), indicating that the fertilizer-hybrid seed technology is not sustainable in the long-term. In Malawi, the use of organic fertilizers has also been recommended since the early 1960s. Similarly, agroforestry technologies too have been recommended to smallholder farmers since the mid 1980', although research results have only began to appear within the last five years. The problem with these is that they have not been fully adopted by many farmers, including resource-poor smallholders who are constrained by cash to Integrated soil management for sustainable agriculture and food security in Southern and East Africa 241
purchase inorganic fertilizers. It would appear that farmers are attracted to technologies that produce quick and dramatic responses, provided they are affordable and appropriate. Inorganic fertilizers offer this opportunity, but unfortunately, they are beyond the purchasing power of smallholder farmers. Smallholders lack adequate cash to purchase farm inputs and have limited access to credit facilities. This leaves the option where organic fertilizers are applied in conjunction with low rates of inorganic fertilizer.
Strategies for managing soil erosion have essentially involved the use of i) the traditional physical soil conservation measures, and ii) the more recent use of biological soil conservation measures. What follows is a brief outline of each of these. Efforts to control soil erosion started in the early 1930s when cultivation of annual crops changed from planting on flat land or circular mounds to planting on ridges that were aligned on the contour. Tied ridging was simultaneously advocated for water conservation. The only exception was cassava cultivation along the lakeshore areas and in the Shire Valley where up to now, farmers insist on planting on flat land. Other measures include: (i) contour bands, (ii) bench terraces (especially for coffee production), and (iii) graded bands. For water harvesting, earth dams have been used effectively to collect water for various uses including: (i) stock watering, (ii) irrigation, and (iii) fish production. Biological conservation measures use technologies that utilize grasses and woody perennials to control soil loss through erosion by water and wind. By and large, this involves planting grasses, e.g., vetiver on marker ridges, and some agroforestry tree species, e.g., Tephrosia vogelii in mixed cropping systems. A combination of all of these are being used by many farmers with varying degrees of success.
SUCCESSFUL CASES OF IMPROVED SOIL MANAGEMENT The Malawi Agroforestry Extension Project (MAFE) is a pilot project on agroforestry within the Land Resources and Conservation Department (LRCD) in the Ministry of Agriculture and Irrigation (MOAI). This is a cooperative extension activity between Washington State University (WSU) and the Government of Malawi (GOM) and has been funded by the United States Agency for International Development (USAID) since 1992. The goal of the of the project is to test, evaluate, and adapt prototype agroforestry technologies and support services provided to smallholder farmers in Malawi. The specific objectives are to improve soil fertility and conservation to increase crop and wood yields. The MAFE project is operating in 13 pilot areas in the districts of Chikwawa, Mangochi, Ntcheu, Dowa, and Mzimba. At these sites, resource conserving technologies are being implemented.
Machecheta Agroforestry Site, Mzimba The Machecheta Agroforestry Pilot Site is located to the east of Mzimba Boma in the neighbourhood of the area where the tarred Lilongwe-Mzuzu Road crosses the Mzimba River. It is located in Kazomba Section of the Manyamula Extension Planning Area (EPA), Central Mzimba Rural Development Project (RDP) in the Mzuzu Agricultural Development Division (ADD). Detailed description of the study area, number of farm families and environmental characteristics of the pilot study area can be found elsewhere (Bunderson et al., 1992). The resource conserving and soil fertility improving technologies, and related activities, being tested and evaluated at the Machecheta Site include the following: · Soil and water conservation : contour ridging, planting vetiver on marker ridges, aligning ridges on the contour, 242 Malawi
· Soil fertility improvement and enhancement : alley cropping, systematic interplanting of maize with Faidherbia albida, improved fallow, green manure banks, undersowing maize with Tephrosia vogelii, intercropping maize with grain legumes (e.g., soybeans), · Energy : woodlots, homestead and boundary planting, living barns (for constructing tobacco curing sheds), · Other resource conserving technologies and activities : gully reclamation, vetiver nurseries.
Several farmers in the study area are testing a combination of the above technologies. The status on land area under each technology/activity and the number of participating farmers testing a particular technology are given in Table 9.
TABLE 9 Land area subjected to different technologies and the number of farmers implementing the technologies, Machecheta, Mzimba Technologies/Interventions Unit Adoption Levels Number of farmers Alley cropping ha 93 162 Systematic interplanting ha 140 135 Improved fallows ha 8 31 Green manures ha 2.3 12 Homestead/Boundary planting ha 605 123 Live fencing ha 1,400 16 Undersowing ha 6.4 55 Woodlots woodlots 110 110 Intercropping maize with legumes Soybeans ha 7.4 104 Groundnuts ha 5.6 127 Common bean ha 7.5 112 Tree nurseries Individual n. 7 7 Communal n. 11 221 Vetiver nurseries n. 9 21 Vetiver hedgerows ha 60 98 Gullies reclaimed n. 30 18 Contour re-alignment ha 321 230 Organic manure ha 54 233 Source: Bunderson and Bodnar, 1997
Maize and legume crops are performing very well at the site, especially in farmers' fields where the above soil conserving technologies are combined with some modest inputs of inorganic fertilizer nitrogen, phosphorus and sulphur. For example, maize performance under alley cropping with and without fertilizer has registered large increases due to hedge effects (combined effects of 3.5 and 4.5 year hedges), between local maize and hybrid maize, and between fertilized and unfertilized plots (Table 10).
The large positive effects of alley hedges on maize grain yields, 3 years after hedge establishment, despite the fact that some hedge species are poorly managed, shows that alley cropping is a technology that needs a gestation period to register gains in yields. As expected, hybrid maize produced more grain yields compared with local maize under similar fertility and climatic conditions. Thus, we can classify technologies into there categories: short-, medium-, and long-term. Alley cropping falls in the second category, interplanting cereals with Faiedherbia albida falls in the third category; whereas undersowing and improved fallows fall under the short- term category. Hence, for sustainable agricultural production, we require a combination of all Integrated soil management for sustainable agriculture and food security in Southern and East Africa 243
three types of resource conserving technologies; and for food security, at both national and household levels, these need to be augmented with modest levels of inorganic fertilizer inputs.
TABLE 10 Maize yield (kg/ha) under alley cropping with and without fertilizer N and P application, Machecheta, Mzimba Fertilizer application With hedges Without hedges increase Without fertilizer Local maize 1 721 (1) - Hybrid maize 2 300 (6) 1 136 (5) 102% With Fertilizer Local maize - - Hybrid maize 4 855 (1) 2 594 (4) 87% Source: Bunderson and Bodnar, 1997
INSTITUTIONAL FRAMEWORK AND POLICIES FOR LAND RESOURCES MANAGEMENT The overall government policy is to improve the well being of Malawians through Poverty Alleviation Programmes (PAP). The overall strategy of PAP is to promote increased participation of poor women, men and youths in economic, social and political affairs with emphasis on economic empowerment of the poor and in stilling the spirit of poverty consciousness in planners, administrators, politicians, extension workers and research workers and the general public; and also provides the spirit of self-determination and self-reliance by encourage participatory approaches to development. As a nation dependent on agriculture, Malawi appreciates the urgently of developing adoptable, production-increasing technologies that preserve the integrity of its natural resource base. However, under existing population and land pressures, smallholder farmers continues to experience a multitude of problems. Given the present situation of food insecurity, malnutrition, chronic rural poverty and the deterioration of the natural resource base, there is an urgent need to develop and execute a strategic plan of action that improves soil fertility and conserves the soil and water resources of Malawi.
Institutions The Ministry of agriculture and Irrigation (MOAI) is responsible for all soil conservation work on all agricultural land grown to crops and livestock in Malawi. Within the MOAI, soil and water conservation, and advice on conservation and correct land use, is the prime responsibility of the Department of Land Resources and Conservation (DLRC), whereas the Department of Animal Health and Industry (DAHI) is responsible for animal health and husbandry, and grazing management. Conservation on land that is not under agricultural production falls under the responsibility of the Departments of Forestry, and National Parks and Wildlife. The overall responsibility for environmental protection in Malawi falls under the Department of Environmental Affairs under the National Research Council of Malawi (NRCM). However, there are a number of activities in soil and water conservation and soil fertility improvement that are conducted by other programmes/projects, and non-governmental organizations (NGOs). These include: (i) Promotion of Soil Conservation and Rural Production (PROSCARP), (ii) Malawi Agroforestry Extension Project (MAFE), (iii) IFAD Smallholder Food Security Project, (iv) Development of Conservation Measures and Messages Projects (DCMMP), (v) International Scheme for Conservation and Rehabilitation of African Lands (ISCRAL), and (vi) several NGOs which include World Vision International (WVI), Action Aid (AA), Concern Universal (CU), and Christian Services Committee (CSC). 244 Malawi
Socio-economic and policy issues Malawi, being an agricultural country, depends on the soil. More than half of the population of Malawi has less than 1 ha of land available for cultivation, and farm size is said to be declining at 3% annually (UNDP, 1991), and yields are estimated to be dropping at the rate 2% annually (Twyford, 1988). The socio-economic issues that hamper the implementation of sound soil and water conservation practices generally centre under land tenure and legislation of soil erosion issues. The lack of legal title to land has often been cited as one of the major constraints to proper soil conservation measures and good land husbandry in Malawi. While this maybe true in some circumstances, it would appear that it is not an important constraint under customary land (Green and Nanthambwe, 1992). This is because land security is assured through inheritance and continued use. This appears to be a good enough security to land ownership. There is presently a legislation in the form of covenants contained in the in the leases granted to tobacco estate farmers. The only problem is that these are often ignored by the lease, because the regulations under this act are not enforced by law. Strong legislation is required to protect steep slopes from improper cultivation.
To effect the necessary legislation for soil erosion control, local communities should be involved and empowered. Low adoption rates of soil conservation practices is generally a result of their medium to long-term benefits, but attitudes are slowly changing due to the visible effects of degradation. As such, farmers today are more willing to undertake soil and water conservation efforts. There is need to put in place policy guidelines for controlling the environment in Malawi, and soil erosion in particular. These policies should include the planting of trees on farm land (already in existence), making it illegal to cultivate steep slopes and fragile areas, such as stream banks and catchment areas. In particular, catchment areas should be protected. Deforestation in and around catchment areas has been identified as one of the main causes of siltation in the rivers, Lake Malawi, and then finally the Shire River. The direct consequences of siltation, accumulated over the past 3-4 years, is reduced water levels leading to low power for electricity generation. This is causing economic disruption and stagnation that is currently a common phenomenon during the dry season.
PROPOSALS OF PROGRAMMES FOR IMPROVED SOIL MANAGEMENT AND PRODUCTIVITY ENHANCING The main constraints to smallholder agricultural production and sustainability are: i) soil fertility decline due to continuous cropping with little return of nutrients through fallows, green manure, crop residues, farm manure, intercropping or external inputs of inorganic fertilizers, and ii) soil erosion brought about by cultivating steep slopes without proper ground cover, with no marker ridges or ridges that are not aligned on the contour, or poor cultivation methods on highly erodible and fragile soil types. Programmes or projects are required to improve or maintain the soil fertility status of cultivated soils and arrest soil erosion to enhance crop productivity and reduce land degradation.
Appropriate, suitable and adoptable soil fertility improving technologies for smallholder farmers will out of necessity be those that are low-cost and low-input. This is because although it is well-known that inorganic fertilizers have the greatest ability to tremendously increase yields in the short-term, these are expensive to purchase. Nearly all smallholder farmers are resource-poor and have limited access to credit facilities, hence are unable to purchase mineral fertilizers. This justifies the need to employ organic manure based technologies. Some of these include the Integrated soil management for sustainable agriculture and food security in Southern and East Africa 245
following: i) use of farm manure (this can either be cattle, goat, sheep or chicken manure), ii) intercropping maize with food legumes (e.g., soybeans, cowpeas, pigeonpeas or groundnuts) or non-food legumes (e.g., Sesbania sesban or Tephrosia vogelii), iii) undersowing maize with legumes (e.g., Tephrosia vogelii, iv) improved fallows (e.g., using Tephrosia vogelii, Sesbania sesban or pigeonpeas), v) mixed intercropping or interplanting maize with nitrogen fixing tree species (e.g. Faidherbia albida), and vi) alley cropping cereals with fast growing N fixing high biomass yielding tree species (e.g. Sesbania sesban, Tephrosia vogelii, Leucaena diversifolia or Gliricidia sepium).
Other possible technologies for enhancing or improving soil fertility include crop diversification and intensification. This would essentially involve the introduction of livestock into the farming system and intercropping cereals with legumes in rotations or between the hedge species in alley farming systems. The livestock for diversification include goats, pigs, sheep, chicken and/or rabbits. Smallholders should also diversify and intensify the growing of high value cash crops such as burley tobacco, and the growing of vegetables, chillies, peppers, and other horticultural crops under both rain-fed and irrigated conditions. Of special emphasis should be the growing of both exotic and indigenous fruit trees.
The soil and water conserving technologies include the following: i) use of marker ridges using the A-frame that are aligned on the contour, ii) making box and tried ridges, during years of low, uncertain and poorly distributed rainfall pattern, and iii) planting of vetiver grass, and other grasses, on the marker ridges, gullies, buffer strips and farm boundaries. Both the soil fertility improving technologies and the soil and water conserving technologies will also conserve the natural resource base. However, for increased crop production to feed the expanding human population, and sustainable agricultural production, strategies that combine the above technologies with modest levels of inorganic fertilizers are required and highly desirable. The strategy is to augment soil organic matter and other soil conserving technologies with low rates of inorganic fertilizer N, P and S. Concerted efforts are required by Government to step up campaigns to: i) promote country-wide use and adoption of low input, low-cost organic fertilizers (especially farm manure, the integration of legumes into the farming systems, and augmenting organic fertilizers with low rates of inorganic fertilizers), ii) promotion of crop diversification and intensification under both rain-fed and irrigated conditions, iii) creating an enabling environment that makes inputs (seeds and fertilizers) readily available to the farmers at cheap and competitive prices, iv) demonstrating commitment to conservation by supporting the efforts of the Ministry of Agriculture and Irrigation, and v) insisting that public land should be properly conserved and that regulations which apply to leasehold land are observed and enforced at all times.
REFERENCES Blackie, M.J. and A. Conroy, 1994. Feeding the nation: breaking out of Malawi’s yield trap. In: D.C. Munthali, J.D.T. Kumwenda and F.W. Kisyombe, (eds.). Proceedings of a conference on agricultural research for development. University of Malawi, Zomba; and Ministry of Agriculture, Lilongwe, Malawi Bunderson, W.T., G.S. Phiri, L.M. Nhlane and S.J. Nanthambwe, 1992. Project description and pre- implementation plan. Publication Series No.1, Malawi Agroforestry Extension Project, Lilongwe, Malawi Bunderson, W.T., and F. Bodnar, 1997. Maize yield in three MAFE sites under four year old hedgerows. A paper presented at the Land Resources and Conservation Branch, Mzuzu, Malawi, June 1997 246 Malawi
Bunderson, W.T. and I. Hayes, 1995. Agricultural and Environmental Sustainability in Malawi. A Paper Presented at the Conference on Sustainable Agriculture for Africa, Abidjan, Cote d'Ivoire, July 1995 DAR, 1965. Annual Report of the Department of Agricultural Research. Government Printer, Zomba, Malawi Green, R.I. and S.J. Nanthambwe, 1992. Land Resources Appraisal of the Agricultural development Divisions: Methods and Use of Results. Field Document No. 32; MAO/UNDP/FAO, DP/MLW/011, Lilongwe, Malawi IFAD, 1993. Malawi: Smallholder Food Security Project. Main Report and Annexes. Africa Division, Project Management Division Maida, J.H.A. and C.Z. Chilima, 1976. Changes in soil fertility under continuous cropping of tea. Technical Bulletin No. 1/Bv/76, Bvumbwe Research Station, Limbe, Malawi Ministry of Agriculture, 1988. The Annual Survey of Agriculture for 1987/88, Lilongwe, Malawi. Mimeographed Ministry of Agriculture, 1995. The Annual Survey of Agriculture for 1994/95, Lilongwe, Malawi. Mimeographed Ministry of Agriculture and Livestock Development (MOALD), 1997. The Annual Survey of Agriculture for 1996/97, Lilongwe, Malawi. Mimeographed Paris, 1990. Erosion hazard model (modified SLEMSA). Land Resources Evaluation Project. Field Document No. 13; MOA/UNDP/FAO, DP/MLW/011, Lilongwe, Malawi Pape, W.J., 1971. Rainfall intensity in Malawi. Bunda College of Agriculture, University of Malawi, Zomba, Malawi Saka, A.R., R.I. Green, and D.A. Ng'ong'ola, 1995. Soil management in sub-Saharan Africa: proposed soil management action plan for Malawi. Ministry of Agriculture and Livestock Development, Lilongwe, Malawi Twyford, I.T., 1988. Development of fertilizer use in Malawi. A Paper for the FAO/FIAC meeting, Rome, 1988. Smallholder Fertilizer Revolving Fund. MOA, Lilongwe, Malawi. UNDP, 1991. Human development: from poverty to self reliance. Advisory note to the Government of Malawi-UNDP Fifth Country Programme (1992-1996), UNDP, Lilongwe, Malawi. UNICEF, 1993. Situation analysis of poverty in Malawi, Lilongwe, Malawi. World Bank, 1995. Malawi Agricultural Sector Memorandum, Malawi. Volumes I and II. World Bank, 1992. Economic report on environmental policy, Malawi. Volumes I and II, Lilongwe, Malawi World Bank, 1989. Sub-Saharan Africa: from crisis to sustainable growth. A long-term perspective study. Washington DC, USA. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 247
Namibia
COUNTRY FOOD PRODUCTION AND REQUIREMENT More than two-thirds of the country is arid to semi-arid having the rainfall between 100 - 500 mm per annum. The mean annual rainfall of the country is approximately 270 mm and typifies the country as being burdened by extremely dry conditions. The potential for dry land agriculture is consequently very limited (van der Merwe, 1983). Four ecological zones are recognized (MAWRD, 1995): the desert region, comprising 22 % of the land area, where mean annual rainfall is less than 100 mm, the arid region, comprising 33 % of the land area, where mean annual rainfall varies between 100 and 300 mm, the semi-arid region, comprising 37 % of the land area, where mean annual rainfall lies between 301 and 500 mm, and the semi-humid and sub-tropical region, comprising 8 % of the land area, where mean annual rainfall is between 501 and 700 mm. Almost 50 % of the Namibian labour force is in agriculture of which only 45 % are unpaid family workers. One third are subsistence agricultural workers. The principal occupation of 60 % of adults in the northern communal regions (Oshana, Omusati, Ohangwena and Oshikoto) is subsistence farming. Out of these only 20 % of household income is derived form agriculture. Karas and Hardap region average only 21 % of income from agriculture, while Otjozondjupa and Omaheke average 44% (Isaacson, 1995). The rest of the country either have very little income from agriculture (Khomas) or do not agriculture as an income-generating sector as the result of their tradition and lack of suitable resource (Kunene and Erongo).
The history of agriculture in Namibia is very inadequately characterized by broad references to colonialism. Rather, as will be demonstrated in detail, three distinct phases can be made out within the period of colonial domination which ended only seven years ago (Lau and Reiner, 1993): German colonial period, 1892 - 1915; Union/Commonwealth period, 1915 - 1961; RSA period, 1962 - 1990. One of these periods was beneficial to the development of the country's agricultural resources, namely the German era; the other two were under developing the country. During the German era, effective planning documents were drawn up, informed by community- intensive ideas of settler autonomy, self-sufficiency, and what today has been rediscovered as appropriate technology. This was the progressive stand in an undertaking which by force took both the land, and the planning out of the hands of Namibia's indigenous peoples. These planning documents came to shape settlement policies; the emergence of smallholdings; the setting up of government plantations or forestry stations, and the planning for agricultural infrastructure, especially water development. The German colonial administration had ordinances related to environmental protection and sustainable utilization: a) protecting existing agricultural resource, b) establishing production and distribution centres to achieve self sufficient subsistence and identify potential cash crops, c) forbidding and/or restricting the cutting of trees, the pulling of out of grass by its roots, burning of the veld, and hunting of game.
Jorry Zebby Ujama Kauriya, Department of Agricultural Research, Ministry of Agriculture, Water and Rural Development 248 Namibia
Dryland cropping is dominant in all regions and irrigated cropping is only practised by some commercial farmers who have the knowledge and can afford conventional irrigation schemes. Crop failure in Namibia is common as the result of mainly drought as well as other environmental factors, such as hailstorm, pest and disease, flood, etc. Two economic systems characterize in Namibian rural (agricultural) community, namely commercial and communal system. Commercial farming system is mainly self-sustainable and economically viable system. Communal farming system is characterized by poverty, exhausted natural resource, high population density and economically dependent on government subsidies. From physical evidence within the rural boundaries, environmental degradation can easily be linked to poverty in Namibia. Namibia had, for centuries if not millennia, various populations of gatherers and hunters, of pastoral nomads breeding and managing small as well as large stock, of sedentary groups supporting themselves largely on undomesticated fruits and vegetables, ocean or fish resources, and veldkos, as well as cultivators of tobacco, vegetables and grain. While the cultivation of grain and domesticated vegetables seems to be limited to northern Namibia, purposefully cattle and stock breeding as well as tobacco and pumpkin cultivation is on record for at least the last 150 years throughout Namibia. Several studies document socially regulated and agriculturally diverse systems which led not only to food self-sufficiency for all, but also to surpluses used for exchange and barter (Lau and Reiner, 1993). The major cereal crops grown in Namibia are maize, pearl millet, sorghum and wheat. Millet and sorghum are grown extensively by the northern communal farmers (mainly by Oshiwambo speaking). These two crops, especially millet is the staple food for these communities and are consumed internally within these communities. Small internal market are created to supply those who did not have a harvest at the end of the season, some to take to urban areas for home consumption. Millet and sorghum are also exchanged for goods across the border to Angola, or exchanged for other nutritious crops such as cowpea, beans, nuts and veld food in areas where such commodities are rare. Maize is produced in the commercial land as well as in the Caprivi mainly under rainfed conditions. Maize under irrigation is only an option to buffer the unreliable climatic conditions. In the Okavango it is restricted to riverine farming community who have excess to free water from the Okavango River. Commercial farmers supplement their irrigation from earth dams and boreholes under restricted quotas. Wheat is mostly grown as off-season (winter) crop under irrigation. The crop has got a good market because it is the only cereal produced in winter and competition is low. National cereal production, as reported in Table 1, has varied in recent years from low of 33 100 tonnes in the drought year of 1991/92 to 118 900 tones in the 1993/94 season.
TABLE 1 National cereal production (tonnes), 1990-95 Crops Year 1990-91 1991-92 1992-93 1993-94 1994-95 Millet/Sorghum 57 700 17 200 43 700 69 100 41 100 Maize 52 000 12 800 26 100 43 500 15 300 Wheat 5 800 3 100 5 700 6 300 3 200 Total 115 500 33 100 75 500 118 900 59 600 Source: Isaacson, 1995
Official market throughout the rest of the country has not yet been created despite tireless efforts from the Government. This is partly because the demand from the rest of the Namibian community is low. Most opt for eating maize and try by all means to produce maize even in small gardens around their homesteads. Millet and sorghum in the northern communities are processed into several delicious food types, from, porridge bread and cake to various soft drinks and alcohol, which are all consumed at household level to a ready-to-consume commodity for the Integrated soil management for sustainable agriculture and food security in Southern and East Africa 249
local market. The tow crops are preferred by those who grow them because of their adaptability to the low water and nutrient requirement and their ability to establish a crop in a very short period. Millet, sorghum, maize, and wheat are produced every year in Namibia, except the year of drought. In addition, cow pea, ground nut, sun flower and sweet potato have been produced on a smaller scale, but increased their production as the result of the Government campaign for crop diversification for sustainability and food security. The cereal production varies significantly according to rainfall (NFSNC, 1995a). With an estimated national demand for cereal of 201,900 tones per year, even in the best years, Namibia must import a significant amount of its cereal requirements (Isaacson, 1995).
EXTENT OF SOIL DEGRADATION AND ITS BIO-PHYSICAL & SOCIO-ECONOMIC IMPACTS Desertification, drought, deforestation, flooding, bush encroachment are some of the environmental degradation processed which received the national attention in recent years and indirectly result in soil degradation. Soil erosion, salinity, alkalinity and acidification, loss of plant nutrients are forms of soil degradation processed which receives little attention on a national level. Having these direct and indirect degradation process it will not be essential to deal with them in isolation due to their interactive nature. Population pressure is one factor contributing to environmental degradation. In the Cuvelai drainage basin where many rural families still depend on hand-dug wells, people have to dig deeper and deeper each year. Too often they find only brackish water because the fresh water aquifer, perched on top of a brine like, has shrunk (Ashley, 1997).
Soil degradation Soil degradation is the loss of fertility in the soil over a period of time, whether it be physical, chemical or biological. The process of soil degradation is usually long and takes several years or sometimes decades or even centuries to be physically visible to a human eye or detected through the new technological instruments used to date. However, there are exceptionally short-term process which cause drastic changes in few minutes. A good example of these is soil erosion, whereby extensive amount of soil is removed from a site in few minutes following a hailstorm over loose sand. A gully of 0.5 m depth has been observed in the eastern part of Namibia (Gobabis district) following a less than twenty minutes shower. Livestock production is dominant and the concentration of animals near the water points has resulted in a remarkable exposure of bare soil surface which gets severely damaged by the first storm following a long and dry season. A second example is the oil and waste disposal that affect both surface vegetation and ground water quality in or near urban area. This phenomenon is minor compared to the former in terms of spatial distribution and intensity. In Namibia most of these processes have not and can hardly be categorized one way or another. Some processes can be man induced and over time, even years after man has left the area nature takes its course and the condition gets worse. In contrast, there are soils which are naturally sensitive and vulnerable to human activities. A good example is the soil with high erodibility factor, thus prone to erosion. As human population increases and more activities are implemented to sustain the growth pressure, these sensitive areas are subjected to human use and get degraded in the process. We cannot live without the soil and it is in that sense that impact assessment need to be carried out and sound management practices should be designed to select and apply the friendliest method. Some of the common soil degradation process are outlined in Table 2. The asterisks indicate the relative geographical distribution and intensity of each process as envisaged in Namibia, each asterisk indicate the relative area where the type of degradation 250 Namibia
has been a concern as well as the people awareness toward such degradation process. The more the stars the more the type of degradation has been recorded in literature, unofficial reports and oral conversations.
TABLE 2 Types of soil degradation processes, causes and their effects on plant production and quality of land Type of soil Causes Effects degradation Biological * Imbalance in microbial activities in the topsoil Deterioration in soil structure, surface crusting, slow turn-over Compaction** Use of heavy machines for tillage, incorrect Increase bulk density, poor management, hard-setting properties aeration and infiltration Water logging** Excessive irrigation, high rainfall intensity, Poor aeration, availability of poor drainage, build up of salts and reduction certain nutrients (Fe, Al, N, etc.) in many nutrients, Fluctuation in ground water table Salinization and Irrigation with salty or sodic water, Availability of certain nutrients, Sodification ***** Evaporation from deeper horizons, high alteration of soil structure water table Toxification and Disposal of toxic waste, release of heavy Toxic soils to plant growth, Pollution* metals from industries or mines, elements pollution of soil and water from ground water or spring water, oil spills, oil disposal, dumps Soil erosion***** Hail storm (erosive), loose soil (erodible), Loss of top soil, burial of top soil, topography, animals destabilization of top soil, poor soil cover Loss of plant Monoculture, overgrazing, tillage systems, Loss of productivity, depletion in nutrients*** poor water management soil physical properties, acidification, poor soil cover Flooding and high rainfall intensity, steep slopes, loose and high runoff, compacted soil Siltation**** barren soil surface surface, crusting, erosion, loss of wetlands, reduced water flow in rivers Deforestation***** Human removal of vegetation, overgrazing high runoff, soil structural deterioration, low soil organic matter, leaching of nutrients Bush Improper grazing systems low carrying capacity, nutrient encroachment*** imbalance in the soil
Acidification* Acid rains, incorrect management practices, Poor soil cover, deterioration of exploitation of the land soil physical properties Notes: * indicates that the degradation process does exist but has not caused any serious concern at all levels (biological degradation, pollution, toxification and acidification) ** indicate a localized condition that is manageable under the current expertise within the country (compaction and water logging) *** is about the mean and indicate a condition that has caused considerable damage in some areas and national research is underway to try and stop or reverse the situation, but in most parts of the country it is non-existent (loss of plant nutrients and bush encroachment) **** stars indicate a condition whereby localized areas can be abandoned because of high costs involved in reclamation and intensive agriculture is not practised or cautious steps are taken not to worsen the situation (flooding and siltation) ***** is the worse Namibian condition; despite national concern, some land portions has been abandoned for intensive agriculture and reclamation is beyond the national capacity of expertise and costs within a short time. Long term efforts are underway but mostly left to nature to take its course (salinization and sodification, soil erosion and deforestation). Integrated soil management for sustainable agriculture and food security in Southern and East Africa 251
Biophysical impact Desertification is the process whereby an area is turned from a resilient, sometimes well vegetated, area into a wasteland no longer able to respond to rainfall in a normal manner (Seely, 1991). In Namibia this process has taken place without notice. It is fortunate that the low population density country wide allowed for recovery after an intense grazing period, drought or deforestation as first steps in the process of desertification, there is no a clear cut as to where one process ends and the other takes over. Whether desertification, drought or deforestation, the danger of soil surface crusting, soil erosion (wind and water), loss of nutrients and organic matter is sky high. Namibia is economically unfit to reclaim the lost land as the result of desertification. The only option left is to manage the resource wisely to prevent desertification from taking place. The increase in population together with the ever-increasing aridity the potential for desertification is threatening. Desertification Convention focuses on the plight of Africa, and aims especially to address issues such as food security, environmental conservation and sustainable development. Indicators of desertification in Namibia include the lowering of ground water table; soil erosion; loss of woody vegetation (trees); loss of grasses and shrubs; i.e. bare soil surface; decrease in preferred grasses and shrubs; bush encroachment, increase soil salt content (salinity) and decrease soil fertility. Desertification need not be a problem in Namibia if natural resources are appropriately used and managed (Seely and Jacobson, 1997). Deforestation here is used to describe the process whereby natural vegetation is randomly and indiscriminately removed. This process disrupt the ecosystem and may either reduce the productivity of the land or cause an imbalance whereby new plant species of little use to human and grazing by animals are introduced. In the north central and parts of northwest Namibia the mopane tree (Colophospermum mopane) has fallen victim to intensive use as building material for houses and agricultural fields. Traditional fences are erected from stacking poles of mopane tree trucks in a row. If one pole is approximately 20 cm in diameter on average, then arithmetically up to 20 000 poles are needed per hectare for agricultural field. This figure can easily go up to four times for the construction of a big traditional homestead. If one tree can supply five poles, then up to 4 000 trees will be used to build one field. The life expectancy of these poles is not documented in the literature cited, but interviews with few farmers indicate to go beyond twenty years in areas where termites do not cause a serious threat. Despite the fact that these tree is naturally termite resistant, the poles do slowly degenerate and new poles constantly replace the old ones.
The demand for poles is far higher then the supply in several regions and more people are encouraged, if not forced by circumstances, to integrate the steel wires for fencing to allow the growing plant to reach maturity. The same appears to be the case with the silver teminalia (Terminalia sericea) and the camelthorn (Acacia erioloba) in the southeast and east of the country, but to a lesser extent. Terminalia grows well in sandy soils and bud before the rain comes to provide food for livestock before the new grass cover becomes edible. This tree is unfortunately regarded as pest in areas where it encroaches the grassland (Bester, 1997). Camelthorn provides nutritious pods during the dry season, succulent leaves and flowers to browsers early in the wet season. The two trees are deep rooted and obtain water from deep subsurface soil layers where only few trees can reach. Mineral nutrients from deep are brought up and with process of shedding their leaves in winter they help recycle nutrients for shallow rooted species to utilize. Like the mopane, they are also major sources of wood and poles for fencing. They are therefore harvested in bulk for these products. Sustainable harvesting techniques need to encouraged. 252 Namibia
Chemical degradation Salinity and alkalinity Namibian soils are generally sandy. Due to a the arid climate soil genesis is rather slow and very little horizonation can be observed. The parent rocks of most of these soils is the Kalahari sandstone and granite which are both acidic, except for the small patches of dolomitic limestone outcrops in the central north from the Grootfontein district in the east stretching west ward though the Etosha National Park into the central Kunene region. The soil are well drained and has poor cementation. Loose particles on the surface of the soil are easily picked up by wind and water and transported to new sites, and the cycle of removal and re-deposition continues. Natural vegetation are the most significant stabilizers of soil movement by physically holding and shielding the soil surface from wind and flood water with their roots as well as providing organic material that helps to bind the soil and form aggregates. Removal of natural vegetation is therefore critical for soil erosion.
Soluble salts are found in all soils as well as in natural waters such as rivers, streams and boreholes. Salts accumulate in soils largely as a result of percolated water, run-off and irrigation water with the resultant concentration of these waters through evapotranspiration (Trippner, in preparation). The main processes causing salinization and alkalinization are as follows: eolian input, salt accumulation by evaporation, capillary rise of ground water, precipitation from episodic heavy rains together with evaporation, desertification and drought, Management (deforestation, irrigation and overgrazing). Indirectly, human activity cause erosion whereby of degraded or saline topsoil is transported to fertile land surface and bury it, thus causing degradation. Several studies of soil in and around the Etosha National Park led to the incorporation of salinity, alkalinity and sodicity in the mapping unit (Buch et al., 1993; Beugler- Bell et al., 1993). These studies also present the only detail soil survey mapping work done in Namibia on a reasonable scale in terms of area covered. The park is protected an man-induced degradation processes are minimal.
The small scale (1:800 000) Soil Map of Namibia has been refined and presented by the Agro-ecological zone (AEZ) project from the original FAO map. The Solonetz and Solonchaks area presented include the above mentioned study area of Buch et al., 1993; Beugler-Bell et al., 1993 and Trippner et al. (in preparation9. Although most of these effects may be viewed as detrimental to most plants. Soil salinity/alkalinity can be used by naturally adapted vegetation to combat the excessive water loss by transpiration. Salty vegetation (e.g. Salsola spp.) also reduces their uptake by animals and therefore protect the soil from being barren in areas prone to overgrazing.
During previous surveys it was determined that the majority of the soils of the Oshanas varied between strongly saline, amorphic, medium textured materials to severe solonetz forms. These soils have no irrigation potential due to the high salinity and very slow to extremely slow internal drainage. Without adequate drainage reclamation through leaching of soluble salts and removal via open drainage works is not feasible. Desalinization by means of flooding and surface drainage with the objective of promoting upward leaching of salts is contrary to both normal practice and current scientific principles and as a desalinization procedure is therefore very unlikely to accomplish any significant success (A.O.C. 1967).
The effects of irrigation on saline soils can be grouped into two categories: Integrated soil management for sustainable agriculture and food security in Southern and East Africa 253
· Irrigation as the way to amend soil salinity and alkalinity. This is the case where the soil is saline and sodic but the irrigation water quality is high. Such cases are only experienced near major dams and/or perennial rivers. In these areas irrigation has been proved to improve the condition of topsoil more than the deep subsoil. · Irrigation as the way to worsen salinity/alkalinity. When irrigation water is drawn from groundwater of low quality, salts are added by this water to the soil. The salts in the soil is gradually increased to a level not suitable for plant production and may lead to the abandonment of once an agricultural land.
Saline soils can be reclaimed by removing the salts from the soil solution as well as replacing the sodium on the colloidal fraction by a divalent cation or the hydrogen cation. Drainage is consequently the first requirement followed by leaching through over-irrigation (FSSA, 1989). This practice has been successfully applied to the Hardap irrigation scheme, but the productivity does not last long. Repetition is required after some period in order to keep the salt levels low and maintain the yield. As far as saline soils are concerned, it is only necessary to drain the soil and to leach out excess salt, but the danger of turning it into a sodic soil is high. With alkali and/or saline-alkali soils it is necessary to first bring the percentage exchangeable sodium to below 15 percent with lime (FSSA, 1989). Then the free and replaced salts must be leached out. This procedure assumes that a large quantity of sodium will be leached out as well. Sodium can be replaced by applying calcium salts a gypsum (CaSO4.2H2O) or acidifying agents like sulphur (S), Sulphuric acid (H2SO4), iron sulphate (FeSO4.7H2O) or aluminium sulphate (Al2(SO4)3.18H2O) (FSSA, 1989). Soil salinity has been extensively reported around the Hardap irrigation scheme in the Fish river and early researchers and soil surveyors classified salinity as high, and sodicity as high or potentially high. Destruction of soil due to drastic changes brought about by levelling operations and consequent excessive movement of soil make the soil prone to erosive forces. This operation brought about high productivity and to be sustainable over a long period these soils need to be monitored and extensive data collection campaign need to be lodged as to the infiltration, compaction, salinity and sodicity, alkalinity/acidity, and drainage capacity accompanying the production capacity of these soils.
Soil acidity Acidification of soils along the perennial rivers has been recorded by the national Agro- Ecological zone project. Fortunately, low agricultural activities exist near the river because wetland conservation techniques practised. Except along the banks of the rivers there is little water drawn from this rivers for inland irrigation use by farmers. The major rivers in the north are the Kunene, Okavango and Kwando and the Zambezi, Orange in the south. In addition, the Hoanib river, Ugab, Omaruru, Omatako, Swakop, Fish and Auob river host most of the country's most important dams and they are mainly used for small scale production of high quality crop and bulk water for urban usage. The soil pH (H2O) map of Namibia produced a very phenomenal results of which the most remarkable is the projection of acid soils along the major rivers and drainage systems except for few localized points (pH<6.79). Below 4.50 is rather rare in this arid climate. These are areas that has water most of the year and irrigation (use of high water quality) can be practised. It should be nodded that this map originates from samples that reached the Soil Laboratory over the years. Blank patches indicate areas where no samples were received for analysis at the time of producing the map. There are no rivers in the eastern part of the country and crop production is almost zero, if excluding small scale when the rainfall is enough to sustain the crop over the growing season (which is rare) of ground water irrigation is practised. Namibian ground water is slightly alkaline and saline. Continuous irrigation usually 254 Namibia
results in salty and alkaline soils and abandonment of the fields for new fields is unavoidable. This process results in an artificial selection of vegetation which are tolerant to such conditions as well as the extinction of sensitive species. In most of Namibia tolerant vegetation are less soil protective from erosion.
Water quality and water harvesting techniques In general, Namibian soils are sandy (95% has less then 5% clay), deep and low in organic matter content. Coupled with contrasting climate and geomorphology the possibility of harvesting surface rainwater is low. heavy thundershowers cause extensive runoff for less than 24 hours in most places. This causes transportation of silt into dams, leaching of soil nutrients down the soil profile or to the catchment, drainage of salts into aquifers which decreases the quality of ground water. High quality rainwater is mainly utilized directly for dryland agricultural production and livestock watering in water pans as well as irrigation of small gardens to a limited extend. In the Cuvelai delta where most of the people rely heavily on surface water during floods (efundja) the water quality changes as the water dries out. Good quality rain water immediately after the flood turn into saline and toxic water few weeks later. Similarly, after the disappearance of surface water good quality water for livestock watering is harvested from hand dug wells. After a while the quality of this ground water goes down to a toxic level which render unsuitable for livestock. In the eastern and southern Namibia where the Kalahari sand dominates the land surface, rain water harvesting is almost zero, except for the small amount caught and stored in drums from corrugated iron roofs for drinking over a short period. Since this is the major livestock production area in Namibia, people rely on deep boreholes averaging 180 meter in depth throughout the year. However, supplementary water during the wet season comes from seasonal dry riverbed that forms pans.
Artificial earthdams are also constructed by individual farmers in the commercial area. The duration of water in this pans is variable and dependent on the amount of rainfall, evaporation rate, the depth of the water table as well as the distribution and length of the rainy season. The water scarcity is a major concern to the Namibian Government. Feasibility studies are underway with the objective to construct earth dams in communal area as a means to enhance the supply of water to rural community. A handful of commercial farmers around the country have constructed their own and some dams are already interfering with the inflow into the larger municipal dams. The Government also embark on the program of charging a fee at an economic rate for war supplied by the State (DWA, 1993) to rural community. Research work is needed to standardize the type of irrigation suitable and economically viable to Namibia. Drip irrigation has gained an upper hand in recent years recommendations (Beyers, 1996; Gomide and Netto, 1996), but the economic viability is not yet assessed.
Economic impact The National Declaration on Food and Nutrition include a clause that deals with the protection of the natural resource which states: We commit ourselves to ensuring that development programmed and policies lead to a sustainable improvement in human welfare; that they are mindful of the environment and are conducive to better nutrition and health for present and future generation. The multi-functional roles of agriculture, especially with regard to food security, nutrition, sustainable agriculture and the conservation of natural resources, are of particular importance in this context. (NFSNC, 1995b). With the exception of 1994, agricultural growth in the commercial land has been negative since independence (Table 3). Subsistence farming, in contrast, indicates an overall positive growth. This is partly attributed to the political changes Integrated soil management for sustainable agriculture and food security in Southern and East Africa 255
that led to the new Government to concentrate on the low income generating population and reduced attention to the commercial farmers. The 1991-92 drought has also taken its toll in the overall agricultural economy. Another point to take into consideration is the incredible fluctuation in the growth of subsistence farmers as compared to their commercial counterparts. The latter appear to be the more stable of the two.
TABLE 3 Growth in agriculture by sub-sector 1988-95 Type of agriculture 1988 1989 1990 1991 1992 1993 1994 1995 Commercial 1.4 9.2 3.5 2.7 -4.5 -3.9 3.2 -0.6 Subsistence 2.6 2.4 3.0 10.9 -45.7 19.7 60.0 -21.8 Source: UNDP, 1996
INSTITUTIONAL FRAMEWORK AND POLICIES FOR LAND RESOURCES MANAGEMENT Soil degradation in Namibia has been going on for years without notice, or proper documentation. The size of the country, her aridity together with low human population has misdirected the attention of her inhabitants as well as the international community away from sustainable resource utilization. The low productivity has been and is still a major concern in agriculture rather then a search for some measures to balance the short-term bumper crops with long term sustainable harvest. Policies and legislation are in place, and other policies are added year by year which take into account the conservation of our natural resource. Implementation of these policies is hindered by the lack of funds, expertise, well-defined programmes and projects, experience and technical facilities. Direction toward conservation of the agricultural resource is also shielded by short-term programmes and projects which are directed toward short-term food availability. The Constitution of Namibia as well as various policies which are designed for the conservation and sustainable utilization of the natural resource are assumed to include soil degradation as part and parcel of the overall environmental degradation.
The new, seven-year-old Government is faced with the challenge to reform these rural structures in order to address the issue of poverty eradication and economical balance between those who suffered and those who benefited in the hands of the apartheid regime.
Policy and Legislation The Namibian Constitution. Namibia is one of the few countries that has a well-defined and internationally recognized environmental protection policy enshrined in the constitution. Article 95 (l) of the constitution states that the State shall actively promote and maintain the welfare of the people by adopting, inter alia, policies aimed at maintenance of ecosystem, essential ecological processes and biological diversity of Namibia and utilization of living natural resources on a sustainable basis for the benefit of all Namibians, both present and future; in particular, the Government shall provide measures against the dumping or recycling of foreign nuclear and toxic waste on Namibian territory. Schedule 5 (1) of the Constitution recognizes communal land as a Government property, while commercial land is under private ownership. In addition, Article 16 (1) ensures Namibians the right to acquire, own or dispose of property anywhere in Namibia. In rural community the right to own land is presently applied out of communal boundaries. However, land can be leased out for agricultural purposes with little restrictions in terms of limiting others from the resource. Traditional authority holds the right to allow/disallow tenure structure within communal boundaries. This present structure is not effective in terms of conservation and protection of the resource within communal boundaries and 256 Namibia
the Government is hindered by the lack of personnel to monitor any deteriorating conditions within these boundaries. Management of the resource will always be ineffective when compared to commercial land.
National Agricultural Policy The National Agricultural Policy (NAP) is a draft document designed by the Ministry of Agriculture, Water and Rural Development to address the difficult problems caused by many years of neglect under the colonial administration. One of its goals and objectives is to ensure that the majority of Namibians to enjoy improvements in their current standard and quality of living and promote the sustainable utilization of the nations land and other natural resources (MAWRD, 1995). In this document the Government makes it clear that agricultural growth will not pursued at the expense of the environment The Government will address the serious problems of desertification and environmental degradation caused by destruction of forest cover, soil erosion, overgrazing and bush encroachment. Environmental impact assessment studies and related regulatory sanctions will be fully considered, particularly when opening up new agricultural areas or when new land use activities are being planned. The Government will promote agricultural entrepreneurship and sustainable farming systems that are consistent with appropriate land use and soil conservation practices (MAWRD, 1995). The policy, however does not refer to the Soil Conservation Act No. 76 of 1969 in terms of improvement and/or application to the independent Namibia.
Soil Conservation Act The Soil Conservation Act no. 76 on 1969 was drafted by the Government of the Republic of South Africa for both South Africa and Namibia during the colonial era. The definition of the act was to consolidate and amend the law relating to the combating and prevention of soil erosion, the conservation, improvement and manner of use of the soil vegetation and the protection of the water sources in the republic and territory of South-west Africa; and to provide for matters incidental thereto. In this Act the Minister of Agriculture by virtue of the power vested in him by the State declare a direction to the protection and amendment of the soil with respect to the cultivation of the land, destruction of vegetation, drainage of vleis, marches, natural water sources, runoff or drainage of rain water, grazing strategies, veld fires, pollution of soil and water. This direction shall be binding upon every owner and occupier of the land with reference to which it has been declared applicable. The specifics of the conservation strategies is not enshrined in this document and the punishment related to the offence and/or ignorance of this act is to be determined in the court of law.
Though the act is in place, it does not address specific problems encountered in the country and how one should go about in preserving the soil quality deterioration. This deterioration results in the lack of vegetative cover (erosion) or an upset in the ecosystem whereby the less palatable and sometimes thorn trees and shrubs invade the area and result in bush encroachment. The application of the act to an independent Namibia requires certain modifications in order to be effective. These includes: · Define the soil as an environmental component that need to be conserved and protected, · Outline specific causes of different soil degradation processes and deal with each in detail, · Asses the most probable reclamation procedure(s) and stipulate the guideline, Integrated soil management for sustainable agriculture and food security in Southern and East Africa 257
· Take the necessary precautionary measures as to prevent any of the processes in Table 1 from initiation or speeding up, · Pin-point the necessary recognizable symptoms as to alert all soil users on the danger of continuing specific practices, · Define the possible penalty for the culprit found guilty of intentionally degrading the soil or ignoring to take precautionary measures, · Form an environmental protection unit in each Ministry to look for various interactions between man and the environment from the various disciplines, · This can be coordinated into one national unit as the one existing in the Ministry of Environment and Tourism (MET), · Weigh the advantages and disadvantages of the existing agricultural practices and look for alternatives, with long-term vision. High productivity now should not be equated with long- term conservation for food security, however a reasonable balance between the two will ensure sustainability.
National land policy Successive colonial regimes dispossessed large numbers of pastoralists and settled them in so- called 'native reserves'. Native reserve policy structured access to land along racial lines. Just over 4,000 predominantly white farmers owned about 43% of agricultural land under freehold title, white approximately 150,000 households engaged in communal agriculture utilize 42%. Given present production techniques and even increasing population in the commercial areas, agricultural land is gradually being over utilized The Commercial (Agricultural) Land Reform Act (1995), (cited by UNDP, 1996) prescribes the procedures, for land acquisition and distribution. All farms offered sale on the market first have to be offered to government Although a Land Reform Act has been passed, government still has not come up with a comprehensive land policy. No legislation exists as yet with regard to ownership of land in the communal areas. In the absence of which, members of the new, block elite and wealthy communal farmers are rapidly enclosing communal land for private use (UNDP, 1996). One of the effects of this process is that access to grazing for small farmers become more difficult, as seasonal pastures become increasingly inaccessible.
Since independence, little more than 100,000 ha of commercial farmland have been bought by government. Government intends to spend N$20 million annually over the benefit of small- scale farmers (UNDP, 1996). The land policy acknowledge the fact that poor people are the most vulnerable part of the society who require protection. The policy secure and promote the interests of the poor, ensuring that they are in practice able to enjoy the rights of which they are assured in principle. Special programmes to help the poor to acquire and develop land are considered (MLRR, 1997). The policy also advocates for full and equal security and protection to all legally held land right, regardless of the form of tenure, the income, gender or race of the right holder. It also recognizes Article 95 (l) of the constitution that highlight the sustainable use of the natural resource.
As with the South African colonial government with regard to settlers, financial and tax incentives together with the necessary new and reinforced legislation will be put in place to promote the use of renewable energy resource, and the protection, promotion and rehabilitation of existing natural environment for all Namibians. Survey and mapping form the backbone of land- 258 Namibia
use planning. The policy provides for the Land Use and Environmental Board to ensure that land use planning, land administration, land development and environmental protection are promoted and coordinated on a national and regional basis to guarantee environmental, social and economic sustainability. Failure to maintain such sustainable use, or the infliction of any other environmental damage, will be cause for Land Boards to cancel a title. New private land enclosure is prevented. This will discourage the private fencing in communal land. Land within the communal boundaries is State land and mobility within this boundaries is regarded as free, provided that traditional authorities give approval. Better-off communal farmers tend to fence off land around villages in order to preserve pasture for their animals during the dry season. Overgrazing occur in the open land and during the dry season this land is left barren and nothing to buffer even a slight drought for those who can not afford fencing. The first rain is always disastrous in terms of soil degradation.
Environmental policy Soil degradation in Namibia is better defined under the Environmental policy. Although agriculture contributes a great deal to the degradation, there is no well-defined policy from the agricultural point of view that addresses to its full. Several policies are in place which are not specifically designed for this country, but rather applied in the general sense. Namibia is guided by the international environmental protection treaties designed and implemented under the United Nations (UN) supervision. Developing strategies to halt and reverse the effects of environmental degradation" was one of the 1992 Rio Earth summit. The Basel convention treaty addresses the issue of the transboundary movement and disposal of hazardous waste, and was adopted in Basel, Switzerland in 1989. The long-term objective of this Convention is to reduce waste generation to a minimum in terms of quantity and level of toxicity. It recognizes the right of any state to ban the import of foreign hazardous waste (as Namibia has done), and stresses that waste should be correctly disposed in its country of origin (Tarr, 1997).
The European Community (EC) has instituted strict regulations governing the permissible levels of chemical residues in meat. Some of these chemicals are anabolics, thyrostatics, sulphonamides, antibiotics, ectoparasiticides, endoparasiticides and heavy metals. The Namibian parliament has passes legislation aimed at controlling the use of these substances in the country (Brown, 1992). The control of tsetse fly with dieldrin and alphamethrin; malaria with DDT; scavengers with strychnine and compound 10 - 80 are also other sources of environmental toxification which need alternative.
Water conditions and water policy Water supply to the Namibian society is undoubtedly the most determining factor in the social behaviour, human population density in rural community as well as the development. Wetlands are the rarest ecosystem type in Namibia, making up only about four percent of our landscape. As an arid country, Namibia values its Wetlands and is committed to protect and manage them through rational and integrated land use planning in accordance with the philosophies of the Ramsar Convention (Hines and Kolberg, 1997). The Namibian Constitution clearly provides for the government to assume responsibility for the overall management of the water resource and request the Government to be clear about its objective and policies. Multidisciplinary committee was elected by Cabinet to serve in the Water Supply and Sanitation Sector Policy (WASP) from the following Ministries (DWA, 1993): · Ministry of Agriculture, Water and Rural Development · Ministry of Regional and Local Government and Housing Integrated soil management for sustainable agriculture and food security in Southern and East Africa 259
· Ministry of Works, Transport and Communication · Ministry of Lands, Resettlement and Rehabilitation · Ministry of Health and Social Services · National Planning Commission · Office of the Prime Minister
The sector policy include: Communities to have the right with due regard for environmental needs and the resource available to determine which solutions and service levels are acceptable to them. Beneficiaries should contribute towards the cost of the service at increasing rates for standards of living exceeding the levels required for providing basic needs. An environmentally sustainable development and utilization of the water resources of the country should be pursued in addressing the various needs. About 60 % of Namibia 's total population lives in the north. Of these, 75% live alongside the perennial or ephemeral wetlands. About 44% live within the Cuvelai drainage system, where a mixed economy is dependent on the flood regime to replenish the water table. regenerate grazing and provide rich protein source of fish. Although severely degraded by overgrazing and adversely affected by the construction of roads and canals, the system still supports a great diversity of biota. Dams which have been proposed in the Okavango River and the uncontrolled extraction of water would severely alter the flood regimes. Water quality in the Okavango and Caprivi has already decreased due to pollution; while erosion and increased siltation has resulted from the clearing of riverine vegetation of agriculture (Hines and Kolberg, 1997). In the high rainfall areas of Okavango and Caprivi development such as irrigation, aquaculture and plantation are water based. These schemes and veterinary and public health programmed can directly of indirectly affect the functioning of wetland systems. Of particular concern is the accumulative affects of water withdrawal, the use of chemical pollutant such as DDT in mosquito control programmed, endosulfan sprays to control tsetse fly, and silt from poor upland agricultural practices (Brown, 1992; Hines and Kolberg, 1997).
Bulk water storage dams in Namibia are only found on the intermittently flowing rivers rising in the central region Although there is concern that these impoundments have negatively affected downstream groundwater levels, they provide important sources of water for industrial and domestic consumption in otherwise arid regions. Excessive abstraction of upper catchment impoundments negatively affect the vegetation along the ephemeral rivers through the lowering of the water table. General habitat degradation has severely denuded riparian forest along the perennial rivers (Hines and Kolberg, 1997).
PROPOSALS OF PROGRAMMES FOR IMPROVED SOIL MANAGEMENT AND PRODUCTIVITY ENHANCING Possible solutions and successful schemes Namibia has made an attempt to assess soil erosion on small scale (1:1,000,000). This process has been hampered by the lack of concrete data available countrywide. Progress has been made in calculating the soil erosivity index from the average annual rainfall data using the Soil Loss Equation Model for Southern Africa (SLEMSA). Extrapolations to areas where no record is available hampered the projection to specific areas, however statistics made it possible to fill the gap. Despite the availability laws and policies that provides for monitoring and assessing the impact of environmental pollution and toxification hazards no attempt has been made to map these impact at a national level. The reason being that these type of degradation has not yet 260 Namibia
caused a national out cry, except for occasional cases reported in the urban and peri-urban environment. So far that has been left to the municipalities to handle.
Reported cases of sewerage water leaks into agricultural fields has gone with the recommendation to abandon the field for a new field, but the impact is only determined by the decrease in yield and stunted crop stand rather than the chemistry in the soil and plant tissue. The lack of proper facilities for determining the type and degree of toxification is largely to be blamed. Soil fertility and fertilizer use as are well as chemical pest and disease control are yet to be assessed but again the national use of fertilizers are very low. Those who can afford are few and the fertilize and soil amendment chemicals have a high price. It is these price that control chemical degradation.
Lowering of fertility is evident in communal areas where chemical fertilization is literally zero. Cutting and burning of vegetation for clearance of new agricultural land is a common practice in Okavango and Caprivi regions. In the Oshana Ohangwena, Otjikoto and Omusati regions shifting cultivation is not common, but rather expansion of agricultural field is a dominant practice. This is mainly the result of population pressure. The yield differences between the expanded portion and the old portion is magnificent in favour of the expended portions. The rest of the country is either commercial or livestock dominated. Livestock in commercial area are the major causes of deforestation, soil erosion and bush encroachment imbalance in vegetation removal allows for clearance of the most palatable plant material closer to water points. The less palatable material spread to this area without control. Bush encroachment is from definition the spreading of unwanted species of woody vegetation into an area.
The Government of Namibia has formulated an Eco-Systems Conservation and Protection program with the objective to improve conditions of food security and nutrition by ensuring the long term sustainable use of the environment and natural resources and conservation of forest, wildlife and Namibia's fragile eco-system. Environmental protection and ecological conservation is imperative to achieve sustainable agricultural and rural development, particularly in achieving food security and improving nutritional status (NFSNC, 1995a). This program is multi- disciplinary and comprised of representatives from the following agencies and organizations (NFSNC, 1995a): · Ministry of Environment and Tourism, Directorate of Environmental Affairs (lead agency), · Ministry of Agriculture, Water and Rural Development, Extension and Engineering Services, · Ministry of Agriculture, Water and Rural Development, Directorate of Planning, · Rossing Foundation, · University of Namibia, Social Science Division, · Council of Churches in Namibia.
Areas of support from the international community The role of soil science in agriculture and environmental sciences is partly misunderstood by many sectors in Namibia. A broader view of soil science need to be presented to all Namibian, and taught at school to the youth. It is a general perception that most Namibians regard soil science as the formulation of fertilizers and manure for increased productivity. New projects are underway to address soil physics, especially soil moisture management. This component is aimed at addressing the issue of climatic aridity with respect to productivity. The first step is investigate the different soil tillage practices (deep ripping, shallow plowing and zero tillage) with respect to soil moisture storage using the gravimetric techniques combined with field moisture meters. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 261
Depending on the funds available, the second step will be to look into the structural deterioration, computability, crusting and nutrient loss when these are continued over several seasons under the same crop. Results from this project will help addressing the shifting cultivation and continuous expansion of agricultural fields which are not used to capacity in the communal farming sector, as well as the selection of the management practice suitable for Namibian condition.
The international community (Food and Agriculture Organization, Southern African Development Community (SADC), Commonwealth, European Community and all first world countries which are providing aid to Namibia for various means are kindly requested to assess the environmental programmes already in place and direct their financial and technical support toward long term environmental programmes which addresses conservation and sustainability. The existing policies and legislation should be regarded as an incentive for a healthy atmosphere and guarantees commitment from the Namibian Government. International schools and technical institutions should consider personnel and student exchange with the Namibian counterparts, as well as making provisions for Namibian students to enrol at their institutions while doing their practical, theses and dissertations on Namibian environmental issues. This will not only raise the level of expertise in Namibia and her environment, but also document the existing environmental conditions with concrete data.
REFERENCES A. O. C. Technical Service (Pty) Ltd. 1967. Report on an agronomic and management study of the proposed first phase irrigation areas in Ovamboland. Annex M supplement. Aschley, C. 1997. Can population growth and environmental sustainability be reconciled. in Tarr, P. Namibia Environment, vol 1. Ministry of Environment and Tourism P/ Bag 13306, Windhoek, Namibia. Beaumont, P. 1989. Dryland; environmental management and development. Routledge, 11 New Fetter Lane, London. Bester, B, 1997. Buch Encroachment, A Thorny problem. in Tarr, P. Namibia Environment, vol 1. Ministry of Environment and Tourism P/ Bag 13306, Windhoek, Namibia. Beugler-Bell, H., M.W. Buch and Ch. Trippner 1993. A Guideline for soil classification in the Etosha National Park and adjacent areas in Central Northern Namibia: DFG/GTZ Cooperation Project 'soil and Environment change in the Etosha National Park', Namibia. Field document No 1.2. Beyers, J. 1996. Rainfall, water collection and irrigation. Meteorological Services, Department of Transport, Ministry of Works, Transport and Communication. P/Bag 13224, Windhoek, Namibia. Brown C.J. 1992. Namibia's Green Plan (Environment and Development) Draft Ministry of Conservation, Wildlife and Tourism. Buch, M. W., M. Lindique, H. Beugler-Bell, W. Du Plessis and Ch. Trippner, 1993. Environmental change in Etosha National Park, Northern Namibia; Aims, Activities and First Results, Part 1. Etosha Ecological Research and University of Regensburg, Okaukuejo, Namibia. Central Statistics Office. 1994. 1991 population and housing census: basic analysis with highlights. Central Statistics Office, National Planning Commission. P/Bag 13356, Windhoek Coetzee, M. E., A. J. Calitz, H. Beukes, H and J. Kutuahupira, 1996. Agro-ecological zone project. Presented at the Annual Steering Committee Meeting of the SARCCUS for Land Use Planning(Windhoek). P. O. Box 13184, Windhoek. Namibia. 262 Namibia
DWA (Department of Water Affairs), 1993. A digest of water supply and sanitation sector policy of the Government of Namibia. Department of Water Affairs, Ministry of Agriculture, Water and Rural Development, P/Bag 13193, Windhoek, Namibia. DWA (Department of Water Affairs), 1994. Hydrological review of the 1992/93 season. Department of Water Affairs, Ministry of Agriculture, Water and Rural Development, P/Bag 13193, Windhoek, Namibia. FAO-UNESCO (Food and Agriculture Organization), 1988. Soil map of the world: Revised legend. Rome. FSSA (Fertilizer Society of South Africa) 1989. Fertilizer Handbook, FSSA Pub. P.O. Box 7438, Hennopsmeer 0046. (34 - 37.) Gomide, R. L. and M. T. Neto, 1996. Education and training program on water management and field evaluation of irrigation systems. Brazil-Namibia Agricultural Cooperation. Hines C, and H. Kolberg 1997, Importance of wetland management in Arid regions. in Tarr, P. Namibia Environment, vol 1. Ministry of Environment and Tourism P/ Bag 13306, Windhoek, Namibia. Isaakson, B. 1995. Namibian Food Security and Nutrition Assessment Report. National Food Security and Nutrition Technical Committee. Windhoek, Namibia. Lau, B and P. Reiner, 1993. 100 years of agricultural development in colonial Namibia: Historical overview of visions and experiments. Archeia No. 17. MAWRD (Ministry of Agriculture, Water and Rural Development), 1995. National Agricultural Policy. Department of Agriculture and Rural Development. P/Bag 13184, Windhoek, Namibia. MLRR (Ministry of Land Resettlement and Rehabilitation), 1997. National Land Policy; White paper. Department of Lands, P/Bag 13343, Windhoek, Namibia. National Food Security and Nutrition Council (NFSNC), 1995a. National Food Security and Nutrition Action Plan. NFSNC. Windhoek, Namibia. National Food Security and Nutrition Council (NFSNC), 1995b. National Declaration on Food and Nutrition. NFSNC. Windhoek, Namibia. Office of Prime Minister (OPM), 1993. Working for a Better Namibia. Government of the Republic of Namibia. OPM. Private Bag 13338. Windhoek, Namibia. Seely, M. 1991. Drought and Desertification. Desert Research Foundation of Namibia. P.O. Box 20232, Windhoek, Namibia. Seely, M and Montgomery, 1996. Managing water points and grazing areas in Namibia. Desert Research Foundation of Namibia. P. O. Box 20232, Windhoek, Namibia. Seely, M and K. Jackobson, 1997. Desertification in Namibia. in Tarr, P. Namibia Environment, vol 1. Ministry of Environment and Tourism P/ Bag 13306, Windhoek, Namibia. Strobach, B.J., A.J. Calitz and M.E Coetzee 1996. Erosion Hazard Mapping. Agricola. No. 8 MAWRD 53-59 Tarr, P. 1997. International Environmental Treaties, in Tarr, P. Namibia Environment, vol 1. Ministry of Environment and Tourism P/ Bag 13306, Windhoek, Namibia. Trippner, Ch. in preparation. Salt content as an Eco-pedological limiting factor in soils of the Etosha National Park/N-Namibia: Draft version. United Nations Development Programme (UNDP), 1996. Human Development Report. UNDP. Windhoek, Namibia. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 263
South Africa
COUNTRY FOOD PRODUCTION AND REQUIREMENT World dilemma World food demand will double by 2025 due to population growth, urbanization, rising income in developing countries and westernization (Sielaff, 1997). In 1994 global food production would have provided a diet with adequate calories for about 800 million more than the actual world population, had it been evenly distributed (Borlaug, 1997). According to the FAO, the 50 countries of the Africa continent could feed three times the present population (Spurling et al., 1992) but in 1990, the continent produced 27 percent less food than in 1967 for each African (Lean, Hinrichsen & Markhan, 1990). SADC’s domestic availability of major staple foods in the 1990/91 marketing season was reported to be 8 percent in excess of requirements. Despite production statistics, 30 million people in Africa are threatened by famine and require emergency food aid, much of which is imported (Rwomire, 1992). These statistics point to two key problems of feeding the world’s people namely producing sufficient quantities of food of desired quality and kind in environmentally and economically sustainable ways and secondly of distributing food equitably (Borlaug, 1997). Both these problems are daunting as a healthy natural resource base is at stake to ensure sustainable food production and as the poor lack purchasing power. The latter explains why 1 thousand million people in the world are starving. An aggravating factor to food security is that on a worldwide basis, only 11 percent of the soils are deemed to be free of limitations (Scotney & McPhee, 1990).
Food production and agricultural potential In South Africa, the diversity, nature and distribution of the natural resources soil, terrain, climate, water and natural vegetation, enable the country to produce a wide variety of food and fibre products which take full command of the people’s nutritional needs. In terms of value and quality the country not only meets its own food requirements, but is a major exporter of certain agricultural products (Van der Merwe, 1995). Land utilization data reflect (Table 1) that out of the 122 million ha of South Africa almost 86 percent is used for agriculture. This excludes subsistence farming, smallholdings and almost 5 percent under forestry. Agricultural land comprises almost 74 percent natural veld and 12 percent arable land of which approximately 1.2 million ha is under irrigation. Irrigation is a stabilizing factor in South Africa’s agriculture characterized by water scarcity, variable and erratic rainfall. Irrigated agricultural production accounts for almost 30 percent of total crop production and four percent of GDP (Scotney & Van der Merwe, 1995; Goodland, 1995) but this may not increase if water is put on a full cost-pricing basis. Modern technology constantly enhances production.
A.J. van der Merwe and M.C. de Villiers Institute of Soil, Climate and Water, Pretoria 264 South Africa
TABLE 1 Present and additional area land (ha) according to potential class (excluding former homelands) Classes High Medium Low Not Unclassified Total cultivable Present area per 5 898 586 5 391 826 3 402 412 452 235 74 353 619 89 498 678 potential class Additional area per 1 061 423 888 575 235 594 -452 235 -3 849 357 0 potential class Total 6 960 009 6 280 401 5 754 006 0 70 052 027 89 046 443
A mere 3 percent of the 13.5 million ha arable land currently utilized by agriculture is of high agricultural potential and presently 0.5 million ha non-arable land is used for agronomic production. Theoretically speaking, only 1.3 million ha is available for horizontal agricultural expansion (Van der Merwe, 1992; 1994), but it is envisaged that this area could be expanded significantly as land, mainly in the former homelands (almost 10 million ha), presently used mostly for subsistence, is brought into production. The Corporation for Economic Development, other agents and commercial farmers in these areas agree that most of the 10 million ha has a high production potential (Van Marle, 1981; Smith et al., 1990). According to Van Marle (1981), the agricultural potential of 100 ha of land in former homelands is roughly the same as that of 147 ha in the former white areas. Grobler, quoted by Van Marle (1981), tasked seven different areas from the former KwaZulu, Northern Black States and Bophuthatswana and classified the sample areas according to production potential and grazing capacity. He concluded that with the rough estimates of agricultural potential and capacity for food production as basis, 25.6 million people could be self-supporting on the 9 618 000 ha. Van Marle (1981) reported that annual maize production in the former Bophuthatswana rocketed by more than 1 000 percent over four years. This increase in production led to employment opportunities, wealth creation and the creation of silo complexes. The reason for prevailing low yields is not low production potential but a lack of agricultural inputs, the attitude by traditional leaders and farmers’ management, technology, personal motivation and the land tenure system. The area should be able to feed a total population of 30 million but present production is sufficient for only 2 million (Van Marle, 1981). This gap is likely to widen unless well-planned and directed corrective action is taken urgently. The ARC-Institute for Soil, Climate and Water initiated a land type survey in 1971 aimed at providing an inventory of soils, terrain forms and macroclimate. The data from this and detailed soil and climate surveys, integrated by a geographic information system, allow reliable assessments of agricultural potential and land suitability. The former Ciskei and Transkei are excluded but ISCW and its partners, the National Department of Agriculture, the Eastern Cape Department of Agriculture and Land Affairs and the University of the Transkei negotiated funds to survey these areas and to develop a natural resources information system for the Eastern Cape Province. Considering area extension possibilities, South Africa can probably feed its population for many years to come (Van der Merwe, 1995) provided the current major problems of poor agricultural land management, land degradation, competition for arable land, population growth and equitable food distribution are addressed in a sustainable manner. Equally important, provided sufficient funds are available to implement effective monitoring, auditing and precision farming systems and to continue critical research and technology development. Most agricultural production extension should come from the former homelands which are less developed and mainly used for subsistence. Affluence needs a stock component as well as gross national product per caput which is an economic flow component (Goodland, 1995). South Africa, where 74 percent natural vegetation occupies the agricultural land area, has a major niche Integrated soil management for sustainable agriculture and food security in Southern and East Africa 265
for cattle. In the former homelands, 80.3 percent of the agricultural land area is utilized as grazing (Van Marle, 1981). According to Goodland (1995) cattle, with a social value to most tribes, are responsible for major land degradation which will become irreversible throughout much of South Africa’s dry and fragile soils, unless cattle are scrupulously managed. It is estimated that 60 percent of the natural veld is in poor condition. Measured against the gross value of individual agricultural products, maize, sugar cane, and wheat are South Africa’s most important field crops, followed closely by hay. Deciduous and other fruit, vegetables and potatoes are the horticultural crops with the highest growth value while poultry and cattle products top the list in 1994/95 of animal products. Table 2 projects the increase in production required to feed South Africa’s nation until the year 2010. In compiling Table 2, cognizance was taken of the country’s mosaic of socio-cultural habits and massive urbanization resulting in new lifestyles. Considering an annual population growth rate of 2.5 percent, crop production will have to be increased by 3 percent per annum (Schulze, Kiker & Kunz, 1993). An even more daunting task than an increase in food production is that of ensuring affordable food and sustainable farming systems as South Africa’s soil mantle is most vulnerable and as the country is largely semi-arid to arid.
TABLE 2 Projection of increase in production required to accommodate population growth Commodity Production estimate (%) Estimated annual growth 2000 2010 rate in production (%) Maize 117.2 137.4 1.6 Wheat 117.2 137.4 1.6 Beef 116.1 134.7 1.5 Chicken 152.4 232.1 4.3 Deciduous fruit 126.8 160.7 2.4 Subtropical fruit 128.0 163.9 2.5 Sugar 129.3 167.1 2.6 Vegetables 134.4 180.6 3.0
Cereal production Table 3 portrays the extent planted to maize, wheat, barley, oats and grain sorghum from 1975/76 to 1994/95 and production yield. Subsistence production is obviously excluded. This information unfortunately, tells nothing of the ecological implications of crop production, the standards of agronomic practices, soil selection or climate influences. Maize, occupying 56.5 percent on average of the land used to cultivate field crops, represents 49 percent of the carbohydrate consumed by South Africa and 59 percent of the energy sector of livestock foods. By the year 2000, white maize consumption could rise from the 3.6 million tons to between 4.3 and 7 million tons, and yellow maize consumption from the present 3.1 million tons to between 4.5 and 5.2 million tons (Van der Merwe, 1994). Table 4 illustrates how maize production can be conservatively increased from the average 2.4 t ha-1 under dryland conditions to 3.5 t ha-1 and from 6 to 8.2 t ha-1 under irrigation to take command of projected requirements. Schoeman & Scotney (1986), ignoring individual farm viability, calculated that if maize in the main production areas was planted according to soil potential a total crop exceeding the 1984/85 level of 8.3 million tons could be reaped from a area one third smaller than the area planted that season. Such general assessments are of little value at the farm level where far more resource information is needed, where management is a critical factor (Scotney, 1987), and where the farmer’s financial position is unknown. Soil productivity is an intrinsic value of soil and long term soil productivity an indicator of soil sustainability. Agriculture involves the rearranging of nature to bring it more in line with human desires. It does not imply exploiting, mining or 266 South Africa
destroying the natural world. Plant nutrient applications (NPK only) for the period 1992/96 (Table 5) illustrate a significant increase in domestic fertilizer consumption in 1996 after a decline since 1985. Skeen (1997) ascribes this to favourable climatic conditions in most parts of the country during the 1995/96 production year and higher than normal farm income. It is significant that the average plant food concentration marginally increased from 28.8 in 1992 to 29.7 in 1996 (Skeen, 1997). Figures in Table 5 reflect domestic fertilizer application only and is not an indication of nutrient balance which takes cognizance of atmospheric and irrigation water deposits besides natural nitrogen provision processes. A NPK balance sheet (Table 6) compiled from 1971-81 data, indicate N and K depletion annually. Annual nutrient loss (42 774 N t annual; 34 219 P t annual; 470 514 K t annual) due to erosion is particularly alarming. K losses due to erosion exceed fertilizer K application 4x while N losses account for 14 percent of that applied and P for 21 percent. Erosion is a serious threat in terms of both sustainability and economic production.
TABLE 3 Average area planted to maize, wheat, barley, sorghum and oats and average yield (1975/76- 1994/95) Crop Area planted Production (000 ha) Arable crop area (%) Total production (000 ton) Yield (t ha-1) Maize 4 369.25 56.47 8 328.80 1.9 Wheat 1 694.05 21.89 2 073.00 1.2 Barley 95.60 1.23 172.80 1.8 Sorghum 232.90 3.01 445.80 1.9 Oats 548.10 7.08 68.40 0.1 Total 6 940 89.68 11 088.80 All other* 797 10.32 18 382** Total 7 737 100.00 29 470.80 * Dry beans, sugar cane, tobacco, cotton, groundnuts, sunflowers and soybeans ** Sugar cane production represents 95.5% of all other crops total production
TABLE 4 Maize yield according to level of management Management level Dryland yield (t ha-1) Irrigation yield (t ha-1) Average farmer 2.4 6.1 Top farmer 3 7.7 Experimental 3.5 8.2
TABLE 5 Domestic fertilizer use in South Africa and related statistics 1992-1996 (000 tonnes) Plant nutrient 1992 1993 1994 1995 1996 Change 1996/95 (%) N 348 408 375 371 415 +117 P 96 106 108 106 112 +5.2 K 99 103 108 112 119 +7.1 Total 543 617 591 588 646 +9.7 Plantfood concentration 28.8 29.1 29.5 29.4 29.7 +1.0 Source: after Skeen, 1997
Considering an annual population growth rate of 2.5 percent in South Africa and the country’s agricultural potential, South Africa is committed to improving and increasing agricultural production to meet the food demands of the people despite the decline since 1960 in agricultural and forestry land by almost 20 percent in favour of urbanization and nature reserves (Dept. Agric., 1994). South Africa’s major task is to ensure that the natural resource base is carefully managed to sustain future generations. This vision can be realized, provided that: Integrated soil management for sustainable agriculture and food security in Southern and East Africa 267
TABLE 6 NPK Balance sheet for 14 million ha cultivated land (1971-1981 average per annum) Application/remov N P K al ton/annum ton/annum ton/annum NPK application/ deposit 310 940 165 579 106 629 Fertilizer 142 580 11 406 114 064 Atmosphere 2 608 544 2 934 Irrigation water Total 313 548 (1) 177 529 223 627 N P K removal 145 (a) (b) (a) (b) (a) (b) Crop & residues 447 Maize 6 552 75.7 44.1 26 446 73.0 48.7 64 223 83.5 28.9 Sorghum 36 573 3.4 2.0 1 917 5.3 3.5 2 369 3.1 1.1 Wheat 1 778 19.0 11.1 7 165 19.8 13.2 9 154 11.9 4.1 Oats 1 674 0.9 0.5 413 1.1 0.8 585 0.8 0.3 Barley 0.9 0.5 302 0.8 0.5 558 0.7 0.2 Total for cereals 192 024 36 243 76 889 Total other agronomic/ 137 946 17 997 145 430 horticultural crops Total all crops 329 970 54 240 222 319 Erosion 42 774 34 219 470 514 Total: crops, 372 744 88 459 692 833 residue, erosion Balance -59 196 89 070 -469 206 Source: after Biesenbach, 1984 Notes: (a) % of cereals; (b) % of all agronomic/horticultural crops; (1) Fertilizer and irrigation water only. N from atmosphere assumed to compensate for N losses due to leaching, denitrification and volatilization
· under- or undeveloped high to medium potential land in the former homelands is developed sustainably, · soil quality is improved, · agricultural management, cultivation practices and precision farming systems are improved significantly, · land use and land management are dictated by the intricate interactions between soil, climate and terrain, · land degradation is reversed, · impact assessments are undertaken prior to South Africa’s development programmes like the redistribution of land, · input cost is reduced.
EVOLUTION OF PER CAPUT CULTIVATED LAND AND TRENDS IN CEREAL CROP YIELDS The cutting edge of Africa’s crisis, says Harrison (1987), is the steady decline in agricultural production per person, especially of food. Between 1965 and 1982 Africa’s food production per person fell by 12 percent in 33 of the SSA countries despite the significant increase in food production at a rate of 2.1 percent per year through the 1970s. In the same period, Southern Africa’s per caput food production fell by an average of 19 percent. Decline in food production 268 South Africa
can be attributed to many factors but the factual causes are the rate of population growth in Africa which was 3 percent per year in the 1970s (Harrison, 1987) and the continent’s long history of continued bad land use and resultant low agricultural productivity (Okigbo, 1990). This endorses the formidable challenge described by SDC (1994) namely to produce enough food for an increasing population while preserving the natural resource base and in particular the soils as key resource for agricultural activities.
In South Africa, the expected annual population growth rate is 2.5 percent. This implies that the population will double in 40 years which is alarming when compared to major parts of Europe where the population doubles every 71 years or more (Luiz, 1994; Goodland 1995; Van der Merwe, 1995). Person-to-land ratios are worsening fast and it is estimated that the area of arable land per caput will drop well below the accepted minimum of 0.4 ha before the year 2010 (Van der Merwe, 1995). Inadequate consumption per caput, poverty and rapid population growth undermines future consumption per caput.
At present, food production per caput in South Africa is sufficient but agricultural output will have to be expanded from more intensive cultivation mainly in areas already used for agricultural production (Greenland et al., 1994) or we will become dependent on food imports which will be conducive to the downward spiral of the poverty trap. If South Africa can succeed in conserving its natural resource base in the face of continued pressure on land, a win-win situation is possible (Van der Merwe, 1995). In most regions of the world, increasing food supply over the past two decades were gained mainly by increasing yields. The major exception to the world was SSA where most of the growth in production has occurred due to expansion of cultivated areas (Borlaug, 1997). South Africa, due to population pressure, scarcity of land, endemic technology and a history of food export, more or less maintained agricultural production over the last two decades.
Fluctuations in areas planted to arable crops and yield per annum can be directly related to climate conditions, and in particular to rainfall and rainfall pattern. Climate conditions and the subsequent financial position of the farmer dictate plant nutrient applications. A comparison between the 1991/92 and 1993/94 maize production seasons shows that the 1993/94 season, with average annual rainfall, yielded an above average 2.8 t ha-1 while the 1991/92 season with a well below rainfall (340 mm in 1992) yielded a disappointing 0.78 t ha-1. Plant nutrient (NPK) application in 1993/94 was 22 percent higher than in 1991/92. Area planted to maize was 10 percent less in 1991/92. As a result of these interactions, 91 percent more maize and maize products were exported in 1994 while the import of maize and maize products was 85 percent higher in 1993 than in 1994. The average area grown to the cereals maize, wheat, barley, sorghum and oats over the past two decades was 89.68% (6.9 million ha) of the total area grown to arable crops (Table 3). Maize, planted to 56.47 percent of the total area planted, stayed South Africa’s major arable crop, followed by wheat planted to 21.89 percent of the total arable area. Table 3 excludes subsistence and non-marketable data. Such partial productivity measures relate output of a single input factor (Thirtle & Van Zyl, 1993) and address indicators of the economic group and to a certain extent, indicators of the physical group, but not those of the social or biological groups. Both social and biological indicators are of critical importance, and in particular biological indicators including aspects like cropping systems, length of and changes in fallow, soil biota and other indicators fundamental to sustainable soil productivity (IBSRAM, 1995). Soil is regarded as more than a production factor by most commercial farmers and they usually try to maintain soil productivity even when it is economically unjustified. This is a major advantage even when the pressure on natural resources is high. However, contrary to intention, Integrated soil management for sustainable agriculture and food security in Southern and East Africa 269
farmers are often forced to neglect soil care when economic returns from agriculture are too low to justify investments in soil maintenance. Liming to ameliorate soil acidity falls in this category. Naturally occurring acid soils affect more than 15 percent of South Africa’s land area but the exact extent of man-induced topsoil acidity is unknown. According to Beukes (1995; 1997), trends in soil analysis indicate increasing soil acidification and Farina (1997) states that almost 15 percent of South Africa’s arable land is likely to be affected by some degree of subsurface acidity. On acid soils, with a low nutritional status, maize yield loss could be as high as 60 percent and in the worse scenario for wheat, yield loss of 71-87 percent could occur (Beukes, 1997). In view of food production, soil acidity is undoubtedly South Africa’s worst enemy as it results in poor vegetative crop growth, impedes root development and subsequent water and nutrient uptake, causes Al, Mn and other toxicities and as it causes poor nodulation in leguminous crops (Beukes, 1997).
The influence that land tenure will have on per caput cultivated land and food security in South Africa is not quite clear. The communal system of land tenure within the tribal context, mostly in the former homelands, is practised on an estimated 13 percent of South Africa’s arable land. Land tenure is often blamed as the cause of agricultural failure as the system, according to Beuster (1981), incorporates a number of inherent weaknesses including : · the absence of sense of value regarding land. Traditionally tribal communities regard the acquisition of the agricultural use of land a right and subsequently land is seldom seen as an economic production factor which has to be used optimally in order to ensure success, · non-differentiation between farmers and non-farmers as land units are relatively small and in most cases the farmer has the option of selling his labour to nearby industrial or mining areas. This leads to neglect and the under-utilization of valuable agricultural resources, · tribal tradition regarding agricultural practices with a retarding influence on the acceptance of modern agricultural practices, · a negative attitude towards agriculture, especially in the eyes of the younger generations. Agriculture is associated with poverty, hardship, subsistence economy, dirty work and of very little scope for real progress. Small farms house large numbers of people who have few alternative sources of employment and income (Van Marle, 1981). In the former Qwaqwa, a very sensitive ecological area due to topography, for example, population density in 1990 was estimated at 163 persons per kilometre compared to the 28 for the whole South Africa (Scotney, Volschenk & Van Heerden, 1990).
Soil management and development programmes should be undertaken with adequate participation of the soil users and mainly small farmers, with emphasis on women. Women have the principal responsibility for over 20 percent of all small farms in developing countries (SDC, 1994). Furthermore, international market policies and practices tend to work against the interest of poorer developing countries. Industrialized countries, through export developing, import restrictions and subsidies to improve the productivity of domestic agriculture, have reduced return on land in developing countries by lowering world market prices. Poorer, less advanced countries are net losers (SDC, 1994) and the poor have little incentive to care for soil productivity in a sustainable way. To change from subsistence farming to a cash economy, money, inputs such as soil nutrients, good seed, appropriate machinery, technology and management are vital. Farmers must be willing and able to accept training, new technology and sustainable soil management practices, and rural infrastructure must be in existence or created (Van Marle, 1981). The Sheila/Verdwaal project in the former Bophuthatswana bears evidence that a communal land 270 South Africa
tenure system can be successful. This community consists of 197 farmers cultivating 3,426 ha of land. With the assistance of and training in modern technology by an economic development agency and an agricultural cooperative, the community reaped 3.25 t ha-1 maize. The same group of farmers yielded 1.68 t ha-1 with the initiation of the project 3 years earlier (Beuster, 1981).
Land reform programmes require long-term perspective, strong political consensus and functional legal institutions, with well-defined property rights as farmers’ investments and their ability to receive normal credit depend on clearly defined ownership of land (SDC, 1994). Land reform, according to Goodland (1995) however widely implemented, will not be sufficient to alleviate rural poverty or food security as the available supply of land is simply not sufficient to grant a useful quantity of land to even the majority. To ensure food security and wealth creation, effort will need to be devoted to generating non-farm employment opportunities in rural, urban and peri-urban areas to meet the needs of future population growth. Most effort needs to be focused on reducing population pressures if all investments are not to be rapidly overwhelmed (Goodland, 1995). The South African Department of Land Affairs is promoting a farm equity scheme. This scheme is a partnership arrangement between a commercial farming enterprise or private sector investor and the beneficiaries namely the landless, farm workers, labour tenants and residents who want to secure an agreement of ownership of land, the sharing of profits and the risks of the venture. Part of this programme is the empowerment of women (Dept. Land Affairs, 1997). South Africa will hopefully avoid mistakes of unsustainable agricultural development in the past. In the 1970s, sub-economic land allocations were made to virtually every tribal family in a section of the former Bophuthatswana. As a result of the sub-economic size of plots, most of the land was unused and neglected while poverty and urbanization thrived. Afterwards, traditional rights to cultivate land were withdrawn and tribal members, willing to become full-time farmers, were allocated economic land units of 100 ha (Beuster, 1981). This was the beginning of moving from survival economics to emerging economics.
EXTENT OF SOIL DEGRADATION AND ITS BIO-PHYSICAL & SOCIO-ECONOMIC IMPACTS According to Sielaff (1997) one quarter of global land is degraded and 4 percent is so badly degraded that it is beyond repair. There has been a 17 percent cumulative productivity loss due to degradation, which has been more than offset by the doubling of world food production during that time. Land degradation or the loss of productive capacity of land to sustain life, is the major source of insufficient food and the poverty trap. The two main components of land degradation are soil degradation and the impoverishment of the vegetative cover. Soil limitations presented on a world-wide basis show that droughtiness (28%), mineral stress (23%), shallow depth (22%), waterlogging (10%) and permafrost (6%) are all important as only 11 percent of the world’s soils are deemed to be free of limitations (Scotney & McPhee, 1990).
The major forms of soil degradations in South Africa threatening a sustainable natural resource base and food security, are soil acidification, organic matter depletion and pollution causing salinization and alkalinization, compaction/crusting, runoff and erosion, infertility and desertification. In the rural subsistence environment, fuelwood collection, concentrated population densities, inappropriate land use and overgrazing are major causes while unsustainable farming systems, incorrect and/or poor planning and catastrophic natural disasters are the major agricultural production causes of soil degradation (Van der Merwe, 1995; Goodland, 1995). International programmes, protocols, treaties and conventions place much emphasis on soil degradation forms like erosion and desertification. These and other are most important to address and reverse in view of a sustainable natural resource base and food security. At the bottom of Integrated soil management for sustainable agriculture and food security in Southern and East Africa 271
virtually all kinds of soil degradation, lies soil acidification, organic matter depletion and pollution. Once these have been addressed effectively, much of the other threats won’t be as imminent. The different forms of soil degradation are briefly discussed with emphasis on soil acidity, organic matter depletion and pollution.
Soil acidification The aspirations of economic growth and the reduction of poverty are imbedded in sustainable production (Schaffert, 1997). Acid soils limit production throughout the world and is a major constraint to crop production in many countries. Soil acidity is of particular importance in areas with low-input agriculture where there are few opportunities to counteract yield depressing factors such as subsoil acidity with or without surface soil acidity, moisture stress and other limiting crop performance factors, specifically P deficiency (Eswaran, Reich & Beinroth, 1997). Acid soils occupy between 26 - 30 percent of the world’s ice free land area. Globally 67 percent of acid soils support forests and woodlands, approximately 18 percent are covered by savannas, prairie and steppe vegetation, 4.5 percent is used for arable crops while a further 33 million ha is utilized for perennial tropical crops. The poor fertility of acid soils is due usually to a combination of Al, Mn and Fe (reduced soil conditions only) toxicity, P, Ca, Mg and K deficiencies while many acid soils are affected by physical factors including low water holding capacity and susceptibility to crusting, erosion and compaction (Von Uexküll & Mutert, 1995; Eswaran, Reich & Beinroth, 1997).
Lack of moisture is rarely a major constraint to plant growth on acid soils in the humid tropics (Farina, 1997; Von Uexküll & Mutert, 1995) where population growth and the subsequent increase in food demand is greatest. The humid tropics have the advantage of few rainfall and temperature constraints to high yield, provided primary nutritional constraints (e.g. P, Ca, Mg, K deficiencies) are removed and the soil is managed expertly. Poorly crystallized weathering products formed as a consequence of extreme acidification and weathering in forest soils revealed an intense destruction of clay minerals and other silicates leading to an accumulation of poorly crystallized to amorphous compounds. Besides Si, the weathering products contain small amounts of Al and Fe (Veerhoff & Brümmer, 1993). which can clog soil pores on penetration causing runoff and erosion. In arid areas like South Africa, P, S, Mo and B deficiencies further complicate nutrition constraints as well as Mo and P fixation due to the use of ammonium fertilizers and the oxidation of organic material when soils are cultivated. Soil management must allow rotation periods between regeneration and cultivation. There are examples of highly successful development on acid savanna in Brazil and according to Von Uexküll & Mutert (1995), the Potash and Phosphate Institute makes use of a fast growing legume cover crop in combination with heavy applications of lime and P to enhance soil fertility on degraded anthropic savanna. Provided that good soil conservation is practised and nutrients replenished, sustained annual yields of 6.10 t/ha maize, upland rice, ground nuts and soybeans in 2 to 3 crops per annum are possible. Unfortunately there is no example of a low-input system working over the long term.
An estimated 659 million ha of Africa’s total area is occupied by acid soils. This is the third largest area on a continental basis and almost 16.7 percent of all acid soils. Eleven million ha (1.7%) is arable or planted to permanent crops (Von Uexküll & Mutert, 1995). Unlike the humid tropics, large parts of the Africa continent is characterized by dry climates. Soil acidification is, without question, the most dominant soil productivity problem. Naturally acidic subsoils occur over a wide spectrum of climate conditions varying from arid (± 500 mm per annum) to humid 272 South Africa
(750 mm per annum). In total, more than 14 percent of South Africa’s land area is affected by naturally occurring acid soils and 15 percent of the arable land is likely to be affected to some degree by subsurface acidity (Beukes, 1995; Farina, 1997).
The exact extent of human-induced surface and subsurface acidity is difficult to establish, and the management of acidity in South Africa is particularly demanding in terms of both quantification and identification (Farina, 1997). According to South African Agricultural Co- operatives (Fourie, 1997), approximately 60 percent of the country’s cropland area is moderately to severely acid (pH(KCl) < 5.1). Should the ideal pH (6.5) for crop production be used as indicator, close to 100 percent of cropland is acid. The human economy with its cultivation, tillage and fertilizer practices, plays a major role in the process of soil acidification. Fertilizer practices are often injudicious, particularly N fertilization, directly affecting the C/N ratio. Du Preez & Burger (1985) for instance, using USA norms on residual inorganic N contents prior to planting, determined that N application should have been one third less on 50 percent of the 82 localities investigated and at least two thirds less on 25 percent of the localities.
A large percentage of N fertilizers in South Africa are ammonium based. Due to nitrification, ammonium transforms into nitrate in the soil, releasing hydrogen ions that promote soil acidification. Cultivation increases oxidation of organic matter and therefore nitrification of reduced nitrogen in organic matter that promotes soil acidification. To optimize the organic matter contents, the C/N ratio, critical in view of a sustainable soil mantle, present cultivation, tillage and fertilizer practices will have to be seriously reconsidered and soils users in South Africa will have to buy into the concept of sustainable farming systems. The first step will obviously be to ameliorate soil acidity. This will be an expensive exercise as 100 percent of the cropland could be acid to varying degrees.
On average, 2 t ha-1 lime will be required in the initial phase to correct soil acidity. The initial phase to ameliorate soil acidity (Von Euxküll & Mutert, 1995; Beukes 1992; Du Toit et al., 1994) will also be marked by correcting other plant nutrient deficiencies with emphasis on P and by establishing leguminous cover crops. As pointed out by Von Euxküll & Mutert (1995), this is, financially wise, an expensive and unproductive phase. It is also the only way to correct the C/N ratio and to ensure sustainability. The three step development cycle (Von Euxküll & Mutert, 1995), from South African experience, will take four years (Beukes, 1992). It should be borne in mind that both natural and human-induced soil acidity should be addressed to prevent other forms of soil degradation and to develop medium to high crop potential land. Soil acidification is further intensified by acid rain. Commercial farmers’ liming programmes largely depend on cash flow. Their often unjustified soil sustainability decisions are dictated by financial means. Since 1981 liming material sales dropped by more than 1 million ton. This decline is despite concerted awareness campaigns, research and extension dedication, and demonstration trials.
As discussed in area extension possibilities for food production, the 10 million ha of the communal agricultural surface area (former homelands) should be developed. Large parts of these areas lie within both the warm and high rainfall areas of southern Africa and 76 percent of the total area receives more than 500 mm rainfall per annum. These areas have at their disposal the necessary natural resources, entrepreneurs and labour. What they do need, says Van Marle (1981), is training skills and enthusiasm to become entrepreneurs, modern technology and development finance. Soils of lower potential in relatively high rainfall and high soil acidity areas have much potential for expanding production provided the soil acidity is ameliorated and high Integrated soil management for sustainable agriculture and food security in Southern and East Africa 273
yielding pasture legumes are introduced into livestock systems. Strydom & Wassermann (1984) computed the area in South Africa suitable for the introduction of legume based pastures at 17 million ha, injecting approximately an extra 400 000 tons of nitrogen into the system annually, through the agency of nitrogen fixation by Rhizobium bacteria. This can lead to the trebling and quadrupling of livestock production per ha. The liming of acid soils will not only optimize pasture production under the favourable rainfall conditions along the East Coast in South Africa but will alleviate the endemic problems of micro-element shortages. Soils limed to pH 6.5 are more resistant to erosion while improved pastures and sustainable crop production systems made possible by liming will prevent further degradation of an important natural resource. The amelioration of natural acidity of soils in Africa can be a major catalyst to economic development.
Approximately 3 million of the 10 million ha in former homelands is potentially arable land. The major portion of medium to high agricultural potential land is found in the former Ciskei, KwaZulu and Transkei areas. These three areas with roughly 1.2 million ha high potential land are blessed with a mean annual rainfall exceeding 700 mm. Van Marle (1981) postulated that if farmers are to be settled on 100 000 ha of land suited for wheat production, 160 000 ha for maize production and 2.6 million ha of grazing in Bophathatswana, then a total of 6 439 farmers can be settled on maize and wheat farms, 625 on irrigation units of 9.7 ha each, and 2 541 cattle farmers on units to carry 169 mature livestock. A total of 9 605 farmers could thus be settled in the transformation from subsistence to cash economy. Van Marle (1981) also pointed out that the total production of maize and wheat would be so substantial that it would provide for export. Grobler, quoted by Van Marle (1981) notes that KwaZulu could successfully accommodate a minimum of 7.5 million self-supporting people instead of the 4.9 million in 1990, the northern areas 10.9 million and the western areas 7.2 million. However, agricultural production potential is seriously jeopardized by excessive soil acidity at a pH of 4.5 on even lower; 100 times more acid than the ideal. In the former Ciskei, KwaZulu and Transkei with the highest agricultural potential, subsistence dominates within tribal and communal land tenure systems. There is an urgent need to develop these areas sustainably and economically. These areas should be used as framework to develop the other former homelands.
Technology and norms, suitable for South Africa with its complex and vulnerable soil mantle and diversity, exist to facilitate the amelioration of soil acidity to levels conducive to optimum crop and pasture yields. Ameliorating soil pH for instance from the present 4.5 and lower to 6.5, will increase maize yields from 0.5 to 8 ton ha-1 on high potential soils. Potential income could escalate over 1 000 percent. Pasture production could be upgraded significantly by introducing legumes which would contribute substantially to sustainable agro-ecosystems as already proofed by the Potash and Phosphorus Institute in Brazil (Von Uexküll & Mutert, 1995). Von Uexküll & Mutert (1995) suggest a three step development approach : · an initial phase that establishes leguminous cover crops supported by liming and P applications to enrich the biological and nutrient cycle of topsoil and prevent erosion, crusting and compaction. This is an expensive and unproductive phase in the sense that little income is generated from harvested materials, · concentrate on deepening and enriching the rooting zone for marketable crops to generate farm income. This phase still requires investment, · balanced nutrition and efficient management to establish an ecologically and economically sustainable and viable system. 274 South Africa
Borlaug & Dowswell (1997) warned that “world peace will not be built on empty stomachs and human misery. Deny the small-scale farmers” (like those in South Africa’s former homelands) “of the developing world access to modern factors of production and much needed agricultural expansion in the acid soil areas to help feed future generations and humankind will be doomed, not from poisoning and environmental melt-down, but from starvation, social and political chaos”. Only where sufficient funds and assistance are provided during the first two phases of ameliorating soil acidity will wealth be introduced to landscapes where poverty would otherwise reign says Von Uexküll & Mutert (1995). This statement is the foundation for sustainable development in South Africa.
Soil organic matter depletion In South Africa, the organic C contents of soil is steadily declining, signalling unsustainability (Du Toit et al., 1994). Factors like South Africa’s isolation over many years and restricted land area, largely necessitated monoculture cereal production, short fallow, the absence of crop rotation systems, as well as intensive tillage. The authors are of opinion that the sustainable utilization of the natural resources for cereal crop production in South Africa can be achieved only if: · the organic matter contents in soils can be sustained and increased, · input costs are reduced, · soil acidification and pollution/sterilization are prevented.
To increase and sustain the organic matter contents of South African soils, the oxidation of organic matter will have to be minimized and the C/N ratio be manipulated by minimum tillage practices, grass ley legume systems, crop residue conservation and nitrogen fertilization practices that will promote the uptake of reduced forms of nitrogen and minimize the oxidation of reduced forms of nitrogen. It is well documented in literature that organic matter in soils is correlated with aggregation of soil particles, a favourable structure, water holding capacity, nutrient supply power and soil biota contents minimizing crusting, compaction, runoff, erosion and leaching of nutrients. Due to microbial and earthworm activity it is possible to reduce cultivation, fertilization and liming costs.
Runoff and erosion The irreversible loss of good quality soil not only influences the capacity of the farmer to produce sufficient food, but also the loss of the capacity of dams. Approximately 159 tons of sediment are transferred annually by South African rivers. The balance between ratios of soil formation and soil loss determines biotic activity. As an estimated 20 percent of the country’s total area is potentially highly erodible, erosion is a serious agricultural and environmental threat (Van der Merwe, 1995). Natural erosion shapes the landscape under natural vegetation and, apart from episodic floods, does not pose a threat as it approximates the rate of soil formation. Accentuated erosion results from human activities and takes place at rates far in excess of those for natural erosion (Scotney & McPhee, 1990). Both water and wind erosion are serious problems in South Africa (Table 7). Wind erosion affects some 1.3 million ha and water erosion almost 1.7 million ha. The estimated annual soil loss of 2.5 ton per hectare far exceeds tolerance levels as the estimated rate of soil formation is 0.31 ton per hectare per annum (Van der Merwe, 1995). Soil loss tolerances (T value) vary considerably for different soil conditions and for arable and non- arable situations. In South Africa, suggested tolerance levels for cultivated land are between 3 t ha-1 a-1 (shallow soils) and 9 t ha-1a-1 (deep clay and organic soils) according to Scotney & McPhee (1990). Even the 3 t ha-1a-1 however exceeds soil formation of an estimated 0.31 t ha-1a- Integrated soil management for sustainable agriculture and food security in Southern and East Africa 275
1. Accurate soil loss quantification is evasive despite reliable soil loss prediction equations and runoff trials. Equations like the USLE and RUSLE are used successfully to predict soil loss under different management practices. Sustainable farming practices and erosion prevention measures can fortunately prevent soil erosion. Scant attention has been given to soil losses from non-agricultural land. High losses result from activities such as road building, quarrying, sand winning, mining and site preparation. Quantitative estimates for South Africa have not been attempted according to the authors’ knowledge.
TABLE 7 Extent of wind and water erosion Type of erosion and land use Seriousness of erosion and area affected Total (ha) Serious Moderate Non-significant (ha) (ha) (ha) Wind - Cultivated land 415 001 1 325 749 1 427 088 - Pastures 569 524 1 700 436 7 932 671 13 370 469 Water - Cultivated land 930 735 2 258 193 2 886 727 - Pastures 801 288 3 128 613 6 973 149 16 978 705 Total 2 716 548 8 412 991 19 219 635 30 349 174
Soil compaction Cultivation and depletion of organic matter has led to several important soil physical problems. Compaction is prevalent in fine sandy (<10% clay) soils which is an estimated 80 percent of the soils cultivated for maize production. Maize yields may be reduced by as much as 30-40 percent on such affected soils (Van der Merwe, 1995).
Soil crusting Soil crusting as a result of organic matter depletion, soil acidification and alkalinization increases runoff from a wide range of cultivated and non-cultivated soils, hampering crop production and promoting erosion. The extent of crusting is unknown but a joint project by ISCW and the Western Cape Province showed an increased wheat yield of 60 percent after soil crusting was alleviated (Van der Merwe, 1995).
Soil infertility The synthesis of chemical, physical and biological soil degradation, influenced by climate and management practices causes soil infertility (Scotney & Dijkhuis, 1989). Physical structure, a desirable pH level, organic matter contents, proper aeration, adequate moisture and an optimal nutrient status must be maintained if sustainable food security is to be maintained. In South Africa, most fields in cultivation consist of different soils with different crop production potentials and soils rather than fields should be fertilized to reduce input cost and to ensure fertilization profitability (Van der Merwe, 1995). Some arid, semi-arid and even sub-humid ecosystems are impoverished by the combined effects of human activities and adverse climate conditions. The financial position of the farmer dictates if the nutritional status of the farm is mined or not. 276 South Africa
Desertification More than half of the surface area of South Africa is threatened by desertification and the resultant decline in biological productivity. Desert encroachment is seldom progressive. Fragile, dryland ecosystems are allowed to degenerate through mis-applied technology, poor land selection and bad management (Van der Merwe, 1995).
Soil pollution/alkalinization/salinization Soil alkalinization and salinization often goes hand in hand with waterlogging and pollution. Alkaline/saline and waterlogged soils can be reclaimed but at great expense and meticulous soil management afterwards. An estimated 10 million ha of irrigated land over the world is abandoned each year as a result of waterlogging, alkalinization and salinization (Van der Merwe, 1995). A survey by the Department of Agriculture (1990) pointed out that 54 000 ha of cultivated land in South Africa is seriously alkaline and waterlogged with 128 000 ha moderately affected. This excludes the former homelands. The management of reclaimed soils in South Africa is negatively affected by deteriorating water quality used for irrigation (Scotney & Van der Merwe, 1995) as well as poorly designed and operated irrigation systems. Unsustainability occurs when the flow of human economy exceeds environmental economy (mainly soil resources and sinks) in the flow of materials and energy from natural resources, used by the human, and then returned to soil sinks as waste (Goodland, 1995). In South Africa, solid waste, effluents, agriculture and acid rain are the major causes of soil pollution. Acid rain is a particular threat to some parts of the highest agricultural production area, responsible for almost 9 percent of the country’s total farming income (Van der Merwe, 1995). As South Africa depends on coal for 80 percent of its primary energy, any transition is unlikely (Goodland, 1995) but the problem of acid rain receives ample attention by Mining Houses (Tanner, 1997). Population pressure and land transformation activities like urbanization, agricultural practices, deforestation and biological invasion are decided threats to the ecosystem and biodiversity. Invasive biota are a major threat to natural biotic communities.
AVAILABLE TECHNOLOGICAL OPTIONS FOR CONTROLLING SOIL DEGRADATION AND ENHANCING PRODUCTIVITY The performance of concerted research and extension has had little success in enhancing sustainable soil management in developing countries. This is attributed by SDC (1995) Pinstrup- Andersen (1982) and Harrison (1987) to : · the lack of understanding or neglect of relations between soil management, economic and political factors at local, national and international level. This includes inadequate foreign aid and aid provided which was irrelevant to core problems, · the lack of dialogue between policy development and research entities involved in decision making with relevance for the sustainable management of agricultural soils, · the priority given to crop improvement programmes, · the viability of research and development to integrate the dimensions of time and space into programmes, · inadequate participation of the majority of soil users, the small farmers and in particular women, in defining policies relevant to soil management, Integrated soil management for sustainable agriculture and food security in Southern and East Africa 277
· the complex task for researchers to identify core soil management requirements by farmers as many factors influence soil management. The lack of farmer involvement in the development of soil management systems, often results in textbooks as origin of promoted innovations, · a short planning horizon in decision making with emphasis on immediate increase in food availability with little concern for possible deterioration of the resource base which is needed for future production.
The truth of these arguments is indisputable but there is also little doubt that the development and use of high-yielding crop varieties, increased use of fertilizers, better production systems and other yield-increasing factors have been of great importance in increasing food availability and in limiting land degradation. The significant effect of modern technology is frequently overlooked (Pinstrup-Andersen, 1982). Goodland (1995) quotes Ehrlich who notes that there is little justification for counting on technological miracles and that technology also damages. It is true that inappropriate irrigation and drainage caused waterlogging and salinization and that agricultural practices can cause soil pollution but soil institutions with a global mandate like ISRIC, IBSRAM, WASWC and ISCO succeeded significantly in increasing yield and in conserving soils in danger of degradation by developing improved soil and management systems. The human factor is probably the most uncontrollable and unpredictable in research and extension application efforts. Düvel (1997) stated that neither soils nor farms have problems. People have problems. Düvel (1997) suggests approaches aimed at behaviour intervention and on a sound understanding of human behaviour which emphasizes the land user participation approach essential to all soil research and management programmes if the integrated cycle of process research, management research, development/economic evaluation, extension, farming systems and feedback described by Robertson (1987) is to be successful.
The major forms of soil degradation in South Africa are organic matter depletion, acidification and pollution. To facilitate improved soil management technologies, ARC-Institute for Soil, Climate and Water (ISCW) developed and maintains national natural resources databanks including those for soil profiles, land types, soil surveys at different scales, agro-climate and NOAA satellite images. These databanks contain results of extensive ongoing reconnaissance and detail surveys, soil and climate classification, characterization, quantification and monitoring. ISCW focuses on the characterization and quantification of the natural resources soil, climate and water, natural resources monitoring and auditing and on the sustainable management of the natural resource base. Research and technology development are aimed at the following programmes to control soil degradation and to enhance agricultural production and food security: Soil inventories, geographic information systems, nutrient management, soil acidity, soil and water management, reclamation of physically disturbed land, remote sensing technology, small- scale farming technology, analytical services (soil, water, plant, ameliorants, fertilizer and growing media), climate monitoring, agroclimate research, soil and environmental protection, soil and water quality, and soil quality indicators. Multi-disciplinary, cross-sectoral programmes are land use planning; precision farming; small-scale farming, food security, job creation and training; risk and disaster management; spatial development initiatives; and monitoring and auditing of the natural resources. The overall objectives of these programmes are : · National welfare and economic objectives namely i) sustainable land use, land use planning also in view of appropriate alternative uses, land reform, and farming systems, ii) the maintenance and increase of physical and monetary agricultural production, iii) the enhancement of values which embody a sustainable perspective in rural communities and societies and iv) early warning of food security, natural disasters and climate change. 278 South Africa
· Sustainable natural resources utilization and ecological objectives to conserve the soil and water resources and to ensure long term soil productivity: i) the prevention of chemical, physical and biological soil degradation, including the maintenance and increase of biotic activity, the maintenance and enhancement of soil organic matter, water quality and quantity as well as the availability of plant nutrients, the maintenance and improvement of physical soil structure and properties, the absence of toxic levels of hazardous micro-nutrients and elements, land husbandry and monitoring, ii) water conservation priorities are aimed at the maintenance of acceptable water quality by investigating and promoting buffer zones/wetlands, catchment, runoff, monitoring systems and integrated catchment management, the maintenance and enhancement of water availability by watershed management, water wise food production and water harvesting. · To empower people, training as an integral part of particularly provincial projects is intensified to supplement present projects which focus mainly on communities in view of household food security, mentorship and hands-on training. The empowering of people in SADC countries will remain a high priority.
Selected ISCW projects over the past five years in view of improved soil management to enhance productivity and to control soil degradation are summarized. Most of the projects are multi-dimensional and therefore applicable to both soil management and soil degradation.
Soil management Natural soil fertility in South Africa is comparatively low because of natural acidity, low organic matter content and a low P and other nutrients status. Supplementary nutrition accounts for one third of input cost for crop production. Both soil factors and management practices are responsible for the sub-optimal utilization of applied fertilizer by crops. Only 33 percent of fertilizer applied annually are utilized by crops, affecting the farmer’s rate of return negatively. Furthermore, chemical fertilizers are often too expensive for subsistence and small farmers. Unutilized fertilizer could cause soil and water pollution as well as soil degradation. The following technology and research were aimed at improving the utilization of both macro and micro-nutrients, at low input food production and at food security: · Stable isotope 15N techniques to quantify nitrogen fixation in soybeans by rhizobium and to determine the effect of nitrogenous fertilizer on rhizobium N fixation. · Organic C and total N in virgin ecotopes prediction, organic matter decomposition rate, organic matter loss due to cultivation and the influence of climatic factors on organic matter loss. · Nitrogen transformation in soil and N fertilizer evaluation to establish N utilization, ammonia volatilization, denitrification, urea hydrolysis, organic C, N and S mineralization, nitrification inhibitors and the utilization of fertilizer ammonium and nitrate uptake from soil. Most of these ISCW projects were in partnership with the National Chung Hsing University in the Republic of China and the South African University of the Free State. · Methodology development to determine low P contents in soil extracts. · Evaluation of fertilizers e.g. zinckated fertilizers utilization/residue to prevent toxic levels in soils. · Heavy metal contents in dam water sediment, benthic organisms and soils irrigated. · Cu, Zn, Mn and Ni leaching. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 279
· The effect of deteriorating water quality on soil. · Irrigability characteristics of different soils to ensure irrigation effectiveness, to prevent crusting, compaction and erosion and to ensure optimal water utilization. · Aerobically produced sewage sludge compost utilization, composting of household waste, also using fungi as reactor and the utilization of household waste and household waste water in low-cost food production. The latter is a multinational project funded by the European Union. · Evaluation of manufactured byproducts as alternative fertilizers. · Soil biota’s role in the soil nutrient cycle. These include studies and recommendations to the Department of Water Affairs and Forestry on the safe utilization of industrial effluents for irrigation and on the dehydrogenase activities and nitrification properties of such effluents. · Soil fertility monitoring. · The contribution of P and K to the protein contents of soybeans. · Evaluation of the effectiveness of agricultural lime sources and methodology development to determine the lime requirements of acid soils. · Feasibility and suitability studies in view of viable and sustainable food production as well as area, regional and national development. Natural resources information systems and algorithm development to determine aspects like soil potential are fundamental to these studies. ISCW also uses a digital terrain model in view of the country’s topography, to supply information for crop growth (including forests) and climate models. Land use maps are produced to indicate agricultural classes, open-cast mining, urban areas and surface water resources in view of development programmes and monitoring. · Precision farming systems and farm input. · Facilitation of workshops with emphasis on problem analyses. · Project management. · Rehabilitation of physically disturbed soil (e.g. open-cast mining) and water balance studies on mine dump rehabilitation sites, also in view of the stabilization of slime dam slopes, and the characterization and production potential of such land. · Water use efficiency studies including crop water use optimization, water quality - soil-crop relationships, water balance on agricultural and forestry land, irrigation scheduling and low- cost irrigation systems for household food security. · Training of extensionists, subsistence and community farmers as well as the practical training of selected technical students. Selected high technology training e.g. on GIS and land use planning which was presented to SADC delegates. · Food security by spatially establishing the extent of cultivated fields and by predicting yield, by ameliorating climate conditions, by changing micro-climate and by modelling.
Soil degradation Soil organic matter depletion/nitrogen fixation/nitrification inhibitors. Projects are noted under soil management. 280 South Africa
Soil acidity · Methodology development and evaluation in view of determining the lime requirements of soils. · Liming materials effectiveness determinations. · Soil acidity determination, monitoring and training to ameliorate. · High value research and technology by e.g. the ARC-Grain Crops Institute, Agricultural Co- operatives, tertiary institutions, fertilizer manufacturers and lime producers are not recorded in this report. These can be cited in the 1997 Proceedings of the Soil Acidity Initiative (venue Mpumalanga) which can be obtained from either ISCW or the National Department of Agriculture.
Soil erosion · Models are evaluated, adapted and used to predict soil loss under different management practices and to predict the siltation rate of dams. The latest study, with the University of Pretoria as partner, determined the siltation rate of the Lesotho Highland Water Scheme. The major advantage of modelling is that the potential irrigability of an area under specific management practices is assessed which enables the prevention of erosion, · A spatial (remote sensing) Bare Soil Index was developed to inventory eroded and overgrazed areas as well as rural settlements, · Remote sensing inventory and monitoring studies including rainfall probabilities; the impact of drought, biomass burning, floods and bush encroachment on agriculture and on the environment; land cover which forms part of a southern Africa initiative to establish and monitor vegetation impoverishment and denudation to supplement land degradation data and to monitor progressive desertification. Indices like the normalized difference vegetation index (NDVI) enables the deduction of the severity and extent of drought, · Characterization of the irrigability of different soils.
Soil pollution/alkalinity/salinity · Historical, analytical and other data are integrated to monitor salinity on irrigation schemes while multi-spectral videography (low level remote sensing) establishes salinity status. This technique is developed in cooperation with the University of the North. · Irrigation scheduling and the effect of different water qualities on soils. · Soil reclamation programmes · Agriculture is both an efficient utilizer and contributor to pollution as listed under soil management projects. Large volumes of organic composted products are being utilized by particularly vegetable producers. Many composted products contain undesirable bio- available trace elements and micro-nutrients which could accumulate in the soil. Most significant results are that: i) lettuce accumulated the most Co, Cd and Zn, wheat the most Cu, and bean pods the most Ni, ii) higher soil pH, with a few exceptions, decreases the concentration of trace elements in plants, iii) existing methods like the EPA 3050 does not predict soil loading. Plant bio-availability of trace elements therefore needs to be re- established and iv) Hg levels in the Loskop Dam catchment are relatively high. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 281
· Background values for health-related elements in South African soils need to be established as micro-nutrients and other health-related threshold values determined for other continents are not suitable for South Africa’s very distinct geology. Values for I and Se were recently determined for the Department of Health to monitor deficient or toxic levels. Initial investigations and methodology development were in cooperation with the University of Bonn in Germany and much of the latest work is in cooperation with the Universities of Pretoria in South Africa and Ghent in Belgium.
The last paragraph of the Heidelberg Appeal presented to the Heads of State at the conclusion of the UN Conference on the Environment in Rio de Janeiro, 1992 is quoted: “The greatest evils which stalk our Earth are ignorance and oppression and not Science, Technology, and Industry, whose instrument, when adequately managed, are indispensable tools of a future shaped by Humanity, by itself and for itself, in overcoming major problems like overpopulation, starvation, and worldwide diseases”.
SUCCESSFUL CASES OF IMPROVED SOIL MANAGEMENT Conservation tillage systems have been researched by several institutions over many years in South Africa but research application over the long term is limited. The transformation of conventional to conservation cultivation necessitates a complete change in mind frame, perseverance and goal-directed planning, observation, study and adaption. Such a transformation is not a flash solution. Beukes (1992), selected an experimental site previously under ley grass to establish a cultivation trial with grain sorghum. Cultivation practices were no-till and tine till with and without stubble removed and a conventional mouldboard/disc tillage system with stubble retained. The study, over a period of six years, indicated that the no-till and tine systems retaining most of the stubble on the soil surface resulted in an increase in aggregate stability as well as soil C and N. The conventional mouldboard/disc system, despite stubble retainment, did no better than the no-till and tine systems with stubble removed. Statistical analyses showed that apart from cation exchange capacity (CEC), aggregate stability is determined primarily by the C/N value of the soil. The following example of a long-term conservation tillage system in practice, substantiates Beukes’ (1992) findings and those of other researchers. Mr A Muirhead, farming in the Drakensberg area near Winterton in the northern KwaZulu-Natal Province, adopted a conservation tillage system 20 years ago. This system comprises minimum till, stubble mulching and crop rotation with an animal factor. Maize yield over the past two seasons was 5 t ha-1 for dryland and 9 t ha-1under irrigation. Major success factors, according to Mr Muirhead (Pretorius, 1997) are meticulous optimal and betimes weed control programmes, crop rotation (maize and soybeans in Mr Muirhead’s case) to control disease cycles and most important, that all crop residue must stay on the land. The following major advantages culminated from Mr Muirhead’s long term sustainable soil management and cultivation practices: · Soil related. The cycle creates a soil top-layer rich in soil biota and humus. Soil biota increase the decay of stubble and maize residue. Humus increases water penetration and the farmer had no runoff the last couple of years while moisture is conserved for planting. The stubble furthermore ameliorates the impact of raindrops and retains water. Soils inclined to become waterlogged, recover very soon. · Financial. This system has the lowest cultivation energy requirement of all cultivation practices and the highest saving in capital investment for farming machinery. Furthermore, as 282 South Africa
less weed grows in a well managed conservation cultivation system, less weedicide is used over the long term.
Provisa for a successful conservation cultivation are: · a very high level of soil management, · continuous and goal-directed planning, observation, study and adaptations. Time planning, particularly in view of weeding programmes is critical. Fields should be free of weeds, · fertilization programmes in strict accordance with soil analysis and plant food requirements. Soils and not fields are fertilized, · annual liming (2 t ha-1 in Mr Muirhead’s case) as soil acidity must be prevented, · rectifying subsoil acidity in the initial phase of the cycle, · that all crop residue must stay on the land. Fine materials are utilized by farm animals only until the first rain. Thereafter animals are withdrawn to prevent soil compaction. For the same reason, vehicle traffic is restricted and the tyres of cultivation machinery are kept flat. Stubble must cover at least 30 percent of the soil if conservation cultivation is to be effective.
In the 1997 season, this farmer is bringing a further area under vegetation into conservation tillage production.
Although data such as organic matter content is unknown, it is obvious that this conservation tillage system followed for two decades is an example of improved soil management conducive to the sustainable utilization of soil, increased soil productivity and the prevention of many different forms of soil degradation.
INSTITUTIONAL FRAMEWORK AND POLICIES FOR LAND RESOURCES MANAGEMENT South Africa has been confronted by significant political, economic and social changes over the past four years. Policy changes in 1994 with emphasis on the adoption of the Reconstruction and Development Programme (RDP) by the Government of National Unity (GNU), meant that different government departments had to redefine their roles and objectives in line with the RDP framework (Molope, 1997). The RDP framework is cohesive and ensures focus by government departments on GNU goals. The process of policy formulation in the post-election years was characterized by the release of a number of documents setting out the vision and strategies of the new government. Building on the RDP, the National Growth and Development Strategy (NGDS) was released early in 1996 and later in the year, the framework for Growth, Employment and Redistribution (GEAR) was adopted. The NGDS and GEAR strategies are aimed at building the economy to higher levels of growth, development, employment and equity (Molope, 1997). Government custodianship for the natural resources rests primary with the National Department of Agriculture (NDA), the Department of Land Affairs, the Department of Environmental Affairs and Tourism, and the Department of Water Affairs and Forestry. The Department of Arts, Culture, Science and Technology is also concerned as the eight parastatal Research Councils are under its jurisdiction. The Agricultural Research Council (ARC) established in 1992 is one of these Councils. ISCW is one of the 15 ARC Institutes. ARC staff, prior to 1992, were the researchers of the Department of Agriculture. The role of national government departments directly concerned with agriculture are discussed briefly:
Integrated soil management for sustainable agriculture and food security in Southern and East Africa 283
National Department of Agriculture (NDA). Prior to 1993, agricultural institutions in the Republic of South Africa were separated according to race. Following the election of the GNU, the former 10 self-governing and TBVC areas were incorporated in South Africa’s land area and all government institutions amalgamated under the authority of NDA. Nine Provinces were delineated and nine Provincial Departments of Agriculture were established as per constitution. Against the background of the RDP, NDA’s aims are to “ensure equitable access to agriculture and to promote the contribution of agriculture to the development of all communities, society at large and the national economy to enhance income, food security, employment and the quality of life in a sustainable manner”.
Department of Land Affairs (DLA). In South Africa, as in many countries in the world, land has always been a sensitive issue and the former dispensation has left a complex and difficult legacy. The mandate of DLA within the RDP is to address the legacy of apartheid in relation to land distribution and to create security of tenure and certainty in relation to rights in land for all South Africans. The three parts of government’s land reform programme constitute land restitution, land distribution and land tenure reform including farm equity schemes, also redressing current imbalances against women (Dept. Land Affairs, 1996).
These two national departments and the other directly concerned with the natural resource base, work closely together.
Socio-economics issues South Africa faces a future of divergent possibilities. Population pressure on land is the major component in the cycle of unsustainability but if the country can succeed in conserving the natural resource base in the face of continued land pressure, a win-win situation is possible. South Africa is characterized by a mosaic of people with different cultures, lifestyles and eating habits. Furthermore, there is a dualism of Third World and First World, particularly in agriculture with tribal and communal forces on the one and well-established commercial farmers on the other hand. In tribal and communal societies, women are the major farmers. The social environment is characterized by urbanization and demographic changes due to, inter alia, population growth, economical conditions and persistent drought. Social changes are indisputably a major threat to our limited natural resources soil, particularly high potential agricultural soil, and water. Poorer people constitute the vast majority of the population and there is a decided need for development assistance to promote the six NGDS core pillars namely investing in people, creating employment, investing in household and economic infrastructure, crime prevention, poverty alleviation and the creation of safety nets, and transforming institutions of governance. Poverty alleviation should reduce pressure on the environment in meeting short-run subsistence needs. The main causes of rural environmental degradation are fuelwood collection, artificially concentrated population densities especially in the former homelands, which exacerbates poverty and denied access to resources, inappropriate land use and much deforestation. Soil losses stem from the conversion to inappropriate land use and overgrazing (Goodland, 1995).
Direct interventions to reduce inequality, to alleviate poverty directly, and to accelerate environmental sustainability are essential. South Africa’s income inequality is probably the worst in the world (Goodland, 1995) where a full half falls below the generally accepted poverty line and a conservative 20-40 percent of South Africans are unemployed. These selected factors explain why stability in general is so important for South Africa. Stability will secure prudent resource balance and equity as well as security for an investment climate (Goodland, 1995). 284 South Africa
South Africa’s economic growth and development does not rate it a world top. Population growth rate is higher than that of GDP and the standard of living is declining. With structural changes favouring health, housing and education, there is a decline in capital available for research and technology development which could jeopardize critical development projects to create wealth. “Sustainable soil management in agriculture is the use of soils for the production of agricultural goods - to meet changing human needs - while assuring long-term socio-economic and ecological soil functions” (SDC, 1994). SDC (1994) established the following socio-economic indicators for the maintenance and enhancement of soil functions which developing countries should take note of : · maintenance or enhancement of values which embody a sustainability perspective in rural societies who see the role of soil as an essential part of heritage, · complementarity with land use patterns, · maintenance or increase of physical or monetary agricultural production.
As discussed earlier, land tenure and tribal community farmers, have little incentive to cross the subsistence bridge and extensionists have little success as behavioural change is only possible once basic human needs are fulfilled. Furthermore, as these people lack financial security, they do not have easy access to loans. Soil improvement plans and the reclamation of degraded land is therefore largely without reach should the necessary assistance not be provided and should demonstration plots not be established to convince people of benefits to be reaped. ISCW was successful with such a project within a squatter camp (Stanza Bopape) near Pretoria. Demonstration trials and training of selected community leaders made household food security a reality without degrading the soil. This multi-institutional project has the full participation of the community and is managed by the community. The Stanza Bopape project is regarded as role model.
Policy issues Legislative responsibility for the natural resource base is not well-defined between the government departments of Environmental Affairs and Agriculture in South Africa, despite different mandates. This seriously jeopardizes much needed natural resources monitoring and auditing to ensure sustainability and to a certain extent, sustainable development in less developed areas as priorities differ and as government finances are restricted. The objective of most developing countries has been rapid industrialization to create employment and wealth. This has led, according to SDC (1994) to a macro-economic mix and agricultural policies of taxes on export products which lower real income of farmers and hence their capacity to invest in soil maintenance. This, to a large extent is also true for South Africa but with an aggravating factor in view of soil maintenance, namely droughts which are detrimental to cash flow. In the new democratic South Africa, transparency, consultation and participation are on the forefront when it comes to policy development.
The 1995 White Paper for Agriculture sets out a broad new vision for agricultural policy framework that is roughly consistent with the spirit of the new dispensation and the RDP. Agricultural policy formulation is complex because of the proliferation of institutions involved. Following the election of the GNU, former agricultural institutions amalgamated under the auspices of NDA and there are nine Provincial Departments of Agriculture as per constitution. Amalgamation also included the agricultural institutions in former homelands. Policy formulation Integrated soil management for sustainable agriculture and food security in Southern and East Africa 285
also involves the broader sector as much as possible. Agricultural policy themes presently considered by various working groups are: · sustainable resources utilization with emphasis on incentives e.g. soil conservation works versus incentives for farmers to utilize land more effectively and sustainable. The FAO definition of sustainable development and criteria for sustainable agriculture and rural development (SARD) are used as basis (Molope, 1997), · food security focusing on household security, · trade, to consider the advantages and disadvantages of different trade regimes for various agricultural sub-sectors within the context of GATT, SACU and SADC, · drought and disaster management focusing on guidelines for distinguishing natural disaster from normal risk situations. In the past, interventions on drought and disaster were reactive and poorly rationalized, · cooperatives, to determine how to support the establishment of new cooperatives to meet the needs of emerging and disadvantaged farmers, · credit and finance, to carry forth the terms of reference of the Commission of Enquiry into the Provision of Rural Financial Services, · farmer support services, which can be divided into human resource development, research and extension, · rural tenure system. The Interim Protection Act lapses by the end of 1997 by which time far reaching and long term measures should be in place, including a tenure security law.
Environmental, political, social and economic issues are inextricably connected and full cognizance is taken of these interaction in framing agricultural policy. NDA correctly believes that the responsibility for achieving sustainable natural resource utilization should be underpinned by the ethic of caring and must be shared by all sectors of South African Society (Molope, 1997). These include central and national governments, local authorities, organized labour, commerce and industry, community groups, civic associations, families and individuals.
PROPOSALS OF PROGRAMMES FOR IMPROVED SOIL MANAGEMENT AND PRODUCTIVITY ENHANCING Two programmes are proposed by South Africa within the framework Integrated Soil Management for Sustainable Agriculture and Food Security in Southern and East Africa. The first programme, on organic matter depletion, is aimed at realizing the soil potential in former South African homelands in view of sustainable rural development, job and wealth creation, food security and sustainable soil productivity. The second programme, also aimed at developing rural areas, concerns the development of a land information system with soil fertility and erosion as main criteria. Such a system is a basic requirement for sustainable land use planning and rapid but non-destructive agricultural development. Both programmes are multidisciplinary and cross- sectoral.
286 South Africa
Project 1. Realization of Soil Potential: a Recipe for Rural Development in the Former Homelands Soil acidity is a major factor limiting agricultural production in South Africa. Naturally acid soils, normally associated with areas of high rainfall, occur over a diverse spectrum of climatic conditions and have been identified in the Northern Province with an average annual rainfall from as low as 500 mm, as well as in the Mpumalanga, KwaZulu- Natal, Eastern and Western Cape Provinces where average annual rainfall is over 750mm. In the communal agricultural areas of South Africa (former homelands), with a surface area of approximately 10 million ha, rainfall and rainfall pattern should favour crop, horticultural and livestock production and development, as well as pasture production. Pasture production could furthermore be upgraded significantly by introducing legumes which would contribute substantially to sustainable agro-ecosystems.
Approximately 3 million of the 10 million ha is potentially arable land. The major portion of medium to high agricultural potential land is found in the former Ciskei, KwaZulu and Transkei areas. These three areas with roughly 1.2 million ha high potential land are blessed with a mean annual rainfall exceeding 700 mm. However agricultural production potential is seriously jeopardized by excessive soil acidity. Soil pH favourable for agricultural production should ideally be 6.5 while this area is characterized by a pH of 4.5 and even lower (100 times more acid than ideal). In 1990, population density was estimated as 153 persons per square kilometre in KwaZulu, 69 in the Transkei and 97 in the Ciskei compared to an average of 25 in the former Republic of South Africa. This emphasizes the urgent need for economic development in the former homeland areas, in which agriculture could provide the driving force for development. Extreme rural poverty in these areas has prevented such development being initiated locally. Strong government support for such development is essential. In terms of the Constitution the National Department of Agriculture is the custodian of these yet undeveloped natural resources. In view of the agricultural potential, surface area and population density in the former Ciskei, KwaZulu and Transkei, this document focuses on these areas without disregarding the importance of the other former homelands.
Technology and norms exist to facilitate the amelioration of soil acidity to pH levels favourable to optimum crop and pasture yields. A pH of 6.5 is optimal for macro and micro- nutrient uptake, nitrogen fixation, soil microbial activity and the like, all essential for sustainable production, optimal yields, and vegetation cover. For example, changing the pH from 4.5 to 6.5 will increase maize yields from ½ to 8 tons per ha on high potential soils. In the areas of high potential (60%) of the former Ciskei and Transkei, potential income from maize production could escalate from R300 to R4 800 per ha. Acid soils are extremely susceptible to water erosion as a result of crust formation. This partially explains the high levels of land degradation in former homeland areas. Soil acidity and unsustainable land use practices are the major causes of desertification.
Proposal The amelioration of yield-limiting soil acidity in former homeland areas by the large scale liming of soils with agricultural potential is proposed. The introduction of legumes as nitrogen suppliers as well as practices to sustain and increase the soils organic matter contents, are fundamental to the success of this project. This will make it possible for the agricultural production potential of such areas to be realized which will subsequently stimulate agricultural development, the establishment of small, medium and micro-enterprises, wealth creation and employment by means of the following: Integrated soil management for sustainable agriculture and food security in Southern and East Africa 287
· the emergence of productive, commercially viable and sustainable smaller scale farm enterprises, · the exploitation of existing lime deposits in the affected areas by local black entrepreneurs, with concomitant job creation. This would substantially reduce the cost of lime in such areas while retaining money in the local economy, · the creation of transport enterprises to move lime to the areas where it is required, · the creation of enterprises to spread and incorporate lime on arable soils, · the distribution of lime on high potential arable land as well as lower potential rangeland soils suitable for the introduction of pasture legumes, · seed supply and eventually production to upgrade rangeland, · the development of storage and marketing infrastructure for increased crop, horticulture and livestock production (and eventually exports), · agri-business development (value adding).
In order to optimally utilize the increase in production potential due to liming the following services will have to be put into place by resuscitating Provincial laboratories (e.g. Umtata) as well as the provision of targeted training services to empower people: · soil analytical services to establish liming and other nutritional requirements on a locality/soil specific basis, · extension services to provide the knowledge/expertise base to enable communal and tribal farmers to optimally utilize the newly created opportunities, · small business training for the newly established entrepreneurs, · planning of programmed infrastructure improvement, · creation of local fertilizer and micro-nutrient distribution enterprises.
Among the many advantages to be derived from this project will be: · rapid and visible economic development within all affected areas, · a highly significant increase in entrepreneurial and employment opportunities and establishment of agri-business (SMMEs), · significant improvement in community health through improved nutrition and elimination of the endemic animal and human health problems associated with soil acidity e.g. micro- nutrient deficiencies and toxicities and the association thereof with aspects such as high incidence of oesophageal cancer in humans and general debilitation of livestock, · improved rural infrastructure and the effective usage of presently under-utilized assets such as the existing rail system for lime, fertilizer and product distribution and irrigation systems at present in disuse, · a sound basis for an agriculture based regional development programme in which the Outreach Programmes of Resource Centres can be optimally deployed. 288 South Africa
Synopsis of Project The Realization of Soil Potential programme will have a radical and sustainable beneficial effect on agricultural production in presently depressed areas. This radical effect will cascade down into all those peripheral areas involved in supplying inputs, processing and marketing outputs and creating and maintaining appropriate infrastructure. The effect on job creation, economic development, food insecurity, environmental sustainability etc. will be greater than that of any existing development project, including the very successful “Working for Water” programme. An estimate of the area of high and medium potential arable soil in the former Ciskei, KwaZulu and Transkei to be brought into effective production is 1.2 million ha. A 16 fold increased maize production will introduce R5 760 million into the rural economy, utilizing maize as a conservative criterion of increased production. Higher value crops will gradually be introduced, thus increasing the agriculture derived benefits. This area is especially suitable for citrus, vegetables, grapes and other temperate crops with export potential.
The introduction of appropriate pasture legumes on more marginal areas would also significantly improve carrying capacity and animal production and will confer similar benefits on those communities largely dependent on outputs from such areas. Export orientated production will serve as a catalyst for port and transport infrastructure development. The lime required for the amelioration of soil acidity in the Ciskei, KwaZulu and Transkei areas will be approximately 2.4 million tons (2 tons per hectare) per year, spread over 5 years. Maintenance requirements after that period will be 0.6 million tons per annum. The cost of the liming exercise, based on present commercial costing (R150 per ton, including transport, spreading and incorporation) will be R360 million for five years or R72 million per annum, and thereafter R90 million per annum. The development of local lime sources will stimulate local developments and job creation. Should medium potential land (40%) be excluded from the liming programme, the cost of liming, spread over 5 years would be R216 million for the 720 000 ha high potential land followed by R54 million per annum for maintenance applications.
In ensuring that the benefits of liming are effectively utilized, the provincial departments of agriculture together with the NDA, the ARC and other relevant organizations, will have to ensure that : · financial support services are available to small farmers for fertilizer, seed and implement requirements, · service infrastructures such as processing, storage and marketing are brought into place, · technology transfer mechanisms to extensionists and from them to farmers and others are effectively put into place, · support to SMME entrepreneurs in terms of finance and training are available, · local and provincial development plans are developed in concert with the deployment of the Realization of Soil Potential programme, · problems related to the apportionment of land use are timeously addressed.
The successful implementation of the programme will require the following, amongst others: · the development of an integrated project proposal by the NDA and ARC, in concert with PDAs, locally based universities and other possible stakeholders, for submission to international donor agencies and national sources of development funding, Integrated soil management for sustainable agriculture and food security in Southern and East Africa 289
· detailed soil mapping, · Mapping of lime deposits and computation of reserves, · computation of lime and nutrient requirements per soil type per locality and mapping thereof · delineation of areas to be limed and prioritization thereof · planning of liming and fertilization operations, annual programmes, dumping points, job creation requirements, etc., · determination of optimal crop production and pasture improvement options and mapping thereof · appointment of area project managers to co-ordinate distribution and incorporation of lime and the integration thereof with existing and improved production systems, · establishment of centres where recommended options can be demonstrated on an ongoing basis. Such centres can be bases from which training and other technology transfer exercises can be launched.
Recommendation In order to present a project or programme proposal capable of drawing international and national funding the following is proposed: · That NDA commissions the ARC to draft a detailed proposal in which the benefits in terms of development, poverty alleviation, job creation, long term sustainability, etc., the steps to be followed and the financial and human resources to be employed are clearly set out. The ARC, with the support of the NDA, will liaise with PDAs and others in order to ensure that the final proposal is acceptable to stakeholders. · The NDA will endorse the final proposal when it is satisfied with it and facilitate the accessing of the necessary funding. · When funds enabling the initiation of the programme have been committed, a Project Steering Committee (PSC) on which the NDA, ARC and PDAs are represented, together with others who can make a significant contribution, will be appointed. · The PSC will appoint a National Project Manager who will be supported by Area Project Managers and Area Project Committees. · The project will be implemented by starting with any necessary refinement of resource information, detailed integrated planning per reasonably homogeneous area, initiation of lime production and finally, leading into the introduction of improved crop production systems and pastures.
Project 2. The Development of a Land Information System for Developing Areas with Erosion Risk and Soil Fertility as Main Criteria The 10 former homelands of South Africa are characterized by high population growth, poverty, accelerated soil degradation, increasing pressure on land, an attitude not conducive to sustainable soil management, and the lack of incentives and means to practice sustainable soil management within tribal, communal or land tenure systems. Most of the former homeland areas have medium to high agricultural potential which needs to be developed in view of food security and wealth creation. To facilitate sustainable land use planning and rapid agricultural development in 290 South Africa
harmony with soil potential and to enable the improvement and maintenance of soil productivity, the development of a land information system is a basic requirement. Much and various types of data and statistics are available but is to no avail if not manifested in sustainable soil productivity and the subsequent prevention of soil degradation.
The human factor is critical in the manifestation process, particularly in the former homelands, where tribal culture differs vastly for that of the western world. South Africa’s highly complex mantle is most vulnerable to the loss of productivity and soil degradation of all forms. Soil erosion is a particular threat to soil productivity and the organic carbon contents is rapidly declining throughout most of the country. A pilot study in the Nsikazi development area (8,000 ha) of the former KaNgawane to establish areas suitable for crop production, revealed that the organic matter contents has declined seriously, that P is seriously deficient and that the area is highly susceptible to gully erosion and moderately to sheet and rill erosion. The fairly deep sandy soils have a low clay contents on granite bedded material, and the annual rainfall is 680 mm which implicates at least medium to high agricultural potential. The area is characterized by communal farming, mainly with cattle while the major crop cultivated is maize. Maize production is sub-optimal. Remote sensing techniques (satellite imagery), supplemented by field work, was used to determine the status of this pilot area. Existing natural resources data was used as the major source of ground truth. The pilot study re-emphasized the desperate need for a land information system (LIS) which will enable rapid but sustainable development and optimal agricultural production.
Proposal Rapid but sustainable agricultural development in the former homelands is essential to halt the downward spiral of the poverty trap and to ensure sustainable socio-economic growth in South Africa. The primary objective of this programme is to develop a digital LIS for developing areas in view of land suitability and soil productivity assessments to facilitate sustainable development. Immediate aims are to: · determine the current status of natural resources (degradation, soil-water and nutrient status) by means of remote sensing data and field verification, · determine the social and economical factors influencing land use planning in the district, · determine the use of digital terrain data (DTD) in soil mapping (refining of land type data) and soil loss modelling, · use GIS based erosion models (adapted for developing areas) in predicting erosion risk, · determine and quantify soil nutrient status and balances, · use land evaluation models and techniques e.g. CYSLAMB and ALES for land suitability ratings (development of settlements, crop production and grazing), · develop and implement an integrated GIS based Land Information System at a 1:50 000 scale.
Research activities · A pilot study area of approximately 30 000 ha will be selected in the developing areas of South Africa. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 291
· The study will be initiated by Provincial contact with those involved in land use planning, GIS and extension. Contact will then be expanded to communities concerned. This will be preceded by contact with the National Department of Agriculture and the Department of Land Affairs. · The initial phase will also be used to determine what relevant information/data is available, to evaluate the data/information, and to investigate compatibility with ISCW’s national natural resources systems. · The current status of the natural resources soil and vegetation will be determined by means of Landsat TM and SPOT satellite data. This type of data proved to be a valuable source of land use information for GIS. On-screen digitizing methods will be used to extract the information from the satellite data. Verification of results will include ground and aerial surveillance. · Close collaboration with agricultural extension and headmen will be necessary to determine the social and economical factors that must be taken into account in developing practical and feasible land use strategies. This information will be integrated into the GIS. · Digital terrain data (DTD) at various resolutions will be used to create digital terrain models (DTM). The DTMs will then be used to produce digital terrain unit maps (DTUM). Integration of DTUM and available land type information to produce soil maps, that can be used in soil loss and land evaluation models, will be investigated. This is a very important part of the project since land use planning strategies are not viable without reliable soil information and semi-detailed soil maps are not always available for developing areas. · Erosion risk areas will be determined by means of a GIS based erosion model adapted to conditions in developing areas. The following information will be integrated into the model: i) soil erodibility (land type, geology, DTM and field trails), ii) slope angle (DTM), iii) slope length (DTM), iv) rainfall erosivity (ISCW AgroMet database) and various other terrain morphological parameters. Integration of erosion risk data with current land use and land management information (remote sensing data) will give an indication of actual erosion or soil loss. The most challenging part of this phase will be the production of a soil erodibility map. This will include rainfall simulation trials on different soils (ecotopes) under different land use practices: · determine soil-water balances for different ecotopes as a function of land use (crop and forage production) practices, · determine and quantify soil nutrient status and balances of the area. Soil and plant samples will be collected and analysed (physical and chemical). This information will also be used in the production of a soil suitability map with the risk of soil degradation, soil fertility and soil- water status as main criteria. Inputs and removal of nutrients from the area will be quantified, · the following step in the project will be to integrate relevant information into a land evaluation model. Different land use scenarios will be evaluated. During this stage experts in crop production and grazing will be consulted, · the final step will be to develop and implement an operational GIS based Land Information System. This system will have to be user friendly and easily accessible for updating purposes. Training of Provincial land use planning and extension staff will form an important part of this stage. 292 South Africa
Products planned · Recommendations on the required data inputs (soils, terrain, climate, social and economical indices) for land use planning at a 1:50 000 scale, · Practical, scientifically based and verified: i) status of the natural resources, ii) soil degradation management,, iii) soil-water and nutrient resources and iv) crop production, · A user friendly GIS based Land Use Planning Decision Support System, · Although the system will be developed for decision makers at district level, small scale farmers will benefit from this project in the sense that the restrictions they have to deal with will be revealed. Improved farming systems can then be introduced by extensionists through active involvement of the community.
Duration of pilot project 18 months
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Eswaran, H., Reich, P. & Beinroth, F., 1997. Global distribution of soils with acidity. In A.G. Moniz, A.M.C. Furlani, R.E. Schaffert, N.K. Fageria, C.A. Rosolem & H. Cantarella (eds). Plant-soil interactions at low pH: Sustainable agriculture and forestry production. Proc.4th International Symp. On Plant-Soil Interactions, Belo Horizote, Minas Gerais, Brazil. Brazilian Soil Sci. Soc. 159-164. Farina, M.P.W., 1997. Subsoil acidity and its management in South Africa. Proc. Soil Acidity Initiative (venue Mpumalanga). Ermelo. In Press. Fourie, M.C.C. 1997. Soil acidity : An Agricultural Co-operative perspective. Proc. Soil Acidity Initiative (venue Mpumalanga), Ermelo. In Press. Greenland, D.J., Bowen, G., Eswaran, H., Rhodes, R. & Valentin, C., 1994. Soil, water and nutrient management research - a new agenda. IBSRAM Position Paper. UNDP/IBRD. Goodland, R.J.A., 1995. South Africa: Environmental sustainability and the empowerment of women. South African Issues. International Association of Impact Assessments. The World Bank. 59 pp. Harrison, P., 1987. The Greening of Africa. Breaking through in the battle for land and food. International Institute for Environment and Development - Earthscan. Papadin Grafton Books, London. 380 pp. IBSRAM, 1995. Highlights 1995. International Board for Soil Research and Management. Mr Opart Sathirakel Publisher. 17. Lean, G., Hinrichsen, D. & Markham, A., 1990. WWF Atlas of the environment. Arrow Book. London. Luiz, J.M., 1994. Constraints facing the socio-economic transformation in South Africa. Africa Insight 24(4), 230-235. Molope, M.B., 1997. Overview of the National Department of Agriculture’s agenda and policy. Proc. Soil Acidity Initiative (venue Mpumalanga). Ermelo. In press. Okigbo, B., 1990. Opening address. Land management and local participation in Africa. Proc. Workshop. Denmark. Danish land development services. Pinstrup-Andersen, P., 1982. Agricultural research and technology in economic development. Int. Food Research Institute, Washington D.C. 176-190. Longmar. London. Pretorius, L., 1997. Bewaringsbewerking vra vasbyt. Landbouweekblad No. 989. 10-12. Robertson, G.A., 1987. Soil management for sustainable agriculture. Western Australia Dept. Agric. Tech. Report No. 95. Rwomire, A., 1992. The political economy and famine. An African perspective. Africa Insight 22(2), 142-145. Schaffert, R.E., 1997. Sustainable agriculture on acid soils - the challenge. Plant-Soil interactions at low pH: sustainable agriculture and forestry production. Brazilian Soil Sci. Soc. Schoeman, J.L. & Scotney, D.M., 1986. Agricultural potential as determined by soil, terrain and climate. Proc. Conf. 11 Asst. Sci. and Tech. Soc. Sth. Afr., Johannesburg. Schultze, R.E., Kiker, G.A. & Kunz, R.P., 1993. Global climate change and agricultural productivity in southern Africa: Thought for food and food for thought. Agri Review, Standard Bank of South Africa. Scotney, D.M., 1987. Crop production and fertilization in the RSA. A futuristic view. Fert. Soc. S.Afr. J. 1, 31-41. Scotney, D.M. & Mcphee, P.J., 1990. The dilemma of our soil resources. Proc. National Veld Trust Conference : The Conservation status of South Africa’s agricultural resources. National Veld Trust. 294 South Africa
Scotney, D.M. & Van der Merwe, A.J., 1992. Irrigation : long-term viability of soil and water resources in South Africa. Proc. Sth. Afr. Irrig. Symp. 50-60. Scotney, D.M., Volschenk, J.E. & Van Heerden, P.S., 1990. The potential and utilization of the natural agricultural resources of South Africa. Dept. Agric. Devel., Pretoria. SDC, 1994. Sustainable management of agricultural soils. Swiss Development Cooperation, Berne. Sielaff, C., 1997. World food demand and supply by 2025. Paper presented at Value-added Agriculture Congr. Oct. 1997, Pretoria. Skeen, J.B., 1997. President’s Report. Fert. Soc. S.Afr. J. 3-10. Smith, D.J.C., Van Rooyen, G.I., Geldenhuyis, I.S., Vosloo, W.A. & Le Roux, P.A.L., 1990. Verslag van die komitee vir die ontwikkeling van ‘n voedsel- en voedingstrategie vir suidelike Afrika. Sentrale Owerh. Spurling, A., Poe, T.Y., Mkamango, G. & Nkwanyama, C., 1992. Executive Summary. Agricultural research in Southern Africa. A framework for action. World Bank Discussion Papers. Afr. Tech. Dept. Series No. 184. The World Bank. Strydom, B.W. & Wassermann, V.D., 1984. Huidige en potensiële bydraes deur biologiese stikstofbindingsisteme tot die Suid-Afrikaanse landbou. Proc. Nitrogen Symp., Tech. Commun. No. 187, 80-86. Govern. Printer Pretoria. Tanner, P.D., 1997. Soil acidity and the mining industry. Proc. Soil Acidity Initiative (venue Mpumalanga). Ermelo. In Press. Thirtle, C., & Van Zyl, J., 1993. Explaining total factor productivity growth and returns to research and extension in South African commercial agriculture, 1947-91. Research project report, Univ. Pretoria. Van der Merwe, A.J., 1992. Die vermoë van ons grondhulpbronne om aan toekomstige voedselvoorsieningsbehoeftes te voldoen. Paper presented at South African Agricultural Union AGRICON Congress, Pretoria. Van der Merwe, A.J., 1994. Agricultural productivity and the challenge of food security. Paper presented at SAFFOT Conf., Cape Town. Van der Merwe, A.J., 1995. Wise land use: the basis for sustainable growth and development in South Africa. Proc. ARC-ISCW Wise Land Use Symp. 2-8. ARC-ISCW. Van Marle, J., 1981. Resources for agricultural development in Southern Africa. Fert. Soc. S.Afr. J. 2, 17-22. Von Uexkull, H.R. & Mutert, E., 1995. Global extent, development and impact of acid soils. In R.A. Date, N.J. Gudon, G.E. Rayment & M.E. Probert (eds). Plant-soil interactions at low pH: principles and management 5 - 19. Kluwer Academic Publishers, The Netherlands. Veerhoff, M. & Brummer, G.W., 1993. Formation of poorly crystalized weathering products in strongly to extremely acid forest soils. Z. Pflanzenernähr. Bodenk. 156, 11-17. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 295
Tanzania
COUNTRY FOOD PRODUCTION AND REQUIREMENT The population of Tanzania is expected to reach 100 million in the second half of the twenty-first century. In 1982, the population was 19.1 million; in 1989 the population was 23.0 million and is likely to reach 39.1 million in the year 2000 and 83.8 million in the year 2025. In the year 1980, the rural population in Tanzania represented 87% of the total population, in 1989 it was 80% and in 2010 it is expected to be 65% and by the year 2025 it is expected to decrease to 55%. The total demand for food and non-food commodities in Tanzania and in the region is expected to have increased by more than three and half times by the year 2025. Although the proportion of the rural population is likely to decrease to 55% by that time, the absolute size of the rural population is expected to increase from 10.5 million in 1989 to 46.1 million which is more than four-fold increase (Table 1). Available information on land use patterns in Tanzania shows that Tanzania is diverse and each region has its own unique mix of crops and animals. Many of the crops grown have a national spread while others are confined to certain regions (Tables 2, 3, 4 and 5).
TABLE 1 Potential rainfed population supporting capacity at different input level and population projections of 20 regions Regions Land Cultivable Potential population Population area area supporting capacity (million) (000 ha) (000 ha) Low Interm. High 1989 2000 2025 plateau Arusha 8 231 1 104 1.05 4.35 15.16 1.39 2.35 5.03 6.00 Coast 3 241 1 049 1.00 4.14 14.40 0.66 1.12 2.40 2.86 Dar es Salaam 139 32 0.03 0.13 0.44 1.40 2.37 5.08 6.06 Dodoma 4 131 410 0.39 1.62 5.63 1.27 2.15 4.60 5.49 Iringa 5 686 3 030 2.88 11.94 41.59 1.24 2.10 4.50 5.37 Kagera 2 839 1 509 1.43 5.95 20.71 1.36 2.30 4.92 5.88 Kigoma 3 704 1 878 1.78 7.40 25.78 0.88 1.49 3.19 3.81 Kilimanjaro 1 331 233 0.22 0.92 3.20 1.14 1.93 4.13 4.93 Lindi 6 605 2 820 2.68 11.18 38.71 0.66 1.12 2.40 2.86 Mara 1 957 346 0.33 1.36 4.75 1.00 1.69 3.62 4.32 Mbeya 6 035 2 678 2.54 10.56 36.76 1.52 2.57 5.50 6.57 Morogoro 7 080 4 713 4.47 18.58 64.70 1.26 2.13 4.56 5.44 Mtwara 1 671 892 0.85 3.52 12.25 0.91 1.54 3.30 3.93 Mwanza 1 959 973 0.92 3.84 27.86 1.90 3.21 6.87 8.20 Rukwa 6 864 4 321 4.10 17.03 59.32 0.71 1.20 2.57 3.07 Ruvuma 6 350 5 218 4.95 20.57 71.63 0.80 1.35 2.89 3.45 Shinyanga 5 078 1 362 1.29 5.37 18.70 1.82 3.08 6.60 7.87 Singida 4 934 6 005 0.57 2.38 8.30 0.81 1.37 2.93 3.50 Tabora 7 615 2426 2.30 9.57 33.31 1.06 1.79 3.83 4.57 Tanga 2 681 851 0.81 3.35 11.68 1.31 2.22 4.75 5.67 Total 88 129 36 600 34.60 143.70 500.4 23.13 39.13 83.80 100.0 Source: Planning and Marketing Division
S. Nyaki, Senior Scientific Officer, National Soil Service, Tanga A.L. Mawenya, Project Manager, Scapa 296 Tanzania
TABLE 2 Area (000 ha) under food crops in 1988/89 Regions Maize Millet Paddy Bean Bananas Cassava Sw/Pots Total Arusha 155.2 47.1 1.3 53.5 11.2 1.6 1.2 311.1 Coast 13.9 8.6 20.7 3.2 2.6 36.5 0.5 86.0 Dar Es Salaam 1.8 0.1 3.0 0.2 2.0 5.5 1.2 13.8 Dodoma 60.2 194.0 0.4 6.8 0.5 0.9 3.0 265.9 Iringa 266.9 23.8 0.8 53.8 0.5 4.4 357.7 Kagera 66.9 7.7 3.4 70.7 127.6 85.0 11.2 372.5 Kigoma 49.7 1.7 6.9 25.9 5.7 14.7 0.8 105.4 Kilimanjaro 47.3 6.6 3.8 22.6 47.5 5.6 0.6 134.1 Lindi 19.2 26.2 10.5 13.1 29.9 98.9 Mara 25.0 39.7 1.5 3.2 5.3 42.9 12.4 129.2 Mbeya 168.1 24.8 32.5 46.2 26.9 13.9 15.4 328.0 Morogoro 125.4 30.9 64.0 13.7 4.9 32.3 0.5 271.7 Mtwara 45.5 54.9 27.5 14.3 89.9 0.2 232.2 Mwanza 122.0 57.2 61.5 47.6 1.7 144.8 55.3 490.1 Rukwa 86.8 48.8 15.2 44.7 0.6 36.8 8.0 241.0 Ruvuma 138.7 7.3 24.6 22.3 0.4 53.2 0.6 709.7 Shinyanga 298.2 124.3 79.5 86.7 54.3 66.7 197.4 Singida 52.6 94.5 1.4 6.0 36.3 6.6 300.3 Tabora 146.0 42.2 37.2 31.1 26.4 17.4 155.0 Tanga 90.4 0.6 6.7 7.3 12.9 36.7 0.2 Total 1,980 841.2 402.4 572.9 249.8 746.9 206.1 5,047.0 Source: National Food Security Unit
TABLE 3 Estimated production (000 tones maize equivalent) of food crops in 1988/89 Regions Maize Millet Paddy Beans Wheat Pineapple Cassava Arusha 304.7 53.1 2.9 52.4 73.5 30.8 3.3 Coast 19.1 7.8 1.9 2.7 0.0 7.2 76.7 Dar Es Salaam 0.9 0.0 1.9 0.0 0.0 0.0 16.3 Dodoma 72.0 150.9 0.3 3.8 0.0 0.2 2.0 Iringa 444.7 19.9 0.8 46.3 8.3 0.0 1.1 Kagera 93.7 6.9 3.1 62.4 0.0 351.6 178.5 Kigoma 71.7 1.1 1.3 25.5 0.0 15.8 30.9 Kilimanjaro 85.9 9.9 9.2 20.6 0.0 130.9 11.9 Lindi 24.2 27.1 6.9 10.9 0.0 0.0 62.9 Mara 28.5 26.8 1.4 1.8 0.0 14.5 88.4 Mbeya 267.4 27.1 39.4 40.3 0.2 74.2 29.2 Morogoro 185.5 33.0 61.0 8.2 0.0 13.5 67.9 Mtwara 61.5 57.1 26.8 14.5 0.0 0.0 188.8 Mwanza 143.1 37.6 85.3 38.3 0.0 4.8 304.9 Rukwa 160.1 58.3 20.5 45.8 0.1 1.5 77.2 Ruvuma 264.5 6.9 20.1 19.3 0.0 1.0 111.7 Shinyanga 444.1 111.0 112.1 88.7 0.0 0.0 113.9 Singida 66.2 112.4 0.5 4.7 0.0 0.0 76.3 Tabora 246.0 46.2 30.1 27.0 0.0 0.0 55.5 Tanga 141.6 0.7 8.0 9.2 0.0 35.5 77.0 Total Food 3 125.5 803.8 833.4 522.5 82.1 682.6 1 573.5 Source: National Food Security Unit
Therefore, the vast agro-ecological resource base is well reflected in the current land use patterns (Table 6). Sixty-four agro-ecological zones have been identified for the whole country based on a scale of 1:2 000 000. The main criterion used in the zoning is the temperature and moisture regime during the growing period. The dependable growing period varies from less than 2 months to 8 - 10 months. The main agro-ecological zones along with the associated farming systems in the northern zone of Tanzania are shown in Table 6. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 297
TABLE 4 National aggregate food production (000 tonnes) Year Maize Paddy Wheat Sorghum Pulse Cassava Potatoes Bananas Millets 1980/81 1 939 200 90 705 310 1 458 n.a. n.a.* 1982/83 1 651 350 58 793 297 1 967 n.a. n.a. 1984/85 2 093 427 83 1 024 510 2 052 n.a. 774 1986/87 2 359 644 72 954 251 1 709 336 792 1988/89 3 125 720 97 804 385 1 948 337 743 1990/91 2 332 624 84 750 425 1 566 291 750 1992/93 2 282 641 59 929 406 1 708 260 800 1994/95 2 567 723 73 1 250 378 1 492 451 651 1996/97 1 831 550 78 845 374 1 528 372 411 Source : MAC-FSD * Data not available
TABLE 5 Total land suitability for grazing, land used for grazing, area infested with tsetse and distribution of animal population in 1984 Region Land fit for Land used for Land infested Animal population grazing grazing with tsetse Cattle Sheep Goats Arusha 12 225 11 000 1 803 1 855 758 1 231 Coast 567 144 302 88 5 19 Dar es Salaam nil nil nil 6 1 10 Dodoma 3 134 1 922 934 1 000 170 540 Iringa 3 689 2 459 480 92 197 Kagera 628 324 177 365 54 344 Kigoma 1 510 305 603 62 36 167 Kilimanjaro 418 377 65 408 221 438 Lindi 2 322 82 1 009 6 9 13 Mara 8 636 3 455 32 970 216 394 Mbeya 2 095 1 271 889 901 101 171 Morogoro 1 644 303 2 305 333 53 140 Mtwara 398 370 175 15 15 85 Mwanza 413 380 108 1 357 250 570 Rukwa 2 622 152 337 392 21 75 Ruvuma 1 800 246 187 39 20 138 Shinyanga 3 991 1 386 1 054 940 487 477 Singida 2 327 1 416 1 776 1 882 280 472 Tabora 28 3 278 926 174 310 Tanga 1 579 489 1 184 473 117 258 Total 50 036 26 084 12 864 12 500 3 080 6 450 Source : Planning and Marketing Division, MALD
Important food crops grown are maize, millet, rice, sorghum, wheat, beans sweet potato, cassava banana and plantain. In 1988/89, the total cultivated area for these crops was just over 5 million ha and the total production (in maize equivalent) was 7.5 million tons. The total estimated consumption of food (in maize equivalent) was 5.9 million tons that represented a surplus of approximately 1.6 million tons. Other important crops are oil seed crops and nuts (groundnuts, sesame, soybean sunflower, and coconuts) cotton, tobacco, coffee, tea, cashew, sugarcane, pyrethrum and sisal. The total area under these crops in 1988/89 was 1.3 million ha. There are approximately 50 million ha suitable for grazing of which 26 million ha are currently been utilized and 12.9 million ha are infested with tsetse (Table 5). In qualitative terms one can anticipate that agricultural production will become more intensive on favorable soils in order to meet market demand. It is also anticipated that as the yield of staple food crops increase the area needed for their cultivation will decrease. The remaining areas are likely going to be used for the production of vegetables and fruits. 298 Tanzania
TABLE 6 Farming systems zoning for the Northern Zone of Tanzania and Kondoa District Farming system Agro- Crops grown Fs Name ecological Major Minor Zone Zone N-2B Intermediate dry lowlands; E2 Maize, Beans pigeon Sorghum, finger millet and maize legumes peas and sunflower cassava N-2C1 Intermediate lowlands; E1 Maize, beans rice, and Spices, coffee cassava, maize beans tree crops some banana sorghum, coconut, cotton mango N-4C1 Intermediate highlands; N4, N5, Coffee, banana, maize Cassava, sugarcane, cloves maize beans systems E12, N1 and beans cardamom sorghum pastures N-4C2 Intermediate lowlands; N1 Maize beans and Coffee, banana, cassava, maize legumes pigeon peas sorghum finger millet and fruit trees N-4C3 Large scale wheat N1 Wheat and barley N-4D Highlands ; coffee banana E12, N4, Coffee banana and Horticultural crops, maize, N5 intensive dairy finger millet, beans yams round potatoes and sweet potatoes N-2A, Arid to semiarid lowlands E12, N3, Pastoralist, bushlands N-3A N6, N7, and gameparks N-3B N8, P1, and P2 N-2C2 Large scale sisal E1 Sisal
Tanzania has approximately 36.6 million ha of rainfed cultivable land Table 1)and 5 million ha of potential irrigable land. Tanzania has a future (year 2000 and beyond) surplus support capacity of 48 to 105 million persons at the intermediate level of inputs (approximately 10 to 20 million tons of food grain) and 400 to 461 million persons at the high level of inputs (approximately 100 million tons of food grain). According to estimates made by the Ministry of Agriculture and Livestock Development (MALD) in 1988/89 by the National Food Security Unit, by the year 2000, 13 regions will not be able to meet their food needs from regional rainfed production at low levels of inputs and by the year 2025 17 out of the 20 regions will belong to this deficit category.
EVOLUTION OF PER CAPUT CULTIVATED LAND AND TRENDS IN CEREAL CROP YIELDS Food crop production contributes 34% of total GDP while export production contributes 5%, livestock 18%, fishing and hunting 4%, and forestry 1%. The whole of the agricultural sector accounts for 61% of the country production. An example of land area and production trends for two regions in Tanzania (Arusha and Shinyanga ) is presented in Table 7. Although there are some considerable variations from one year to another for both regions, which could be attributed to seasonal variations in weather conditions as well as differences in production potential between the two regions, it should be noted that the contribution of subsistence farming is only estimated using indirect methods while the informal sector is dominated by agricultural production which is not recorded. The quality of the production data has also deteriorated further because of the declining role of state owned marketing companies. A large amount of food crops and export crops is smuggled out of the country. The production trends for the food crop sector has been very responsive to changing policies which may have direct or indirect effects on soil degradation. An indication of the responsiveness of the agricultural sector to changing policy environment is the GDP. growth in the sector which increased from about 2% per year in 1981/82 to around 5% in 1986 - 1982. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 299
The agricultural sector has grown more rapidly than the other sectors of the economy after the structural adjustment program which was launched in 1986 and now represents more than 60% of the GDP. compared to about 40% in the mid-seventies. Unfortunately, the share of the government resources spent on the agricultural sector is only 6% of the total expenditure and has shrunk from about 10% in the early 1980s to less than 3% today. Private capital must constitute the largest share of new capital investments in Tanzania, Currently, there are many positive signs of increased interest from the private sector including funding of research activities in general as well as extension. Therefore, activities related to development of improved technologies for soil and water management will likely benefit from such a support.
TABLE 7 Cropping pattern and production in Arusha and Shinyanga regions 1986/87 to 1993/94 (000 ha, 000 tonnes) Season crop 1986/87 1988/89 1990/91 1993/94 86/94 Area Prod. Area Prod. Area Prod. Area Prod. Arusha region Maize 143.0 169.7 154.8 227.2 163.1 222.6 1.4 Sorghum 301.5 244.2 38.0 37.9 28.6 32.2 1.2 Wheat 24.0 30.9 28.5 36.1 33.9 60.3 39.7 63.7 1.7 Bean local 34.6 60.7 32.6 65.5 31.8 50.8 56.3 52.5 0.8 Sunflower 39.1 46.4 42.2 28.2 3.3 2.4 Shinyanga region Maize 239.2 188.4 314.1 220.3 275.2 251.5 218.1 178.3 0.8 Sorghum 138.1 131.4 91.2 77.1 129.5 206.3 151.3 118.2 1.1 BR millet 17.1 12.3 18.4 14.9 26.6 20.9 30.1 16.4 0.8 Rice 58.4 106.7 76.1 142.7 75.2 `98. 56.7 50.4 2.0 Sunflower 10.2 6.1 0.8 0.5 0.0 0.0 5.7 4.0 1.5 Source : Ministry of Agriculture Arusha and Shinyanga
The state, supported by donors has a role to play with respect to investment in the agricultural sector which is also closely related to soil degradation either directly or indirectly. Besides the government policy to liberalize and to deregulate the agricultural sector, the government priority areas are agriculture and livestock research, expansion of small-scale irrigation, provision of basic infrastructure as feeder roads in rural areas as well as storage and processing facilities. The government has also accepted the role of making sure that harvesting of natural resources is done in an environmentally sustainable way which has also a strong implication on soil degradation. About half of the Tanzanian population have incomes under the poverty line. Poverty in Tanzania is by large a rural phenomenon. It is estimated that 83% of all the poor people live in households where the main occupation is farming. Poverty does not seem to be related to access to land but rather access to education, health, off-farm employment, and distance from efficient markets. Therefore, poverty alleviation in Tanzania should have a rural agricultural profile particularly with respect to increasing the returns to labor in the agricultural sector. Therefore, restructuring should support systems that give smallholder access to inputs such as fertilizers ploughs transport, roads and credits and advice farmers to use environmentally sustainable methods of farming and forestry management. A major obstacle to private business and investment in the agricultural sector in Tanzania which according to (Semu et al., 1992) contributes significantly to soil degradation is the poor legal environment. Property rights and land entitlement by pre-nationalization landowners, cooperatives, villages and individuals is still unclear. Therefore, laws governing land tenure 300 Tanzania
systems should be revised to give way to further investments and provision of credits to small scale farmers which will also have a bearing on soil conservation strategies.
EXTENT OF SOIL DEGRADATION AND ITS BIO-PHYSICAL AND SOCIO-ECONOMIC IMPACT Causes of land degradation in Tanzania Land degradation in most parts of Tanzania is triggered by human intervention on the natural setting. Thus, the present status and rates of land degradation can be attributed to natural processes inherent in the physical setting of an area and the influence of human action in such areas. Land degradation begins where human and animal activity disturbs the geological and biological balance between landscape setting climate and vegetation cover. Inadequate Extension Services. Even though the extension officers have to attend to large geographical coverage, they are often without means of transport. Poor linkage between the extension staff and research is another factor which contributes to delayed or poor transfer of technology from research to farmers. This problem is magnified by the fact that the majority of the people involved in agricultural land use are as a whole resource poor peasants with very low level of formal education. Their access to extension messages and the media is limited. The family labor has to be divided between food and cash crop production, provision of water for the family and livestock and activities related to the provision of shelter and fuel. Land which is poorly managed deteriorates rapidly thereby becoming less productive. Inappropriate cultivation practices. In many parts of the country flat cultivation is practiced where animal drought or tractor power is used and cultivation is commonly done down slope. Both these methods are in effective against soil erosion and may even accelerate the process. Protection measures such as contours terraces etc are employed to a very limited extent and usually not done correctly. In areas where commercial agriculture is practiced e.g. (Northern Mbulu) the continuous use of heavy machinery has led to destruction of topsoil structure and formation of a plough pan. Poor policies have resulted in high pressure on arable land, rangeland, forests and water resources. The contribution of stock routes to erosion is significant. May spectacular forms of erosion are linked to the movement of livestock along specific routes. Grazing and trampling destroy the vegetation cover along these routes. Initially, narrow paths gradually merge to form broad bare strips which readily develop into gullies because in most cases they run along slopes. In addition, woodcutting for fuelwood, for construction and timber has lead to substantial land degradation. Construction of roads down slope has also caused many roadsides to develop into deep gullies. Policies on tenure, as well as appropriate use and management of land resources have been absent or not enforced. Major parts of land in Tanzania continues to be freely accessible and changes in policies such as removal of subsidies on agricultural inputs such as fertilizers have had a negative effect on agricultural production and land conservation.
Types of soil degradation The intensity and types of erosion are related to vegetation cover, slope gradient and types of soils. The main agents of soil erosion are wind, runoff water and seepage of rainwater. Wind erosion is very important during the dry season. Soil survey studies in Mbulu district (Magoggo et al., 1994) showed that 8.5% of the district was severely eroded 20.1% moderately eroded 55.2% was slightly eroded and 16.2% was not affected by erosion. Gullies develop readily in the red and black soils of the volcanic area in the north even on gentle slopes. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 301
Physical degradation. The common form of physical soil degradation is destruction of soil structure. This is common in areas where there is continuous cultivation particularly where tillage is done using tractors or cases of excessive trampling by animals. Structure deterioration is also manifested by plough pan formation and surface capping. Surface crusts are also observed in areas where physical degradation is common e.g. Mbulu Kondoa and Dodoma. They are particularly common in cultivated and over grazed areas which have sparse vegetation particularly when the soils are low in organic matter. Chemical Degradation. Chemical soil degradation refers to the change in chemical characteristics of the soil in terms of decreases in plant nutrients and/or increased adverse effect of chemical elements and salts. Tanzania's arable soils lost nutrients at an average rate of 27, 9, and 21 kg N, P205 per ha per annum in and the rate of loss was projected to increase to 32, 12, and 15 kg N, P205 and K20 per ha per annum by the year 2000 if current trends are not reversed. The ability of the soil to supply nutrients differs significantly from one place to another as well as from time to time. Physical properties of the soil such as depth texture and structure also contribute to their productivity. Each soil has its inherently productive potential (Tables 8 and 9). Acidic soils have a high potential to fix P in forms that are not easily available to plants leading to phosphorus deficiency symptoms in such crops.
TABLE 8 Soil characteristics for selected sites in Arusha and Kilimanjaro regions - Northern Zone District Altitude* PH (H20) Tot. N O.C. Avail. P (%) (%) (ppm) Arusha Sites SARI-Farm Arusha Medium 7.5 0.09 2.0 22 Kikatiti Arumeru High 6.1 0.44 5.7 16 Himiti Hanang High 7.0 0.13 1.0 Trace Endamarariek Mbulu High 6.5 0.10 1.2 2 Eyalabe Mbulu-Karatu High 6.8 0.15 2.4 84 Kilimatembo Mbulu-Karatu High 6.9 0.14 2.5 42 Mbuyuni Monduli high 7.2 0.23 1.3 18 Mguu/Zuberi Monduli High 7.3 0.18 2.3 14 Kibaya Kiteto Low 5.7 0.07 0.6 8 Dosidosi Kiteto Low 5.8 0.17 1.0 17 Average 6.7 0.17 2.0 25 Kilimanjaro Sites Kindi Moshi rural High 5.7 0.24 3.6 47 Lyamungu Moshi rural High 5.5 0.22 2.6 34 Urori Moshi rural High 6.4 0.27 3.5 80 Kiraeni Rombo Medium 6.2 0.09 1.5 10 Mkuu Rombo High 5.8 0.21 2.1 2 Usseri Rombo High 6.7 0.16 2.0 18 Miwaleni Moshi Medium 7.7 0.09 1.1 23 Sanya juu Hai Medium 7.3 0.24 3.3 18 KIA Hai Medium 7.4 0.13 1.5 Trace Lambo Hai Medium 6.6 0.14 2.3 68 Average 6.5 0.18 2.4 33 Notes: *Low altitude: - <800 m above sea level; Medium altitude: - 800-1300 m above sea level; High altitude:- >1300 m above sea level
Heavy application of fertilizers can be profitable on soils that have high productive potential but which are low in fertility. Declining soil fertility is very severe in most parts of the country particularly on sandy soils. In all cropping patterns the total nutrient removals is usually greater than corresponding amounts removed by various processes. Most of the losses occur through crop harvests and crop residue removal. Certain crops need larger amounts of particular nutrients 302 Tanzania
than others. Legumes for instance require large amounts of phosphorus whereas cereals require proportionately more nitrogen. Improved varieties are more responsive to higher doses of fertilizer. Therefore, nutrient mining is mainly responsible for the decline in soil fertility and productivity in many ago-ecosystems. In areas with low rainfall soils lose very limited amount of nutrients through leaching. However such soils are very susceptible to salinity problems. It is estimated that 3.6 million ha of salt affected soils are in Tanzania and of these 2.9 million ha are saline while the remaining are sodic. (Mkeni 1996). Most of the salt affected soils in Kilimanjaro region are found in the lowland areas surrounding the Kilimanjaro and Pare Mountains. Lack of proper drainage in the layout of irrigation schemes was identified as one of the main causes of the build up of salts. Salt-affected soils fall into two main categories i.e. saline soils containing excess of neutral salts which are dominated by chlorides and sulfates whereas sodic or alkali soils have a high content of sodium salts
TABLE 9 Soil characteristics for selected sites in Shinyanga Region - Lake Zone Location District pH OC N Available CEC (H20) (%) (%) P (ppm) Mwanhuzi Meatu 7.6 1.28 0.30 1.6 39.0 Isagehe Kahama 4.9 0.50 0.02 1.6 7.9 Ngulyati Bariadi 5.9 0.69 0.07 4.0 10.3 Mwambegwa Meatu 8.0 1.41 0.16 1.6 69.0 Nyalikungu Maswa 7.6 0.62 0.09 2.0 10.7 Gula Maswa 6.5 1.55 0.13 2.0 15.0 Nyakabimbi Bariadi 6.6 1.04 0.10 8.0 10.6 Nyashimbi Kahama 6.6 0.32 0.03 2.0 4.3
Irrigation poses special problems in the use of fertilizers and also provides some unique ways to supply nutrients not encountered in non-irrigated agriculture. Crop yields must be high for irrigation to be profitable and this is usually associated with greater nutrient uptake by crop. In order to maximize irrigation efficiency nutrient needs of irrigated crops must be met by an - - adequate fertilizer program. It is also well recognized that anions such as NO3 , Cl and SO2- are mobile in the soil especially under neutral and alkaline irrigated environments. The three broad irrigation methods furrow, flood and sprinkler irrigation have implications for fertilizer use efficiency. Furrow irrigation leads to marked redistribution of most mobile nutrients. In flood irrigation movement and eventually losses of mobile ions is more effective. Biological Degradation. Biological degradation is a decrease in soil biological activities which are essential for maintaining the physical structure of soils and their ability to supply chemical elements to plants which is usually controlled by the organic matter content of the soil. The production and deposition of organic materials provides substrates for microbiological processes and accumulation of soil organic matter. Mineralization of the OM is a major source of plant nutrients in soils with low inherent fertility. Organic matter improves the water holding capacity of soils, improves nutrient retention and storage.
Evidence of chemical/fertility decline The main evidence of soil fertility degradation in Tanzania can be obtained from the wide responses of various plant nutrients in form of mineral as well as organic forms of fertilizers. (Nyaki 1997 and Kamasho 1997). Mineral fertilizers were first introduced in Tanzania in 1956 for use in cash crops particularly tobacco, cotton and coffee. In 1976 the National maize programme was launched and the use of mineral fertilizers in food crops, particularly maize was Integrated soil management for sustainable agriculture and food security in Southern and East Africa 303
spread in most parts of the northern zone as well as other zones in Tanzania. (Urassa and Isaac, 1997, and Nyaki 1997). Responses to mineral fertilizers were quite evident in some parts of the northern zone (Table 10). During the 1980s other projects such as Kilimo/ FAO Fertilizer Programme followed by SG2000 were initiated and these demonstrated the importance of mineral fertilizers in increasing food production throughout the country. The maize improvement Programme funded by USAID through CIMMYT also created awareness in the use of mineral fertilizers by small holder farmers in the southern highlands of Tanzania. Fertilizer trials conducted in the southern highlands showed strong responses to N as well as phosphorus and in some instances responses in micronutrients such as Cu in crops such as wheat, which also clearly indicates that these nutrients are highly deficient in such soils. Nitrogen is the most limiting nutrient for TABLE 10 crop production in Tanzania. Unfortunately, Some-up-to-date fertilizer advice to agro- the use of most nitrogen fertilizers for ecological zoning economic optimum rate improvement of soil fertility in most parts of calculation -1 -1 Tanzania has also declined substantially in Agro- N(kg. ha ) P205 (kg. ha ) recent years largely due to the high costs of ecological Zone inputs in relation to crop prices, particularly Maize maize. The most common types of mineral H5/H6/H7 60 0 fertilizers normally used in Tanzania include S2 40 0 SA, urea CAN and NPK. (Urassa and Isaac, H2 (1) 40 0 1997). Due to removal of subsidies in most H2 (2) 30 20 E7 60 0 agricultural inputs including mineral fertilizers R1 30 20 the economic optimum rates of N for the E2 60 0 production of most crops in Tanzania has N2 50 0 dropped to rates between 40 and 60 kg N per N4 50 0 ha when compared to rates as high as 112 kg Wheat 70 0 N per ha when fertilizers were fully subsidized H7 H2 (1) 60 0 (Table 10). In fact, at the moment very few H2 (2) 50 30 farmers in the northern zone of Tanzania are E7 40 20 applying mineral fertilizers in their maize N4 40 0 fields. It is estimated that until recently 70% of Beans the amount of fertilizers consumed in the All 30 20 Potato country went into maize while small amounts H7 60 50 are applied to paddy potatoes and wheat. H2 80 40 E7 80 50 Fertilizer use in tobacco is increasing due N4 60 40 to the role of the tobacco buyers are applying Paddy E9/E10 60 0 and the low profitability on maize of NPK. P4/P8 40 0 95% of 6:20:18 goes into tobacco while 95% S2/E7 50 0 of the 25:5:5 is applied to tea. Based on the agronomic data available so far and the prevailing economic environment (high fertilizer prices and relatively low crop prices ) it appears that the most fruitful contribution to alleviate chemical soil degradation is to assess the effect of factors which can significantly decrease the amount of mineral fertilizers applied while maintaining significant increases in yield since complete removal of subsidies in fertilizers has resulted in a sharp decline in the consumption of fertilizers except for a few profitable crops such as potato, tobacco and cotton. 304 Tanzania
It should be noted that the decline in the use of mineral fertilizers in most parts of Tanzania will likely result in very rapid decline in the fertility of the soils unless other alternative forms of plant nutrition are established. Integrated Plant Nutrition Studies (IPNS) conducted in Tanzania so far clearly show that organic forms of fertilizers such as FYM can be used as a source of plant nutrients, particularly N. However, its utilization is labor intensive and demand facilities to transport it from the homestead to distant fields. In some areas of Tanzania FYM availability is also very limited and the amount required can not be met to satisfy the needs of crops. Some studies have also shown that it is possible to increase crop yields without using fertilizers by using improved farming practices such as ridging cultivation for maize, improved water management for paddy fields, improved tillage for different crops, crop rotations and intercropping practices.
SUCCESSFUL CASES OF IMPROVED SOIL MANAGEMENT Due to agro-ecological diversity within the country, different soil management systems have evolved over time to produce husbandry practices which conserve the soil and ensures effective use of available water. Most of the systems developed involve small holder production systems and very limited cases of large scale farming (Antapa and Angen 1990)
The case of the Soil Conservation and Agroforestry Program in Arusha Region (SCAPA) in Northern Tanzania The Soil Conservation and Agroforestry Program SCAPA is a community based land husbandry and agroforestry program. It is funded by the Swedish International Development Agency (SIDA) and employs integrated land husbandry strategies to increase agricultural productivity in medium and high potential areas of Arumeru and Arusha district in Arusha region. The low cost easily disseminated and adaptable techniques have convinced the farming community in the program area that appropriate land husbandry practices are among the possible strategies to increase and sustain agricultural production in the area. Along with the planning activities aimed at assisting the farming community SCAPA also creates awareness on the techniques and processes involved in promoting improved land husbandry strategies. Major components of the program include training, soil and water conservation techniques through water harvesting /conservation, agroforestry, livestock husbandry and crop management. Field activities at the village level are implemented by the Village Soil Conservation Committee (VSCC) under the guidance of the village extension officers (VEOs). Soil erosion is one of the major constraints to increased agricultural production in Arumeru district. Arumeru has a total area of 2 900 km2. According to Semu et al. (1992), 70% of the area in the district is affected by soil degradation mainly through soil erosion. Large gullies of up to 10 m wide can be found in areas such as Oloitushula and Oldonyosambu area in Muklat Division. Rill erosion is also evident in cultivated fields in Sakila destroying large tracts of land. Severe siltation of water reservoirs in some parts of the district is additional evidence of the extent of land degradation in the district.
The major causes of land degradation in Arumeru district are the following: · High population density in high potential areas resulting in lack of arable land which tempts farmers to open up fragile land for crop production. The population density for Arumeru district is the highest in all the districts of Arusha region. Arumeru district has an annual population growth rate of 3.8% which is among the highest in Tanzania. The population density of 108 persons per Integrated soil management for sustainable agriculture and food security in Southern and East Africa 305
square km in the district is also considered as very high. In fact, in some areas around mount Meru the population density can be as high as 200 people per km2. The average family land holding is less than 0.8ha. About 98% of the population is engaged in agricultural production. · Deforestation and poor forestry management resulting from lack of adequate supplies of fuelwood and timber also contributes to soil degradation there is a strong evidence supported by the inhabitants of the area that at one time a large part of the district such as the Sakilla and Oloitushulla area were covered with heavy forests. Gradually, these forests were cleared to provide land for farming and grazing as well as fuelwood and building materials. · Overstocking, and consequently overgrazing in low potential areas is also one of the main causes of land degradation in the district. On the lowland areas the pressure on land mainly originates from large livestock populations. According to the 1984 livestock census the whole of Arusha region had 2.4 m livestock units. (L.U.). (1 L.U.= 1 cow averaging 250 kg). The land available for grazing in the district is about 5.6 m ha. Therefore, there is 2.5 ha of land for every L.U. However, the optimum carrying capacity of the land is 4 ha per L.U. Therefore, the land in the district is overstocked by a factor of 40% which contributes substantially to soil degradation in the lowland areas of the district. · Poor farm management practices. · Low level of awareness regarding land and environmental degradation within the farming community and among government and political leaders. · Inadequate facilities and skills within the extension system to solve soil degradation problems.
Implementation strategies of soil conservation measures by SCAPA The objectives of the SCAPA Program are the following: · To improve and increase agricultural production on a sustainable basis through soil and water conservation with emphasis on small holder farmers in the medium and high potential areas in Arumeru and Arusha districts. · Formulate a suitable extension package for integrated soil conservation in relation to rural development · Provide sites for training and demonstrations for soil conservation practices.
The target groups in the program were mainly small scale farmers in Arumeru and Arusha district in Arusha region. There are more than 160,000 small scale farmers in Arumeru district and more than 78,000 small scale farmers in Arusha district. These farmers are characterized by the use of poor farming tools and very limited use of improved agricultural inputs. Average household /family size of small scale farmers in the program area ranges between 6 - 8 people who depends entirely on land to satisfy their basic needs. The majority of the farmers in the program practice mixed farming, raising agricultural crops and rearing livestock for both food and cash. Pastoralists mainly occupy the low potential and marginal areas in the region where average land holding is relatively high. Except for a few plots of farmland grazing land is communally owned with free range grazing system. The basic soil conservation structure promoted by SCAPA is the contour band or ridge. Farmers in the district are trained by the PCT on the procedures of laying out such ridges using such simple equipment as line levels. A line level assembly consists of two poles or sticks of 306 Tanzania
equal length (about 1.5 m). The upper ends of the poles are connected by a string (usually 10 m long). On the middle part of the string a small (pocket size) spirit level is fixed so that it is horizontal when the string is tightly stretched between the two poles, when held in a vertical position. Three people are needed to layout a contour. Two of them hold the poles vertically with the string tightly stretched in the direction of the contour line The third person monitors the spirit level and advises the person holding the front pole to move either up slope or downslope until the spirit level indicates that the string is now level. Pegs are then placed in the positions occupied by the poles. The rear pole is then moved ahead and the process starts again. For effective soil conservation ridges the spacing between the contour ridges depends on the slope. A general consensus was that for slopes below 25% vertical intervals of 2 meters were satisfactory. But for slopes above 25% vertical intervals should not exceed 1.5 meters. Once the contour lines were established furrows were dug on the up slope side of the contour line and the excavated soil was hipped on the established contour to form a ridge. The procedure is first demonstrated by the PCT and the extension staff and then farmers continue on their own. Most farmers were initially concerned about decreases in cropping areas in incidences where the intervals were too short. However, they latter realized that in the process of stabilizing the ridges, new opportunities for increased fodder and fuelwood as well as building materials were opened up. Napier grass (Pennisetum purpureum ) is then planted using cuttings on the entire length of the contour ridge. The grass establishes quite well within the first year and contributes significantly to the stabilization of the ridge due to its extensive root system. In some fields agroforestry tree species are planted either along the slopes or downslope. These include species such as Sesbania sesban, Grevillea robusta and Leucaena leucocephala. All the tree species were strongly believed to contribute further to the stability of the ridges in addition to providing the community with fodder (grass spp.) Sesbania spp. and Leucaena spp) as well as fuelwood and eventually building materials (Grevillea spp). Initially, the grass and tree species seedlings were provided free by the SCAPA Project, but it was later learned that the exercise was very expensive. Therefore efforts were initiated to promote village based, private groups and individual based nurseries in the villages involved in the Project. Soil degradation in the drier areas of Arumeru district is closely linked to livestock production. In the highland areas improved dairy cows are very common. Zero grazing is widespread since livestock in such areas is not allowed to graze freely in order to protect the soil cover. Farmyard manure from livestock is usually collected and spread in the fields to improve soil fertility. In the rangeland, the number of livestock is very high and has resulted in serious overgrazing. Unlike the highland areas the grazing lands are usually communally rather than individually owned Therefore no individual takes the responsibility to take care of the grazing land by limiting the number of animals to the carrying capacity of the land. Livestock keeping is a deep rooted tradition for the tribes living in the dryland areas of the district. A large number of cattle to them provides economic security as well as spreading the risk. It is also important to note that improved breeds are very susceptible to diseases and are also more demanding when it comes to feeding and water requirements during the dry season, Therefore the issue of destocking in such areas has to be handled with care, and in most cases it should involve the farmers themselves. Inadequate moisture is one of the major limitations to optimum crop production in some villages of Arumeru and Arusha districts. In such areas soil conservation measures practiced are also complemented with other water harvesting techniques SCAPA in collaboration with Sida RSCU is implementing a pilot intensive watershed management in selected program areas. The SCAPA creates awareness on land husbandry and environmental conservation among the farming communities, government and political leaders through training. It is also through Integrated soil management for sustainable agriculture and food security in Southern and East Africa 307
training that soil and water conservation issues are incorporated into the agricultural and related extension systems.
Institutional aspects The SCAPA program usually follows the set up of the government administration. However, to some extent, the program is more or less semi-autonomous. The program manager is the overall supervisor while the program coordinator is the team leader of the Program Coordinating Team (PCT).The program administrator is responsible for monitoring and evaluation of the program implementation. There are three soil and water conservation committees, one at the regional level and two at the district level. These committees ensure that SCAPA activities are incorporated in the district annual development plans and that the integrated approach is adhered to by all parties involved. At the program area level SCAPA activities are organized and implemented by the PCT. The PCT is a multi disciplinary team comprising of technical staff from the forestry, agriculture, community development, livestock and water development. The SCAPA is a program operating through the normal government extension system. Therefore, it is the task of the PCT and district functional managers to ensure maximum cooperation with extension staff in the mechanism of the implementation of the program. The PCT also assists extension staff in the planning and implementation of program activities in their areas of jurisdiction. In many respects there are the equivalent of a catchment or subcatchment soil conservation committees depending on the size and nature of the area confined in the village administrative boundaries. The major reason of including these subcommittees in the program is to ensure active participation of farmers in the planning and implementation, and therefore, sustainability of the program achievements. The SCAPA has initiated collaborative activities with other government and non- governmental organizations located in Arusha and Arumeru districts working for rural development. Since its inception SCAPA has extended good and effective co-operation with Heifer Project International (HPI)I. Through this cooperation SCAPA has trained and assisted farmers to conserve and manage their land with the main focus of increasing productivity. Promotion of fodder production necessitate zero grazing systems as well as optimization of time and labor resources. At community level the SCAPA proposes to HPI a list of potential farmers who qualify for in calf heifers. The Mbulu District Rural Development Program (MDRDP) is an integrated rural development program. The implementation of a program in this project in regard to soil conservation started in 1989. The Land Management Program in Babati (LAMP) is an integrated rural development program supporting sustainable development in agriculture forestry and livestock. Other areas include water resources wildlife and fisheries communication and community development. It is a district based program operating through the district council and is partly funded by Sida and partly by the Tanzanian Government. The Monduli development Program SNV is funded by the Netherlands Development Organization and Monduli district council and focuses on integrated rural development programs. Farm Africa is an agricultural development program based and operating in Babati district. It started in the United Kingdom in 1985 and is currently operating in four African countries (Kenya, Ethiopia, Tanzania and South Africa). The project is intended to boost the economies of the poorest farmers through appropriate agricultural, livestock and forestry activities. Including rearing of dairy goats, agroforestry, primary school activities. Involvement of women in development activities in rural areas has been of great concern to the program at all time. In fact, women stand for a large part of the farm production activities. SCAPA is assisting in the 308 Tanzania
formation of women working groups in the program area The program is providing technical and material support to the group to enable them attain their development aspirations.
Summary of SCAPA achievements for the period 1989 -1996 · More than 10 079 farmers have been covered in soil conservation and agroforestry activities. · More than 1 900 km of contour bunds have been laid out of which 95% have been planted with grass or multipurpose tree species. · 1 113 900 multipurpose tree seedlings have been distributed and planted on the farmland and farm boundaries The survival rate of the seedlings is estimated at 75%. · 374 tons of grass material for planting on the contours were distributed to farmers. The survival rate is estimated at 90%. · 117 extension staff have been included in study tours involved in promoting appropriate land husbandry practices and water harvesting. · More than 10 878 farmers have been provided with basic training on soil and water conservation as well as appropriate land management practices. · The program has assisted establishment of 87 on-farm tree nurseries in various program areas.
The impact of SCAPA activities in Arumeru and Arusha districts has been estimated as follows: · Increased awareness on importance of soil conservation: There is a rapid build up of awareness of the importance of soil conservation among the farming community as indicated by increased number of people requesting for conservation services through the VSCCs, which has received a considerable amount of training on such activities. As a result, the PCC team has reduced the number of visits to many of the initial programme sites because most of the activities are now been implemented by the VSCCs (Annual report 1997). The introduction of improved breeds of cattle in the program area has significantly reduced the incidence of free grazing in many villages. Very effective by laws are in place and closely monitored by the VSCCs to ensure that free grazing in conserved areas is non existent even in ones own field. The conservation technology promoted by SCAPA has been adopted by over 75% of farmers in the Programme areas. It was also reported that most of the farmers who were not initially interested in the installation of contour bands in their fields are now asking for such services because the benefits of such practices have become more and more obvious to them. There are also several requests for fruits trees, and assistance to establish trees nurseries. Unfortunately, such efforts are being constrained by water shortage particularly during the dry season as well as the high costs of the respective inputs. · Increased crop yields due to soil conservation: The yields of crops in areas such as Kingori village particularly maize were quite low (6-8 bags per acre) before intervention of SCAPA and other NGOs particularly SG2000 because most farmers used to grow local varieties of maize without any consideration for improved agronomic practices. Today, about 75-80 percent of farmers in the village use improved maize seed, and about 80 percent apply mineral fertilizers in their maize fields and plant in rows to attain optimum plant populations. Average maize yields in the conserved areas now range between 20 and 25 bags/acre in good years. It is very likely that the higher yields may largely be attributed to both the soil and water conservation aspect of the SCAPA Programme as well as adoption of some of the Integrated soil management for sustainable agriculture and food security in Southern and East Africa 309
improved technologies promoted by SG2000. Some of the farmers who did not practice the soil conservation technology have already noted the significant increases in grain yields and are rapidly changing their minds in favour of adopting soil conservation measures in their fields. · Increased livestock productivity: The farmers contacted clearly acknowledge the fact that establishment of grass strips (Napier grass) and establishment of fodder tree species such as Leucaena, Calliandra and Sesbania on the contour bands, has led to increased supply of fodder from the contour bands, for zero grazed animals, particularly at times of adequate precipitation. Excess fodder has also become an attractive business to some farmers in the village. Some farmers are now selling fodder to other farmers in the programme area particularly those who did not adopt the conservation technology. Most farmers have now shifted from free grazing to zero grazing practices thereby eliminating the overstocking problem in the area which contributed substantially to accelerated soil erosion. Improved dairy cows produces between 10 to 14 litres of fresh milk a day when compared to 4 litres or less per day which was usually produced by local breeds. · Reduced Nutrient Mining from lowland areas: Increased availability of fodder from conserved structures coupled with high costs of transportation of crop residues from lowland to upland sites, has also significantly reduced the incidence of transferring crop residues from the lowland areas to the upland areas. This practice used to contribute substantially to nutrient mining in the lowland areas through grain harvests as well as crop residues. Currently, arrangement are made such that some farmers who have settled in the lowland area utilize the crop residues generated by farmers residing in the uplands with the understanding that in return they will till their fields during the following season. Most of these arrangements are working quite well because often times the farmers who settled in the lowlands are related to farmers who reside in the upland areas. · Reduced soil erosion: construction of contour bands and planting of grasses as well as various trees species has reduced both water and wind erosion in most farmers fields in the area. Incidences of water erosion that was seriously causing damage to the agricultural land through large gullies as well as sheet erosion has been reduced to less harmful levels. The large gullies that used to be quite evident in the area that have more or less disappeared and evidence of sheet erosion (rills and sediments/siltation) is also non existent even at times when the amount and characteristics of rainfall received was adequate to cause some erosion problems. · Improved environmental conditions due to afforestation: several multipurpose tree species such as fodder trees have been introduced in the Programme area. There has also been an increased emphasis to plant and maintain most of the indigenous trees species in the area which include Grevillea, Miruka, Mijohoro, Mringaringa, Mfurufuru, and Msesewe, as a source of timber, building polls, fuelwood and stakes. Therefore, the vegetation cover has increased significantly as a result of the SCAPAs efforts. It is currently estimated that about 40% of the surface is planted with permanent trees. Increased vegetation cover has a bearing on the extent of soil erosion and moisture conservation as well as nutrient cycling. Trees also act as windbreaks in the area which contributes to reduction of wind erosion and conservation of soil moisture. The presence of a large number of trees in the area has also created a cool microclimate when compared to the hot environment which used to persist when the area was relatively bare. By laws afforestation are in place and are closely monitored by the VSCCs to ensure that they are adopted by the respective farmers. According to the farmers contacted 310 Tanzania
implementation of the by laws in the area has been very successful in promoting afforestation in King’ori village. · Improved standards of living: the standards of living of people in the rural areas has improved considerably due to adoption of the SCAPA technology of soil conservation. Higher crop yields have earned them more income and improved their food security. Their feeding habits have also changed in favour of a more balanced diet containing enough carbohydrates, proteins and vegetables. Most farmers are also getting more income from milk sales and using some of the milk as part of their meals to improve their health standards. A few farmers have also started building some improved houses as result of increased income from farming activities. More children are also being enrolled for primary schools, secondary schools and technical colleges. Therefore, the number of youths migrating to towns seeking for employment has been reduced. In previous years most of the young people were largely involved in grazing of animals. Higher incomes has also enabled some farmers to hire equipment for land preparation as well as increased their ability to purchase limited amounts of inputs (improved seed pesticides and fertilizer to improve their productivity). · Improved gender relations: some of the activities which were not originally shared between men and women including fetching water for animals, milking, cleaning of cowshed, cutting and carrying fodder to livestock in the homestead are now equally shared by both men and women. Due to greater involvement of women in the SCAPA activities the freedom of expression by women has also improved considerably. Both men and women now hold joint meetings to discuss issues that affects their lives. Women today have more freedom to work together through women groups involved in activities such as raising vegetables gardens and tree seedlings. Zero grazing and increased availability of fodder closer to the homestead has reduced the workload on the woman in that they don’t have to wait for the animals to come back for milking Therefore they are more free to do other things including more time to socialize. · Increased interaction with local regional and international visitors: because most villages have successfully adopted the soil conservation technology promoted by the SCAPA many visitors have shown keen interest in the technology and have forwarded applications to the SCAPA management to visit the programme areas to get an experience of the achievements. Some of the visitors received so far originate from other parts of Arusha region East Africa as well as the international community. Traditional cultivation practices and their linkages to environmental /soil conservation - The case of the Ngoro cultivation system in Mbinga district - Southern highlands of Tanzania Rapid population growth in Mbinga district has forced people to clear more land on steep slopes for growing crops. Therefore, land degradation is becoming a serious problem in the area if appropriate soil conservation measures are not observed. Land degradation processes taking place in the area include loss of fertile top soil and water through runoff. Such losses leads to losses in productivity as well as environmental degradation. Currently, in the matengo highlands water from streams is being polluted by soil sediments and silt particles from cropped land using the ridge system of cultivation as well as poorly designed ngoro systems. The Matengo pits (Ngoro) cultivation system is an indigenous method of land preparation which has been practiced by the Matengo small scale farmers for a long time. The system was developed before 1890 for the control of run-off erosion on steep slopes (Allan 1965). The Ngoro system of cultivation is estimated to be currently practised on approximately 18 000 ha of land in Mbinga district (Martin et al 1996). The system consists of a series of pits Integrated soil management for sustainable agriculture and food security in Southern and East Africa 311
surrounded by ridges on which crops are grown. Its construction involves an in situ composting of the grasses in the ridges. The grass rows are arranged down slope and across slopes, thus forming ridges around the pit. The Ngoro system of cultivation is a common feature of steep slopes (10 - 60%) of the Matengo highlands. The activity involves three main steps namely cutting of the grass (kukyesa), arranging the grass in rows (kubonga) and construction of the pits (kujali) i.e. piling the grass in squares 2 m x 2 m and then using a hand hoe to cover the grass with soil from all sides. During the process of constructing the pits there is a distinct gender division of labor. The first two steps are done by men while the third stage is mostly done by women. The construction of the structures is done when the soil is wet but the rains are about to tail off (March/April).The pit system has also been linked with crop rotation and fallowing practices (ICCRA 1991). The main rotation system associated with the Ngoro system in the Matengo highlands involves fallow-beans-fallow-maize-fallow-beans. Maize is sown by making planting holes on the Ngoro ridges in December following a July to November fallow following the harvesting of the midseason bean crop. Beans are usually sown by broadcasting on newly half formed Ngoro ridges in March after fallow following the harvesting of maize in August. The Ngoro system has also sustained soil productivity in highly sloping lands of the Litembo area in Mbinga District for over 100 years without the use of mineral fertilizers. In the past fallow periods were much longer (up to 10 years) to sustain productivity, depending on the population. According to ICCRA (1991) fallow periods are now as low as one year on the hills and are much shorter on the plateaus due to increasing population pressure. Due to increasing labor constraints, the Ngoro system is slowly been replaced by the less labor intensive ridge cultivation system and modified forms of the original ngoro system although crop yields are usually less than yields from the original ngoro system.(Ellis Jones et al. 1996). The Ngoro pits currently been practiced are no longer square in shape as they used to be but rectangular in shape and are also much shallower. The ridge system was found to be less effective in controlling runoff and soil erosion when compared to the ngoro system Thadei (1995) demonstrated that soil losses of up to 7.3 t/ha were recorded in a slope of 8.9 and 14.3t/ha in a slope of 20.9 o in the ridge cultivation practice. For similar plots soil losses were 2.4 t/ha and 5.8 t/ha when the ngoro system was practiced. Some of the most important features of the Ngoro system can be summarized as : · in situ conservation of runoff water into the soil for use by crops, · prevention of both physical and chemical soil degradation, · improved soil fertility management through decomposition and mineralization of plant residues during the pit construction process, · promotion of crop rotation and fallowing practices.
The case of large-scale mechanized wheat farming in northern Tanzania - Evolution of large- scale soil conservation practices Land clearing practices in relation to soil conservation. Due to the serious soil eosin problems that were experienced on the farms during the 1980s soil conservation structures were surveyed and installed on such farms. These included grass strips, absorption and graded channel terraces In general, the structures were moderately effective but the main disadvantages were high incidences of weed infestation and poor movement of farm machinery between strips, reduction of total cultivable land and sometimes structural failures. Farms that were opened later involved leaving of a 5-8 m wide strip of natural vegetation on contours and natural waterways untouched. 312 Tanzania
This approach proved to be very effective in controlling soil erosion. Current efforts to control erosion on originally opened land also include construction of broad base terraces and conservation tillage practices which have also been shown to be very effective. Soil erosion control structures. Extensive surveying at the HWC enable the farms to install soil conservation structures on 7,585 ha of land from 1988-1991. The exercise is still in progress today. Studies conducted at HWC have shown that absorption channel terraces were quite effective in controlling erosion on 2-4% slopes particularly on medium to course textured soils. On the other hand absorption channel terraces were very ineffective. (Antapa and Sayulla, 1991). Graded channel terraces are similar to absorption channel terraces except that they are gently sloped to discharge water into grassed waterways. They are commonly used in areas with slopes in the range of 4-6 percent. Broad based terraces have also been found to be very popular since they do not take any land out of production. Unfortunately, like absorption channel terraces Broad based terraces are not very effective in controlling soil erosion on heavy textured soils because water collects on the upper channels, which delays field operations and causes water logging problems. Tillage practices. During the early stages of the establishment of the wheat farms the dominant tillage implements were disc ploughs and harrows. Generally, the disc ploughs tended to pulverize the soil and incorporated most of the trash, thus increasing the erosivity of the soil surface. In the later years of the Wheat project cultivators attached with sweeps were introduced and are now the major tillage implements being used. These tillage implements are designed in such a way that up to 70% of the crop residues is retained on the soil surface after the tillage operation. Substantial amounts of soil can be lost through runoff water if the soil is left bare after tillage operations or contains very limited vegetation due to overgrazing. Excessive tillage is sometimes practiced in an effort to control weeds, but in many instances it has been shown to promote accelerated erosion. In recent years herbicides such as roundup have been introduced to substitute for some of the tillage operations to minimize excessive tillage. Air seeders have also been introduced and are increasingly been used by the wheat farms to promote minimum tillage. The equipment is capable of eliminating some tillage operations since it can perform the tillage and seeding operation in the same path. Implications of current tillage practices on moisture conservation and nutrient availability to crops: · The duration of weeds in the field has a direct effect on the extent of moisture depletion on the wheat fields. Therefore, weed control practiced close to the planting time will likely result in less available moisture to the crop when compare to tillage practices which ensure weed free fields for a significant part of the season. · The effect of substituting tillage operations by using herbicides may also have some negative implications on the quality of organic matter as well as soil microbiological aspects. · Decomposition of wheat straw to release nutrients to the wheat crop after the tillage operation will likely be influenced by the timing of the tillage operation. Wheat straw is known to have a wide C:N ratio and therefore requires more time for decomposition to release nutrients to crops. Control of weeds using herbicides also leaves most of the residue on the surface. Therefore, it is only through the second tillage operation using the air seeder that microbial decomposition of the residue is initiated. · Continuous tillage operations using heavy duty equipment may also result in considerable compaction of the soil which may limit the infiltration capacity of the soil and encourage Integrated soil management for sustainable agriculture and food security in Southern and East Africa 313
runoff. Tillage operations by most small scale farmers is done either using the handhoe, oxplough or small tractors. Therefore, the problem of compaction is almost non existent. Management of Vertisols in relation to their physical and chemical characteristics. Vertisols occupy about 50% of the total area under wheat production in large scale wheat production farms in northern Tanzania usually refereed to as the Hanang Wheat Complex (HWC). Vertisols usually occupy the depressions as well as lower slope positions. Other soils include Mollisols, Inceptisols, Alfisols, and Ultisols which occupy the upper slopes and mid slope positions. Although the Vertisols of the Hanang wheat complex area are high in natural fertility and have a high water holding capacity the high content of montmorillonite type of clay which is also a characteristic of such soils promotes water logging under wet conditions and very hard and cracking surfaces when dry. These effects have several implications in the management of such soils: · Post harvest tillage operations need to be conducted at the appropriate moisture content to avoid equipment damage which can be expected when tillage is done when the soil is too dry, · Appropriate choice of tillage equipment as well as appropriate adjustments is also essential (Antapa and Angen 1990), · Seeding operation- Usually, due to the large acreage involved in mechanized wheat production the lighter textured soils are tilled and seeded first while the heavy clay soils are seeded late because of their higher moisture holding capacity, · High pHs of Vertisols on depressions in this area shows that investigations into the possibility of application of P fertilizers should be explored. In fact, soil analysis data the P levels on such soils are relatively low.
INSTITUTIONAL FRAMEWORK AND POLICIES FOR LAND RESOURCES MANAGEMENT The improvement of government capacity has now emerged as the most important issue in the ongoing structural adjustment effort. Reforms required now involve efforts to increase the effectiveness of various research activities including soil management activities. Future strategies include: · a shift from central to district and even levels below, · capacity building and sustainability shall have top priority, · gender equality reflection will be observed, · land tenure and land policy issues and their effect on the projects under preparation should be considered and analyzed during the identification and preparation of support programs, · district projects shall build on priorities made by the land users, · Tanzania shall monitor and evaluate not only technical subject matter areas but also socio- economic effects of the donor supported projects, · support to district projects shall aim at increased productivity among smallholder through sustainable use of natural resources including support for land tenure and land management, · in addition to high and medium potential areas support shall also take low potential areas into consideration. 314 Tanzania
Currently, there is a significant shortfall in the policies on soil and land resources management, conservation and rehabilitation. Where these policies exist, they do not adequately address problems of soil degradation because they lack legal framework and concrete action plans to tackle the problem. Nevertheless, the government has some positive steps in combating land degradation such as the establishment of the National environment Council (NEMC) and the National Land Use Planning Commission (NLUPC). The NEMC has already formulated a National conservation strategy for Sustainable Development and the National Environment Action Plans which have established a framework for integrating environmental issues in the nations overall economic and social development. However, the absence of a comprehensive environmental policy clearly indicating goals objectives mandates and responsibilities of different institutions casts doubts to the successful implementation of the action plans. Besides, there was very little input from the grass roots. The National Land Use Planning Commission (NLUPC) has produced a draft on national land policy which addresses mainly the issue of land tenure which as indicated earlier plays a significant role in soil degradation. Unfortunately, most of the plans in the draft consist of rigid land use zoning which is not suitable for proper management of rural land resources. Therefore, there is a need to formulate a policy that takes into account the different environments and a scientific criteria for land use planning. A national policy on soil will contribute towards attaining national development policy by protecting and conserving the environment which is likely to reduce poverty and increasing food security through sustainable use of soils. Although laws on soil conservation exist most of them have not been applied for decades now. These need to be revived, revised and if possible enact new ones to conform with new soil policies. The separation of environment, natural resources, land and soils into different line ministries and organizations is a hindrance towards attaining intersectoral and multi disciplinary approach to environmental management and conservation. Lack of infrastructure and well trained personnel in soil characterization classification evaluation correlation management conservation and rehabilitation compounds the problem even further.
PROPOSALS OF PROGRAMMES FOR IMPROVED SOIL MANAGEMENT AND PRODUCTIVITY ENHANCING Based on the experiences learned from the SCAPA and other sources of available information new strategies to combat soil degradation will have to take the following aspects into consideration: · Institutional Framework: Although there are many institutions engaged in soil and water conservation they lack coordination cooperation and linkages. They are sectoral and employ different approaches and methodologies and have different formats. Therefore, they should be harmonized. Most national institutions are inadequately funded ill equipped and poorly managed due to inadequate human resources. Donor funded projects are sometimes not sustainable. · Policy and Legislation. The country needs a comprehensive land use and tenure policies as well as straggles and program of action in order to adequately address issues of sustainable soil and water management. Such policies will optimize the use of land as well as minimize conflicts between different land users and stakeholders. · Land Use Planning. Lack of scientifically based, flexible land use plans at national, regional district and village level often results in soil degradation. Land use planning will also guide rational and judicious use of land at different levels. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 315
· Research and Extension services. These are institutions charged with the development and propagation of land use technologies. As such they need to direct their efforts to on farm, problem oriented research which addresses farmers problems and provide them with practical solutions that are within their socio-economic circumstances. Critical is the research - extension - farmers should participate fully in the planning and implementation process of research projects. Therefore, their local knowledge, skills and technologies should be respected. Emphasis should be concentrated on resource - poor small scale farmers who are the majority. · Mass awareness and Mobilization. Local communities need to be abdicated to raise their awareness on soil degradation, conservation, and rehabilitation. Past experiences have shown that adoption of new technologies was very limited without involving farmers and their willingness to cooperate. · Information. is an important tool in facilitating planning processes of soil and water conservation. It is essential for creating awareness and mobilization, training and policy formulation. Information must be easily accessible in a timely manner. It must be collected, processed stored and disseminated. · Training. Rural populations are characterized by low levels of literacy. This limits their capability to assimilate packages and technologies on land husbandry practices and conservation. Farmers must therefore, be literate in terms of the basics of soil and water management conservation and rehabilitation. Extension staff also need training in both technical aspects as well as approaches necessary to encourage motivate and mobilize farmers to actively participate in soil conservation and rehabilitation. · Poverty. The rural communities are generally poor and spend a lot of time and energy in search of fuel, food and water and have very little time left to consider environmental issues. · Sometimes environmental issues are in conflict with their activities. Socio-economic environment involving aspects such as schools health care facilities, and services, water etc are either lacking or very limited. Credits and markets for increased agricultural production are often lacking. These problems often result in poor soil management practices leading to degradation of the soil. · Gender issues. The bulk of agricultural activities in rural areas are carried out by women. In addition to field activities women are responsible for the supply of fuelwood fetching water, cooking and taking care of the family. Unfortunately women have very limited participation in decision making issues when rural development programs are started. Therefore, often times the role of women in soil management issues is often overlooked. Integrated soil management approaches can be considered as the most logical strategy to adopt in most parts of the country due to rising costs of inputs such as fertilizers and the increasing concern for environmental degradation. Such an approach should be developed to include aspects such as tillage, soil conservation crop rotations agroforestry and contributions of legumes through BNF, crop residues, FYM. The IPNS should adopt a holistic approach to also take into consideration all the socio-economic aspects of the clients being addressed. Collaboration between various Institutions and NGOs should be promoted to maximize the use of limited resources such as manpower transport and equipment. Institutions such as SCAPA could be adopted elsewhere. Collection of adequate background information through surveys and PRAs should be emphasized for easy identification of priority areas of intervention and potential solutions. Such information should include characteristics of 316 Tanzania
natural resource base as well as socio-economic and environmental data and should include the development of a data base which could be updated regularly for improvement purposes. Most of the key actors in agricultural production require frequent training at different levels in aspects of soil management and related inputs (seeds, fertilizers and pesticide). The coordination between the various partners should also be strengthened. Extension services directed to farmers or farmer groups should be targeted to improved productivity and production. Farmers at the village level should be assisted to form farmer organizations in order to strengthen their bargaining power with respect to marketing of their crops as well as access to credit facilities required to improve productivity. Some of the recommendations developed such as those with soil and water conservation technologies developed by the SCAPA should be implemented on a community based action plan in order to promote their adoption. Such aspects as management of forests, communal grazing land and wildlife areas should be addressed on a community basis, hence participatory land use planning. To improve land security aspects surveys, border demarcation and mapping of village lands should be supported. Land rights should be clearly known to including processing of titles of ownership. Village and District capacity building should be considered to address the problems and constraints of intermediate target group. Improved revenue collection efficient and cost effective delivery of services are the main issues organizational development and in service training of District Council Administration (DCA) and village level government is essential. Local populations and their local governments representatives are increasingly been viewed as the custodians of natural resources. Therefore, issues of land tenure are key components of this. Therefore, studies on indigenous knowledge systems in land use as well as evaluation of land tenure aspects are essential in order to develop straggles to empower communities to manage their resources.
REFERENCES Allan W. 1965. The African Husbandman Oliver and Boyd, London pp. 505. Antapa P. L. 1991. Soil conservation measures on the Vertisols of the Hanang Wheat Complex, Tanzania. Paper presented in the annual review meeting on Africaland Management of Vertisols in Africa held in Nairobi Kenya 4-6 March 1991. Antapa P. L. and T.V. Angen 1990. Tillage Practices and Residue Management in Tanzania. State of the Art. Paper presented to the 3rd Regional Workshop on Tillage and Organic matter management in Humid and subhumid Africa Antananarivo, Madagascar 9-15 January, 1990. Enwezor W.O., E.J. Udo and N.J. Usoroh 1989. Fertilizer use and management practices for crops in Nigeria. Series # 2. Ensar Rennes 1992. New challenges for soil research in developing countries. A holistic Approach EC Workshop held in March 1992 in France. Gosta Ericsson and A. Berger 1995. Agricultural Research in Tanzania. Desk study requested by SIDA to explore possible options for Swedish support to Agricultural Research in Tanzania. Haki J.M, S.D. Limo and R. Ngatoluwa 1997. An overview of Research Capacity and Activities at Selian Agricultural Research Institute (SARI) in the Northern zone of Tanzania. Paper presented to a workshop on Research support to LAMP in the Tanzania-Sweden Local Management of Natural Resources Program held in Morogoro 16-18 September 1997. ICCRA. 1991. Analysis of the coffee based Farming systems in Matengo highlands; Mbinga district Tanzania. Working Document series 15 ICRA. Wageningen, The Netherlands. pp. 20. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 317
Ellis Jones, J.Kayombo B. Martin H.L. and H. Dihenga. 1996. What future for the Ngoro soil and water conservation system. An interim evaluation. Ministry of Agriculture and the Program office in Arusha. Soil Conservation and Agroforestry Program in Arusha (SCAPA), 1996. Kirway T.N., S.D. Lyimo, B.W. Rwenyagira, L. Chalamila I. Mshare, and E.J. Mbise, 1997. Research- Extension-Farmer Linkages in Tanzania and the Impact and Future direction of the DRT/ISNER Project on Linkages. Paper Presented to the Regional Workshop on Sharing experiences and drawing lessons from the DRT/ISNER Project on Linkages held at the White Sands Hotel DSM. 27-29 August 1997. Martin H.L., T.J. Willcocks and B. Kayombo 1996. Technical aspects of the Ngoro/Matengo pit system of cultivation from the soil and water conservation viewpoint. Proceedings of Environment Research Project Regional Workshop (ERPRW) Nyeri and Embu Kenya 26-29 May 1996. SRI Report No IDG/96/15. Mkeni P.N.S. 1996. Salt affected soils their origin, identification reclamation and management. A compendium of graduate course notes on salt affected soils, Sokoine University of Agriculture, Department of soil Science, Morogoro. Ngazi H. 1993. Women and soil conservation in Rural Shinyanga. Paper presented to the 18th Annual General Meeting of the Soil Science Society of East Africa held in Mwanza Tanzania Nov.29 to Dec.1993. Nyaki A.S. 1996. Review of Status of Wheat research and Production in Tanzania. Paper presented to the Maize and Wheat Prioritization Workshop held in Nairobi Kenya June 10-13, 1996. Nyaki A.S. 1995. A review of Research Activities in Plant Nutrition in the Northern zone and Proposals for future collaboration between SARI and Kilimo/FAO Plant Nutrition Program. Paper Presented to the Kilimo/FAO Plant Nutrition Program Regional Coordination meeting held in Arusha, September 22, 1995. Nyaki A.S. 1991. Management of Vertisols in Northern Tanzania in relation to their physical and chemical properties. Paper presented in the annual review meeting on Africaland Management of Vertisols in Africa held in Nairobi Kenya 4-6 March 1991. Nyaki A.S. 1997. Review and assessment of Kilimo/FAO Plant Nutrition Data in the Northern and Lake zones of Tanzania. Consultant Report for Project GCF/ART/106/NET. Nyaki A.S., C.J. Lyamchai and H. Mansoor 1997. Status of the current activities in Agroforestry/natural resource management Research in Northern Tanzania. Paper presented to the Research Planning meeting of AFRENA-ECA held in Embu Kenya 10-14 February 1997. Scaglia J.A. 1997. Synthesis of Project Prominent. Findings and Recommendations Consultancy report for Project GCPF/URT/106/NET. Kilimo/FAO Plant Nutrition Program in Tanzania. Semu E. Goran Bergman and E. Skoglund, 1992. A report on Evaluation of the Soil Conservation and Agroforestry Program - Arusha (SCAPA) in Tanzania. Ugen M.A., P.K. Jjemba and M. Fischler 1992. Farmer Participation in Soil Management Research in Matugga Village (Mpigi district) of Uganda. An Alternative Approach. Urasa S.J. and F. Isaac, 1997. A survey on fertilizer use survey conducted in Iringa, Mbeya, Ruvuma, Tabora and Arusha Regions of Tanzania mainland. Field Document for Project GCF/ART/106. Thadei S.Y. 1995. Evaluation of Erosion by Modeling. A progress report Miombo woodland project. Sokoine University of Agriculture. VSCC. 19997 Annual report. 318 Tanzania Integrated soil management for sustainable agriculture and food security in Southern and East Africa 319
Uganda
COUNTRY FOOD PRODUCTION AND REQUIREMENT Uganda has a total area of 236 000 square kilometres out of which 194 400 square kilometres of dry land, 339 226 square kilometres open water and 7 674 square kilometres of permanent swamps. Much of the country lies on the African plateau at an altitude of 900-1 500 m above sea level (ASL). Towards the South, the characteristic scenery consists of flat-topped mesa like hills and broad intervening valleys frequently containing swamps; towards the north, the landscape is more subdued consisting of gently rolling open plains interrupted by occasional hills, mountains and inselbergs. To the South-west, broken hill country characteristically encircling lowland embayment forms the transition to the deeply incised plateau that reaches its greatest hill height levels of over 2 000 m ASL in Kabale district. The Rift Valley, which runs near the western border, is represented by two troughs, that of Lakes Edward and George and that of Lake Albert. Between these depressions lies the glaciated horst mountains of the Rwenzori Range, rising to the highest peak in the country at 5 100 m.
Uganda's food production has changed very little over the years, especially when compared with population increases of about 3%. Most of the increase has been attributed to increase in area of production by moving in virgin land including forest and swamps. The three major sources of food are cereal crops, root crops and bananas. Table 1 and Figure 1 show the evolution of food crop production from 1987 to 1997: cereal and banana production increased by 48% and by 30.9% respectively, while root crops production decreased by 6%. Consequently, total food crop production increased by 18.8%, from 13 219 000 tonnes to 15 703 000 tonnes. In the period 1981-1995 population increased from 13.68 millions to 19.57 millions, or 42.9%. Population is increasing much faster than the food production. Since the population growth rate increased from 2.8% (1981-90) to 3.1% (1995-97) the food situation in the country is likely to become very alarming.
TABLE 1 Food crop production 1987-97 (000 tonnes.) Year Cereals Root crops Banana Total 1987 1,220 4,960 7,039 13,219 1989 1,637 5,474 7,469 14,580 1991 1,576 5,268 8,080 14,924 1993 1,880 5,417 8,222 15,519 1995 2,030 4,849 9,012 15,891 1997 1,805 4,682 9,216 15,703 Note: cereals are: finger millet, maize, sorghum, rice, wheat. Root crops are: sweet potatoes, Irish potatoes and cassava
Julius Y.K. Zake, Charles Nkwijn and M.K. Magunda Makerere University, Department of Soil Science, National and Agricultural Research Organisation KARI 320 Uganda
FIGURE 1 Food crop production 1987-97 (million Mt)
Bananas occupy the largest cultivated area of all staple food crops and are produced by over 75% of the farmers in Central, Southern and South Western regions of the country. Uganda produces about 7.0 million tonnes of bananas annually which makes her the world's largest producer (third monitoring survey, 1995-96) and consumer, representing nearly 20% of the total world production (Rubaihayo, 1991). Over the last 2-3 decades, however, banana production has stagnated with serious decline in the outputs and yields. Any increases that have been registered have been largely due to the opening up of new land. Thus, banana production has been shifting from its traditional homelands of Mpigi and Mukono districts (Central Region) to further west. Because of the dwindling yield of bananas, the people in the Central region are now the greatest producers and consumers of cassava and sweet potatoes, while the Western region is the greatest producer of bananas (Matooke).
There was a sharp drop in the area under cultivation in 1979 and 1980 from which the country has still not recuperated. The total area cropped fell from an all-time peak of 5.5 million ha in 1978 to 3.5 million ha in 1980. This may be due, in part, to statistical problems associated with the deterioration of Government statistics collection during the Amin regime. The sharp drop may also reflect a one-time adjustment for the gradual decline in area cultivated from 1970 (0.5 ha per caput) to 1980 (0.3 ha per caput). Since 1980 the data gathering effort appears to have been more consistent. The area under food crops expanded from 1970 to 1978, and dropped sharply during the war years of 1979 and 1980. In spite of rapid growth during the 1980s, areas under cultivation for food have still not reached the level of 1976 - 78, and less food is produced per caput, now than in the early 1970s. Despite internal dislocations and economic uncertainty, or perhaps because of them, the area under bananas has increased continuously since 1970 to 1.4 million ha in 1990 at a trend-growth rate of 1.8% per year.
EVOLUTION OF PER CAPUT CULTIVATED LAND AND TRENDS IN CEREAL CROP YIELDS A large proportion of Uganda's area can be cultivated. After lakes, swamps and forest reserves are excluded, more than 75% of the country's 18 million hectares is available for cultivation, pasture or both. It is not clear what share of this is unsuitable for cultivation. Much further work is needed to determine what protective measures are justified to ensure that production systems are sustainable. Out of the 17 million hectares classified as arable on a preliminary basis by Langlands (1974), only 4-5 Integrated soil management for sustainable agriculture and food security in Southern and East Africa 321
million hectares are under cultivation. Comparing the 1974 Langlands data on cultivable area and census information, rural population density on cultivable land has increased from 53 people per km² in 1969 to 88 in 1991. Eleven of the thirty-two districts analysed had a rural population density exceeding twice the national average in 1969 and 1991. The distribution of these densely occupied areas has not shifted. In Eastern, Southern and Western Uganda, more than half of the districts have a rural population density of 180 persons per km² of cultivable land. A rough calculation of the share of cultivable land actually cultivated in each district, based on the cultivation capacity of the rural family, shows that only 30% of total cultivable area are being used. Of the thirty districts reviewed, nineteen did not cultivate 50% or more of the available arable area. These assessments indicate that many districts appear to have substantial land of moderate to good potential available land for crop-based production.
With the return of security and stability, and the migration of small farmers from the densely populated southwest and northwest into under-utilized zones in the west, the cultivated area will continue to be expanded as it has in the past.
An estimated 4.6 million ha were under cultivation in 1990. However, it is likely that the actual area is somewhat smaller, since there is no registration available indicting percentages of double cropping and intercropping. Of the total area under cultivation in 1990, 36% was under perennial crops. Of the 1.7 million ha under perennials about 1.4 million ha was under bananas, and 0.25 million ha was under coffee. Sugar was grown in about 50,000 ha and tea covered about 50,000 ha. Except for about 70,000 ha of cotton and 4000 ha of tobacco, annual crops were all food crops. Of the 2.9 million ha in annual food crops, 1 million ha were in pulses and 0.4 million ha in oil seeds. Annual crops like maize and cassava remove a lot of nutrients and if they are grown yearly without replenishment, the soil would get exhausted. If maize is interplanted with cassava, soil nutrient depletion would be faster, and yet this is a common practice in Uganda where population density is high. Table 4 indicates the amount of major nutrients removed by the major food crops in 1989. In the annual crop zone with a more severe dry season, finger millet has been the staple food but has recently been replaced significantly by maize, cassava and sweet potatoes. These food crops are cultivated in rotation with cotton and groundnuts. Uganda has been a significant oil seed producer, groundnuts and simsim (sesame) being two major crops. Within the zone, groundnuts have predominated in the east in Teso, Busoga and Bukedi Districts, while sesame is mainly grown in Luwero and Bunyoro Districts. Increase in population growth has accelerated soil degradation, land fragmentation, deforestation and leaching. Sanchez (ICRAF) has shown significant losses of nutrients when the land is cultivated (Table 2).
Since Uganda's population has been growing at the rate of about 3% soil productivity should have also increased at a similar pace. However, agriculture has been growing at the rate of only 1.5% by increase in the area rather than in productivity per unit area. The highland areas which carry over 50% of the population are therefore threatened by soil degradation due to soil erosion and intensive cropping without rotation or addition of manure and fertilizers. According to Bagoora (1988) the areas of high erosion risk lie between 1.500 and 2,500 m. In the Southern and Western crop zone, the main crop, bananas or plantain, is grown mixed with Robusta Coffee on a smallholder family farm. Bananas are the staple food in this zone. Favourable natural conditions have fostered the development of this system for cultivation of these two major perennial crops. 322 Uganda
TABLE 2 Comparison of nutrient balances between an undisturbed tropical rainforest and a small farm agro- ecosystem Nutrient Balance Amazon Rainforest* Kenya Farms ** N P K N P K Inputs Atmospheric deposition 6.1 0.2 10.6 6 1 4 Nitrogen fixation 16.2 - - 8 - - Organic manure - - - 24 5 25 Mineral fertilizers - - - 17 12 2 Total 22.3 02 10.6 55 18 31 Outputs Crop harvest removal - 0 0 55 10 43 Crop residue removal 0 0 0 6 1 13 Runoff and erosion - - - 37 10 36 Leaching 14.1 0 4.6 41 0 9 Denitrification 2.9 - - 28 0 0 Total 17.0 0 4.6 167 21 101 Balance +5.3 0 +6.0 -112 -3 -70 Notes: * Oxisol in Venezuela (Jordan 1989), ** Kisii District (Smaling 1993), - Not determined or negligible
TABLE 3 Production of cereals and bananas, 1987 to 1997 Year Area under Total cultivated Area under Per caput Cereals (has) land Bananas cultivated land (000 ha) (ha) (ha) 1987 855 3624 1988 972 3934 1989 1079 4148 1990 1055 4277 15 720 0.27 1991 1099 4385 16 700 0.26 1992 1139 4498 17 522 0.26 1993 1220 4673 18 102 0.26 1994 1295 4769 18 682 0.26 1995 1292 4862 19 263 0.25 1996 (Estimated) 1318 4960 19 484 0.25 1997 (Projection) 1335 5033 20 438 0.25 Increases 56% 39% 30% Source: Republic of Uganda Statistical Abstract 1997
Cultivation of bananas in a well established farm will provide a family with their basic starch requirements for a lifetime and helps to free the family labour for the cultivation of Robusta Coffee as a cash crop. According to Tumuhairwe (1996) most of Uganda's bananas soils are currently of low soil fertility status especially in terms of K, P, N and organic matter. The plateau in the Southern and Central region which used to be the traditional major banana growing area has now poorer soil fertility status than the highlands in South-western, Western and extreme Eastern regions. Data presented in Table 3 indicates that the area under cereal production increased by 56% over a ten year period 1987 to 1997 and the total cultivated land increased by 39%. Since the rate of food production has not coped up with population increase as seen above, it is the increase in area that has mostly catered for the increase in food production. Accordingly the per caput cultivated land has decreased slightly form 1990 to 1997 indicating the trend in land pressure. What is making the situation worse is the tremendous increase in the cultivated land under cereals which (as seen above, Table 1) tends to lose tremendous amounts of nutrients Integrated soil management for sustainable agriculture and food security in Southern and East Africa 323
EXTENT OF SOIL DEGRADATION AND ITS BIO-PHYSICAL AND SOCIO-ECONOMIC IMPACTS Background information Land is by far the most important natural resource in the country. About 90% of the country's population live in rural areas and directly depend on the land for cultivation and grazing. Most of these farmers are engaged in small scale arable and livestock farming. The national average farm holding is about 2.5 ha and about 8.4 million hectares are farmed annually under small scale agriculture (National Biomass study, 1995; Magunda, 1993). Consequently Uganda's economic, social welfare and its environmental quality depend on effective and efficient empowerment of the resource-poor small-scale farmer. Low and insecure incomes at the grass root level leads to inability to promote and apply new technologies (equipment, seeds, soil and water conservation measure etc.). The low income levels prohibit the resource poor farmers from hiring additional labour. Consequently most of the labour is provided by the family with women and children providing the largest proportion. Low ownership of production assets (ploughs, sprayers, shellers etc.) is an additional limiting factor. The numerous production constraints lead to subsistence farming (low acreage, simple hand tools etc.) and consumptive spending. Consequently production per unit area is low and the farmers have remained poor. The current pattern of land management and utilization as well as the increasing demand for land present numerous environmental problems. Inappropriate farming practices/systems are ranked second in the underlying causes of land degradation in Uganda; poverty and land fragmentation leading to over exploitation with inadequate soil and water conservation is ranked first. Land degradation is the loss of utility or potential utility, or the reduction, loss or change of features or organisms which cannot be replaced (Barrows, 1991). Soil degradation is the partial or total loss of the productivity of soil in quantitative or qualitative attributes. Vegetation degradation is the reduction in vigour and/or species diversity or a decline in regeneration which may spread over decades.
Types of soil degradation Soil erosion is the most important form of soil degradation and a large part of the country has been affected to one extent or another (NEAP, 1995). Some of the most seriously affected areas include the steep slopes of Kabale, Kisoro, Bundibugyo, Mbale and Kapchorwa districts. Even in the relatively flat areas such as Iganga, Kamuli, Tororo and Kumi, soil erosion has occurred at an alarming rate largely through rill and sheet erosion and thus leading to gradual but steadily increasing losses in soil productivity (NEAP, 1995). Soil erosion is very severe in the semi-arid areas of Uganda where fragile vegetation cover has been degraded by over stocking under nomadic grazing. The seriously affected semi-arid areas include Karamoja, Soroti, Katakwi, Mbarara, Rakai and North Luwero. These areas suffer from both water and wind erosion. There is extensive wind erosion in Kumi, Soroti, Katakwi, Kotido and Moroto during the dry season because soils remain exposed during prolonged dry months after the cultural practice of uncontrolled bush burning. Apart from the rapid decline in fertility and productivity of the original land, soil erosion has also led to the siltation of rivers and lakes. In addition to the physical obstruction, the sediment is also rich in nutrients and thus encourages eutrophication. This, in turn, deprives the fish population in these waters of oxygen when the excessive vegetative growth decays as a result of bacterial action. This phenomenon is observable in most of the rivers and lakes but more particularly in the Manafa, Kafu, Nyamwamba and the Nile river (NEAP, 1995). Rainfall can be singled out as the most important climatic factor contributing to erosion in Uganda. Several workers (Bagoora, 1990; Tukahirwa, 1996; Magunda et al., 1997) have investigated various aspects of the causes of soil erosion and made recommendations on remedial measures. These studies have shown that the soils in the Kabale highland areas (>1500 m a.s.l.) are very stable and exhibit high infiltration rates (>100 mm hr-1). They have shown that in the highland areas the main causes of soil erosion are a combination of the slope and rainfall factors. Soil fertility decline or nutrient depletion is 324 Uganda
basically due to inappropriate or poor farming practices as explained before. Fertilizer use is restricted to large estates because the majority small scale subsistence farmers cannot afford fertilizers. Available data show that fertilizer consumption in Uganda declined 10 fold between 1962 - 1980, reducing the input of phosphates (P) and nitrates (N) to virtually zero except in large estates. Quantities of fertilizers imported into the country between 1990 - 1995 averaged 6,000 tonnes per year while quantities of pesticides and herbicides imported averaged 435,000 litres/year and 105,000 litres/year respectively (Magunda, 1995). These quantities, though increasing, compared to those used between 1962 - 1980, are very low considering that approximately 90% of the population in Uganda is engaged in farming. Besides nutrients depletion through crop harvest, leaching and erosion, nutrients are also lost fast when high yielding improved seeds are introduced without at the same time, introducing appropriate soil management packages. Soil degradation in Iganga District is partly attributed to the growing of heavy feeder soybean during the Amini era (1971 - 1979) without any fertilizer input or use of rhizobia inoculant. Crops following soybean yielded poorly. Soil compaction is serious in those districts of Uganda which are over stocked and overgrazed. These are the rangelands or the "Cattle Corridor" districts of Moroto, Kotido, Mbarara. Luwero, and Masaka. These rangelands cover an area approximately 84 000 square kilometres. These areas are seriously degraded because of the high animal population in most areas. The immediate impacts of the high numbers are de-vegetation and compaction which subsequently leads to serious erosion. Soil compaction occurs in most areas where large-scale mechanized farming is practised. It is particularly notable on large estates where heavy machinery is used for bush clearing and other field operations. This is common in parts of Mukono and Jinja districts, where large - scale commercial sugar cane growing takes place. Kigumba in Masindi district where large scale mechanized farming has been introduced in recent years is also beginning to show symptoms of soil compaction (bulk densities >1.5 gm cc-3). The districts of Kumi, Soroti, Katakwi and Lira which were heavily stocked and ox ploughing was practised also had problems of soil compaction, until the recent rustling that deprived them of their cattle. Surface crusting is extensive but "salient" in Uganda because many farmers are not aware of its existence and effects. Structural and depositional crusts are very prevalent in Uganda although they are not well documented. Their formation is mainly attributed to poor soil structure (particularly on soils that are under continuous cultivation), low organic matter content leading to unstable structure, heavy rainfall providing the required kinetic energy to shatter the soil aggregates or particles, soil management with heavy machinery, heavy silt loads in running water (Magunda, 1981). The consequence of crusting, is quite severe sometimes and replanting must be done due to the failure of seedlings to emerge through the surface crust. Experience at Namulonge Agricultural Research Institute showed that cotton had to be replanted on several occasions due to severe crusting (Magunda, 1981). The ultimate consequence of replanting is not only the costs of repeating seedbed preparation in order to break the crust, but also the fact that the most optimal planting period is lost. Waterlogging or the excessive saturation of soil by water is common and severe in most river valleys, swamps and areas adjoining lake Victoria and Lake Kyoga, where hydromorphic soils are most affected. After the peak flood period the soils become excessively dry, compact and crack into large lumps especially during the dry season. These areas require ox ploughing or use of tractor drawn implements because of the heavy nature of these soils i.e. in most cases small-scale farmers, that depend on hoes, cannot effectively till these areas because of their high tillage power requirements. In areas where tillage power is limited these areas are not utilized. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 325
Causes of soil degradation The causes of soil degradation are complex and involve interaction between several factors. Land tenure and the related socio-economic factors are among the important causes of soil degradation. Close to 40% of agricultural holdings in Uganda are comprised of two or more non-contiguous small holdings. Furthermore, 85% of the rural households produce both food and cash crops and raise livestock on holdings of 2.5 hectares. Land fragmentation is most serious in the heavily populated districts of Kisoro, Kabale, Mbale, Kapchorwa and Bushenyi. The most notable consequence of land fragmentation is continuous cultivation often without adequate soil conservation or regeneration measures. This situation has led to the two major forms of soil degradation - massive loss of soil through erosion and rapid decline in soil productivity or nutrients mining. There are nine farming systems in the country each with its degradation problems. The magnitude of the degradation in each system is largely driven by population pressure, land pressure and other bio-physical factors. The majority of farmers have inadequate knowledge of or few opportunities to learn about improved farming methods. The lack of exposure to better practices has been blamed on the inadequate/poor extension system. Overgrazing is extensive in the cattle corridor extending from Moroto and Kotido in the north east through the flat areas of Lake Kyoga down to the Masaka and Mbarara regions. These areas are seriously degraded because of the high animal population. Close to 70% of the livestock in the country is in the hands of traditional keepers while the rest is commercial ranching. In these areas overgrazing is a serious problem. Particular areas affected are the counties of Ruhama, Nyabushozi, Kazo, Buruli and the whole of Karamoja region (NEAP, 1995). The resulting effects of overgrazing include soil compaction, erosion (particularly gully erosion) and the emergence of xerophytic species with subsequent decline in carrying capacity and therefore low productivity. Although purchased physical inputs (agro-chemicals, seeds and tools) represent less than 30% of the total cost of crop production in Uganda, the current trend indicates that the use of pesticides is becoming widespread. The recent developments in the cut flower industry, in the last three years, have shown a tremendous increase in the use of agro-chemicals on large estate. It is however important to note that the small holders have had little, if any, training or skills in pesticide application/ use, storage or disposal. Overall use of agro-chemicals is still very small and limited to large estates. Acaricides are commonly used for the control of ticks, especially in the rangelands, however their degradation effects are localized. While there are several causes of deforestation, the conversion of forested lands into agricultural areas has been the principle contributing factor to loss of forest cover. Deforestation for agricultural purposes has occurred in gazetted forest areas through encroachment or official de- gazetting, as well as on unprotected public areas. It is estimated that between 1973 and 1986 Uganda lost a net acreage of 256 Km-2 of natural vegetation to agriculture, thus exposing the land to agents of soil degradation (FAO/UNEP, 1993). The seasonal burning of grass and bushes occurs widely in Uganda and carried out as part of land preparation for cultivation or for rejuvenation of pastures or to facilitate hunting of game. The exposed land, after burning, is subjected to wind erosion during the dry season and water erosion on the on-set of rains. This cultural practice is widespread in Uganda but is particularly intensive in eastern Uganda in the districts of Kumi, Soroti, Katakwi, Moroto and Kotido. 326 Uganda
Severity of soil erosion in Kabale Area Kabale area is taken for the assessment of the extent and severity of one form of degradation - soil erosion. Erosivity of the rainfall, steepness and length of slope, vegetation cover and land management influenced by anthropogenic factors are the most important factors that influence the amount of run off and soil erosion in Kabale. Several workers (Bagoora, 1990; Bagoora, 1993; Tukahirwa, 1996) have carried out assessment of causes and effects of soil erosion, in Kabale district, with the aim of providing information for the design of more accurate conservation policies and strategies. Bagoora (1993) obtained very high erosion values of 106.08 g per M-2 soil loss in a single rainstorm on a recently opened plot on a valley side slope (14.3o). Tukahirwa (1996) on a different site found low run off and soil loss (run off was 6.25, 14.83 and 13.76 mm per ha per year and soil loss was 1.4, 38.29, and 19.40 tons per hectare per year) on 10%, 25% and 45% slopes respectively. Under green house conditions with simulated rainfall Magunda et al. (1987) obtained 0.19 kg/ M-2 soil loss on 5% slope in a storm of 63 mm hr-1 of a duration of one hour; this was on a Palehumult soil from Kachwekano. It is important to note that none of these workers addresses the economic impacts of this mode of degradation. Soil erosion estimates extrapolated from the run off plot studies have over estimated the actual micro-catchment soil loss. Data on the different forms of degradation are very scanty in Uganda. Consequently there is hardly any data on economic analyses of degradation. Yields have been quantified on plots under different management practices in soil erosion studies but detailed economic impact assessments have not been carried out. Accessing data in Uganda is further complicated by the lack of databases in the relevant line institutions handling natural resources management research. Information dissemination is still very poor in Uganda.
Socio-economic constraints for the control of soil degradation In situations where farmers have no permanent title to land, there is a reluctance to adopt improved land management and conservation practices. The less secure the land ownership the greater the tendency for the farmers to exploit it using non-sustainable practices. Credit is often unavailable to tenant farmers and consequently they are unable to invest in new seed varieties, agrochemicals and new technologies. In the Central Region the majority of land operators are tenants since also women traditionally were not supposed to possess land titles, gender has something to do with poor land management and soil conservation. Increasing population. Population growth increases the pressure on the land. In the absence of sound soil management practices and adequate amounts of inputs, the soil is "mined" of its nutrient content and eventually becomes unproductive. The Eastern and Western Regions are very highly populated and soil degradation is quite extensive in these areas as well as in the Central Region. The Northern region which is not so densely populated is less degraded. Poverty in rural areas. Most small-scale farmers produce at the subsistence level using very low inputs of external resources. Yields are often poor and farm incomes are too low to sustain the family, let alone to maintain the resource options for maintaining soil fertility using crop residues which are severely constrained by competing uses for a scarce resource. Presently poverty has deepened in the countryside as agricultural productivity dwindles. Awareness. Farmers may be aware of declining soil productivity as indicated by reduced yields but they may have no knowledge of improved methods of soil management. They would have used some of the locally available inputs to rehabilitate the degraded soils. Technology transfer. Effective research and development in agriculture involves vertical and horizontal transfers of information. Vertical transfers involve the flow of information from the farmers to Integrated soil management for sustainable agriculture and food security in Southern and East Africa 327
researchers and back to the farmers through extension services. Often research priorities have not been set with a clear appreciation of farmers' needs and constraints. The horizontal transfers involve exchange of information between the farmers and between African states of experiences and solutions to common problems. This can be achieved through conferences, workshops, scientific exchanges and information media. Transfers of new technologies from advanced research institutions outside the African sub-region must also involve assessment of their applicability to local agro-ecological conditions.
AVAILABLE TECHNOLOGICAL OPTIONS FOR CONTROLLING SOIL DEGRADATION AND ENHANCING PRODUCTIVITY There are a number of technologies existing in the country, which can be used to combat soil degradation. What is required is awareness through various media and demonstrations.
Use of chemical fertilizers. Data shown in Table 4 indicate that Uganda uses very small amount of chemical fertilizers despite the fact that allot of nutrients are lost through crop harvest. This is so because fertilizers are expensive (on average shs 600/= per kg) and there is a very strong campaign by politicians and NGOs against the use of chemical fertilizers in preference for organic farming. As a result, some farmers even fear to touch fertilizers. Presently it is only commercial farmers who use chemical fertilizers, yet these fertilizers give very good responses when used properly. For instance Zake et al (1996a) reported an increase of 125% for the yield of bananas by using only 25 kg K/ha of muriate of potash.
TABLE 4 National consumption of N1, P2, O5 and K2O in selected years from 1962 to 1988 Year N P2O5 K2O Total 1962 1200 1100 300 2600 1964 1500 1200 500 3200 1966 1864 1500 1000 4364 1968 1709 1327 740 3776 1970 2220 1150 1200 4570 1972 4400 2500 1200 8100 1974 4000 2400 787 7187 1976 872 660 157 1689 1978 300 500 300 1100 1980 0 0 0 0 1982 500 100 0 600 1984 0 0 0 0 1986 200 0 0 200 1988 500 0 0 500
Organic-inorganic fertilizer combinations. This is one of the most important options in controlling soil degradation and also in enhancing productivity. It may be used in different soils. The Levels of combinations may vary according to soil type, crop and nature of organic matter. Zake et al (1996) obtained different combination results in different places using coffee as a test crop. Treatments consisted of four levels of coffee husks, 0, 5, 10, and 15 t/h a represented as OM1 OM2, OM3 and OM4. N, P, and K were applied in the form of N:P2O5: K2O fertilizer, at rates 0:0:0, 14:100:30, 80:200:60 and 120:300:90. These were symbolized as NPK1, NPK2, NPK3 and NPK4. It is especially, convenient with organic matter of high C/N ratio and also moderates the unfavourable properties of chemical fertilizers. Ashes normally lack nitrogen, whereas cow dung is deficient in phosphorus. A combination has been found effective in the production of bananas. This technology is common where 328 Uganda
bricks for building are fired, using a lot of firewood. Phosphorus rock with composts manure - used around the source of the rocks; it has been found effective in increasing the availability of phosphorus. Since Uganda mostly use fresh food e.g. bananas, potatoes, cassava, fresh maize, vegetables and fruit, there is a lot of urban garbage which tend to cause health hazards. Composting the urban wastes has contributed to the food productivity in some of these areas. In the city of Kampala alone over 1 000 tonnes of garbage are produced every-day. Appropriate placement of organic material Depending on the texture of the soil, different crop yields have been obtained according to whether the organic material was applied on the surface, completely incorporated or half incorporated and half surface applied (Zake et al., 1996a). In heavier soils, there are advantages of incorporating some organic materials into the soil, especially around Lake Victoria area (Figure 14, Zake et al.,1996a). Use of organic mulching materials Different mulches have been found to give significantly higher yields of bananas compared with the control, but live mulches when permanent in perennial crops may depress yields (Zake et al., 1996a). Mulches are used widely in banana growing areas. Integrated Pest Management-IPM Rubaihayo (1992), indicated that some of the reasons for the disappearance of bananas from around Lake Victoria to Western Uganda were because of extensive infestation of weevils and nematodes as well as soil nutrient depletion. Many farmers are now using concoctions of various herbs, animal urine, wood ashes and hot paper. This has a dual action of killing the diseases and pests as well as providing the major nutrients especially N and K. This technology was developed and it is being extended by farmers themselves. Crop Residue Management. The objective of this technology is to harvest the minimum and leave in the field all the rest. This is in response to burning the crop residue or putting it at the boundaries as part of clean weeding. Before this technology is recommended the problems caused by diseases and pests should be watched. Green Manuring. Inoculated legumes are turned into the soil before flowering. This protects the soil when the major crop is harvested and increases the level of nitrogen. Zake (1988) and Wortmann et al. (1994) have demonstrated the use of this technology in Uganda. Inoculated legumes together with phosphorus Rock Since the application rate of phosphorus rock is high, this technology is convenient for use in areas near the source of the rock, such as Tororo near Sukulu rock and Mbale near Busumbu rock. Zake (1988) obtained promising results using this technology which would avail both nitrogen and phosphorus to crops. Biological Nitrogen Fixation as a low-input technique. The Department of Soil Science, Makerere University, produces rhizobia inoculants for various legumes. It also exports some to Rwanda. Locally, this technology is slowly picking up for use in producing soybean, beans, groundnuts and tree crops. The major concern is that the technology does not work well for beans which are the most widely grown legume in the country. However, this technique provides feasible crop management that increases legume crop yield and crop residue. The cost of rhizobium packets required to inoculate seeds enough to plant a hectare of land is U.Sh 4800/= compared with the cost of a 50 kg bag of Urea of U. Sh 28,000/=. Nkwiine et al. (1993) have obtained good results in BNF technology. Appropriate tillage and surface management For lighter soils there is minimum or zero tillage while for heavy soils such as Vertisols there is deeper regular tillage requirement (Zake 1993). In heavy soils many farmers are aware of higher yields after tractor ploughing. Water harvesting. Various methods of water harvesting have been used, especially in places which experience drought or in places with heavy surface soils such as Vertisols. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 329
Improved fallow. The traditional fallow period takes many years for the soil to recover the depleted nutrients and organic matter. With improved fallow there is an inclusion of inoculated leguminous trees which help to increase the level of nitrogen in a short period. The fallow period in this case may be only three years. This technology is becoming popular in the Western highlands of high population. Animal - Crop (Cereal) - Forestry farming system. The forestry trees are normally leguminous shrubs which can be fed to animals (cattle, goats) and the manure from the animals is put into the crop field. In the peri-urban area where zero grazing is practised, this system is becoming popular. Agroforestry. A combined stand of plants of different growth habits and phenotype. Mechanical soil conservation measures such as contour bunding, contour trenching and bench terraces have not been widely adopted by small-scale farmers in tropics because of high installation and maintenance costs and lack of short-term benefits. Yet some agroforestry techniques have great potential for soil conservation and the scope of their adoption is also high because they combine production with soil protection. The relevant technologies for sub-humid to humid tropics are: Contour (or barrier) hedgerows on sloping lands, trees on conservation structures, and multi-strata systems (Rao 1994). In Uganda a number of these techniques are used in the Western region. Appropriate intercropping. This provides balanced nutrient uptake from different soils horizons and a more continuous ground cover, protecting the soil against erosion. Alley cropping. Farmers' acceptance of this technology is limited because of the loss of income from the space taken by the hedgerows and lack of returns from the efforts required to maintain the hedgerows. SUCCESSFUL CASES OF IMPROVED SOIL MANAGEMENT The Nangabo Farmers Association is an association which was set up by the local farmers in Nangabo Sub-County, Mpigi district. The county is situated around 15.5 kilometres north east of Kampala. The members of the association practice all types of occupation including some professionals. The majority of the Nangabo people (60.8%) get their income from agriculture. About 70% of farmers have less than 2.5 hectares of land per household. Very few farmers (9.9%) have 5 or more hectares of land. However there is a ready and near market for agricultural products in Kampala City. The majority of the farmers (98%) grow root crops, followed by legumes (88.2%) and third was bananas (86.3%). Many farmers kept poultry (64.7%) followed by those who kept cattle (49%) and third animal type kept are pigs (41.2%). Many farmers are knowledgeable of the soil management practices like mulching, crop rotation, land fallowing, construction of soil bunds and furrows, and use of inorganic and organic fertilizers. It is indicated that farmers who practice the soil management practices range between 40% to 83%. The least practised soil management practice being the use of inorganic fertilizers (41.2%); very small percentage of farmers did not practice and did not know the practices. In order to benefit to develop agriculture in their area, farmers of the sub-county set up their association with three objectives: to be self sufficient in food especially to be able to once again grow the liked staple foods for example bananas, to alleviate poverty through agriculture and to sustain production without damaging the environment. The strategy laid by Nangabo farmers to develop agriculture in their area : mainly persistent in farming business, effective cooperation, proper leadership of their association, accessibility to practical agricultural information and practising good farming systems according to agricultural information obtained from different sources. Agricultural Programmes of Nangabo Farmers Association have been successful mainly because of efficient association of farmers with active farmer participation in the diagnoses and implementation. Exemplary leadership (i.e. leading people in what you are also practically doing) or farmer to farmer extension has contributed much to the success. Raising awareness of farmers 330 Uganda
in seeking for agricultural information is also identified as a requirement for development of agriculture. Radio programmes as source of agricultural information in this case is very effective. In fact when we discussed this Mrs. Ruth Nsubuga Nalongo, 55 years old of Katta village, Nangabo, praised the agricultural radio programmes put on Radio Uganda. She could not imagine missing any of them. Her problem was to get constant availability of dry cells for her radio. The members of the association have benefited from agricultural radio programmes to the extent that the association now has a weekly radio programme to inform the members and other people from other districts.
INSTITUTIONAL FRAMEWORK AND POLICIES FOR LAND RESOURCES MANAGEMENT Institutions The ministries and institutions having something to do with conserving soil degradation are the following: · Ministry of Agriculture Animal Industry and Fisheries which is the ministry responsible for policy formulation regarding crop production, strategic planning, management systems reform and information strengthening. The Ministry also supervises the National Agricultural Research Organisation (NARO), responsible for national agricultural research. · Ministry of Natural Resources. The role of the environmental protection department in relation to agriculture is, among other tasks, to co-ordinate inter-disciplinary activities with the responsibility to monitor the use of chemicals and fertilizers, to advise on their effects and to assess the environment impact of all projects. · Ministry of local Government. The 21 000 kilometres of rural feeder roads, essential for transportation of agricultural products to domestic and export markets are responsibilities of this ministry through its objective administration.. · Ministry of Trade and Industry, responsible for developing marketing policies for various crops. Movement permits to traders and internal marketing are controlled by the various authorities within the ministry. · Ministry of planning and economic Development. Since Agriculture is the main foreign exchange earner; this ministry is central in overseeing agricultural productivity together with the Ministry of Finance. The Uganda National Council For Science and Technology is under the Ministry of Planning. · Uganda Commercial Bank. In addition to banking, the bank undertook agricultural lending through Rural Farmers Scheme. This scheme however, has not produced the desired effects. · Makerere University - Faculty of Agriculture and Forestry - also carried out agricultural research and extension. It should be noted, however, that the University is under the Ministry of Education and Sports. In the East Africa region the soil Science Society of East Africa was set up over twenty years ago and scientists have been meeting yearly rotating in the East African Countries of Kenya, Uganda and Tanzania. A lot of soil information in the region is contained in the proceedings which are compiled after each conference. The African soil science society was also started in 1988 and so far two conferences have taken place. A number of local journals also exist in different countries, regions and continentally. All these, however, are spoiled by the acronym "Publish or perish". The researchers' only objective is to publish Integrated soil management for sustainable agriculture and food security in Southern and East Africa 331
at any cost, without regard to the impact of the end-users of new technologies, the farmers. Over 99% of the farmers are usually not aware of the published information. Moreover, it is not clear whether this information is applicable to the farmers' situations. Land Reform Law. The Parliament of Uganda is currently debating the Land Reform law with the objective of giving peasant farmers Land security. This is supposed to limit the subdivision of agricultural land in unprofitable units. It will also ensure commitments of the farmers to the issues of soil conservation and rehabilitation. However, this issue is very delicate and it may take several years to reach a consensus. Since the poor tenants may have to pay the land lords to obtain the land titles.
Policies Before Independence in 1962, Uganda had very effective soils policy and both soil conservation and soil productivity were very high. There were strong decentralized systems of political administration and there were bye-laws in each district pertaining to soil conservation and crop productivity. Chiefs were responsible for enforcing the bye-laws. When the bye-laws were broken, the offenders received standard punishments just like for civil offences, since the same chiefs were also responsible for enforcing other social obligations such as collecting taxes, maintaining roads and ensuring proper health. Therefore both soil conservation and crop productivity were considered as civil obligations by the people; that is why the public responded positively. It is true force was used. After Independence, however, the political system changed towards very strong central governance. There was an emergence of agricultural extension officers replacing the chiefs in enforcing the bye-laws, but not in punishing the culprits. These officers drew their authority from the centre in Kampala. Consequently both soil conservation and crop productivity collapsed. With the emergence of concern over the environment regarding natural resources and concern over local administration, there are different organs of Government responsible for these areas. There is therefore often, general lack of co- ordination of activities between various departments of the ministries and between land-use related institutions, NGOs and agencies. This adversely affects the development of effective land-use policies within the country. Consequently there is often duplication of research efforts and the development and dissemination of different technological packages on similar topics to the same target group of farmers. The latter group often gets confused and the desired goal of improved management practices is defeated. The Agricultural Development strategy of the Government are: · Increase agricultural productivity, especially in food production, raising incomes and preventing expansion into marginal agricultural lands, · Diversify the production base and reduce the heavy dependence on coffee for exports and government revenue. · Raise yields by the adoption of appropriate technology through strengthened agricultural research and extension institutions, · To promote self sufficiency in food. 332 Uganda
PROPOSALS OF PROGRAMMES FOR IMPROVED SOIL MANAGEMENT AND PRODUCTIVITY ENHANCING Inventory of resources A semi-detailed survey should be conducted at national, and if possible, at finer scales in order to quantify the magnitude of resource degradation, and to assist the extrapolation and improvement of management practices. Rapid reconnaissance surveys are needed to collect data on the circumstances of farmers and resource utilization within their farming systems, as well as external sources of inorganic fertilizers, pesticides and organic matter. After the initial inventory is obtained, there should be periodical monitoring of soil degradation through crop yield, soil analysis and vegetative cover data.
Stream lining research and extension system in the country and in the region Agricultural research is the responsibility of NARO, Parallel to this, there is a strong research system by the University. These two bodies are linked loosely. Above these bodies there is the National Council for Science and Technology. The Ministry of Agriculture Animal Industry and Fisheries, however, does not house the National council for Science and Technology. There should be a clear National Vision, Mission, Strategy and objectives for agricultural research at any one time. This should be set from the top and the bodies below should realign towards the national strategy. In order to avoid duplication of research and conserve scientists, the University agricultural research system should be more strongly linked with the national research system. Extension should be integrated in the various sections of research just like the Land Grant colleges of the United States which incorporate national research, extension and training. Dissemination of research findings has always been the responsibility of extension staff. There should be a stronger linkage between the researcher, the extensionist, the administrator and the farmer, in every section of research envisioned by Cecilio R. Arboleda (Figure 18). The role of opinion leaders should be emphasized in research formulation and extension dissemination of results. That is why pre-independence extension by chiefs was very effective since they were respected by society. International organizations should be asked to facilitate networking among African Scientists and between African and non-African Scientists in the provision of facilities for publication and bilingual translations in the compilation of electronic data bases on relevant information and provision of exchange opportunities among African Scientists. They should also support the regional and continental scientific conferences. In fact Networking is the most cost-effective means of collaborative research. It helps cooperators to identify their priority targets and it is the most cost effective way of tackling research problems (Plucknett et al. 1984 and Greenland et al. 1987).
Training for improved soil management and sustainable agricultural productivity Many institutions of higher learning have abolished the Departments of Soil Science. They are no longer effective in combating soil degradation. Suggestions. Institutions should be created to encompass soil science. Such studies as agronomy, animal science and forestry should be attached to the studies of soils. The naked expansion of the subject of soil science is making the students of soil science redundant. In this respect the University of Philippines, Los Banos, has proposed the cluster of the Institute of Agricultural Resource Management to include soil science, farming systems and meteorology. To isolate soil science as a separate study eliminates its attention to the public. It should therefore be initiated in all sectors of study pertaining to the public. Another reason why soil conservation and food productivity succeeded before independence is that these areas were regarded as among other social aspects of society. A new area of study “social soil science" should be emphasized in the curriculum just like social forestry is succeeding in maintaining forests. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 333
Introduction of new technologies to the farmer When introducing new technologies, there should be several of these technologies including the use of locally available materials. It is not necessarily the technology that gives the best results that should be forwarded. The new technologies should start with the use of the ones which are partly familiar to farmers. This makes innovations more acceptable than would be the introduction of completely new ones at a go.
Liaison between National Research System and IARCs It is cost-effective for Uganda to have appropriate updated information from IARCs tested and transferred to the farmer as soon as possible. It has been observed that many technologies developed by the IARCs have as yet had very little impact in Uganda in contrast to some other countries in Africa. Therefore, it is recommended that a post be created in NARO to be responsible for contact with IARCs in order to be constantly aware of the latest available technologies for possible adoption trials and eventual use in Uganda (Hartmans 1989).
Soil science Soil Science is increasingly becoming a theoretical discipline rather than a field one. Every year there are volumes of books and articles written on such subjects as nitrogen, phosphorus, potassium equilibrium, CEC, synchrony etc. without any additional field impact. Although there are no available data, it is right to estimate that only about 1% of what is written and discussed in conferences yearly actually pertain in the field, in developing countries. In fact many soil scientists have acquired their expertise only by writing about rather than by influencing the management of the soil. it is high time the practice of soil science also acquired as much recognition. Some professional soil scientists should be encouraged to partake field experiences on a commercial basis and more funds be devoted to observing and understanding success stories especially of small scale farmers. There should be establishment of Soils Laboratories in the different ecological zones as a basis for research work in soil structure, soil biology and fertility problems. This will also help in appropriate recommendations to the farmers.
Research Long-term fertilizer usage for perennial and annual crops. There are currently only relatively long-term projects on banana and coffee management at Makerere University Agricultural Research Institute Kabanyolo (MUARIK). The Banana research started in 1992 and it is testing different mulches, fertilizers and different application practices of coffee husks. The Coffee research is testing seven different soils inputs including locally available low-input ones. This will avail several soil input options to the farmer. One new research for annual crops should be started to rotate maize in the long rain season with beans in the short rain season. This will give information on the rate and level of soil degradation under annual crops management. Research to test the interaction of inorganic fertilizers- organic matter and lime in different soils of Uganda. This is to respond to the current soil nutrient depletion, soil acidification making P unavailable as seen earlier, organic matter depletion and soil compaction. The output of this research will be appropriate soil management and use of locally available material in the case of organic matter. The degraded soil will be rehabilitated. Study on Soil Rehabilitation and soil fertility Management under Intensive cropping in Uganda: As the population increases, the traditional method of rejuvenating soil fertility through shifting cultivation can no longer sustain crop productivity. On the other hand the popular low input -agriculture cannot sustain intensive soil productivity especially with high yielding crops. However, chemical fertilizers 334 Uganda
alone may acidify the soil, cause soil physical problems and pollute the environment resulting into biodiversity imbalance. Therefore a long-term solution in necessary which increases soil productivity without damaging the environment. The proposed Study has the following objectives : · to provide balanced soil inputs that are based on locally available materials which would ameliorate soil fertility on a long-term basis without damaging the environment, · to avail to the farmer several soil ameliorating options. The scope of the Study is to provide fertilizer recommendations that shall be location specific. The question should be not what the optimum application rate is but rather how little fertilizer is enough. The research should involve the farmer in deciding on the different option combinations in a participatory manner after both the researcher and the farmer have agreed on the nature of the soil problem. The methodology would be as follows: · Recognize the nine Farming Systems identified in Uganda. · In each zone detailed soil and social economic surveys will be carried out to give: a) soil status according to the researcher and according to the farmer, b) dominant crop residue or organic matter resources e.g. green manuring materials, Coffee husks, water hyacinth, rice husks etc., c) identification of other soil resources available in the area e.g. phosphate rock, peat, wood ashes etc., d) identification of major cropping systems, e) identification of gender biases in farm operations; · Treatments will involve interacting organic materials in the area with non-organic materials based on those locally available, but usually to include low rates of NPK. · There will not be more than four treatments for each farmer including the control; but farmers will be able to opt for the suitable combinations deemed necessary by the farmers themselves; · Awareness sessions will be carried out for the existence of a number of options at the disposal of the farmers including the existence of new technologies such as biological nitrogen fixation, composting, green manuring and mycorrhiza. New practices such as planting in raw, proper spacing and water harvesting will also be pointed to the farmers; · Monitoring of the effects of the new approach will be made every year.
REFERENCES Bagoora, D.F.K. 1993. An assessment of some causes and effects of soil erosion hazard in Kabale highland, south-western Uganda, and people's attitude towards conservation. Utilization et Conservation des Resources. Montagnes et Hants, Pays de l'Afrique (2). Bencherifa, A. (ed.). pp 215-236. Bagoora, D.F.K., 1990. Soil erosion and mass wasting risk in the highland area of Uganda. Africa Mountains and Highlands, Problems and Perspectives. Messerhirwa, B. and H. Hurni (ed.). African Mountains Association, Walsmorth Press. USA. pp 133 - 135. Barrow, C.J. 1991. Land Degradation. Cambridge University Press. Bagoora, F.D.K. 1988. Soil erosion and mass wasting risk in the highland areas of Uganda. Mountain Research and Development 8 (2), 173-182. Cecilio R. Arboleda: Agricultural Technology Development and Transfer in the Socio-Economic Transformation of the Countryside: Professor and Dean College of Agriculture, University of the Philippines, Los Banos (UPLB) Integrated soil management for sustainable agriculture and food security in Southern and East Africa 335
FAO/UNEP. 1993. A Suggested National Soils Policy for Uganda. pp. 30. Greenland, D.J., Craswell, E.T and Dagg, M. 1987. International networks and their potential Contribution to crop and soil Management research. Outlook on Agriculture 16 (i):42-50 Hartmans, E. 1989. Five year Food Crops Research Plan 1989-1994; Republic of Uganda. Ministry of agriculture; USAID/MFAD Project. Langlands, B.W: 1974 Soil Productivity and Land Availability Studies" Makerere University, 1974. Magunda, M.K. 1981. A study of the effects of crust formation on germination and means of improvement. M.Sc. Thesis; Ghent State University, Belgium. pp 65. Magunda, M.K. 1993. Population pressure effects on watershed management practices in Lake Victoria basin : A review. Paper presented at the workshop on "Fisheries and Socio-Economic Changes in Lake Victoria Basin". (Unpublished). Magunda, M.K. 1995. Non Point Pollution in the Lake Victoria Basin. Lake Victoria Environmental Management Program Preparatory Country Papers. (Unpublished). Magunda, M.K., W.E. Larson, D.R. Linden and E.A. Nater. 1987. Changes in microrelief and their effects on infiltration and erosion during simulated rainfall. Soil Technology 10 (1997); pp 57-67. National Biomass Study. 1995. Land Use/Cover distribution -Uganda. Forestry Department, Ministry of Natural Resources. NEAP. 1995. The National Environment Action Plan for Uganda. Ministry of Natural Resources. Nkwiine C., J.Y.K Zake, P. Ebanyat and D. Siriri (1993) Biological Nitrogen Fixation As a low-input Technique For Sustainable Agriculture. A paper presented to the 6th Regional IBSRAM Seminar 24-27 May 1993 Kampala, Uganda. Plucknett D.L, and Smith, N.J. H. 1984. Net working in international Agricultural Research. Science 225:989- 993 Rao M.R. 1994. Agroforestry For Sustainable Soil Management in Humid and Sub-humid Tropical Africa. A paper presented at the IBSRAM Planning workshop on "Strategies for the Management of Uplands Soils of Humid and Sub-humid Tropical Africa "April 6-9, 1994 Abdijan, Ivory Coast. Rubaihayo, P.R. 1991. Banana Based Cropping Systems Research. A Report on a rapid Rural Appraisal Survey of Banana Production. Research Bulletin No. 2. Sanchez P.A. Tropical Soil Fertility Research: Towards the second Paradigm. ICRAF. P.O. Box 30677, Nairobi, Kenya. Ovational Paper. Third Monitoring Survey, 1995-96. Ministry of Planning and Economic Development Statistics Department. Draft third Monitoring Survey, 1995-1996 (Crops) Tukahirwa, J.M., 1996. Measurement, Prediction and Socio Ecology of Accelerated Soil Erosion in Kabale District. Ph.D. Thesis, Makerere University. Tumuhairwe J.Y. 1996 Soil Fertility Status of Banana growing Areas of Uganda. Paper presented at the first International Conference on Banana and Plantain for Africa, 14-18th October 1996, Kampala, Uganda. Wortmann, C.S. Isabirye, M., Musa, M, 1994. Crotalaria Ochroleus as a green manure crop in Uganda. African Crop Science Journal, Vol. 2 No. 1 pp. 55-61. Zake, J.Y.K. 1988. Research an application of Tororo rock phosphate as a fertilizer in Ugandan soils. United Nations commission for Africa. A paper presented during regional conference on development and utilization of mineral resources in Africa, Kampala, Uganda June 6-15 1988. Zake J.Y.K 1993 Tillage systems and Soil Properties in East Africa. Soil and Tillage Research (1993) Elsevier Science Publishers B.V. Amsterdam. 336 Uganda
Zake Y.K., D.P Bwamiki and C. Nkwiine 1996a Soil Management Requirements for Banana Production on the Heavy soils Around Lake Victoria in Uganda Paper presented at the First International Conference on banana and Plantain for Africa, 14-18th October 1996, Kampala, Uganda. Zake J.Y.K; D.P. Bwamiki and C. Nkwiine 1996 b Potential for organic and Inorganic Fertilization for sustainable Coffee production in Uganda. In Improving Coffee Management Systems in Africa. Proceedings of IACO workshop, Kampala, Uganda. 4-6 Sept. 1995. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 337
Zambia
COUNTRY FOOD PRODUCTION AND REQUIREMENT Zambia covers about 752 600 square kilometres. A large part of Zambia is on the central African plateau between 1 000 and 1 600 metres above sea level. Although Zambia is tropical, temperatures are modified by altitude. Zambia is subdivided into 36 agro-ecological zones; these have been grouped up into three agro-ecological regions mainly on the basis of rainfall. Region I covers the semi-arid, rift trough areas of Zambia, largely the Luangwa, Lunsenfwa and Zambezi valleys, the low altitude plateau areas in the south and south-west, that is Sesheke and the Senanga west. The region is characterized by high temperatures, high evaporative losses and a short growing season due to low and poorly distributed rainfall of less than 800 mm. Region II includes the entire plateau stretching from Eastern through Central and Lusaka Provinces to the Western and also covering Southern Provinces. This region has an annual rainfall ranging from 800 - 1,000 mm. Region IIb consists of the Kalahari sands area. Region III is popularly known as the high rainfall area. This covers the Northern, Luapula, Copperbelt, North-Western and part of Central Provinces. Annual rainfall ranges from 1 000 – 1 400 mm. Zambia has a rapidly-growing population. In 1990, the population was 7.8 million and the annual growth rate was about 3.2 percent (Population Census 1990). At that growth rate, the population in 1995 is estimated to be 9 million. By 2010, it could be 14.6 million, unless there is a reduction in the growth rate. About 43% of the country’s population were classified as urban in 1990, and the proportion is projected to increase to between 50 and 60 percent by 2006 (Ndiyoi and Tembo, 1995). The growth rate of Zambia’s agricultural production has not kept pace with population growth in recent years. Accordingly, the country faces serious and chronic food deficits in the coming years unless measures are taken to reverse the adverse trends. The country has faced food deficits in the past, mainly as a result of droughts. Equally, low food production especially cereals, have dropped in response to unfavourable agricultural policies. These drops in food production have not been matched with the country’ population growth. In the period 1992-94, the total value of food imports was 47.1 million US dollars. In the same period, the country received 795 077 metric tons of food aid in 1993. The 1992 drought highlighted the vulnerability of the country’s food supply to rainfall while the 1993 bumper harvest equally underlined the role of policy and institutions on agriculture. Assuming that the population continues to grow at the current rate of 3.2%, Zambia was expected to produce 1.5 million tons of cereals in 1996, rising to 2.0 million tons in 2006. This means that by 2006, the country’s cereal demand is projected to increase by 41% from the current level (Ndiyoi and Tembo, 1995).
Nawa Mukanda and Douglas Moono Mt. Makulu Research Station, Chilanga and Golden Valley Agricultural Research Trust, Chisamba 338 Zambia
In contrast, the projections of current trends indicate a cereal production increase of only 3%. In particular, using similar assumptions, national maize demand is projected to rise by 37% between 1996 and 2006, whereas total maize production is projected to decline by 2% in the same period. Cassava is the third most important food crop in Zambia after maize and sorghum. Like for maize, the demand for cassava is projected to rise by 37% from 247 000 Mt. in 1996 to 339 000 Mt. in 2006 while production in this period is projected to increase by only 2%. The projections suggest that unless prompt measures are taken to increase food production rapidly, the periodic food deficits observed could become chronic during the next decade and would need to be offset by food aid or commercial food imports on a large scale. Maize production figures and demand trends are presented in Table 1 and in Figure 1. Much of Zambia’s land is grossly under-utilized. Of the country’s total area of 753,000 sq. km, almost one-quarter (about 18 000 000 ha) is considered arable, but only 11 percent of this is cropped annually. Unfortunately, the population increase over the years has depended on this 11 percent causing land pressure. From 1990 to 1993, the agricultural sector’s contribution to GDP at constant 1977 prices was estimated at 15%, 16%, 11% and 16% respectively. The estimated GDP for the same period at current prices was 15%, 16%, 18% and 23% respectively.
TABLE 1 Maize production and demand trends in Zambia (tonnes) Year Estimated Maize Maize trend Maize Improvement Maize population production without NAP demand rate production trend with NAP 1984 6 456 786 871 740 1 246 186 891 037 1986 6 876 632 1 230 594 1 228 592 948 975 1988 7 323 779 1 943 219 1 210 997 1 010 681 1990 7 800 000 1 092 671 1 193 403 1 076 400 1992 8 307 187 483 492 1 175 809 1 146 392 1994 8 847 354 1 020 749 1 158 215 1 220 935 1996 9 422 644 1 409 485 1 140 620 1 300 325 0.000 1 140 620.46 1998 10 035 342 1 123 026 1 384 877 0.054 1 186 740.29 2000 10 687 880 1 105 432 1 474 927 0.147 295 329.39 2002 11 382 849 1 087 838 1 570 833 0.245 1 440 728.77 2004 12 123 007 1 070 243 1 672 975 0.332 1 602 085.82 2006 12 911 294 1 052 649 1 781 759 0.409 1 781 095.78
EVOLUTION OF PER CAPUT CULTIVATED LAND AND TRENDS IN CEREAL CROP YIELDS Maize, rice, wheat, other cereals (sorghum, bulrush millet, finger millet) and cassava are Zambia’s staple food crops. Maize generally accounts for 60 – 70% of the total cropped area and for over 90% of total cereal production. National area and production figures for important crops are shown in Tables 2 and 3. The tables given below show that production of staple food crops has varied greatly over the past decade. Contributory factors have been variations in annual rainfall and its seasonal distribution, and changes in economic policy. The production of cereals fell below potential demand in half the years of the past decade, but there was a surplus of more than 70% in 1988, a year with good rainfall and favourable prices. On the other hand, in 1992, severe drought caused a deficit of more than 50%. The food production and consumption projections shown in Figure 1 are based on historical trends. However, their relevance for future Integrated soil management for sustainable agriculture and food security in Southern and East Africa 339
FIGURE 1 Maize production and demand trends in Zambia
planning has been thrown into question by the effects of market deregulation since 1992. The 1995 trend appears to indicate that the production of maize, wheat and rice are to decline and for those of sorghum, millets, soybeans(plus other legumes), and possibly cassava to increase.
TABLE 2 Crop production (hectares and tonnes) in 1987/88 and 1993/94 Crop Maize Sorghum Millet Season Area Production Area Production Area Production 1987/88 753 244 15 526 831 33 964.5 214 534 35 462 279 951 1993/94 679 356 55 245 82 302
TABLE 3 Maize production and fertilizer application, 1996/97 Province Area planted (has) Production Fertilizer application (kg) (90 kg bags) Basal Top Central 93 455 1 703 611 3 805 551 3 983 Copperbelt 39 266 590 023 934 340 1 442 6 Eastern 198 996 2 756 589 1 970 979 2 306 786 Luapula 17 366 375 628 962 932 994 082 Lusaka 26 980 493 924 873 425 1 196 520 Northern 45 703 1 080 54 3 183 157 2 999 560 N-Western 25 216 425 094 307 711 397 384 Southern 158 757 2 799 285 4 531 688 4 356 179 Western 43 330 444 037 704 938 764 116
Tables 2 and 3 show very serious inconsistencies particularly for maize production. Two areas of interest can be compared here. These are Regions II and III. Region II has been the grain basket of Zambia, mainly represented by central, eastern and southern provinces. 340 Zambia
After independence in 1964, the Zambian government popularized maize production to the point where monocropping in Central, Eastern and Southern Provinces became the norm. This resulted in serious soil degradation. Over the years, southern province slowly lost its number one position in maize production mainly due to soil mismanagement as we have already seen under another chapter of this report. Over just an eight or nine year period from 1987 to 1996/97 both area planted and production have slowly but steadily been declining in Region II. For example, area planted under maize in central, eastern and southern provinces in the 1987/88 season were 119,047, 344,986 and 155,757 ha respectively; in the 1993/94 season the figures were 161,208 174,816 and 130, 745 ha respectively. In a summary form, Table 4 below gives areas planted under maize for 1987/88, 1993/94 and 1996/97. It is clear that things are happening in both central and southern provinces. The declines per caput cultivated land and maize yields are mainly due to two main factors: reaction to unfavourable agricultural policies and general land degradation. The main causes to the decline per caput cultivated land and cereal yields in Central, Eastern and Southern provinces are the high population growth rates; poor cultural practices such as low plant density, late planting, untimely weeding, poor crop cover, inappropriate tillage practices and tillage equipment; decline in soil fertility, soil erosion; frequent droughts, deforestation and inadequate financial services to smallholders. These have brought about a general decline in cropping land area per farm family and decline in crop yields and general land degradation. The major effect of these problems in Zambia has been widespread household food insecurity and poverty. The trends observed in Region II are supposed to be the opposite of those in Region III. Region III is characterized by high rainfall, and historically the region has not been a major maize growing area. But over the years, especially following the popularization of maize, there has been a steady increase in both area planted and production. Table 5 below give a summarized picture of maize production in the four provinces of Region III.
TABLE 4 Maize production areas (ha) and production figures (tonnes) in Central, Eastern and Southern provinces, 1987/88, 1993/94 and 1996/97 Years/area planted and production Province 1987/88 1993/94 1996/97 Area planted Production Area planted Production Area planted Production Central 119 047 3 44 515 161 208 - 93 455 1 703 611 Eastern 344 986 3 306 204 174 816 - 198 996 2 756 589 Southern 155 757 5 300 484 130 745 - 158 757 2 799 285
TABLE 5 Maize production areas (ha) and production (tones.) in Region III, for 1987/88, 1993/94 and 1996/97 Province Years/area planted and production 1987/88 1993/94 1996/97 Area planted Production Area planted Production Area planted Production Copper belt 24 947 842 886 29 785 - 39 266 590 023 Luapula 10 415 317 747 16 898 - 17 366 375 628 Northern 55 581 1 262 996 70 818 - 45 703 1 080 570 N/W - - 24 595 - 25 216 425 094
The drop in area planted in the 1996/97 season is the general reaction to the liberalized maize marketing policy. Since 1992, farmers producing maize are required to find market for their produce. This has disadvantaged rural provinces as transport costs have discouraged buyers who need to haul maize to the line of rail where the market is large. In the same period, there has been a very serious drop in the availability of financial services to smallholders resulting in the Integrated soil management for sustainable agriculture and food security in Southern and East Africa 341
abandoning of commercial maize production, and reverting to traditional crops such as beans, cassava, finger millet and sorghum.
EXTENT OF SOIL DEGRADATION AND ITS BIO-PHYSICAL AND SOCIO-ECONOMIC IMPACTS The causes of land degradation in Zambia relate to both bio-physical as well as socio-economic factors. The bio-physical and socio-economic causes and effects of environmental degradation are also inter- related. For example, deforestation will lead to environmental degradation. But the causes of deforestation are usually economic, social and cultural. This relationship tells us that when we are dealing with land degradation, we should approach it from a holistic point of view, thus, policy instruments must offer benefits as well as deterring options.
Deforestation Deforestation for agriculture is at a wider scale in Zambia. In the slash and burn (Chitemene) shifting cultivation systems, the distances to the chitemene fields are getting longer. The depletion of forests will reduce shifting cultivation. Thirty years ago, it was common to find chitemene fields under fallow of 15 years or older. But today, trees are rarely allowed to regenerate for about 10 years. In large urban centres, the demand for charcoal and wood fuel is increasing all the time. This demand is contributing to the fast depletion of forests and to desertification for example, in Mapangazya area of Mazabuka District and Monze East both in Southern Province, Mansa and Samfya districts in Luapula Province and the Kagoro area of Chipata District in Eastern Province. The role of forests in controlling natural soil erosion, nutrient recycling and water catchments has been negatively affected. This has resulted in increasing degradation of arable land and water supply.
Soil fertility decline One of the main reasons for shifting cultivation in Region III of Zambia is the inherent low soil fertility and inherent soil acidity and its associated aluminium toxicity. The majority of subsistence farmers in Zambia apply little or no fertilizers to crops. Since most of the soils of the country are already infertile, continuous cultivation is only possible for a few years after which people have to move to new land. This practice can no longer continue under increased population pressures. The direct consequences of soil infertility in rural Zambia is the perpetuation of poverty. The majority of farmers are resource poor. They cannot afford fertilizers, therefore, rely heavily on the slash and burn cultivation system, whose lifeline, the forest resources, are diminishing. Without fertilizers with less trees to cut for Chitemene; this translates into reduced yields. With increasing population, there will be less food to go around, thus leaving a weak and malnourished population with less energy to conserve the environment. Again the excessively long distances that have to be covered to well wooded areas for Chitemene fields, have resulted in reduced cropped land and indeed in the production of inadequate amounts of food. Elsewhere in the country, particularly in Southern, Eastern and some parts of Central Provinces, soil infertility has come about mainly due to over-use resulting in both chemical as well as physical soil degradation. Chemical soil degradation includes loss of soil fertility through leaching of bases or nutrients beyond the plant roots and the acidification and toxification of soils by the application of fertilizers. Leaching of nutrients beyond the plant root zone occurs in all soil types and is more prevalent in Region III where the rainfall is high (1 000-1 400 mm) and the soils are generally sandy. Over the years the soils have become acid due to the washing down of the bases such as magnesium, potassium and calcium by heavy rains. The result has been the build-up of elements such as aluminium, which is toxic to plant growth. The loss of soil fertility through leaching may be prevented by maintaining 342 Zambia
adequate soil vegetation cover, as this helps in recycling plant nutrients. Once the vegetation is removed, as in the slash and burn shifting system of the high rainfall areas of Zambia or when the stover is grazed as in the maize-cattle cultures of Eastern and Southern Provinces; or when other improper cropping systems are followed such as burning of crop residues, the nutrients in the soil are washed down very rapidly. Costly ameliorative measures such as liming and the application of fertilizers, which unfortunately cannot be met by the majority of small scale farmers have to be made to retain soil fertility. The application of mineral fertilizers to increase crop yields is not always beneficial to the soil. Particularly in Southern; Eastern and Central Provinces, experience has shown that on commercial as well as on medium scale farms where fertilizers have been intensively used over many years crop yields have been declined. This is partly due to increased soil acidity. All the fertilizer compounds presently in use make the soil acid after years of application. Some fertilizer materials, such as sulphur compounds, acidify the soil more quickly than others thus lowering the productivity of the soil after only a few years of use. Therefore, occasional liming of the soil is essential to maintain its fertility. Sodicity or salinity is more prevalent in Region I which has high evaporation rates and low rainfall. The Gwembe and Luangwa Valleys have a considerable occurrence of highly sodic soils. Exchangeable sodium percentages (ESP) usually exceed 15% in subsoils. Calcium carbonate levels are also generally high. The generally weakly developed soil structure and highly compacted layers in these valley soils may be attributed to high sodium levels. This is a serious threat to crop production mainly because these conditions promote low infiltration and permeability rates and secondly reclamation by use of gypsum would seem to be ineffective due to the already high calcium carbonate levels. On the other hand, saline soils inhibit plant growth by stopping plant uptake of nutrients and water. Application of sulphuric acid or sulphur on highly sodic soils with high calcium carbonate levels and adequate drainage to prevent the build-up of salts are alternative measures to improve these soils. In the Gwembe valley sodicity/alkalinity is a natural phenomenon due to the nature of the soils. Elsewhere, such as at Nakambala Sugar Plantation in Mazabuka, southern province and Mpongwe Farms on the Copperbelt severe sodicity/alkalinity has affected crop production as a result of continuous irrigation. Heavy operations to reclaim some parts of these schemes are taking place. In addition to high maize grain yields, the Sesbania sesban improved fallows resulted in production of 10, 15 and 20t/ha of oven dry wood following 1, 2, and 3 years respectively. This wood though of lower calorific value than the Bracystegia spp of the miombo, is substantial. It can relieve women and children the burden of firewood collection. At a land use system level, fuelwood produced on the farm could reduce miombo deforestation and conserve its biodiversity. In Region II this problem is highly prevalent on commercial farms where irrigation takes place. This problem is wide spread, but appears to be concentrated in the Lusaka and parts of Central Provinces, perhaps an indication of the kind of bed rock found in these places. This is exacerbated by improper or non-availability of, and/or poor drainage structures in place and possibly by the poor quality of water. Analysis of irrigation water for various elements, especially from the Lusaka and Chisamba areas have shown exceedingly high levels of calcium above threshold levels. Physical soil degradation manifests itself mainly in the reduction of soil porosity or through the loss of topsoil due to water or wind erosion. Most Zambian soils have coarse textured topsoils and are thus susceptible to erosion and compacting, mainly due to the destruction of the soil structure. Once the land is cleared of natural vegetation, the soil is exposed to high rainfall intensity and solar radiation. The result is rapid decomposition of organic matter by micro organisms and consequently a decline in soil aggregate stability and in water holding capacity. The decline in soil structure increases the risk of erosion. Soil compaction may also be caused by heavy tillage implements. In Southern, Central and Eastern Provinces of Zambia, soil structure and organic matter content deterioration is a serious Integrated soil management for sustainable agriculture and food security in Southern and East Africa 343
problem on cultivated land. It is a major contributing factor to the decline in crop yields. In the field, the destruction in soil structure is often observed by the formation of crusts on soil surfaces and hardpans or compacted layers below the topsoil. Soil surface crusts reduce water infiltration rates, hinder emergence and increase water run-off. Compacted soil layers reduce water storage and restrict water movement and hinder root penetration into the subsoil. This results in localized soil droughts leading to stunted growth and the eventual death of plants. To maintain good soil structure, crop residue incorporation, crop rotations, use of green manure, mulches and proper tillage practices must be employed. It is clear that most farmers who have over-used or misused their land have no financial resources, no labour or no enough land to practice any of the known ameliorative measures. This failure to practice some minimum conservation measures perpetuates low yields, poverty and hunger. Soil erosion by water is the most important in Zambia, though significant amounts of erosion by wind may occur on unprotected lands especially during and after ploughing time. The intensities of rainfall in Zambia are high, and this is the major factor influencing erosion rather than the total rainfall. Soil erosion is a major threat to crop production, more so in Central, Eastern and Southern Provinces. In Eastern and Southern Provinces, the physical causes of soil erosion are due to deforestation, dense human populations, overgrazing and poor crop cover and land management practices. In most of these areas, crowded cattle kraals are built around villages and both human and animal tracks create rills which eventually develop into deep gullies. Where gullies are common, they are reducing the area of arable land at a fast rate. In Central Province, the major factors causing soil erosion are the unsuitable soils and poor crop and land management methods such as ploughing down slope rather than across the slope. Most of the soils have sandy topsoils overlying heavier-textured subsoils, which, if not well protected, easily erode. Reduced soil fertility is the first consequence of soil erosion, especially in the Mkushi Farm Block where the soils are generally sandy. Burning as practised in chitemene kills most soil flora and fauna which are responsible for maintaining good soil physical properties. The destruction of organic matter denies the microbes the feed on which they depend during mineralization; thus reducing their numbers and making the soil inert. During mineralization, the breakdown of organic matter releases nutrients which are directly used by plants. Continuous cultivation without ploughing back crop residues into the soil enhances soil biological degradation. The ploughing of plant residue back into the soil, and also leaving land under fallow are, therefore, measures that can help maintain yields. The removal of vegetation cover or cultivation increases soil temperatures and reduces microbial activity. When all the organic matter is broken down the number of living organisms in the soil drops drastically rendering the soil inert. The slash and burn cultivation systems of Region III, the continuous cultivation and overgrazing problems in many parts of Region II contribute to biological soil degradation. A compacted soil due to various factors usually does contain very low levels of microbes and in such cases biological fertility of the soil is very low to the extent that crop production is hampered. The conditions which support the growth of these organisms in the soil are the available moisture, amount and type of nutrients, degree of aeration, temperature, etc. The ecology of soil microbes which is considered biologically fertile should contain a minimum 105 – 108 numbers per gram of soil with seasonal fluctuations. Soil microbes prefer moist soils for maximum microbial activity of decomposing organic matter. A study which was conducted in the Eastern Province of Zambia at Kagoro found that the bacterial plate count, a technique used in determining the total microbial counts per unit soil, was correlated with the soil chemical data for Mzime which recorded a higher nutrient level and organic matter (Tables 6 and 7). 344 Zambia
TABLE 6 Correlation of organic carbon (%) and microbial counts in the Kagoro Area, depth 0-15 cm Parameter Cultivated Fallow land 76 years O.C.% 0.57 1.62 Microbial count cells/g soil. 4.6 x 106 7.6 x 106 Source: After Bunyolo, et al 1995
TABLE 7 Yield of maize (kg/ha grown continuously without the return of stover) Treatment 1964-65 1965-66 1966-67 1967-68 1968-69 1969-70 No stover 7 840 7 572 7 809 3 194 3 379 2 760 Single stover 8 014 8 398 8 475 5 518 4 011 4 900 Double stover 8 120 7 596 8 113 5 306 5 599 4 780 After Bunyolo, et al 1995
Food insecurity Rural Zambia is generally food insecure. The major deficits are in staples, vegetables, and concentrated energy sources. The causes of food insecurity in most rural households of Zambia are many. The removal of fertilizer subsidies by Government has caused a decline in land productivity. Farmers have resorted to extensive use of the land with serious consequences on the environment. Other causes have been attributed to decreased household food production due to the infertile soils and the diminishing trees for chitemene. Poor on-farm food storage facilities result in less food stored for hunger periods. Staples such as cassava and maize are always in short supply between January to March every year. Vegetables are always in short supply during the cold dry season between June and the beginning of the rains in November. The long distances to fields has caused reductions in the size of chitemene fields, because more time is spent on walking to and from the fields. This translates into lesser yields and lesser available food. Lack of education on food preservation and lack of credit for non-cash-based crops such as beans, groundnuts and cowpeas have contributed to food insecurity in the country. Poor feeder roads in the country have amplified the problem of accessibility to support services such as credit, markets, agricultural supplies and health services. Lack of seed and other planting material are a major bottleneck for improving crop production as well as encouraging crop diversification. The shortage of both groundnuts and oil (no cash) means that the diet of most people is low in fat. The incidence of malnutrition among children in Zambia is recorded as 15%. However, some parts of Zambia such as Luapula Province have recorded up to 34% which is too high. In adults, protein energy malnutrition leads to weak bodies, easy attack of diseases and less productivity. There is urgent need to promote groundnuts and beans as these are some of the important sources of vegetable protein. The low availability of fats and oils is likely to affect the transport and utilization of vitamin A in the body. This scarcity of energy supplements is the principle weakness in the food security-situation in Zambia.
Population increase, land scarcity and land tenure In 1990, the total population of Zambia was estimated at 7.8 million while the cultivated land area is estimated at 2.5 million hectares thus giving a ratio of rural population to arable land for the whole country of 3 persons per hectare. In some parts of Zambia such as Eastern and Luapula provinces, population density is reported to be quite high. For example, in Luapula Province, population density for the valley area is reported to be about 200 persons per square kilometre. Such densities are far much higher for a purely chitemene based system to be sustainable. The increase in population has exerted tremendous pressure on agricultural land resulting in reduced fallow periods from 15 years to 8 Integrated soil management for sustainable agriculture and food security in Southern and East Africa 345
years and thus leading to low productivity. People are crowded where amenities such as good roads, schools, clinics, marketing facilities, etc. are available. Since well placed and accessible agricultural land is not adequate for all the people, its intensified use has led to serious degradation. The private ownership of land has been increasing since 1985. This has aggravated the pressure on land resources in some provinces. As the total land area under title deeds increase, gaining access to new land becomes more difficult, and the pressure on the land already under cultivation increases. This is likely to affect soil fertility as farmers will have to shorten the period of bush fallowing to maintain production levels on old fields. The traditional land tenure is very strong in Zambia. The rights over fallows or surrounding forest areas are very strongly developed and these rights are getting stronger as the population pressure is increasing. This breakdown of traditional distributive mechanisms of land have had and will continue to have a negative impact on the household food security and the living standards of the disadvantaged and vulnerable households.
Labour constraints Labour constraints have direct consequences on sustainability or on production that goes with conservation. Most rural households in Zambia are dependent on outside labour hired for agricultural work, like cultivating, or for food production preparation such as harvesting, pounding maize, etc. Recent studies further show that labour shortage was on land clearing, land preparation, planting, weeding, harvesting and transportation of produce from the fields to the homesteads. Despite other findings that show that labour shortage was mainly due to the disproportionate division of labour between males and females, the fact stands that implementation of environmental considerations into farming activities using hired labour will remain an issue of list priority. It is clear that as the environment gets more degraded, and food availability is reduced, the health of the people will decline; malnutrition will be on the increase leading to high infant mortality and reduced life expectancy, thereby reducing the population, especially the rural family sizes. This in turn will reduce the labour available; labour-demanding technologies might only lead to a worsening of the food availability or shortage in the country.
Poor infrastructure development The infrastructure development in the rural areas of Zambia are generally very poor. There are few good roads, clinics, schools, shops and marketing facilities. This has forced people to crowd in areas where these amenities are available. As a result there is tremendous land pressure for agricultural activities which leads to serious land degradation. If these amenities are not improved upon, feeder roads in particular, with the liberalized marketing arrangements now in place, private traders will shun inaccessible areas. Thus the delivering of inputs and the buying of farm produce will be determined by well maintained feeder roads. A deliberate attempt should be made to construct or maintain improved feeder roads in areas where agricultural production is of great potential on one hand, and areas where nutrition variables are critical on the other.
AVAILABLE TECHNOLOGICAL OPTIONS FOR CONTROLLING SOIL DEGRADATION AND ENHANCING PRODUCTIVITY The extension of soil and water conservation practices to small holders in Zambia has in the past been the responsibility of the Department of Agriculture, MAFF. Efforts have concentrated on training extension staff in conservation practices and the production of pamphlets and handbooks on soil and water conservation measures. Recommendations have focused primarily on formalized conservation and agroforestry activities, such as contour bunding and ridging, storm 346 Zambia
drains, gully protection, vetiver strip planting, etc. The adoption of these recommendations by smallholders has been negligible, primarily due to the high labour requirements, the failure to integrate conservation measures with crop husbandry practices and the lack of immediate benefits to farmers.
Recent initiatives by the Department of Agriculture It was in 1985, when the Department of Agriculture with the support of the Swedish International Development Authority (SIDA) and the assistance of its Regional Soil Conservation Unit in Nairobi, launched a programme in Eastern Province to take soil conservation to the people. This proved successful such that it was included in SIDA’s country frame in 1988 to become what is now known as the ‘Soil Conservation and Agroforestry Extension (SCAFE) Programme. The programme concentrates at present on the most threatened Provinces: Eastern, Southern and Central Provinces; limited activities have also been started in Lusaka and Luapula Provinces. The programme works fully through the extension system of the Government, involving officers from the Department of Agriculture, the Department of Forestry, the National Agricultural Information Service, and Department of Natural Resources on a Provincial and District Team basis. The SCAFE programme had been following (after an ad hoc approach in previous years) since 1991 a participatory, holistic village/catchment approach, which has helped to increase its achievements substantially. Significantly increasing figures for the 1991/92 and the 1992/93 seasons in all activities clearly indicate, that the programme is finally taking off. The following list gives the figures for the agricultural season of 1992/93: · physical soil conservation measures have been adopted by more than 5 000 farmers (double the amount of the previous year), · soil fertility improvement measures were adopted by more than 4 000 farmers in the reporting season, · about 1 000 000 trees were planted by 5 000 farmers, · almost 400 tree nurseries were established by farmers, women groups and field days, · almost 6 000 farmers attended training courses and field days, · almost 6 000 farmers watched dramas, slide and film shows, · the staff training was beneficial to more than 800 officers (almost double that of the previous year).
It should be emphasized, that three reasons are responsible for this success: · the consequent training of staff and more and more of the farmers themselves, · the participatory village/catchment approach, · the investment in facilitating transport. Other organizations have also been trying to tackle some of the land degradation issues: · Lusume Services of the family farms in Mazabuka had started a project in Southern Province where some agroforestry methods were being introduced and encouraged. · The Forestry Department through FAO funding, started two projects dealing with tree planting in Mapangazya area (Southern Province) and Mbala Island (Luapula Province). Integrated soil management for sustainable agriculture and food security in Southern and East Africa 347
· The Animal Draught Power Development Programme supported by the Netherlands Government has developed a range of equipment including the Magoye Ripper and Subsoiler designed to provide farmers with draught equipment more suited to MT/CF. · Detailed assessment of these equipment in conjunction with local farmers is being undertaken at Magoye Technical Assessment Site in Southern Province. Trials to compare the yields of conventional and CT Ox-draught and hand hoe systems are also being undertaken at Magoye. · The Research Branch of the Department of Agriculture have long realized that the major reason for shifting cultivation, is the rapid decline in soil fertility and deterioration in the soil physical conditions usually after one or two years of cultivation. This is worsened by reduced fallow due to population pressure and higher demand for land. · The Agricultural Research Division of the Department of Agriculture has been carrying out un-systematic soil fertility and soil conservation research since the early 1940s. Most programmes kept suffering from discontinuities due to staff movements. · A soil and water management research activity worth reporting is the experiment on tie ridging. Tie ridging may be a very useful soil water conservation measure in regions prone to drought. Work done at Lusitu Research Sub-Station, Zambezi Valley, in Region I, for example, gave consistently highest crop yields with tie ridges made before the start of the rains (Honisch, 1974). Mean yields of maize, sorghum and bulrush millet were higher on the ridges than on conventionally prepared land by 168, 159 and 17 percent in the 1968-69 to 1970-71 seasons respectively. In these experiments, tie ridging before planting created improved soil moisture conditions. Despite these good results, tie-ridging is not being practised in Region I, and the area continues to suffer from crop failures every year. Some of the reasons given by the farmers for their failure to adopt the tie ridging system are high labour requirements for construction, practical difficult in planting, ridge maintenance and weeding. Since the advantages of some of the soil and water conservation measures were not immediate, their adoption by traditional farmers required better Organisation and effective extension services. Enforcement of these practices created resentment as was the case in the pre- independence times. It is necessary to identify the socio-economic factors of the community before the practices are introduced. In 1981, the Research Division created the Soil Productivity Research Programme under the sponsorship of the NORAD. The team’s approach is to develop environmentally sound, sustainable, easily adaptable, and economically viable cropping and farming techniques. Some of their research activities include (a) the use of cheaper sources of nutrients to enhance soil fertility (these include organic and green manure, legumes in rotations and crop residues recycling); (b) encourage management practices that will increase soil organic matter content to neutralize soil acidity and improve the soil physical conditions; (c) the use of managed fallows to regenerate the fertility of abandoned lands; (d) evaluation of the use of green manure in the mound (fundikila) system to increase land productivity; the selection of effective and adapted Rhizobia strains for optimum nitrogen fixation for small-scale farmers; and to tackle aluminium toxicity and other problems related to managing acid soils. The NORAD programme has an agroforestry component. This component is being tackled at two levels - that of the cultivation system level, and that of the farming system level. Research at the cultivation system level focuses on ways in which the main cultivation systems could be improved by agroforestry techniques, and is carried out mainly at the research station. Research to understand how the cultivation systems fit together with each other to form the different farming systems, and to integrate agroforestry interventions into the whole system, and such takes 348 Zambia
place mainly in selected farmers’ fields. This programme is expected to assist the small holders in achieving sustainable yields. It is also expected to develop a more stable system of agriculture which will produce semi-permanent or permanent farming systems in the high rainfall areas for farmers at different levels of technology. In region II, the Zambia/ICRAF Agroforestry research programme has made headway in producing very useful agroforestry technologies. The use of Sesbania sesban in improved fallows to overcome land depletion and low soil fertility has proved successful. The use of Sesbania sesban improved fallows for one year results in increased maize yields (from 1.5 to 3 tons/ha), two years fallow yields up to 5t/ha and 3 years fallow can give up to 6t/ha of maize. These results have proved that the use of expensive inorganic fertilizers can be substantially reduced. This is and will be a relief to the majority of the small scale farmers who cannot afford inorganic fertilizers after the Government removed subsidy on the commodity following the structural adjustment programmes.
Initiatives by the Zambia National Farmers’ Union In the late 1980s Mr. R. Landless pioneered commercial minimum and zero tillage production systems based on maize, soybeans and wheat on his farm at Landless Corner, Chisamba, in collaboration with ART Zimbabwe for a number of years. As a result of this initiative, in mid 1995 discussions between Donors, the Ministry of Agriculture, the National Farmers’ Union and the Golden Valley Agricultural Research Trust (GART) centred on the need to establish a cost effective and productive unit to coordinate and promote the adoption of Conservation Farming Systems (CF) among smallholders initially in the more drought prone regions of Zambia, and thereafter throughout the Agro ecological Regions I & II (low to medium rainfall). In November 1995 with interim support from the World Bank and the EU, a Conservation Farming Unit and Conservation Farming Liaison Committee was established under the Zambia National Farmers Union (ZNFU). The Committee has representatives from all organizations and agencies interested in promoting sustainable agricultural systems in Zambia, including ZNFU, Palabana ADP, MAFF, SCAFE, GART, and LONRHO. The Committee meets every two months and has the following responsibilities: · ensure standardization of technical messages, methods and approach, · act as a forum for exchange of ideas and experiences, · recommend priorities for research and seasonal demonstration CF in the field.
During the 1996/97 season Golden Valley Agricultural Research Trust (GART) on behalf of the Conservation Farming Unit (CFU) started conducting long term CF trials and demonstrations for small holder farmers. These replicated trials are investigating: · Tillage practices. Three tillage practices of Minimum tillage (MT), conservation tillage (CT) and Residue tillage (RT) are compared with full (or conventional) tillage (FT) for their effectiveness to capture rainfall (water harvesting) during years of drought, hence reducing risks of total crop failure, increase crop productivity and Food Security to the farmer. · Intercropping practices. Among other practices conservation farming requires rotations with legumes. During the 1995/96 cropping season, 60,000 small scale farmers grew cotton for LONRHO in Central Province as a monocrop. The cotton has to be sprayed to control pests. Cowpea is a suitable legume for small holders to grow in rotation with cotton. However field pests can severely reduce the cowpea grain yields. Therefore the purpose of the trial is to assess the effects on cowpea yields from cotton spray drift and direct row spray when cowpea is grown as cotton/cowpea inter-rayed with cowpea monocrop as control. If the cotton Integrated soil management for sustainable agriculture and food security in Southern and East Africa 349
insecticide can be able to control cowpea pests in these cropping configurations, then the farmer has managed to kill two birds with one stone. · Herbicide weed control. One of the main agronomic problems facing the small scale farmer, who is practising conservation tillage (No till + water harvesting techniques) is control of the early flush of weeds which occur at the onset of rains. These early rains which may not necessary be planting rains are received at the end of October or first week of November. At this time the farmer would have prepared his planting holes (hoe) or planting lines (ceemattine) during the dry season (August - October). By the time planting rains are received, mainly after the second week of November, this flush of weeds would have grown up. Instead of starting with planting the farmer has to scratch out or clean their planting lines which have been invaded by the fresh weeds.
In this situation an application of a post weed emergence, pre-crop emergence herbicide is necessary, such as Roundup (glyphosate). This can assist the farmer plant early without worrying about the weeds in the next 30 to 40 days. The purpose of the trial is to assess the efficacy of Roundup herbicide at three rates of 0.7 litres, 1.0 litre and 1.5 litres per hectare when compared with conventional hand weeding. The GART/CF trials initiated during the 1996/97 season are designed as a backup to the series of demonstrations carried out by CFU with various Non- Governmental Organizations (NGO) in Southern, Central and Eastern Provinces. The purpose of these series of CF demonstrations by CFU is to show and make farmers aware that conservation farming (CF) systems provide the benefit opportunity for farmers to reduce their costs, increase their productivity, ameliorate the effects of drought, improve their food security, and protect the agricultural resource base from further degradation.
Key CT/CF practices presently recommended One of the most important requisites being propelled in conservation farming is the retention of crop residues. Crop residues are retained on the land and not burned. If residues are scarce they are raked into ‘trash lines’ across the slope to capture rainfall and reduce run off. Ideally a minimum ground cover of 30% residue is recommended. Residues reduce soil temperatures, protect the soil, minimize run off and in time improve fertility. Secondly, land preparation is recommended to commence in August or even earlier. The labour requirement can be spread over a period of 3 to 4 months. In this way the farmer is ready to plant his/her crop as soon as the first planting rain falls. Planting is finished in a day and early weeding can commence as soon as weeds emerge. Farmers are encouraged through on farm demonstrations which they themselves carryout. Planting basins of 30 cm x 15 cm x 15 cm are dug with the hoe (these may be smaller in higher rainfall areas). These basins are permanent and are never moved. Successive crops are planted in the same basins each season. Carefully measured applications of basal dressing and/or manure and apart from weeding operations the inter-row soil is not disturbed. This approach has many advantages. The basins remain concave after planting and concentrate the early rain around the seed and help to reduce run off. Fertilizer and manure are placed where needed and wastage is minimized. Successive crops can take advantage of the root channels and residual fertilizer applied the previous season. Because the inter-row is not ploughed and weeds are not allowed to seed, the weed bank diminishes in time. Basins are spaced so inter-row weeding can be done by hand or oxen. Ox farmers have been encouraged to use the new low draught CEEMAT tine rip in the dry season and then establish their basins over the rip lines using the hoe. Alternatively they can use 350 Zambia
the Palabana Furrower to open planting furrows over the rip lines as soon as the first planting rains have fallen. Ripping reduces compacting, breaks plough pans and reduces the crop's susceptibility to poor rain distribution. In the drier areas of Zambia demonstrations are carried out to encourage farmers to use the hoe to make pot holes in the inter-row during the first weeding. This technique captures (harvests) rainfall, improves infiltration, and reduces crop stress during dry periods. CF combines sound husbandry and management practices which enable farmers to spread out labour demand and get their work done on time. The technology can be applied to a wide range of farming groups from resource poor to commercial with good results. The adoption of CF practices produce immediate, medium and long term benefits and the technologies involved are easy to understand and implement. A Conservation Farming Handbook for small holders in Region I and II was produced in July 1997 by Conservation Farming Unit (CFU), with the support of FAO Integrated Crop Management Food Legume Project. The agricultural sector has a major impact on the environment and the promotion of CF is in harmony with the wider goal of introducing more environmental friendly methods of agricultural production in Zambia.
INSTITUTIONAL FRAMEWORK AND POLICIES FOR LAND RESOURCES MANAGEMENT he history of soil conservation in Zambia spurns from the 1940s. Prior to 1950, soil conservation was limited to the construction of dams and weirs. Such works in European farming areas qualified for a 50-60% Government Subsidy. In the African farming areas the soil conservation programme promoted improved farming methods which aimed at minimizing nutrient and structural deterioration of the soil through the use of cattle and green manure, crop rotation and construction of contour ridges and grass strips. These soil conservation works on African farmlands (in the tribal areas) were financed from a native fund growers. Between 1939 and 1944, over 1,600 km of contour ridges and 180 km of grass strips were laid down in Southern Province while 24,000 km of ridges were surveyed and pegged in Eastern Province during 1946- 50 (Chiti, et al, 1989). In 1950, the Natural resources Board (NRB) was established under the Natural Resources Ordinance to exercise supervision over natural resources, including soil conservation. In European farming areas, farmers were encouraged to form intensive conservation area (ICA) committees. This programme failed. In the African farming sector, the maize levy was replaced by the payment of a graduated bonus on a hectarage basis in the 1950s. The bonus payment was based on the area of land that was green/or cattle manured (Chiti et al., 1989) but for a farmer to qualify he had to practice certain laid down farming methods and good land husbandry which included soil erosion control. In 1953, the Government through the Department of Agriculture started to promote soil conservation through the implementation of regional conservation plans. This programme emphasized on soil and water conservation works and alignment and construction of farm and feeder roads. By 1964, fifty-four regional plans covering over 1.4 million has in the European farming areas were formulated. However, contrary to the belief that farm planning would naturally follow once a regional conservation plan was implemented, farmers were reluctant to carry out farm soil conservation measures, and the programme failed to secure the protection of farmlands from erosion. In 1970, the Natural Resources Board (NRB) was dissolved and a new law - The Natural Resources Conservation Act - was enacted. This act brought about the Natural Resources Advisory Board (NRAB) which replaced the Natural Resources Board. The new board was responsible for ensuring the wise exploitation of natural resources and their conservation, including soil conservation. The NRAB operated through committees without a competent technical staff. The NRAB and its committees failed. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 351
In 1972, the Department of Natural Resources was established to serve the NRAB. The department has continued to suffer from inadequate competent technical staff since its inception. Consequently, the Department concentrated on the propagation of theoretical natural resources conservation education while the Land Use Section of the Department of Agriculture continued to carry out the practical aspects of soil conservation on farmlands. In the meantime, the Extension Branch of the Department of Agriculture has over the years paid more attention to crop production at the expense of soil conservation. The legacy that was inherited after independence was carried over even during the period between 1970 to the mid 1980s. During this time the same organizations that tackled conservation problems were still doing so. The Land Use Branch of the Department of Agriculture for example continued to carry out measures on cropland only. In most cases this was on commercial farms. The Natural Resources Department addressed the problems in a rather general way, and its main activities were directed at curing gullies and reforestation programmes. What was seriously amiss with both programmes was to take soil conservation to the small scale farmers. It is clear from the historical perspective that soil conservation was well articulated to address the various effects of environmental degradation. However, the approach by the colonial masters provoked resentment instead of creating a sense of economic gain into the people. Independence meant being free from the labours of soil conservation. Thus where soil conservation structures existed, these were either slowly being destroyed or not maintained at all. Most of these structures have since disappeared. Using the holistic approach, we can link several social, political, economic and environmental factors to causes of land degradation. In Zambia the political economy of the first Republic which emphasized on consumption instead of production killed the agricultural sector. Farmers concentrated on increasing production instead of sustainability. As the economy of the country got worse and worse, the rural - urban migration increased. This denied the rural areas of the much needed labour, not only for essential food production activities but for soil conservation works as well. This migration left the aged and the children to man very labour demanding activities. When the Rhodesia declared UDI the government’s reaction cost Zambia all its foreign reserves. The consequence was devaluation of the Kwacha and expensive imports. Fewer farmers could afford most inputs. This led to rapid soil fertility decline, which also led to less food in most households. A survival strategy cropped into the lives of people. The slash and burn shifting cultivation increased. Soil fertility had to come from the available natural resources by depending on the ash. No farmer was legally bound to control overgrazing, over-stocking, indeed even the discriminate cutting down of trees as long as it was outside a protected forest area. Government institutions such as Extension and Research continued to get less and less funding. This naturally meant lack of transport, lack of motivation and lack of resources. The farmer, who was already faced with severe financial problems for inputs and labour shortages saw less and less of the extension worker. Even where the extension worker appeared, the short term economic benefits of soil conservation is difficult to sell in the absence of soil erosion research data which we still lack up today. This vicious cycle has far reaching consequences on our society. The economic and social consequences of environmental degradation are both short and long term. Deforestation and overgrazing brings about immediate economic and social problems. Women have to walk long distances to look for fuel wood. Those who depend on charcoal burning have to cover long distances to find good tress as well as to ferry the charcoal back to the markets. The long term effects of destroying vegetation on catchment areas are increased surface run-off, thus causing soil erosion and eventually silting of streams and dams. 352 Zambia
PROPOSALS OF PROGRAMMES FOR IMPROVED SOIL MANAGEMENT AND PRODUCTIVITY ENHANCING There are already a number of organizations in Zambia addressing the issues of soil management and productivity enhancement. Some of the organizations include: · The soil conservation and agroforestry extension project (SCAFE). This project is funded by SIDA and covers three out of the nine provinces of Zambia. It addresses physical structures on smallholder farms. Recently, however, the programme has included soil fertility amelioration in its activities. These mainly concern organic matter management and general conservation farming approaches such as minimum tillage (MT). · The International Centre for research in agroforestry (ICRAF) project operating in the Eastern and Lusaka provinces of Zambia have concentrated on nodulating and high biomass producing tree and shrubs mainly for soil improvement. In Region III there are efforts to introduce low input sustainable technologies to overcome low soil fertility (high acidity) and improve yield of traditional crops, and also to develop alternatives to traditional shifting cultivation for eventual evolution to semi-permanent/permanent agriculture. This is proposed to be achieved through the introduction of agroforestry technologies, e.g., use of multipurpose trees and their advantages in biological N-fixation, mycorrhizae association and efficient nutrient recycling mechanisms into the traditional farming practices, e.g. improved fallows and alley cropping: · The soil productivity research programme based in Northern Province is funded by NORAD. This programme endeavours to find answers to acidity and aluminium toxicity which inhibit proper crop growth, and also addresses the issues of the slash and burn type of cultivation. · The Conservation Farming Unit which is a wing of the Zambia National Farmers Union have concentrated on conservation farming, mainly working with small scale farmers in minimum tillage as well as organic matter management. Over 800 farmers are participating. · The Golden Valley Agricultural Research Trust (GART) in collaboration with the Conservation farming Unit (CFU) of the Zambia national farmers union have in the last 2 years been involved in conservation farming research promising results from the first season have already been recorded. · The European Union (EU) have so far funded a proposed regional conservation farming network, to incorporate Botswana, Lesotho, Malawi, Zimbabwe and Zambia. If approved, Zambia hopes to bring all key players within the country and collectively address, through research and extension, land degradation. Three major problems identified by the five participating countries include declining crop yields, declining cropping land area per family farm and land degradation. There seem to be very strong programmes either already in place or being proposed for implementation. But for a long time to come Zambia is going to continue experiencing serious legal issues and institutional constraints contributing to land degradation. The regulation and rights on land is a very sensitive issue. It is generally held by some farming communities that title to land carried with it the individual right to farm the land as one pleases. Yet responsibility should be and is a voluntary act to manage land in the landholder’s own long term interests. Failing this hope of good will, soil conservation legislation must have clear objectives and provide the administrative and legal structures and procedures to attain those objectives. Lease hold under land tenure creates incentives for land user to follow practices which accelerate the renewal of a lease. But the lack of full compensation for the land on termination of Integrated soil management for sustainable agriculture and food security in Southern and East Africa 353
lease creates insecurity for the leaseholder. The unregulated, self-interested use of land results in degradation. A continuation of the present legislative policy based largely on voluntary action by land holders, is not the answer. But it is necessary to adopt the principles of adult education whereby land holders learn through seeing the economic benefits and accepting to undertake the responsibility of developing and implementing managing policies for their properties. Landholders on the other hand should be obliged to conserve their soil. This could be done through : · strict liability -where soil degradation beyond a certain point be liable to prosecution, · carryout land utilization determinations which decides the use to which land should be put, · production and extension through demonstrations of proven soil management and productivity enhancement packages.
REFERENCES Aagaard, P.J. 1997. Conservation Farming Handbook for Small Holders in Regions I & II of Zambia. CFU/FAO Integrated crop Managment Food Legume Project. ARPT 1992. Monitoring household food security in Mabumba, Luapula Province. Dept. of Agriculture, Mansa. Bunyolo, A.M. 1989. Soil crop management for low-input systems, especially directed towards soil fertility, soil erosion and weed control. Possible Application to Region II of Zambia, Mount Makulu, Zambia. Bunyolo, A.M. et al 1995. National Environmental Action Plan. Agriculture and the Environment. Mount Makulu, Zambia. Chiti, R.M. et al 1989. National Soil Conservation and Agroforestry Needs Assessment. NSCU, Department of Agriculture, Lusaka, Zambia. Clayton, D.B. 1985. A Geomorphic Legend for Zambia. Department of Agriculture, Lusaka, Zambia. FAO. 1974. Shifting Cultivation and Soil Conservation in Africa. Soils Bulletin No. 24 .Rome. FAO. 1984. Improved production systems as an alternative to shifting cultivation. Soils Bulletin No. 53. Rome. Gossage, S.J. 1991. Soil and Water Conservation; a manual for extension workers with emphasis on small scale farmers in Zambia. Department of Agriculture, Lusaka. Grunder, M.; Herweg, K. Seventh Progress Report, Soil Conservation Research Project. Ministry of Agriculture, Addis Abeba Ethiopia. Grunder, M. 1993 Soil Erosion and Watershed Management. An issue paper presented at the first Zambian National Forestry Action Plan Workshop. ILACO B.V. 1981. Agricultural Compendium for rural development in the tropics and subtropics. Elsevier, Amsterdam. Keyser, J.C. and Mwanza, H.M. 1996. Conservation tillage in Zambia. Findings of field survey of hand hoe farmers in Mumbwea District. Institute of African Studies, UNZA, Lusaka. Kokwe, M. and Chileya, C.K. 1993. Farming systems update of Luapula Province. LRDP, Mansa. Kwesiga, F. 1996. Agroforestry Research in Zambia. Highlights. Msekera Regional Research Station, Chipata, Zambia. Mickels, G. 1994. Natural Resources and sustainability in Luapula. LRDP, Mansa. Mukanda, N. and Grunder, M. 1993. Assessment and control of land degradation in Zambia. A country Appraisal. Department of Agriculture, Research Branch, Chilanga, Zambia. 354 Zambia
Mukanda, N. 1994. Environmental Impact Assessment and sustainable agricultural development in Zambia. A framework for understanding land degradation using the holistic approach. Department of Agriculture, Research Branch, Chilanga, Zambia. National Soil Conservation Unit, Annual Report 1988. Department of Agriculture, Lusaka, Zambia. Ndiyoi, C.M. & Tembo, S. 1995. Special Programme for Food Security Project Document. FAO, LUSAKA, Zambia. Robinson, D.A. 1978. Soil Erosion and Soil Conservation in Zambia: A Geographical Appraisal. Zambia Geographical association occasional study no. 9. Lusaka, Zambia. Yerokun, O.A and Mukhala, E. 1995. A systems approach to long term soil productivity. Proceedings of the national symposium. UNZA, Lusaka, Zambia. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 355
Zimbabwe
COUNTRY FOOD PRODUCTION AND REQUIREMENT The total area of the country is 389 000 km2. There are three major relief regions in Zimbabwe which are recognized on the basis of their general elevation. These are the Lowveld (below 900 m.a.s.l.), the Middleveld (900 - 1 200m a.s.l.) and the Highveld (1 200 – 2 000 m.a.s.l.). The Highveld includes a relief region commonly referred to as the Eastern Highlands which consists of a narrow belt of mountains and high plateau ranging in altitude from 2 000 m to 2 400 m.a.s.l., and has a characteristic micro-climate and associated vegetation. The country receives almost all of its rainfall during the five summer months, November to March. The mean annual rainfall ranges between 400 mm to 2 000 mm, depending on the relief region. A significant feature of the rainfall is its unreliability both in terms of amount and duration. The onset of the rains, which is critical for planting, is rather unpredictable. The variation from year to year is such that as little as a quarter of the arithmetic mean may fall while in other years 200 - 300% of the mean may be realized. Climatic factors are the major determining factors in crop production in any given situation. In Zimbabwe, rainfall has been used as the single most important parameter in defining agro- ecological zones and their potential for agricultural activities. As rainfall decreases, the seasonal variability also increases, thereby increasing the risk of poor yields. Crop production in Zimbabwe has tended to vary in relation to agro-ecological zones and also with seasonal variations in weather patterns. Seasonal quality has tended to decline, with the frequency of droughts being significantly higher over the last 20 years than during the long term (1910 - 1997) period (Vhurumuku and Eilerts, 1997). Other factors that affect the levels of crop production, particularly in the smallholder sector are level of agronomic management, access to inputs such as fertilizers, availability of finance and credit, infrastructure condition and availability of marketing facilities. These factors however, tend to be overshadowed by the impacts of seasonal quality.
Cereal production Maize, pearl millet and sorghum are the most important cereal food crops that play a significant role as carbohydrate sources in the diets of most Zimbabweans. These crops are allocated 45- 50%, 15-20% and 10-15% of the cropped area respectively. Maize is the dominant staple food crop that is grown across all agro-ecological zones within the communal areas. This crop occupies 50 - 70% of cropped areas in natural regions I and II; and 40 - 50% of cropped areas in Natural Regions III, IV and V within any given season. Conditions for crop production become more marginal as one moves from natural region I to natural region V.
C.F. Mushambi, L.M. Mugwira, J.K. Nzuma and G. Nehanda Chemistry and Soil Research Institute, Causeway, and Institute of Agricultural Engineering, Borrowdale, Harare 356 Zimbabwe
Sorghum and pearl millet are dominant in natural regions IV and V where rainfall is extremely low and unreliable. Table 1 illustrates the trends in food production from the 1980-81 to the 1995-96 seasons. The figures in Table 1 show that there was a dramatic increase in maize production in the early 1980s. This increase, particularly in the smallholder sector was influenced by provision of a whole package of support that included research and extension, price support, market infrastructure and finance. In spite of all the support, improvements in the levels of production experienced in the smallholder sector were more due to expansion of land under maize rather than improved yields. When real maize producer prices dropped during the late 1980s and emphasis was placed more on industrial and horticultural crops, commercial farmers were more responsive than their counterparts in the smallholder sector to price signals and market imperatives. Commercial farmers quickly moved out of maize production when real producer prices for this commodity were falling relative to oil seed and horticultural crops. The smallholder sub-sector, on the other hand, increased production of maize, in spite of falling real producer prices (World Bank, 1991). On average, there was an increase in maize production in the communal areas during the 1980s as compared to the 1970s. This increase was eroded in the 1990s when more severe and frequent droughts were experienced. The 1990s saw a significant 33% drop in food access and availability than the 1980s averages.
TABLE 1 Commercial and communal grain production over time in tonnes, 1980-96 Years Maize Sorghum Communal Total Cereals Communal Commercial Communal Commerc. Munga Rapoko 1980-81 1 000 000 1 833 400 100 25.1 81.31 50 194 3 090 004 1981-82 595 1 213 400 50 17,4 1 875 800 1982-83 285 624,8 44 7,5 55 932 5 164 1 022 396 1983-84 670 678,5 37,4 18,1 51 344 42 989 1 498 333 1984-85 1 558 000 1 153 000 76 54 252 539 111 524 3 205 063 1985-86 1 348 000 1 064 00 66,2 65 71 382 45 491 2 660 073 1986-87 627,7 466 40,4 11,9 68 349 33 223 1 247 572 1987-88 1 609 300 643,8 163,1 12,7 177 166 81 473 2 687 539 1988-89 1 188 200 743 65,3 16,1 81 168 51 953 2 145 721 1989-90 1 262 300 7312,5 72 18,4 99 194 143 734 2 327 628 1990-91 1 019 300 566,5 51,3 16,8 59 388 38 738 1 752 026 1991-92 115,2 245,8 10,35 21,42 130 192 393 092 1992-93 1 133 600 878 25 69 51 20 99 003 67 598 2 267 961 1993-94 1 313 800 1 012 400 90,8 30,92 100 384 52 073 2 600 377 1994-95 399,4 440,2 16,73 12,75 12 874 6 831 888 785 1995-96 1 687 000 922 173 851 0 114 692 42 242 2 939 785 80s Av. 1 014 350 915,14 71,49 24,62 104 264.89 62 860.56 2 176 012.9 90s Av. 944 716.67 677 525 68 756.83 16 981.67 64 411.83 34 612.33 1 807 004.33 Source: Economics Division Ministry of Agriculture
The high crop yields of the 1995/96 season may indicate that the low crop yields of the 1990s were more due to droughts rather than deterioration of the fundamentals (i.e. soils, input availability etc.) of communal sector farming (Vhurumuku and Eilerts, 1997). Maize production has been declining consistently in the commercial farming sector from the 1970s to the 1990s as farmers diversified into better paying enterprises such as horticulture. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 357
Small grain crops have experienced a general decline in production from the 1970s to the 1990s in spite of emphasis given by research and extension on these crops as security food crops for the marginal areas. This is most likely a reflection of farmers’ preference for maize over small grain crops. Table 2 demonstrates the negative impact of population growth on levels of available maize consumption. Population growth has reduced available maize consumption per caput to 114 kg compared to the high figure of 157 kg/caput in some years of poor production (1991/92 season). Food consumption has been declining over time, possibly due to reduced access. Over the 90s food availability from production and stocks has generally been declining. Food imports to meet food shortfalls increased in the 1990s. This picture also demonstrates that the position of Zimbabwe as the breadbasket of the SADC region may have been eroded. Food shortfalls are likely to increase in Zimbabwe as population continues to increase (growth rate is 3.1%) and droughts become more severe and frequent. Currently, another severe drought has been predicted for the 1997-98 season due to the activity of the El Nino phenomenon that normally brings droughts to the Southern Africa region.
TABLE 2 Maize balance sheet for Zimbabwe, 1985 to 1996 Year 1985-86 1987-88 1989-90 1991-92 1993-94 1995-96 1996-97 Population 834 886 946 1 008 1 072 1 140 1 175 thousand) Consumption 142.5 414.5 119.7 156.8 153.2 142.5 114.6 /capita (kg/ s/Yr) Total supply 3 680 2 900 2 871 2 312 3 497 2 155 2 636 Domestic 3 680 2 900 2 871 2 229 2 829 2 029 2 636 availability Opening 1 426 1 806 940 643 267 1 189 27 stocks Monitored 1 426 1 806 940 643 267 822 7 Unmonitored 0 0 0 0 0 367 20 Gross 2 254 1 094 1 931 1 586 2 562 840 2 609 harvest Imports 0 0 0 83 668 126 0 Commercial 0 0 0 83 668 126 316 imports Food aid 0 0 0 0 0 0 0 Total 3 680 2 900 2 871 2 312 3 497 2 155 2 724 utilization Domestic 1 944 1 772 1 553 2 060 2 163 2 084 1 826 utilization Food use 1 189 1 257 1 133 1 580 1 643 1 624 1 346 Feed use 550 400 300 360 400 340 350 Other uses 205 115 120 120 120 120 130 and losses Exports 310 373 170 187 0 44 298 Closing 1 426 755 1 148 65 1 334 27 600 stocks Monitored 1 426 755 1 148 65 934 7 600 Unmonitored 0 0 0 0 400 20 0 Unbalanced 0 0 0 0 0 0 210 residual Source : Vhurumuku and Eilerts, 1997 358 Zimbabwe
EVOLUTION OF PER CAPUT CULTIVATED LAND AND TRENDS IN CEREAL CROP YIELDS The total land area of Zimbabwe is 39,075,900 ha, of which 42% is communal land. The rest of the land area is occupied by commercial farms, resettlement and urban area; forests, and game reserves. This land area is shared by a population of approximately 11,933,000 with a natural population growth rate of approximately 3.1% per annum. Distribution of population by Sector/land use type shows that half the population is in the communal areas. Population density in Zimbabwe has risen from 19 persons/km2 in 1982 to 27 persons/km2 in 1992 (CSO, 1992). This density will continue to rise with respect to the rate of population growth. Total area of land cultivated in the communal areas has been expanding over the years as the population continued to grow and the need to grow more food crops increased. Since land is a static resource, land cultivated per caput or per household has declined in relation to population increase. Table 3 shows the trends of total amount of land in the communal and commercial sub- sectors allocated to the main cereal food crops from 1980 to 1995. The total area under crops in communal areas in 1996 stood at 2,234,616 hectares; an increase of 26% over the 1990s average of 1 773 658 and 24% over the 1980s average of 1 794 855 (Vhurumuku and Eilerts, 1997). Total area cropped to maize, millets and cash crops per caput in the 1980s stood at 0.393 ha. In the 1990s this dropped to 0.325 ha. In 1996, the per caput area cultivated increased marginally over the 1990s average to 0.376 ha. The vulnerability of communal areas may be rising due to a declining land area available for cropping relative to a fast expanding population. In fact as early as 1975; 57% of the communal areas had been described as overpopulated or grossly over populated (Kay, 1975). Maize area cultivated per caput followed the same trend as described above. During the 1980s total land cropped to maize per caput equalled 0.210 ha. This figure fell during the 1990s on average to 0.168 ha and then recovered to 0.203 has in the 1996 season. Expansion has generally been due to encroachment onto previously unused marginal lands; a development which renders communal areas more prone to forces of land degradation. Small grains area cultivated per caput dropped from 0.101 ha in the 1980s to 0.075 ha in the 1990s and then rose slightly to 0.087 ha in the 1996, season.
TABLE 3 Communal and commercial land area planted to cereal food crops (hectares), 1980-96 Years Maize Sorghum Communal Total Area Commun. Comm. Commun. Commerc. Munga Rapoko 1980-81 1 000 000 363 400 200 000 9 300 171 636 108 870 1 853 206 1982-83 1 050 000 283 900 280 000 7 700 220 107 35 459 1 877 166 1984-85 1 018 000 238 000 210 000 15 000 297 438 148 813 1 927 251 1986-87 1 064 000 147 100 172 700 7 500 196 2224 107 205 1 694 729 1988-89 1 030 000 168 300 158 000 7 300 144 070 113 508 1 621 178 1990-91 926 200 175 000 106 200 7 600 139 735 111 765 1 466 500 1992-93 1 040 000 198 000 138 000 10 110 147 652 93 750 1 628 112 1994-95 1 209 200 188 700 126 000 4 250 224 976 40 489 1 794 355 1995-96 1 330 000 205 000 234 714 0 183 779 93 063 2 046 556 80s Average 1 059 250 231 050 186 750 10 230 192 725 116 553 1 765 629 90s Average 1 067 100 191 950 138 815.6 7 410 167 703 93 430 1 666 409 Source : Economics Division Ministry of Agriculture
The declining land holding per caput with time paints a gloomy picture in terms of food production to meet food security requirements in the communal areas. This decline has not been matched by intensive production on a per hectare basis. Instead crop yields have tended to decline or remain stagnant over time. Table 4 illustrates the yield trends of cereal grain crops from the 1980 to the 1995 season. In the 1970s average maize yields in the communal areas were 623 Integrated soil management for sustainable agriculture and food security in Southern and East Africa 359
kg/ha. Yields went up to 957.6 kg/ha in the 1980s that marked the peak of maize production in the smallholder sector. N fertilizer and hybrid seed have had the greatest impact on the yield of maize. the increased use of N fertilizer in the communal areas in the 1980s can be attributed to the sector’s improved access to AFC seasonal loans. During the drier regime of the 1990s yield levels dropped to an average of 885.3 kg/ha. Sorghum shows a decline in yields in the communal areas from 1031.1 kg/ha in the 1970s to 382.8 kg/per ha in the 1980s. The crop shows a slight recovery in the 1990s to a yield level of 495.3 kg/ha. Munga and rapoko show a decline in yields from 541 kg/ha and 539.3 kg/ha in the 1980s to 384.1 kg/ha and 370.5 kg/ha in the 1990s respectively.
From the 1980s to the 1990s yields of all crops fell due to frequent droughts (Table 4). But judging by the yields of 1996, which were generally better than the 1980s yields, it appears like the droughts were the main feature of those declines and continuing good rains in future years might reverse those temporary declines. Looking at the general trends of rainfall, there has been a decline from the 1970s to the 1990s. More frequent and severe droughts have been experienced during the 1990s. If this trend of events continues, yields will continue to fall, further reducing food security chances in the communal areas in particular, and in Zimbabwe in general. This situation will be exacerbated by a rapidly expanding, population that is expected to increase to 18 million by the year 2025 before stabilizing at 28 million.
TABLE 4 Yield trends of cereal grain crops, 1980-95 Crops Maize Sorghum Communal Years Communal Commercial Communal Commercial Munga Rapoko (kg/ha) (kg/ha) (kg/ha) (kg/ha) (kg/ha) (kg/ha) 1980-81 1 000 5 045 500 2 699 474 461 1981-82 541 3 835 250 2 122 1982-83 271 2 201 157 974 254 146 1983-84 590 3 021 240 1 828 391 342 1984-85 1 530 4 845 362 3 600 849 749 1985-86 1 255 4 433 441 2 955 383 439 1986-87 590 3 168 234 1 587 348 310 1987-88 1 400 4 292 766 1 814 815 718 1988-89 1 154 4 415 413 2 205 563 458 1989-90 1 300 4 091 567 2 190 583 747 1990-91 1 101 3 237 483 2 211 425 347 1991-92 158 1 607 162 2 121 1 2 1992-93 1 090 4 436 502 1 978 671 721 1993-94 1 124 4 364 558 2 494 492 495 1994-95 330 2 333 132 3 000 57 169 1995-96 1 268 4 498 741 64 454 80s Average 957.6 3960.8 382.8 2406.6 541.0 539.3 90s Average 885.3 3529.7 495.3 2291.7 384.1 370.5 Source : Vhurumuku and Eilerts, 1997
EXTENT OF SOIL DEGRADATION AND ITS BIO-PHYSICAL AND SOCIO-ECONOMIC IMPACTS Soil degradation can be described as a loss of soil productivity through various physical and chemical processes such as wind erosion, water erosion, depletion of plant nutrients in soils, salinization, waterlogging, deterioration of soil structure and pollution. The most serious forms of physical degradation in Zimbabwe are erosion and removal/decline in organic matter due to devegetation. The most serious forms of chemical degradation are acidification and nutrient depletion and/or leaching. Both these physical and chemical forms of soil degradation are more 360 Zimbabwe
prevalent and more intense in the smallholder farming sectors, particularly the communal areas (CAs) than in large-scale commercial farming areas. The CAs have both the most fragile environments and the highest population densities.
Erosion Soil erosion is the most widespread type of land degradation in Zimbabwe. It has been estimated that there are about 1.8 million hectares or 4.7 % of the land in Zimbabwe which is eroded, about 83% of which is in the communal areas (Whitlow, 1988). The erosion distribution was estimated as: negligible (about 40%), very limited (25%, limited-moderate 20%) and the rest as being severe-very severe. The importance of the land tenure system was further reflected in that 48.7% of the commercial farming areas have negligible erosion compared with 18.5% in the CAs and 79.7% in non-agricultural land. The corresponding percentages of severely- very severely eroded land were 27% in the CAs, 2% in the commercial farming areas and 0.5% in the non-agricultural land. Levels of soil loss in CAs have been estimated at 50 t/ha/year (Elwell, 1985; Vogel, 1993). This is far in excess of rates of soil formation, estimated at 400 kg/ ha/year for granite-derived sands (Whitlow, 1988). At this rate of erosion about 30% of the available rainfall is lost as surface runoff, along with an estimated 535 kg/ ha of organic carbon and about 50 kg of nitrogen and 8 kg/ha of phosphorus (Elwell and Stocking, 1988).
Soil fertility decline Most soils of Zimbabwe are naturally of low potential productivity but much of the actual production depends on their management. In the communal areas, their condition is made worse off by poor management, usually reflecting a poor resource base. It has been estimated that about 30% of croplands in the communal areas have been fallowed/abandoned due to reasons of depleted soil fertility (Anderson et al., 1993; FSRU, 1993). However, recent surveys in Chinamhora, Murehwa and Mhondoro communal areas have revealed that about 44% of the 500 maize fields sampled had depleted levels of at least one nutrient. Normally such soils are characterized by multiple nutrients of N, P and S, and at advanced stages the depletion of Mg and Zn (Grant, 1970). Maize yields on depleted sands in the communal areas may be as low as 0.2 tonnes per hectare without fertilizer or manure, and yet with proper fertilization using manure and/or fertilizer, organic yields can be increased and maintained in the range of 3 to 5 tonnes (Grant, 1970; Grant, 1981). The available N values in worked out sands indicate that often the maximum yields without added fertility would be about 0.2 t/ha, as has been found in practice (Grant, 1976).
Salinization In Zimbabwe saline soils are of very limited occurrence. Saline and sodic soils are found in areas of low rainfall and high temperatures (Natural Regions IV and V). However, deteriorating yields of many crops have been attributed to the salinization and/or sodication of soils in many irrigation projects (Kanyanda and Mushiri, 1991). Irrigation is often used to supplement natural rainfall for main season crops, and to supply water for winter crops in the dry season. The two types of water that may give rise to salinity problems are "regeneration waters" i.e. underground waters and drainage waters from irrigated area (du Toit, 1972). Underground water resources in low rainfall areas have more dissolved salts than those from high rainfall areas due to high evapotranspiration rates. An assessment of 204 irrigation waters, samples in tobacco growing districts indicated that 95% of the samples had low to medium salinity. However, water quality downstream of some urban centres is usually poor as a result of serious pollution of streams and dams that are fed directly by domestic, commercial and industrial effluent (Zvomuya, 1996). Integrated soil management for sustainable agriculture and food security in Southern and East Africa 361
Therefore, in some parts of the country such as the Save Valley, salinization has been artificially induced by irrigation since most schemes in such areas do not have drainage installations and the water is unsuitable. With the Government's drive to improve crop production and sustainability in the communal areas part through irrigation, various problems of salinization and/or sodication are bound to increase in future.
Highlights of soil fertility decline Decline in soil fertility is a major constraint to agricultural production and economic growth in the smallholder sectors of Zimbabwe; with its impacts reverberating throughout themational economic sectors. Fertility decline results in food insecurity in the smallholder sector, thereby putting enormous pressure on national resources as the government is called upon to feed the affected communities. Some of the most important consequences of soil fertility decline in the smallholder sector economy have been summarized by Huchu and Sithole (1994) and other workers. These include the following socio-economic consequences: · poor crop yields which leads to decline in household and national food security, labour production and revenues, and increased urban drift, · the need for large capital investments for procurement of on fertilizer to improve soil fertility in order to get satisfactory crop yields on these soils. These costs increase with degree of soil degradation, further impoverishing resource-poor farmers, · cropping encroachment into marginal areas which is done in an effort to get sufficient produce. A most assured consequence of this practice is increased environmental degradation, · encroachment of cropping into grazing areas which leads to overgrazing on the remaining areas, contributing to erosion and decline of soil fertility on the "new" cropping after a few years, · encroachment of cropping into vleis and other wet areas which has resulted in the formation of gullies due to erosion, and in the siltation of rivers and dams.
The Department of Research and Specialist Services (DR&SS) has conducted two types of long-term trials on changes in the fertility of sandveld soils which may be used to quantify production losses and economic costs of declining in soil fertility. The first type of trials were on the restoration of productivity of depleted sands in the CAs which were started in 1956. The second type was on the assessment of changes in the fertility of a sandveld soil under continuous cultivation which was started in 1962 at Grasslands Research Station. As soil N, P and K data for the different cropping seasons is apparently not available in published literature production losses and replacement costs are based on optimum yields obtained and corresponding fertilizer rates recommended for such yields under normal or un-degraded soil conditions. Degraded conditions are represented by low or no fertilizer and yields obtained. Manure was used in these trials and data from its application are included purely for comparisons with data from inorganic fertilizers. Table 5 shows production losses and replacement costs in the maintenance of the fertility of a sandveld soil under continuous cultivation with plots on new land as reference.
The data shown in Table 5 lead to the following conclusions: 362 Zimbabwe
TABLE 5 Production losses and replacement costs in the maintenance of soil productivity fertilizer and manure on new land and land under continuous maize cropping at Grasslands Cropping Nitrogen Manure Yield (t/ha) Lost Production (Z$) Replacement Cost (Z$) kg/ha/yr Yearly Yr 1 Yr 5 Yr 10 Yr 1 Yr 5 Yr 10 Yr 1 Yr 5 Yr 10 New land 130 0 4.52 5.11 6.56 continuous 20 0 2.17 1.07 2.03 2 820 4 848 5 436 740 continuous 130 10 4.52 5.06 3.86 0 0 3 240 continuous 20 7t/ha 2.94 3.88 5.38 1 896 1476 5 436 continuous 130 7t/ha 5.70 6.70 7.61 -1 416 -1 908 -1 260 Source: Original yield data (Grant, 1976) Note: All plots received 66 P205, 55 K2O and 25S kg/ha/yr. Production 1997 maize sale price $1200/t; replacement costs : Ammonium nitrate $2490/t, single superphosphate $1725/t.
· when little fertilizer (20 kg/ N/ha/yr) was used yields remained at about 2 t/ha for about 10 years of the trial, · good yields were maintained with high fertilizer (130 kg/N/ha/yr) for 5 years and then response to nitrogen decreased to 59% of the potential yield in the tenth year, presumably due to deficiencies of other nutrients which developed and limited yields, · years of Continuous cropping with high rate of unbalanced or single-nutrient (130 kg/N/ha/yr) eventually resulted in lost production, · lost production increased with continuous cropping but it could be reduced by application of even small amounts of manure i.e. 7 t/ha.
Major causes of soil fertility decline The major causes of soil fertility decline in the smallholder sectors of Zimbabwe are continuous cultivation without adequate fertility inputs, organic residues such as manure and/or fertilizer, to replenish nutrients removed by crop and other losses. Specific practices which contribute to decline in soil nutrient levels include the following: · low adoption of fertilizer use. Growth in fertilizer consumption in the smallholder sectors of Zimbabwe since 1984/85 has not been sustained (Conroy, 1990), · application of sub-optimal rates of fertilizer. Only about one-third of communal farmers even in the high rainfall NR I and NR II who use fertilizer apply the recommended rates (Page and Chonyera, 1994) Little or no fertilizer is applied in the semi- arid areas NR 3, NR 4 and NR V because of the associated risk factors, · non-application of fertilizer/manure to crops in rotation with maize. Crops in rotation with maize such as groundnut (Huchu and Sithole, 1994) or pearl millet and sorghum grown in the semi- arid areas (Ahmed et al, 1977) often receive little or no fertilizer, · use of blanket fertilizer recommendations which do not allocate scarce fertilizer sources efficiently since they do not take into account important variability in soil fertility. During the 1987/88 to 1990/91 seasons the number of soil samples submitted to the Soil Testing Laboratory from the communal Areas decreased annually from 593, 391, 165 to 72 (CSRI, 1991), · lack of application of lime which leads to acidification of soils and leaching of nutrients, Integrated soil management for sustainable agriculture and food security in Southern and East Africa 363
· loss of topsoil including nutrients and organic matter through erosion due to lack of inadequate conservation works, · poor resource base i.e. inadequate amounts and/or sources of nutrients e.g. manure, · use of depleted/marginal lands. More than 67% of the communal areas exceed their carrying capacity in terms of human and livestock populations (Huchu and Sithole, 1994). Population pressure has resulted in the use of depleted/marginal soil for crop production which has lead to losses of topsoil and nutrients, · removal of crop residues from fields. Crop residues are removed from fields and used as livestock feed in the dry season. This contributes to nutrient and organic matter removal from cultivated lands.
Major constraints Poor soil fertility and climatic risk are the major factors that directly affect Zimbabwe farmers' ability to produce enough food for subsistence and for cash (Huchu and Sithole, 1994). The natural poor soil fertility is further exacerbated by the following factors: · inadequate supply of organic sources of plant nutrients. Manure, the traditional organic fertilizer, is becoming more scarce due to poor grazing, while litter for composting is now not available in many communal areas, · lack of capital to purchase chemical fertilizers. There are no reliable credit facilities for communal area farmers because financial institutions are reluctant to lend money to farmers who cannot provide security e.g. title deeds, · population pressures. High population pressure in the communal areas forces farmers to cultivate continuously the same pieces of land usually with little/or no rotation. Crop residues have to be removed from fields to supplement feeding of livestock during the dry season due to poor grazing i.e. overgrazing due to high livestock densities.
AVAILABLE TECHNOLOGICAL OPTIONS FOR CONTROLLING SOIL DEGRADATION AND ENHANCING PRODUCTIVITY Technological options for improving soil fertility and crop production emanate from work programmes within DR&SS, extension and development agencies. To sustain agricultural production under soil and climatic risk experienced by the small holder farmer, there is need to fill in gaps that exist between research technology and farmer innovations. This process begins with the recognition that the search for management options for sustaining soil fertility requires community input and the integration of indigenous knowledge into scientific research and agricultural development. Farmers have some indigenous technology judging from conditions of high variability and uncertainty in which they live. There is a great potential of indigenous information to be expanded into scientific technological information which will benefit its owners i.e. small holder farmers. This section looks at available technological options for improving soil fertility in the small holder sector, Tables 6, 7, 8 and 9 illustrate this picture. However, not all of the promising technologies have been tested on-farm for adoption. 364 Zimbabwe
TABLE 6 Soil fertility constraints and possible solutions Soil Fertility Constraints Possible Solutions à sandy soils inherently infertile i.e. à use of lime to reduce imbalances in some nutrients (Mg à low cation exchange capacity, low and Ca) (increase awareness) pH à use of appropriate recommended mineral fertilizers (use à ranges (4.2 to 4.8 (CaCl2) strategies to increase fertilizer use-efficiency à low available soil N (<30ppm=45 à supplementation with high quality manure with a narrow kg/ha) C/N ration and low % lignin provide readily available N, à low P content (< 25 ppm) energy and nutrients to the soil ecosystem and build soil à low organic matter content(o.3% to fertility and structure over the long term. (Use 0.5%). management options to increase quality of manure à soils cultivate 40 to 50 years ago à use of other available organics on farm for composts without regular application of à exercise recommended crop sequencing (i.e. crop fertility ameliorants now show rotation) à multiple deficiencies not only in N, à legume intercropping contribute to N budget of cereals P and S but in Cu, Zn, Mn, Mo and and have residual N to subsequent crop (estimated net Bo. N of 23-110 kg/ha from pigeon pea; à 50 kg/ha from dolichos beans; 25 kg/ha from groundnuts). à use of improve fallowing with legumes (increase awareness) à agroforestry (increase awareness)
TABLE 7 Available strategies for increasing fertilizer use efficiency Reasons for low fertilizer use-efficiency Strategies for increasing fertilizer use-efficiency à blanket fertilizer recommendations à appropriate recommendations based upon soil analysis, not appropriate to farmer's à increase proportion of locally produced OM to maintain problems which are location soil OM, specific, à apply high quality organic matter to reduce cash cost for à declining levels of organic matter mineral fertilizers; to improve nutrient (OM) in communal soils, à cycling and to reduce nutrient losses from leaching and à application of low quality organic denitrification, matter à maximize use of limited amounts of fertilizer that a à high fertilizer costs. typical small holder is able to purchase by exercising the following: i. appropriateness of types and amounts ii. timing iii. placement: a) use planter with fertilizer attachment, b) fertilizer in furrows made by ox driven tine, c) complementary tillage plus basal fertilizer application at planting
SUCCESSFUL CASES OF IMPROVED SOIL MANAGEMENT After drought, the problem of soil fertility has been identified as the most limiting environmental constraint to agricultural production. This has led to a decline in crop production and yields, particularly in the small holder sector. Various technologies have been developed to minimize both soil fertility and climatic risks in the sector. Techniques such as crop rotations, tied ridging, winter ploughing, use of fertility inputs such as inorganic fertilizers and organic materials like manure have been promoted. However, local literature reports low adoption rates to some of these technologies. Several factors have contributed to the limited performance of agriculture especially of the resource-poor farmer. These include inappropriateness of agronomic research, which has largely been on-station. The physical, social and economic conditions of the resource poor farmers are considerably different from those of research stations. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 365
TABLE 8 Management options for improving quality of manure in the small holder sector Reasons for low quality manure management options for improving quality of manure à poor quality grazing, à improvement of pastures by planting legumes, à manipulation of biological processes during storage and à ambient temperature, moisture handling of manure reduce N losses and increase levels and length of exposure to the availability of nutrients, environment can trigger nutrient à anaerobic treatment results in better quality manure losses (particularly as NH3 by than aerobic treatment, volatilization and leaching), à storage of manure in pits minimize drying and leaching à imperfect storage and handling during hot and rainy seasons and maintains the conditions (manure is stored in available N in organic fractions, heaps which allow for aeration and à co-composting with inorganic fertilizers (however, there results in aerobically dried and is need to establish whether farmers are likely to put decomposed manure low in fertilizers in kraals rather than on maize crops), nutrient supply (N content less than à use of DPR (Dorowa rock phosphate during composting) 1.2%). which is a cheap source of P, à use of stover as a urine absorbent is a promising tool which can minimize losses by volatilization (efficacy of residues needs to be established), à increase bulk with the use of grass, residues and leaf à low use of residues in the kraal litter both in summer and winter storage. results in dung contamination with sand (50 to 90%) and loss of N from urine à little amounts available.
TABLE 9 Available options for controlling soil and water loss Reasons for soil and water loss Possible solutions for controlling soil and water loss
à surface run-off and sheet erosion à winter-ploughing à mixed cropping à conservation contours à conservation tillage: a. no-till tied ridging b. mulch tillage (more grass from fallows) c. no-till strip cropping d. furrow planting e. tillage rotation
à soil erosion arising from poor cover à reduction of areas planted to maize crops à increase area planted to drought resistant crops
à rill erosion à contour ridges à storm drains à grassed waterways
active farmer involvement all options (extension bottom-up approach)
Simple and high input packages do not fit in well with the complexity and diversity of the small holder farming systems. Resource-poor farmers also lack reliable access to purchased inputs which are often expensive. However, cost is not only the overriding factor as farmers may show resistance to adoption of low-cost innovations. The reason why technologies are often not adopted is because researchers have inadequate understanding of the circumstances and 366 Zimbabwe
production objectives of the small holder farmer. Identifying farmers' priorities and constraints and helping farmers to meet them often leads to innovations which are environmentally sustainable and are subsequently adopted. This section highlights the history of research approaches in Zimbabwe. It reviews the extent to which available technologies for improving soil fertility and controlling soil degradation have been adopted by the small holder farmer. The section also sites a case study in which "participatory" or "interactive approaches" have been implemented to generate new innovations (to effectively interact with farmers without resorting to the top-down approach).
History of research approaches in Zimbabwe Prior to 1980, agronomic research was biased towards developing technologies for the high potential and input intensive agriculture. The "resource- poor" small holder farmer did not benefit much considering the population dependent upon this type of agriculture. The little efforts directed towards the communal farmer saw an emphasis on maize monoculture, crop rotations and tillage (using the plough). Dissemination of these technologies tended to be top-down following a package approach based on ecological zones and being transferred through a medium of a special class of farmers. Small holder research was tackled in the same way in which agronomic research was conducted for the commercial sector. Unfortunately, results of such an approach failed dismally when applied to the small holder farming systems and farmers continued to use their traditional practices. After independence in 1980, the Department of Research and Specialist Services (DR&SS) (the major player in agricultural research) was also tasked to design appropriate technologies for the "resource- poor" farmer taking into cognizance specific problems common to a large proportion of these farmers namely: · climatic risk (low and erratic rainfall, · soil fertility risk (sandy soils poor in nutrient reserves, low water holding capacities and highly acidic), · limited resource procurrence capacity, · limited scope to take risks due to fragility of most of the enterprises.
The establishment of the Farming Systems Research Unit (FSRU) in 1984, saw another major shift in focus of research towards improving productivity of resources devoted to particular crops. The research involved characterization of farming systems, testing and adopting agricultural technologies as well as methodologies with a "systems perspective (FSRU, 1993). Several technologies were tested (both on station and on-farm) on new crop varieties, general crop husbandry, soil fertility management and minimizing drought. In most on-farm trials, the farmer's role was limited to providing land, and researchers would identify problems, solutions, design and implement trials, monitoring and evaluation. Farmers would normally gather at research initiated field days to learn successful stories of crop production and soil fertility management. Recent approaches (i.e. participatory rural appraisal) which encourage farmers to participate in technology generation have made it possible for researchers, extension agents and farmers to become equal and active partners in agricultural research, technology generation, transfer and adoption process. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 367
Rates of adoption of soil fertility management practices in the small holder sector The majority of technologies aimed at enhancing soil fertility have been targeted for areas growing hybrid maize and high value crops like cotton. The most common practices that have been promoted by researchers and extension agents include: · inorganic fertilizers · organic materials (e.g. manure) · crop rotations · contour ridges · soil and water conservation strategies
The successes and limitations of these strategies are highlighted below.
Use of inorganic fertilizers. A survey conducted in Mangwende communal area (Mudhara and Chibulu, 1996) reported extensive use of inorganic fertilizers. Over 98% of farmers indicated that they use both Compound D (8%N, 14%P, 7%) as basal fertilizer and ammonium nitrate (AN) (34.5%N) as top dressing on maize. Only about 2% of farmers do not apply any mineral fertilizer to their crops. Different fertilizer types are also applied to other crops. Compound L (5%N, 18%P, 10%K and AN are used in sunflower and cotton. Gypsum (17.5%S) is used by 35.7% of farmers as top dressing in groundnuts. This scenario implies that fertilizer usage by small holder farmers is dependent among other factors on value of the crop to the farmer. The bulk of the fertilizer goes to the maize crop which is a staple food crop (Table 10).
TABLE 10 Adoption of basal fertilizer in selected crops in Wedza & Shurungwi-Chiwundura in 1990-91 Crop Wedza (% growers) Shurungwi - Chiwundura Maize 48.8 41.7 Groundnut 19.6 21.8 Sunflower 4.4 3.8 Source : Huchu and Sithole, 1993
It is well documented that one of the major costs faced by small holder farmers in producing maize is fertilizer. In many households, cash required to buy fertilizer and other inputs outweighs total cash income. The lack of cash is the dominating factor governing decision making at household level and also influence the development of adoptable technology.
Inorganic fertilizers are expensive. The use of chemical fertilizer in the small holder sector has been declining with each announcement of new fertilizer prices. Poor farmers simply can not afford it. In a study carried by Sithole and Shoko (1991), lack of money was given by 60.4% of non-users as the main reason for not using fertilizers. In general, non-farm income and use of inorganic fertilizers declines from the wealthiest stratum to the poorest. Poorest households apply less inputs on both fields and gardens although they have a more diverse range of inputs for gardens. Although there are credit facilities such as the Agricultural Finance Company (AFC) many farmers particularly those in the semi-arid areas are afraid to take risks. These shortcomings have forced farmers to review their fertility management systems. A significant number of farmers have reduced their application rates. In Mangwende communal area 370 kg/ha of compound D is applied in maize systems by about 70% of farmers whilst 270 kg/ha of AN is used by 75% of farmers. In crops like sunflower, application rates of 120 kg/ha for both basal and topdressing are common (Mombeshora, Mudhara 1994). These levels are well below the crop 368 Zimbabwe
and soil maintenance requirements. Although these levels reflect in inefficiency use of fertilizer, studies carried out in Wedza communal area (Sithole and Shoko, 1991), indicated that topdressing is better adopted than basal fertilizers. Farmers who have livestock substitute manure for basal fertilizers. In the 1990-91 season 40.8% of farmers in Wedza who applied manure did not use initial fertilizers. Top dressing on the other hand has no substitute which could explain partly its higher adoption relative to initial fertilizer (Table 11).
TABLE 11 Fertilizer use on maize in Wedza and Shurungwi - Chiwundura Fertilizer Application % of Users in Wedza % Users in Chiwundura Basal 48.8 41.7 Top dressing 28.9 90.9 Source : Huchu and Sithole, 1993
Apart from high costs in fertilizer prices, several authors have reported that fertilizer recommendations are frequently unattractive to the small holder farmers. Recommendations often ignore soil and climatic variation in the area farmed by small holders and are incompatible with their resources. Of The 32% of farmers who followed fertilizer recommendations for their maize crop in the satisfactory season of 1990/91, 48% failed to recover the value of the fertilizer (Page and Chonyera, 1994). Thus the profitability of fertilizer usage was reduced. An example of inappropriate recommendation is related to the application of basal fertilizers. Farmers are instructed to apply basal fertilizer for maize at planting. Instead farmers almost always apply this type of fertilizer at 3 to 4 weeks after establishment which is easier and less risky and results in negligible loss of yields under their circumstances (Shumba, 1985). This practice allows farmers to plant a larger area and get better crop establishment. Another example cited of an inappropriate recommendation is based on the type of fertilizer used. Mashiringwani ( 1983). A rare response to K on sandy soils common in the small holder sector is reported. The recommended compound fertilizer contains K as well as N and P. Adoption of could be enhanced by applying a cheap N alone immediately after planting and cheaper forms of P at other times. Adoption of inorganic fertilizer has also been influenced by farmer's attitude. Informal interviews in Mutoko communal area (Carter, 1993) revealed that some farmers will not apply inorganic fertilizers particularly basal dressings because they believe it weakens the soil structure. In Gokwe, although cotton is a priority crop, the majority of farmers were found not to use basal fertilizers (76%) or top dressing (77%) on this crop (Mudhara 1993). The main reason was that soils were still fertile. This, however, contradicts to extension messages which encourage farmers to apply inorganics. Where fertilizer was applied by users, there were marked differences in yields. Average yields of cotton were 38% higher where basal dressings were used and 30% higher where AN was applied (Table 12).
TABLE 12 Effect of fertilizer on average farmer's, yields (kg/ha) of cotton in Gokwe in 1990-91 season Used Basal fertilizer No Basal Fertilizer Used Top Dressing No Top Dressing 723 523 704 542 Source : Mudiwa, 1993
Use of organic amendments. Cattle manure is one of the low cost management options which farmers use to sustain soil fertility and cropping programmes. This has become evident particularly with the increases in commercial fertilizer costs. Substantial use of manure is only limited to those farmers who own a large number of livestock. A survey conducted in Mangwende communal area in 1982 indicated variation in cattle ownership (from 20% to 70% of households with average of 46%). The survey reflected that 73% of farmers owned cattle some ten years ago, Integrated soil management for sustainable agriculture and food security in Southern and East Africa 369
with an average of 6.86 compared to 3.29 at the time of the survey. Amongst owners 52% applied manure in the first year of a maize - maize - legume small grain rotation compared to 12% of non-owners. Additional 75% applied manure in the same field in the consecutive years compared to non-among non-owners of cattle. Supplementation of manure with chemical fertilizers is quite common particularly in maize- based system. However, farmers lack knowledge and understanding of the combined use of the 2 nutrient sources together. To make recommendations for combined nutrient use, information on fertilizer equivalency of organics is needed. Farmers also lack knowledge on how much of manure or other different quality organics to apply to get yields equivalent to those obtained from inorganic fertilizers. Manure application rates range from 4.5 to 20 t/ha depending upon availability. The Alvord rotation recommended for small holder areas of Zimbabwe application rates of 30 - 40 t/ha to a maize crop followed by another maize-crop, then by groundnuts and lastly by a fine rooted crop such as pearl millet (Grant 1987). This system has collapsed due to scarcity of manure in most households. The situation has been made worse by poor quality of manure produced, which is attributed to poor quality of the veld, imperfect storage and handling conditions in the kraal (which trigger nutrient losses particularly NH3 by volatilization), moisture levels, ambient temperature and exposure to the environment, (Nzuma and Murwira, 1997). Cattle manure is applied in a dried, aerobically decomposed form often with a high sand content (50% to 90%) and an N of less than 2% (Mugwira and Shumba, 1986).. The same scenario prevails even today. Recent studies in Mangwende CA reported low nutrient status of manure samples collected from households. Ninety-seven percent of samples collected were acutely deficient in N whilst 94% were deficient in P. (Nzuma and Murwira 1997). Current efforts are being made to improve the quality of communal area manure by minimizing nutrient losses through manipulation of biological processes (Nzuma Murwira, 1997). Dhliwayo and Mukurumbira (1996) initiated benefaction cattle manure with P fertilizers. However, the sustainability these systems is questionable. Although CA farmers have traditionally used manure as a soil amendment, there are other less common soil fertility management practices such as use of wood ash, compost, anthill, leaf litter and incorporation of crop residues along with crop rotations (Carter and Murwira 1995, FSRU 1993). Nyathi and Campbell (1993) reported that 73% of farmers in Masvingo collect large amounts of miombo leaf litter, most of which were cured in kraals. Further, 86% of farmers mix their litter with manure or with manure and fertilizer before application. Though it appears that there are satisfactory quantities of organic materials on and around the farm, most of these materials have a low nutrient supplying capacity. The challenge is to get more higher quality organic materials on farm. Use of hybrid seed. The major success in maize research in Zimbabwe has been in maize breeding. This is indicated by high adoption rates of hybrid maize even though average yields are 1t/ha (Rohrbach 1989). Adoption of hybrid seed particularly early maturing varieties have been strongly recommended for CAs with poor rainfall. The advantage is short growing season and attainment of maturity stage before rains cease. Adoption of hybrid seed, particularly maize has been very high. Study carried out in Wedza (Sithole and Shoko 1991) showed that 98% of the Communal farmers used hybrid seed. Crop rotation. Crop rotation is vigorously promoted by extension agents for improving soil structure and facilitating the transfer of nutrients between crops via soil. It also helps control pests and diseases. Adoption of crop rotation is high, perhaps because of no labour and no direct cash costs involved into the practice. The rotation is not a planned sequence of different types of crops but rather a haphazard movement of crops to areas within the fields. Most farmers rotate the grain crops mainly and rarely include leguminous crops because of limited area grown to 370 Zimbabwe
them. In studies carried out in Wedza in 1991, 74.8% of communal farmers interviewed were found to practice crop rotation in their fields. A similar percentage of farmers (75%) in Mangwende were reported to practice some crop rotation. The figure for Gokwe and Nyanga was found to average 76% in 1992 for both areas. In some areas adoption of this practice is quite low. The main factor limiting adoption of crop rotation is poor access to resources such as land labour and agricultural inputs, maize tend to be the dominant crop using 80% of the arable land and very small acreages are left for other crops. Thus much of the land is always under continuous maize crop and only small portions are rotated with groundnuts, sunflower and cotton. Soil and water conservation The majority of small holder farmers (75%) in Zimbabwe are concentrated in semi-arid areas of the country. These areas are situated in natural regions IV and V and marginally some parts of natural region III. Rainfall in these areas is low (about 600 mm per annum) and erratic. Drought induced crop failure occurs in one out of every 4 years. Soils are generally sandy inherently infertile (Grant 1967, 1981). High water losses are common from arable lands. Sheet erosion results in further soil loss, and the agricultural potential of the area continues to deteriorate each season. Soil losses in the order of 50t/ha per year through sheet erosion, and run-off losses of the order of 35% of total seasonal rainfall have been estimated (Elwell, 1985). Tillage offers the most promising tool to manipulate and control erosion and ameliorate the fragile semi-arid soils (Chuma and Hagmann, 1995). Experience has shown that adoption of new interventions has been hampered by the lack of participation by beneficiaries in the development process (Chambers et al 1989). Various agencies in Zimbabwe have shown a necessity for change in agricultural and rural development towards farmer participation in order to increase efficiency of development activities and to effect adoption (FSRU 1993, Mlambo, 1994; Makado 1994). It has been realized that sustainable resource management utilization can only be achieved if community based participatory approaches are developed and applied rather than present top-down approaches which do not involve farmer participation (Hagmann, et al 1995). In view of these facts, researchers/extension/development agencies Zimbabwe are currently working towards soil and water conservation packages that can be adopted by the small holder farmer (GTZ- ARDA/PPU,1995). This approach requires new roles and attitudes of both parties involved in technology generation and its dissemination. Farmer Participatory Research In soil and water Conservation Tillage. The Conservation Tillage (Contil) for sustainable crop production systems project was initiated in 1988 and is on- going. It is a collaborative program between GTZ (German Aid Agency) and Institute of Agricultural Engineering (IAE, Agritex). A very positive development of this Contil project was the initiation of complementary adaptive on-farm trials (Hagmann, 1993), which uses a conservation tillage approach known as the "KUTURAYA". The "Kuturaya" (meaning to try) is focused towards research and farmer participatory in soil and water conservation. (Nyagumbo 1996) It plays a role in influencing adoption of technologies by creating awareness and inspiring farmers to try and assess the feasibility of certain animal powered conservation techniques under farmer's management. These techniques include: · conventional (or clean ripping) · tied ridging · mulch ripping · hand hoeing · bare fallow Integrated soil management for sustainable agriculture and food security in Southern and East Africa 371
Specific objectives are to develop these systems further and to adapt them to the farming systems of small holders in various natural regions. The approach is based on the hypothesis that only farmers themselves can develop and or adapt a technology to their specific needs and requirements. This approach inter links technical and socio-economic aspects of agricultural production systems. The trial is voluntary and farmers participate out of their own interest. Once farmers have become familiar with experimentation the research process becomes solely farmer driven and the role of researchers is only to facilitate the process. (Nyagumbo, 1996). To enhance active farmer participation in the Kuturaya process, training for transformation (TFT) (Hope et al., 1984) is applied in farmer workshops. TFT has increased farmers evaluation capabilities and strengthened the social Organisation of communities (Hagmann 1993). The impact achieved during the last 3 years in Gutu, Zaka and Chivi communal areas has been encouraging in terms of farmer participation (Hagmann et all 1995). Farmers are reported to have initiated their own trials resulting in gain in confidence. Farmers have also shared their experiences in farmer initiated and self organized field days. Results from the 4 years of data indicate that no - till tied ridging (Inttr) is the best conservation and production technique for the sub-humid north of Zimbabwe whilst mulch ripping has been recognized as the most favourable tillage option for the semi-arid areas.
TABLE 13 Advantage of no-till tied ridging as perceived by both participants and non participants Advantage Participants % Non-participant % Moisture conservation 57.5 27.7 Soil conservation 27.5 8.4 Crops mature fast 7.5 0 Better yields 2.5 4.8 No idea of importance 2.5 30.1
However due to limitations in availability of residue, (residues grazed by livestock) no mulch is available and tied ridging with its reduction in the run-off losses and associated low soil loss appeared to be the most applicable sustainable tillage system. Nutrient losses under tied ridging have been reported to be lower than in the conventional till as water infiltration losses are confided to the furrow leaving nutrients in the ridge (Hagmann 1994). A majority of farmers involved in the demonstration and trials (57.5%) have indicated appreciation of this system as a moisture conserver, while 27.7% of non participants shared the same view. The aspect of soil conservation was appreciated by 27.5% participants and 8.4% of the less informed non- participants (Table 13). The beneficial effects of tied ridging have been reflected in yields of cotton in Gokwe Sanyati and Sebungwe communal area where it is currently extensively used (Mudiwa 1993). This is illustrated in Table 14.
INSTITUTIONAL FRAMEWORK AND POLICIES FOR LAND RESOURCES MANAGEMENT Government objectives since Independence in 1980 have been to create an enabling institutional and policy environment to stimulate production and sustainable development in the smallholder sector. A number of institutions previously set up to service the large scale commercial farming sector had their mandates changed either to give priority to the smallholder sector or to take the smallholder sector on board. A whole package of support which included research, technical and extension services, marketing infrastructure, finance and favourable prices was given to stimulate production in the smallholder sector. Smallholder farmers responded to this gesture by increasing production levels significantly. However this increase in output was due to more land being brought into production rather than improvement in yields on a per hectare basis. The benefits brought about by the change in institutional and policy environment were short lived as problems 372 Zimbabwe
associated with the magnitude of the change and declining resources began to surface. Institutional support by government could not be sustained at the required levels. Whilst government policy statements have continued to be dominated by the need to increase production in the smallholder sector, environmental problems and rural poverty have continued to take centre stage.
TABLE 14 Average yield responses of seed cotton (kg/ha) to four moisture conservation techniques by two levels of fertility for Gokwe, Sanyati and Sebungwe Communal Areas, 1984-90 Season 1984-85 1985-86 1986-87 1988-89 1989-90 1990-91 Mean Flat % No. sites 9 10 12 8 4 5 Average Rainfall 668 786 378 587 542 516 (mm) Planting and 1,319 1,212 741 1,672 569 1,067 1,207 100 fertilizer treatment Flat Flat fertilized 1,529 1,626 861 2,080 756 1,166 1,500 124 Flat + potholes 1,473 201 781 1,778 600 1,295 1317 109 Flat + potholes + 1,824 1,651 920 2,061 711 1,407 1,631 135 fertilizer Ridges 1,323 1,221 930 1,601 675 1,450 1,321 109 Ridges + fertilizer 1,620 1,743 1,031 2,000 880 1,515 1,675 139 Ridge + cross ties 1,412 1,294 946 1,596 723 1,597 1,375 114 Ridge + cross ties 1,713 1,857 1,134 1,996 982 1,932 1,814 150 + fertilizer s.e. (conservation 52.3 42.6 26.3 65.4 43.8 81.5 mean) s.e (fertilizer 17.5 30.1 18.6 46.3 27.0 41.6 mean) Mean (unfertilized) 1,375 1,232 849 1,662 642 1,352 1,304 Mean (fertilized) 1,672 1,719 987 2,034 832 1,505 1,655 significance: NS * *** NS ** *** conservation significance: *** *** *** *** *** * fertilizer conservation lsd - 118.1 72.9 - 121.4 225.9 0.05 fertilizer lsd 0.05 48.5 83.4 51.5 128.3 74.8 115.3 Source: CRI
Institutional framework There are a number of government institutions whose functions have a bearing on environmental management. These institutions are sectorally structured, an arrangement which leads to confusion of hierarchy, duplication of programmes; and ultimately inefficiency. Conflicts have arisen from uncoordinated parcelling out of responsibilities among departments. A good example is the allocation of conservation responsibilities between the Department of Natural Resources (DNR) and the department of Agricultural Technical and Extension Services (Agritex). Whilst DNR is responsible for policing the state of conservation, and more recently extension in the same area; Agritex is responsible for extension and providing technical solutions to the problems. Another example is the parcelling out of responsibilities between the department of Agritex and the department of Rural Development under the Ministry of local Government in Land Use Planning (LUP) programmes. Agritex is responsible for determining issues of access and use of Integrated soil management for sustainable agriculture and food security in Southern and East Africa 373
resources through LUP, while local government is responsible for implementing land use re- Organisation programmes.
Following independence in 1980, government adopted a policy of decentralizing planning institutions to provincial, district, ward and village levels. These institutions have in practice however proved to be more politically oriented than developmental oriented. These planning levels have virtually no power to plan or allocate resources. Prior to independence in 1980, powers to allocate and manage resources in the communal areas were vested in the traditional leadership. They used to set rules and regulations on utilization of resources which were respected and followed by their subjects. This type of arrangement proved to be fairly effective in the management of natural resources. Traditional leadership were however relegated to non- functional roles after 1980 and replaced by local government structures. This actually undermined the traditional power structures which used to control natural resources effectively.
Planning for resource management initiatives has proved difficult within the constraints of the new administrative structure of the Village Development Committee (VIDCO) due to artificial boundaries demarcated to fit an administratively defined user group. A VIDCO was defined as 100 households in each village irrespective of existing boundaries, kinship and without taking cognizance of the underlying resource endowments. The institutional framework suffers from a serious problem of fragmentation and poor co-ordination. there is insufficient co-ordination of the responsibilities of institutions at various levels (national, provincial, district, ward and village) for managing or enforcing policy, planning ; and monitoring information and technical programmes. The framework, especially at implementation level in the communal areas has remained regulatory with a conspicuous absence of appropriate incentives.
Policy and legislation There are several pieces of legislation that deal with land issues in Zimbabwe. These include; the Natural Resources Act (1941), Forest Act (Amended in 1981) Mines and Minerals Act (1961), Rural District Councils Act (1988) and the communal Land Act (1982). These pieces of legislation suffer from two main problems: · There is lack of hierarchy, i.e. there is no one act which supersedes others in terms of environmental protection. The legislation is sectionalized and overlaps, allowing too many ministries decision making powers on environmental issues. The end result is a fragmented approach to management of natural resources. · Legislative and organizational apparatus have not been designed in a manner which encourages people to participate in improving their environments. Most of them place greater emphasis on controls (criminalization) than providing incentives for sustainable resource use and encouraging communities to develop their own resource management solutions.
In general terms, there is insufficient co-ordination of policy and legislation. The current policy environment has failed to address the population pressures on agricultural land and the environment at large. There is need to put in place policies that encourage investment in technology and research in order to increase production in low potential areas and minimize environmental pressures. Clear policies on issues such as tenure and environmental management; together with clearly elaborated action plans that take all stakeholders on board, would be required to facilitate effective natural resources management. 374 Zimbabwe
Research and extension linkages The Ministry of Lands and Agriculture through the departments of research and specialist services (DR&SS) and Agricultural Technical and Extension Services (Agritex) play a pivotal role in influencing land-use patterns and productivity in the communal areas. DR&SS is a research department which carries the mandate to do research in all agricultural commodities with the exception of tea, coffee, tobacco and pig production. Agritex is the main extension arm of the Ministry with extension personnel deployed throughout the country. The need for strengthening research and extension linkages was realized during the early 1980s when the Committee for on- farm research and extension (COFRE) was established in 1986. The objectives of COFRE were to co-ordinate on-farm trials and demonstrations as well as give researchers and extension staff an opportunity to interact in a real farm situation (Pazvakavambwa, 1990). The COFRE mechanism, while well intentioned has not resulted in a focused and quality research programme going for smallholders. The activities of COFRE were severely curtailed by institutional problems such as inadequate funding, shortage of experienced staff and shortage of transport. The following paragraphs give a description of specific problem that have affected the activities of each department.
Department of Research and Specialist Services. Upon attainment of independence, priority for research and extension was focused on the smallholder sector forcing the government to increase the size of the institution in terms of scientist staffing levels. However, this expansion was not matched by resources with which scientists would carryout their investigations. Most of the resources were channelled towards meeting salaries rather than developing technologies suitable for smallholder farmers. Added on to this, was the brain drain problem resulting in the loss of experienced staff at a time when the real challenge was to address the complicated research needs of communal areas. In 1981, DR & SS initiated an adaptive on-farm research programme. This was intended to improve research - extension - farmer linkages. This programme was short lived as it was frustrated by lack of resources such as vehicles and travel allowances, resources which are absolutely essential to keep such programmes running. The budget of DR & SS was reduced by 25% in real terms between 1980 and 1989. This forced DR & SS to scale down on on-farm research which had been well intentioned to benefit small-holder farmers. (Shumba, 1990). Importantly, DR & SS has not had resources to address itself to the agricultural problems of the poorest, less developed sectors of the rural economy who try to farm in areas that have long been recognized as having low agricultural potential. This has contributed to serious land degradation problems in the smallholder sector.
Department of Agricultural Technical and Extension Services. The Department of Agricultural Technical and Extension Services (Agritex), as an institution, was not spared from the problems of brain drain and under funding which afflicted its sister department, DR&SS. Although in nominal terms, the funds allocated for extension have been increasing, there has been considerable fluctuations in real terms, with annual allocations between 1984 and 1993 averaging Z$13.8 million and with the allocation for 1993/94 well below the level for 1980/81. The national allocation to agricultural extension as a proportion of national expenditure actually declined by 50% from 0.8% of national recurrent budget in 1980/81 to 0.4% in 1993/94. At the same time, the operating part of the budget has declined from about 30% in 1980/81 to 20% in recent years, with the balance of expenditure going into salaries.
The Extension Worker to farmer ratio of approximately 1:800 is too low for effective coverage. Group approaches have been adopted to make up for the gap, but these strategies tend to leave out the poor farmers who regard these as elitist groupings. Extension staff also need Integrated soil management for sustainable agriculture and food security in Southern and East Africa 375
mobility in order to do their work effectively. Transport is one area were the extension department has been hit hard, and therefore has far reaching negative implications with respect to environmental conservation.
Financial support to the smallholder sector In the early 1980s, the government of Zimbabwe adopted a policy of financial support through provision of credit as a strategy for smallholder farmer development. This was done through the Agricultural Finance Co-operation (AFC), a parastatal lending institution. AFC loans to the smallholder sector increased from 18 000 in 1980 to 77 526 in 1985; but the in attention to sound lending practices meant a collapse of smallholder lending, with a decline in loans to a low 15 973 in 1993 (AFC, 1993). The decline in the loan portfolio was due to both reduced demand and stricter procedures on the part of AFC. Improved access to loans was associated with increases in the use of inorganic fertilizers in the smallholder sector. There is now a general decline in the fertilizer market share of the smallholder sector since the late 1980s. This has been linked to loan repayment problems and the rising cost of fertilizers on the market. But even at its lending peak in 1985/86, AFC was only reaching 10% of communal area farmers.
Extent of data/information on land resources Most information relating to land resources is unconsolidated and lies with different institutions involved with land management issues. The department of the surveyor general normally flies the country every five years to produce aerial photographs. These are produced for the consumption of institutions involved with land use planning, land surveys, environmental management and even individual land owners. The department of Agritex is a key player in producing farm, village, ward and resettlement plans. Most of these plans are available as hard copies at the Agritex offices. Efforts are now under way to store some of the information in digital form through the Remote Sensing/GIS project. To date, information from 6 wards of Lupane communal area and some parts of Gokwe has been computerized. This information includes drainage systems, and capability classification, vegetation, contour lines, Ward boundaries and Infrastructure. Some information on soils is available with the department of research and specialist services. The department of Natural Resources produced a fairly comprehensive report on Land Degradation in Zimbabwe (Whitlow, 1988). There have been very little efforts to update the report in recent years.
Land tenure There are five major land use types in Zimbabwe. These are communal areas, commercial farms, resettlement areas, state land and national parks, and urban areas. Communal areas occupy 42% of Zimbabwean surface area and accommodate about 75% of the population of approximately 11.9 million people. The majority of communal areas are located in the marginal areas of the country where rainfall is low and poorly distributed. The soils are mostly granitic sands with very low inherent fertility. Communal farms are small and are allocated by traditional leaders. Land degradation in the communal areas is primarily a result of mismanagement problems related to ploughing, stream bank cultivation and insufficient application of organic and inorganic fertilizers. Continuous cultivation of land, lack of crop rotations and poor soil management schemes have resulted in poor soil structure and declining crop yields. Communal farmers have generally not adopted technologies developed for large scale commercial farmers because most of these technologies are not appropriate to their circumstances 376 Zimbabwe
PROPOSALS OF PROGRAMMES FOR IMPROVED SOIL MANAGEMENT AND PRODUCTIVITY ENHANCING Changes in soil fertility In the majority of research trials conducted in Zimbabwe on the use of cattle manure for soil fertility the increase in crop yield has been employed as the sole indicator of soil fertility improvement. Comparatively few trials have assessed the effects of manure on specific soil properties such as increases in pH, CEC, N mineralization and available P etc. As done by Grant (1967a, b). There is a need to assess the effects of CA manure on changes in soil fertility factors and other soil conditions which may indirectly affect soil fertility. These investigations include: · assessment of changes in available soil P as affected by repeated application of manure and fertilizers in the CAs to establish if application of CA manure helps to increase availability of P applied with fertilizers, and incipient soil P, · establishing critical evidence on the residual effects of manure which will be useful for assessing the value of manure as a liming and nutrient source when considering integrated nutrient management in the CAs, · assessment of rates and frequency of application of CA manure which would help maize to withstand soil pests such as nematodes which adversely affect yield on sandy soils and limit fertilizer response, as found by application of heavy rates of manure at Grasslands by Grant (1987).
Restoration of soil productivity to depleted croplands · A quantitative survey of depleted lands should be conducted by DR&SS and Agritex to find out where most of these lands are located with a view to properly targeting research on the restoration of soil productivity. · Soil characterization under conditions of nutrient depletion should be made to establish baseline levels of pH, organic matter and nutrients as well as physical properties related to soil productivity. · It is necessary to establish nutrient requirements for the restoration of depleted lands since the rates of manure and inorganic fertilizer normally used in croplands are obviously too low under depleted conditions. Elements of a high input strategy to recapitalize the soil fertility of exhausted soils are needed. · Long-term trials on the same fields should be conducted to enable proper evaluation of soil fertility changes due to fertility inputs with a view to extrapolation the technologies. · Screening to establish the most appropriate legumes for different areas should be conducted. · The need to raise the availability of green manure seed should be addressed.
Improving capacity and use of site-specific or location specific fertilizer recommendations Mapping crop and nutrient status for improved fertilizer recommendations in the CAs.
Targeting research to neglected soils and agro-economical zones Most of the research on soil fertility, particularly the use of manure, has been concentrated on upland soils in NRII and relatively little has been done in Regions III, IV, and V. The following research is suggested: Integrated soil management for sustainable agriculture and food security in Southern and East Africa 377
· investigations on crop responses to manure application in NR III, IV and V, both in terms of quantity and quality, · investigations on crop responses to manure applications on vlei (hydromorphic) soils which play a major and unique role in the CA agriculture, · further investigations on the use of small amount of manure applied annually in combinations with inorganic fertilizers on the restoration and maintenance of soil productivity on a wide scale.
Strategies for combining organic and inorganic fertilizing materials to optimize nutrient availability to plants Establishing fertilizer equivalency of organic materials: in order to make meaningful recommendations for the combined use of organics with mineral fertilizers it is necessary to determine first the fertilizer equivalence of the organic materials, then: · conduct research on fertilizer N equivalencies of organic materials of different quality in the field trials using crop yield response as basis for effectiveness of these materials, and · combine the organic and inorganic sources based on the results from the fertilizer equivalency values.
Establishing manure and fertilizer requirements: · there is a need for research specifically aimed at establishing the quantities of manure and fertilizer necessary to maintain soil productivity or fertility (Mugwira and Murwira), 1997. This calls for closer collaboration between researchers in the country in establishing amounts of manure and fertilizer to be tested in trials, taking into account that manure is applied to soils primarily as a fertilizer and as such, its a fertilizer replacement value, · develop research for establishing optimum application rates based on the N content and especially the rate of release of N from manure. From established rates of release, it could be possible to make estimates of residual N availability in later seasons, · develop a rational basis for the use of manure based on decomposition rates and tests of nutrient availability for making proper recommendations, · the time of application of N fertilizer to fields which have received manure should be further investigated in order to synchronize N supply in the soil and N demand by the crop.
Improving the effectiveness of manure Improving of manure quality: it has been firmly established that cattle manure from the CAs of Zimbabwe is low in nutrient contents and that this poor quality contributes to the low effectiveness of manure in improving plant growth and crop yield (Tanner and Mugwira, 1984; Mugwira and Mukurumbira 1984; 1986). The following research options are recommended to ameliorate the quality of manure: · expand the work on beneficiating cattle manure in the CAs through co-composting with chemical fertilizers (see Dhliwayo and Mukurumbira, 1996) under different environmental conditions, · investigate technologies and management of resources within the reach of the farmer such as: - improvement of pastures by planting legumes at village level or small watershed scale. 378 Zimbabwe
- management practices at kraal level which will reduce nutrient losses and sand content of manure - the efficacy of crop residues and other plant materials as absorbents of urine to reduce nutrient losses - handling techniques for anaerobically treated manures to improve quality.
Improving techniques for manure application for optimizing crop response: the most efficient and effective way of applying cattle manure for meeting crop nutrient requirements and producing optimum yields is a very important aspect for the smallholder farmers who often have limited amounts of manure to apply at recommended rates to their croplands. Research should emphasize the following aspects: · systematic assessment of method and rate of application of cattle manure on crop yields in different agro-ecological zones, · further research on comparisons of different methods of application of varying manure rates for optimizing the efficiency and effectiveness of the limited amounts for the potential benefit of the resource-poor farmers on sandy soils, · more research comparing the benefits of applying small rates of manure more frequently, and those of larger rates applied at longer intervals, · management strategy for application of inorganic N by delaying so as to reduce N losses and increase synchrony of N availability and uptake by the crop. A simplified approach is to develop a relationship between total N content of manure, N mineralization rate and minimum fertilizer to be added (Mugwira and Murwira, 1997), · identify obvious characteristics associated with manure that can be used by extension workers and farmers to determine manure quality.
Fertilization for all crops in rotation As the starch staple for most Zimbabwean maize receives better fertilization through both organic and inorganic inputs than other crops grown in the smallholder sectors. Manure is usually applied directly for maize in rotations with subsequent crops while inorganic fertilizers are applied at small rates or not applied at all to other crops (e.g. sunflower). These factors are major causes of soil fertility decline. The following aspects need to be investigated: · rationalization of nutrient-use efficiency in the common rotations currently practised in different areas of the country with a view to improving these rotations and/or introducing more efficient crop sequences, · assessment of the cost effectiveness of organic and inorganic fertilizer inputs on crops such as groundnut or sunflower which are becoming increasingly important not only because of their food value but also due to their increasingly commercial value as cash crops under the free market systems i.e. crops now perceived by smallholder farmers as having niches in their food security and income generation. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 379
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Annex 1
Opening and closing addresses
WELCOME ADDRESS: Ms. V. Sekitoleko, FAO Subregional Representative
Distinguished Country Delegates, Director of AGRITEX, Ladies and Gentlemen
FAO is particularly honoured in organizing this workshop in cooperation with the Government of Zimbabwe on one of today's most important subjects, particularly in Africa: Integrated Soil Management for Sustainable Agriculture and Food Security.
The majority of developing countries are faced with great challenges to sustain and increase food production for their rapidly growing population. Countries with limited land resources, particularly those which cannot easily finance increased food imports, will be faced with serious hardship. The various forms of' land degradation are seriously affecting the land resources base contributing to considerable yield decline and loss in food production. It is evident that no food security could be expected without effective planning and improved management of land, water and nutrient resources to ensure sustainable and increased production.
Technical options and appropriate soil management and conservation practices are available for correcting or minimizing the degradation of' the soil base, for maintaining and enhancing land productivity, and thus improving food production and security.
Nearly 1,4 billion ha of' land in developing countries are subjected to various forms of degradation, resulting in severe decline in productivity. About 490 million ha, in Africa alone, are affected by degradation. Poor and inappropriate soil management is the main cause of degradation of cultivated lands. Increasing population pressure, particularly in vulnerable regions, has caused serious soil fertility decline, especially under extensive farming practices. As a result, farm productivity and revenues from agriculture are falling, migration to urban areas is increasing and household and national food security is declining.
With recent emphasis and priority programme of FAO for food security, issues related degradation and its negative impacts on food production as well as land improvement for enhanced productivity are receiving special attention. Successful experiences and initiatives for soil improvement in a specific country or socio-economic and agro-ecological environment have taken place, but their wider dissemination for the benefit of other countries, even in the same region, is still limited.
At present there are 86 low-income food deficit countries (LIFDCs), including 43 countries in Africa and 9 in Latin America and the Caribbean. These countries are home to majority of the world's 800 million chronically undernourished people. Many LIFDCs, particularly in Africa, do not grow enough food to meet their needs and lack sufficient foreign exchange to fill the gap by purchasing food on the international market. 384 Annex 1: Opening and closing addresses
After the approval of the Council in June 1994, a special programme for food security was launched by FAO and at present it is operational in 20 countries. Initially launched with modest FAO regular programme funds, the SPFS is now supported by several donor countries and international agencies, including the World Bank, African Development Bank, WFP and UNDP. In the short and medium term the technical packages for enhancing productivity in the SPFS may heavily rely on low-cost/low-risk options. As such, appropriate and integrated soil and nutrient management for conservation and improvement of the soil base, besides proper water harvesting and small irrigation management, are among the essential elements for enhancing crop production and ensuring food security.
The FAO strategic framework for the Post World Food Summit Period, consists of two main streams of priority programme areas: one emanating from the objective of "Food security” and the other is arising from the objectives embodied in "SARD" (Sustainable Agricultural and Rural Development, Chapter 14) of Agenda 21. In both streams, areas relevant to land resources, integrated soil, nutrient and water management are emphasized.
I have no doubt that this expert consultation is an excellent opportunity to discuss critical issues of appropriate soil and water management to address food security. I am sure that your contributions to this workshop will make it a turning point and a success with the appropriate actions.
Thank you.
OPENING ADDRESS: Cde Kumbirai Kangai, Honourable Minister of Lands and Agriculture FAO Subregional Representative for Southern and East Africa, Ms Sekitoleko, Distinguished Guests, Ladies and Gentlemen
I would like to thank you for according me this opportunity to address this expert consultation on Integrated Soil Management for Sustainable Agriculture and Food Security in and Eastern Africa. Mr Chairman, I believe this to be one of the most complex issues we face today not only in this country but in the continent and the world at large. I am glad this forum is going to address the issue of integrated soil management and I stress because problems of soil management are multi-sectoral.
The goal of achieving and sustaining farming resources is now the top priority concerns for policy makers in agricultural and environmental policy in many countries. Mr. Chairman, both renewable and non-renewable resources are inputs to and outputs from the agricultural system. Agricultural systems convert these resources into food and other agricultural products, ensuring food security for the communities. Sustainable agriculture, therefore, calls for a growth strategy that does not comprise the welfare of our future generations. Such a strategy is possible only when policy makers in general and farmers in particular, recognize that management of the environment and economic development are basically connected.
The environment consists of closely intricate systems. Trees and grass for example only provide fuel and fodder but also build soil fertility, prevent soil erosion, provide water catchment, reduce effects of climatic changes and provide wildlife habitats. These systems undersign human welfare now and in the future since it is these that man must utilize wisely in order to maximize economic gains over the years ahead. Integrated soil management for sustainable agriculture and food security in Southern and East Africa 385
About 320 million hectares in Africa alone are affected by moderate to excessive degradation. The main causes of physical and chemical degradation of cultivated land have been cited as poor and inappropriate soil management. It is also estimated that, without proper conservation measures, one heavy storm at the start of a season can remove up to 20 tonnes of soil from every hectare of land. Thus, 100 tonnes of soil can easily be lost every season if sound environmental practices are not adopted.
Increasing population pressure particularly in vulnerable regions has caused serious fertility decline, especially under extensive farming practices and this is manifested by declining yields, decreasing vegetation cover and increasing soil erosion. As a result, farm labour productivity and revenues from agriculture are falling, migration to urban areas is increasing and household and national food security is declining. If this vicious cycle of land degradation cannot be stopped, the source of existence of' the majority of the population especially in Africa will be severely affected. Africa will not only be left at the periphery of development but will increasingly find it difficult to meet food requirements of her increasing population.
There exists much information on land degradation and its implications for the sustainable management of soil resources. However, the information is either wholly empirical or vague and unsubstantiated. There is a need to synthesize and consolidate the best quality experimentally derived quantitative information on the relationship between sustainability and productivity. To make predictions of long term trends on the quality of soil resources and of agricultural production for food security, scenarios relevant to tropical Eastern and African situations, are also required in order to examine the range of control measure which could address these predicted outcomes. The demand for this information is increasing given the threats of droughts the region is facing.
Earlier approaches to the management of 'our environment were based on assessment of the impact of individual projects and investment programmes in terms of' pollution control, afforestation or water management. However, this project by project approach has tended to address symptoms rather than root causes of environmental problems. Sound strategies should look beyond individual projects to the broader issues, to take full account of the links between sectors. The problem of soil erosion has in the past been regarded as a physical process to be controlled by the correct physical methods such as terraces, contours and check dams. The problems were regarded as requiring engineers alone. However, land planners have realized that the basic causes are land management strategies which require an integrated approach thus drawing planners, farmers, policy makers and scientists together to make plans on land degradation. I believe even in this workshop we have a mixture of these to plan for an integrated soil management.
I am glad to note that FAO since 1984 has been supporting the Network on Erosion Induced Loss in Soil Productivity which provides information which helps in identifying the agro- ecologies where concerted action is needed now or in the near future to avert substantial agricultural production loss and the consequent food security threats brought about by soil erosion.
Let me conclude by giving special thanks to FAO and AGRITEX for organizing this consultation. 1 do hope that at the end of the consultation, strategies for better soil management would be designed. It is important to note that much of the land being lost due to erosion or has become dangerously saline could be reclaimed and brought back into full production in an 386 Annex 1: Opening and closing addresses
environmentally sound manner. Corrective measures are needed in order to achieve a sustainable food production base. The responsibility for this lies on the governments and people of our countries. Rectifying land degradation and sustaining crop production through appropriate soil and water management and conservation are, therefore, important components in the efforts towards food security. Mr Chairman, there is an urgent need to develop and implement sub- regional and national programmes as well as community based projects, to control land degradation and to improve land productivity. I do hope you will come up with sound collaborative programmes for the sub-region.
Thank you.
CLOSING STATEMENT: Honourable S.K. Moyo, Minister of Mines, Environment and Tourism
Mr Chairman, Representatives of FAO and AGRITEX, Distinguished Guests and Participants, Ladies and Gentlemen
First of all, 1 would like in my capacity as Minister for Mines, Environment and Tourism, to welcome you all to Zimbabwe.
Particular welcome goes to Dr Mashali, the Technical Officer for the Soils Resource Management and Conservation Services of the FAO Headquarters in Rome, Ms Sekitoleko, the FAO Subregional Representative of Southern and East Africa, FAO resource persons, and the rest of the countries who were invited to this Expert Consultative workshop (Eritrea, Ethiopia, Kenya, Tanzania, Uganda, Malawi, Zambia, Namibia, Africa and Zimbabwe). I also wish to recognize the efforts put by the Department of Agricultural Technical and Extension Services (AGRITEX), the FAO Land and Water Development Division based in Harare, and the rest of the organizers for the tremendous effort that you put into organizing this workshop.
Land degradation is an issue that affects every country and is at the heart of every Government in this region. All our countries are dependent on Agriculture for food sufficiency, and food security. Since land degradation results in a decline in the capacity of soil to produce more, governments are concerned about the continued land degradation processes taking place, because the end-results will have negative impacts on the economy of each country.
The excellent papers presented by the Resource persons as well as your country papers highlighted various issues regarding land degradation. Of particular reference were issues concerning wind and water erosion, deforestation/devegetation, crusting/compaction, acidifícation, salinization, soil nutrient depletion, excessive leaching, and many others. These processes have caused great havoc in our countries resulting in reduced land for crop cultivation and grazing for livestock.
Deforestation has contributed to reduced soil cover with the end-results being erosion depleted soil organic matter. People are being encouraged to plant trees in their respective areas as a way of replacing the lost vegetation. Only last Saturday His Excellency President Mugabe led the nation in commemorating the beginning of our tree-planting season in Zimbabwe. For those forests that are still available, the public is being discouraged from cutting more. Overgrazing is extensive in many parts of the region where livestock and wildlife populations are Integrated soil management for sustainable agriculture and food security in Southern and East Africa 387
high. This scenario leads to serious land degradation such as soil compaction, erosion, etc, resulting in gully formation.
Fires occur widely in communal areas, and this practice exposes the land to both wind erosion during the dry seasons and water erosion during the on-set of rains. Vast areas of Zimbabwe suffered from extensive fires and my Ministry is taking the necessary steps to reduce the incidence of fires.
Decline in soil fertility is basically due to poor or inappropriate farming practices, which include population pressure resulting in land pressure. For the majority of countries Saharan Africa, the use of fertilizers is restricted to large estates and large farms, because most small- scale subsistence farmers cannot afford them. Furthermore, the quality of used in this sector is of poor quality.
The causes of soil/land degradation are complex and involve interaction between several factors. Land tenure and the related socio-economic factors are among the important causes of soil degradation. Because of Africa's high population growth rate, coupled with increased land pressure, agriculture land is continuously cultivated for decades with minimum inputs. As a result, the land becomes highly degraded and very expensive to reclaim. It is hoped that governments will raise the standards of living for their people so that they can afford financially to take care of agricultural land around them, for sustainable production of food and cash crops.
It is with pleasure to learn that your field visit to Mangwende on Wednesday 10 December 1997 was good and informative. You managed to see the reclamation as well as the bank conservation programme that my Ministry is undertaking at Juru Growth Point. I hope these examples you saw were educative and will help in your programmes back home. I also hope that other conservation programmes both in this country and in your countries will be able to reverse the degradation processes taking place and then up-lift the standards of living for our people.
Finally, Mr Chairman, 1 want to reiterate the importance of conservation and sustainable use of our natural resources especially in our regions as most of our economies are agro-based. We should step up our efforts to achieve sustainable development without destroying environment.
With these few words it is my singular honour to declare your Workshop closed. I wish you all a safe journey to your homes and Merry Xmas and Prosperous New Year to all of you.
I thank you. 388 Annex 1: Opening and closing addresses Integrated soil management for sustainable agriculture and food security in Southern and East Africa 389
Annex 2 Programme
Monday, 8 December 1997
08.00 – 09.00 hrs Registration
09.00 – 09.15 hrs Welcome address by the FAO Subregional Representative, Ms. Sekitoleko
09.15 – 09.45 hrs Objective of the consultation and adoption of agenda Introduction to the technical sessions (P. Koohafkan, AGLS-FAO, Rome)
09.45 – 10.15 hrs Coffee break
SESSION I Land degradation and its impact on food security
Chairperson: Van der Merwe, AGLS-FAO, Rome Rapporteur Mushambi
10.15 – 11.20 hrs Land degradation and its impact, with focus on salinity and fertility decline and their management (Amin Mashali, AGLS-FAO, Rome)
11.20 – 12.00 hrs Erosion induced loss in soil productivity, its implication on land use and food security (Michael Stocking) Discussion
12.00 – 12.15 hrs Summary by chairperson
12.15 – 13.45 hrs Lunch break
Session II Enabling environment and technologies for controlling soil degradation and improving productivity
Chairperson: P. Nyathi, Deputy Director, Department of Research & Specialist Services Rapporteur Mushambi
13.45 – 14.30 hrs Socio-economic and policy issues (AGRITEX/DR&SS) Discussion 390 Annex 2: Programme
14.30 – 15.15 hrs Methodologies of soil degradation assessment, with focus on ASSOD/SOTER, Asian experience (G. van Lynden - ISRIC) Discussion
15.15 16.00 hrs African soils, constraints and potentials with focus on ISCRAL (Omar Khayre, APO FAORAF, Accra) Discussion
16.00 – 16.30 hrs Coffee break
16.30 – 17.30 hrs Presentation of the country papers by the country participants and discussion Botswana, Eritrea, Ethiopia (20 minutes each)
17.30 – 18.00 hrs Summary by chairperson
19.00 – 21.00 hrs Cocktail at St. Lucia Park
Tuesday, 9 December 1997
Session III Land degradation, management technologies and proposals for land improvement schemes/projects in the countries of the subregion
Chairperson: Mashali, AGLS-FAO Rome Rapporteur: Mushambi
08.30 – 10.10 hrs Presentation of the country papers by the country participants and discussions: Kenya, Malawi, Namibia, South Africa, Tanzania (20 minutes each)
10.10 – 10.40 hrs Coffee break
10.40 – 11.40 hrs Presentation of the country papers by the country participants and discussions: Uganda, Zambia Zimbabwe (20 minutes each)
11.40 – 12.30 hrs Land degradation and food security, synthesis of country papers (Mushanibi) Discussion
12.30 – 12.45 hrs General discussion
12.45 – 14.15 hrs Lunch break
SESSION IV Approaches and technologies for overcoming soil physical deterioration improving water harvesting and irrigation
Chairperson: Senzanje, University of Zimbabwe Integrated soil management for sustainable agriculture and food security in Southern and East Africa 391
Rapporteurs Mushambi
14.15 – 15.00 hrs Soil and water conservation, soil moisture management and conservation tillage in Zimbabwe (AGRITEX - Nehanda) Discussion
15.00 – 15.45 hrs Water harvesting and/or small-scale irrigation (AGRITEX Chitsiko) Discussion
15.45 – 16.15 hrs Coffee break
16.15 – 17.30 hrs Testing and scenarios of soil productivity changes in relation to degradation and field evidence by slides Discussion
17.30 – 17.45 hrs Summary by chairperson
WEDNESDAY, 10 DECEMBER 1997
08.30 – 16.00 Field visit
THURSDAY, 11 DECEMBER 1997
Opening session
Chairperson: Permanent Secretary Ministry of Lands and Agriculture, Government of Zimbabwe
8.30 - 09.15 hrs Opening address by the Honourable Minister of Lands and Agriculture, Government of Zimbabwe
Working group sessions
08.15 – 09.15 hrs Introduction to working group (Mushambi/Mashali/Stocking) Selection of chairperson, facilitators and rapporteurs for 2 or 3 working groups
09.15 – 12.30 hrs Working groups discussion
Optional working groups (two or three groups of countries/participants according to geographical distribution/climate or agro-ecological condition and interest): Suggested issues to be discussed: - Present and outlook for food production 392 Annex 2: Programme
- Identification of land degradation, dominant type, magnitude, extent and distribution - Causes and processes of land degradation - Existing assessment of degradation, methodologies for assessment - Interpretation and prediction methods and availability of methods - Bio-physical, environmental and socio-economic impacts - Technologies available for improving for the productivity: constraints for adoption and solutions - Policy and land tenure, institutional set-up, government responsibility, monitoring, farmer participation and extension services, decision maker awareness - Applied research requirements, integrated approach, monitoring system - National and regional plans, regional co-ordination, proposal for national follow up actions - Network proposal on management of degraded soils in Africa - Country and sub-regional project proposals - potential donors - national support
12.30 – 14.00 hrs Lunch break
14.00 – 15.30 hrs Working groups discussions (continued)
15.30 – 16.00 hrs Coffee break
16.00 – 18.00 hrs Drafting the working groups' findings, conclusions and recommendations
FRIDAY 12 DECEMBER 1997
Chairperson: Stocking, AGLS-FAO Rome Rapporteurs Mushambi
08.30 – 10.00 hrs Plenary presentation and discussion of the findings, conclusions and recommendations of the working groups
10.00 – 10.30 hrs Coffee break
10.30 – 11.30 hrs Presentation and adoption of the recommendations of the Consultation (Mushambi)
Closing session
Chairperson: Permanent Secretary Ministry of Mines, Environment and Tourism of Zimbabwe
11.30 hrs Closing address by the Honourable Minister of Mines, Environment and Tourism, Government of Zimbabwe Integrated soil management for sustainable agriculture and food security in Southern and East Africa 393
Annex 3 List of participants
COUNTRY SPECIALISTS
ERITREA NAMIBIA Anwar ul-Haq J. Kaurivi Head-Soil and Water Conservation Agricultural Extension Office Department, University of Asmara Ministry of Agriculture, Water and Rural P 0 Box 1220 Development Asmara, Eritrea P 0 Box 272 Tel: 291-1-162607 Tsumeb, Namibia Fax: 291-1-162236 Tel: 264-67-220263 E-mail: [email protected] Fax: 264-67-220323
ETHIOPIA SOUTH AFRICA Sahlemedhin Sertsu Dries Van der Merwe Head of the National Soil Research Laboratory Institutefor Soil, Climate and Water (ISCW) Ethiopia Agricultural Research Organization P 0 Box 79, Pretoria P 0 Box 147 South Africa Addis Ababa, Ethiopia Tel: 27-12-3264205 Tel: 251-1-517657 Fax: 27-12-3231157 Fax: 251-1-515288 E-mail: [email protected] E-mail: [email protected] TANZANIA KENYA Adolf S. Nyaki Patrick Thuku Gicheru Director Head of Kenya Soil Survey Agricultural Research Institute Kenya Agricultural Research Institute Mlingano National Agricultural Research Laboratories P 0 Box 5088 P 0 Box 14733 Tanga, Tanzania Nairobi, Kenya Tel: 255-53-42577 Tel: 254-2-444140-44, 444029-32, 444250-56 Fax: 255-53-42577 Fax: 254-2-443376 E-mail: [email protected] E-mail: [email protected] UGANDA MALAWI Julius Yefusa Kitungulu-Zake A. Saka Department of Soil Science Assistant Deputy Director Makerere University Department of Research P 0 Box 7062 Ministry of Agriculture, and Irrigation Kampala, Uganda PO Box 30750 Tel: 256-41-540707 Home: 256-41-541128 Lilongwe, Malawi Fax: 256-41-541641 Tel: 265-767 222, 252/784299 E-mail: [email protected] Fax: 265-784 184 394 Annex 3: List of participants
ZAMBIA D. Taonezvi Nawa Mukanda Department of Agricultural, Technical & Soil Scientist Extension Services (AGRITEX) Soil & Water Management Division P 0 Box CY 639 Mount Makulu Research Centre Causeway P 0 Box 7 Harare, Zimbabwe Chilanga, Zambia Tel: 263-4-707311/6 Tel: Office: 260-1-278087/278429/278008 Fax: 263-4-730525 Fax: 260-1-278390/278130/278141 E-mail:[email protected]
ZIMBABWE C.F. Mushambi Head, Chemistry and Soil Research Institute J.M. Makadho Department of Research & Specialist Services Director P 0 Box CY 550 Department of Agricultural, Technical & Causeway Extension Services (AGRITEX) Harare, Zimbabwe P 0 Box CY 639, Causeway Tel: 263-4-704531 Harare, Zimbabwe Home: 263-4-307602 tel: 263-4-707311/6-794601/6 Fax: 263-4-730525 Katherine Verbeek E-mail: [email protected] Department of Soil Science & Agricultural Engineering R.J. Chitsiko University of 'Zimbabwe Deputy Director (Engineering) P 0 Box MP 167 Department of Agricultural, Technical and Harare, Zimbabwe Extension Services (AGRITEX) Tel: 263-4-303211 ext. 1721 P 0 Box CY 639 E-mail: [email protected] Causeway Harare, Zimbabwe A. Senzanje Tel: 263-4-707311/6-794601/6 Department of Soil Scíence & Agricultural Fax: 263-4-730525 Engineering E-MAIL: [email protected] University of Zimbabwe P 0 Box MP 167 Michal Oppenheimer Harare, Zimbabwe Department of Agriculture, Technical and Tel 263-4-303211 ext 1412 Extension Services (AGRITEX) P 0 Box CY 639 Joseph Zvakwidza Chizororo Causeway USAID/Harare Harare, Zimbabwe P 0 Box 6988 Tel: 263-4-707311/6 Harare, Zimbabwe Fax: 263-4-730525 Tel: 263-4-720630 E-mail: [email protected] Fax: 263-4-720722 E-mail: [email protected] P. Nothando Sithole Department of Agricultural, Technical and G. Nehanda Extension Services (AGRITEX) Institute of Agricultural Engineering P 0 Box CY 639 P 0 Box BW 330 Causeway Borrowdale Harare, Zimbabwe Harare, Zimababwe Tel: 263-4-707311/6 Tel: 263-4-860136 Fax: 263-4-730525 Fax: 263-4-860136 E-mail:[email protected] Integrated soil management for sustainable agriculture and food security in Southern and East Africa 395
Jane U. Gonese Susan T. lkerra Tobacco Research Board Research Officer P 0 Box 1909 TSBF/AFNET Liaison Officer Harare, Zimbabwe National Soil Service E-mail: Jane- [email protected] Agricultural Research Institute Mlingano P 0 Box 5088 TROPICAL SOIL BIOLOGY AND FERTILITY Tanga, Tanzania PROGRAMME (TSBF) Fax: 255-53-42577
Mwenja Gichuru Mary J.N. Okwakol TSBF/AFNET Coordinator Associate Professor UN Complex, Gigiri Department of Zoology UNESCO~TSBF Makerere University P 0 Box 30592 P 0 Box 7062 Nairobi, Kenya Kampala, Uganda Tel: 254-2-622635 Tel: 256-41-533803/531902 Fax: 254-2-622733 Fax: 256-41-533528/530134 E-mail: mwenja.gichuru@@tsbf.unon-org E-mail: [email protected]
Stephen Nandwa Humphrey Goma Head, Soil Fertility & Plant Nutrition Research Soil Scientist Programme Misamfu Research Centre Kenya Agricultural Research Institute P 0 Box 410055 National Agricultural Research Laboratories Kasama, Zambia P 0 Box 14733 Tel: 260-4-221215/221135 Nairobi, Kenya Tel: Home: 260-1-221863 Fax: 254-2-444029/443376 Fax: 260-4-221135/221092/221664 E-mail: [email protected] E-mail: [email protected]
Jean Niyungeko Petros Nyathi DRC - ex - Zaire Department of Research & Specialist Services c/o TSBF/UNESCO UN Complex, Gigiri P 0 Box CY 594 P 0 Box 30592 Causeway Nairobi, Kenya Harare, Zimbabwe Tel: 254-2-622584 Tel: 263-4-704531 Fax: 254-2-622733 E-mail: [email protected] E-mail: [email protected]
George Ley RESOURCE PERSONS National Coordinator Soil and Water Management Research Godert W. Van Lynden Programme International Soil Reference and Information National Soil Service Centre Agricultural Research Institute P 0 Box 3536700 MLINGANO AJ Wageningen, The Netherlands P 0 Box 5088 Tel: 31-317-471711 Tanga, Tanzania Fax: 31 317 471700 Fax: 255-53-42577 E-mail: VANLYNDEN@ISRIC or [email protected] 396 Annex 3: List of participants
Anna Tengberg Omar Khayre Physical Geography APO, Soils Earth Sciences Centre FAO Regional Office for Africa Guidhedsgatan 5A P 0 Box 1628 S-413 81 Goteborg Accra, Ghana Sweden Tel: 233-21-666851-4/665389 Tel: 46 31 773 1000 Tlx: 2139 Foodagri(GH) Fax: 46 31 773 1986 Fax: 233-21-668427/233999 E-mail: [email protected] E-mail: [email protected]
Michael Stocking René van Veenhuizen Professor of Natural Resource Development FAO Farmesa School of Development Studies P 0 Box 3730 University of East Anglia Harare, Zimbabwe Norwich NR4 7TJ Tel: 263-4-758055 United Kingdom E-mail: [email protected] Tel: 44-1603-592339 Fax: 44-1603-451999 E-mail: [email protected]
FAO Parviz Koohafkan Chief, Soil Resources Management and Conservation Service Land and Water Development Division Viale delle Terme di Caracalla 00100 Rome, Italy Tel: 39-06-57053843 Fax: 39-06-57056275 E-mail : [email protected] Internet: www.FAO.org/agriculture/AGL
A. M. Mashali Technical Officer, Soil Reclamation Soil Resources Management and Conservation Service Land and Water Development Division Viale delle Terme di Caracalla 00100 Rome, Italy Tel: 39-06-57053418 Tlx: 625852 FAOI Fax: 39-06-57056275 E-mail: [email protected]
Karen Frenken FAO Sub-regional Office P 0 Box 3730 Harare, Zimbabwe Tel: 263-4-791407 Fax: 263-4-703497 E-mail: [email protected] Integrated soil management for sustainable agriculture and food security in Southern and East Africa 397
Annex 4
Maps
Soil degradation severity 398 Annex 4: Maps
Water erosion severity Integrated soil management for sustainable agriculture and food security in Southern and East Africa 399
Salinization 400 Annex 4: Maps
Chemical deterioration severity Integrated soil management for sustainable agriculture and food security in Southern and East Africa 401
Loss of nutrients 402 Annex 4: Maps
Acidification Integrated soil management for sustainable agriculture and food security in Southern and East Africa 403
Areas affected by overgrazing 404 Annex 4: Maps
Areas affected by agricultural activities Integrated soil management for sustainable agriculture and food security in Southern and East Africa 405
Areas affected by overexploitation of vegetation 406 Annex 4: Maps
Areas affected by deforestation The FAO Land and Water Development Division, in collaboration with the Subregional Office for Southern and East Africa and the Agricultural Technical and Extension Services of Zimbabwe, organized an Expert Consultation on “Integrated Soil Management for Sustainable Agriculture and Food Security”, held in Harare from 8 to 12 December 1997. The main objectives of the Consultation were to discuss the status of land degradation under contrasting agro-ecological and socio-economic conditions; exchange experiences on constraints for controlling land degradation and examine possible solutions to overcome these constraints; and proposals for enhancing soil productivity, in support of food security in the region. This publication includes the overview and country papers presented by senior specialists from ten African countries of Southern and East Africa, FAO Headquarters and from some relevant national, regional and international institutions. Addressing and reversing the process of soil degradation and sustaining crop productivity through appropriate soil management and conservation are important aspects of food security. Although cost-effective options are available to address soil degradation, there is a need to increase the awareness, at high policy-making level, with sound scientific evidence, about impacts of degradation on productivity in order to achieve the food security goals. It is, therefore, important to document the information on the extent of soil degradation, its biophysical, economic and social impacts as well as successful examples of soil improvement programmes within the region.