THE BIOLOGY AND FERTILITY OF TROPICAL SOILS
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(0 (0 ARCHIV 102854 iORC Ub. - TSBF Report: 1994
The Biology and Fertility of Tropical Soils
Report of the
Tropical Soil Biology and Fertility Programme
TSBF
1994
Edited by
P.L. Woomer and M.J. Swift
TSBF do Unesco-ROSTA UN Complex, Gigiri, P.O. Box 30592 Nairobi Kenya Front cover photograph: Changes in world coffee prices may render this crop unsustainable but result in more frequent conversion to intercropping with annual food crops and the availability of coffee prunings as an organic resource.
Copyright: Tropical Soil Biology and Fertility Programme
1995
Published by the Tropical Soil Biology and Fertility Programme
Nairobi, Kenya
Printed by Instaprint LTD, Nairobi, Kenya
ISBN 9966-9892-1-9 TSBF Repoil: 1994
MAB
ROSTA
ACKNOWLEDGEMENTS
This report was prepared from data and text submitted by Principal Investigators and Collaborating Scientists at TSBF research sites throughout the world. Contributions from J. Alegre, N. Asakawa, T. Bach, M. Bekunda, R. Blanco, D. Bwamiki, B.M. Campbell, F. Charpentier, S.E. Carter, E. Cuevas, R. Dalal, M. de Leon, T. Deacaëns, E.T Elliot, E.C.M. Fernandez, S. Frey, E. Garcia, J. Hatton, M. Izquierdo, K.K. Kajondo, A. Serra King, P. Lavelle, J. Lekasi, A. Martinez, J. Matos, P.P. Motavalli, G. Msumali, L. Mukurumbira, H. Murwira, B. Mwakalombe, S. Nandwa, P. Nyathi, J.R. Okalebo, M. Okwakol, C.A. Palm, W.J. Parton, B. Pashanasi, M. Gonzelez Perez, N. Pina, E. Ruiz, M. Scholes, R. Scholes, P.D. Seward, R.J. Thomas, R. Villegas, N Wangari, H. Ydrogo, J. Zake are gratefully acknowledged as was the assistance provided by Alice Ndung'u, Mary Kinyanjui and Anthony Njenga in the preparation of this report. Research results from this report should not be quoted except with permission of the authors concerned.
TSBF research and training is funded by the Rockefeller Foundation, IDRC (Canada), UNESCO, International Union of Biological Sciences, SAREC, UNEP, UNDP and the European Community. TSBF is accommodated by UNESCO's Regional Office for Science and Technology for Africa (ROSTA) in Nairobi, Kenya.
11 TSBF RepotI: 1994 TABLE OF CONTENTS
FOREWORD iv
THE TSBF RESEARCH PROGRAMME IN BRIEF 1
RESEARCH THEMES: SOME CASE STUDIES 6 SYNCHRONY 6 SOIL ORGANIC MATTER 8 SOIL BIOTA 10 RESOURCE INTEGRATION 12
AFNET RESEARCH HIGHLIGHTS 14 INTRODUCTION 14 COUNTRY REPORTS 15 NETWORK SUMMARY 32
SOUTH ASIA REGIONAL NETWORK 34
GLOBAL NETWORK REPORT: FOCUS ON LATIN AMERICA... 35
AUSTRALIAN PROGRAMME CENTRE FINDINGS: GOOD SOIL IN A DRY SEASON 39
ALTERNATIVES TO SLASH & BURN 40
RHIZOBIUM ECOLOGY NETWORK OF EAST AND SOUTHERN AFRICA 42
TSBF AND GLOBAL CHANGE 44
THE MACROFAUNA NETWORK 46
TRAINING BY TSBF 47
RECENT PUBLICATIONS 48
SELECTED PUBLICATIONS BY TSBF SCIENTISTS 49
TSBF BOARD OF MANAGEMENT AND HEADQUARTERS STAFF 52
111 TSBF Repoii: 1994 FOREWORD
This report, summarising the activities of the TSBF Programme over the 1993-94 biennium, is the third in our series of research reports. 1994 has also marked the end of the first decade of TSBF. The inaugural workshop of the programme, supported by our long-term patrons, the UNESCO Man and Biosphere Programme, took place in January 1984. Research at the global network of 'Programme Centres was initiated in 1986, followed by the establishment of the African Network (AfNet) in 1988. It is particularly pleasing that a major part of this report is devoted to a summary of the results emerging from the projects within AfNet.
Since its inception AfNet has been nurtured by the core support of the Rockefeller Foundation, UNESCO-MAB, and (until 1993) the Natural Environment Research Council of the UK. Research projects at the sites have also been financed by IDRC (Canada) and SAREC (Sweden). The UNESCO Regional Office for Science and Technology in Africa (ROSTA) continue to give invaluable support by acting as our hosts in Nairobi. The development of AfNet has also benefited from the work of the three scientists who have acted as coordinators over its six year history, John Ingram, Paul Woomer and, during 1993-94, Paul Seward. The latter is now leaving the Programme and while thanking him for his devoted service, we also look forward to a new period of AfNet research under his successor, who will continue to receive the support of our Social Science Officer, Simon Carter and post-doctoral anthropologist, Eve Crowley who joined the Programme on a two-year Rockefeller Fellowship in 1994. 1995 may indeed be recognisable as the start of a new generation of AfNet research as many of the original projects are being completed and published, and new projects are being planned and implemented, some by scientists who conducted their higher degree studies in the earlier phase of Programme. The emergence of these scientists into a leadership role is perhaps the most exciting success in the Programme record.
If TSBF's main focus of activity lies in East and Southern Africa, it also continues to gather strength elsewhere. The South Asian Regional Network is now well established in India and ably managed by the coordinator, Ashesh Das. TSBF's contribution, led by Cheryl Palm and Paul Woomer, to the Alternatives to Slash and Burn Initiative, has taken us back into Latin America and South-East Asia to complement and build on the work established through our original network of Programme Centres in these regions.
A major event in 1994 was the publication, by Wiley-Sayce, of the book, Biological Management of Tropical Soil Fertility. This, together with our practical manuals, now provides the Programme with a unique documentary basis for our research and training activities (see page 48). Due to the generosity of UNESCO-MAB we are able to distribute this book free of charge to a large number of scientists in the tropical countries.
The TSBF Board of Management, under the Chairmanship of Dr Peter Salema, continues to play a very important role in the activities of the Programme. Our Board members are far from being figure-heads but active participants, contributing to the intellectual health of the Programme, and acting as a check on the relevance and impact of the Programme.
I can not close without acknowledging the quality and commitment of all our staff at Headquarters, without whom neither this report, or the work described within it, would have been possible.
Mike Swift TSBF Director
iv TSBF Report: 1994
THE TSBF PROGRAMME IN BRIEF
The TSBF mission & goals. The TSBF Programme aims to contribute to human welfare and the conservation of environments in the tropics by developing adoptable and sustainable soil management practices that integrate the biological, chemical, physical and socioeconomic processes that regulate soil fertility and optimise the use of organic and inorganic resources available to the land-users. To achieve the target set by this mission the TSBF programme aspires to the following goals:
1. To improve understanding of the role of biological and organic resources and their management for improved tropical soil fertility and the sustainability of land-use systems. 2. To enhance the research and training capacity of national institutions in the tropics in the fields of soil biology and management of tropical ecosystems. 3. To make available to land managers in the tropics methods for soil management which will improve agricultural productivity but conserve the soil resource. 4. To contribute to increasing the carbon storage equilibrium in tropical soils in the face of global changes in land-use and climate.
Biological management of soil fertility. TSBF was initiated in 1984 under the patronage of the Man and Biosphere programme of UNESCO and the Decade of the Tropics initiative of the International Union of Biological Sciences (TUBS). The programme was founded with the aim of promoting the biological management of soil fertility as an essential component of sustainable agricultural development.
Biological Management of Soil Fertility is an holistic approach integrating the biological, chemical and physical processes that determine the natural fertility of soil with farmers' management practices. The approach is unique and distinct from those of other institutes and programmes concerned with soil fertility management in the tropics in that it has a specific focus on the importance of the organic and biological resources of soil (see Box 1) but is distinct from organic farming in that it recognises the need under many circumstances for inputs of inorganic fertiliser.
Research Approach. TSBF has developed an approach to soil management research involving an iteration between system research and process research of of nutrients, the synthesis and breakdown of soil organic matter and the biological modification of soil physical structure in tropical ecosystems (see Box 2 on p.5). These process-level studies are however intimately linked with ecosystem-level research which integrates the measurement of key biological factors with assessment of the economic potential and opportunity and human decision-making processes at scales ranging from the cropping system to the village management zone (Figure 1). The ultimate step in this iteration is the linkage to policy implications at both national and international scales. The activities of process research and systems research proceed at different scales of analysis, and with different methods, but they are strongly analogous, convergent, and mutually reinforcing.
Clients. TSBF ultimately seeks to provide the means for improved soil and ecosystem management for the farmers, foresters, plantation managers and ecologists of the tropical region. TSBF scientists conduct studies right across the research continuum from strategic investigation of soil processes to on-farm participatory technology adaptation. The planned outputs from the programme are however generic rather than site-specific or empirical. The primary target for TSBF results is therefore the national and international research community (Figure 2) through the normal processes of publication and scientific communication. TSBF Repotl: 1994
Box 1 SOIL BIOLOGY AND SOIL FERTILiTY
TSBF focuses on the organic and biological components of soil fertility:
Organic matter inputs: such as plant litter, crop residues, dead roots, manure, compost and household or industrial wastes, are major resources available to farmers to manage soil fertility by manipulation of soil biological processes. Organic inputs control the rate, extent and pattern of growth and activity of the soil organisms and provide the source of carbon, energy and nutrient for the synthesis of soil organic matter (SOM).
Soil organic matter: a keystone ecosystem resource acting as a reservoir of plant nutrients such as N, P and S; contributing to cation exchange capacity, particularly in tropical soils dominated by low activity clays; modifying the effects of toxic elements such as Al; and improving soil structure and water retention.
Soil organisms: bacteria, fungi, protozoa and invertebrate animals contribute to soil fertility and thence ecosystem sustainability as agents of:
* Nutrient cycling, regulation of the retention and flux of nutrients in the system by the processes of decomposition, mineralisation and immobilisation;
* Soil organic matter dynamics; control of the equilibrium level of SOM by the processes of synthesis and decomposition;
* Soil structure maintenance; modification of soil physical structure and water regimes by the processes of soil aggregate formation, macropore development and particle transport;
* Plant symbiosis; enhancement of the amount and efficiency of nutrient acquisition by the vegetation through the agency of mycorrhizal and nitrogen fixing symbionts;
TSBF s focus on these resources is encapsulated in the TSBF Programme Research Themes, Synchrony, Soil Organic Matter and Soil Biota (see Box 2 on p.5).
The TSBF development model is essentially one which provides the means for farmers to optimize the efficiency of their soil resouices to increase and sustain productivity and increase their incomes. In circumstances of low resource availability, the increased efficiency of resource use can help to conserve levels of production; in circumstances of increasing resource availability the same mechanisms can be harnessed to increase and sustain production.
In order to promote this type of approach TSBF also interacts with and seeks to influence, various other agents who function at different levels in the development process (Figure 2). For instance TSBF results may be directly implemented through the national research and extension agencies or through NGO's and the Programme seeks to provide tools, such as decision support systems which can be used by these agencies. The potential for implementation of improved practices for soil management and ecosystem conservation is, however, dependent on the policy environment. The incorporation of TSBF recommendations in national or international policy is facilitated by collaborative interaction with influential national and international research and development agencies. This may be the most important pathway in the long term for dissemination of recommendations for integrated soil management. TSBF Report: 1994
IiSYSTEMRESEARCH PROCESS RESEARCH
Describe resources & envIronments resource quaUties and resouroe use practices1 constraints and opportunIties Define resource transformation processes Model processes and regulators dynamIcs and process
Develop elements of Improved
1 resource use practice Test and develop Improved management practices
Develop policy recommendations
Figure 1. Interactions between TSBF systems and processes-level research leads to improved land management practices and land policy recommendations.
Participation in TSBF. TSBF is a voluntary participatory international research programme whose members are committed to the concept that the fertility of tropical soils is controlled by biological processes and can be managed by the manipulation of these processes. Membership of TSBF is open to any scientist conducting research in the tropics within the framework of the TSBF research strategy. Most TSBF Research is structured into Collaborative Networks with the following features:
* Shared objectives, principles and research approaches * Use of standard methods * Standard site characterisation package * Networked experiments based on mutual objectives * Shared data and joint synthesis * Shared evaluation and review * Joint and mutual training
Giving the following advantages:
* Replicated and reinforced results * Accelerated progress * Mutual support, both personal and institutional * Reinforced training capacity * Focus on regional as well as personal and national goals
3 1SBF Repoil: 1994
.,,4 T ment Agencies I Secondary interactions: $r t impactOfpOIicy 4 1 recommendations Governments
—4 ExtensionServices Secondary interactions I Iocalirnpact of.technology reconirnendations 1
Earmers & other Land-users
Figure 2. The direct beneficiaries of TSBF research are the international and national research communities with secondary impacts occurring through policy and technology reconmiendation.
The TSBF programme philosophy is flexible, open and participatory.
* The Programme is more a college than an institution as the networks are primarily formed round individuals rather than agencies
* All TSBF research is collaborative; all projects are based at national sites and most funds are directed toward those national sites
* Within the networks there is collective determination of objectives and priorities, leading to jointly drafted proposals
* The role of TSBF staff is largely facilitory. For example, they promote research and training by hands-on activities, coordination of the core networks, collaboration with other international institutes and programmes and by consultancy.
4 TSBF Report: 1994
Box 2 The TSBF Research Themes
1. Resource Integration: Effective biological management of soil can be achieved by the integration of the contributory soil processes with the other factors regulating ecosystem function including those of resource availability and access and farmers' decision-making processes.
Soil fertility is controlled by a number of processes which are the focus of strategic research described in the three following themes - plant nutrient demand, root growth, decomposition, mineralization of SOM and soil biotic activities - interacting with climate and soil chemical and physical properties. Management of these properties and processes to maximise desired outputs from the system (whether crop yields, timber products or conserved ecosystems) can only be achieved at the scale of the ecosystem. The TSBF goals for biological management of soil will be attajned by adopting an iterative interaction between on-farm diagnostic and adaptive research with strategic process level research.
2. Synchrony: The release of nutrients from above-ground inputs and roots can be synchronised with p/ant growth demands
The synchrony principle is based on knowledge of the processes of decomposition and nutrient uptake by plants that lead to efficient nutrient cycling in tropical ecosystems; its aims are to improve the efficiency of nutrient cycling in agricultural systems by manipulation of these processes, in particular by management of organic inputs, with or without interaction with inorganic fertilisers.
3. Soil Organic Matter: Soil organic matter can be separated into functional pools each of which plays a particular role in nutrient release, cation exchange and soil aggregation
Soil organic matter (SUM) plays key roles in nutrient retention and availability, soil structure maintenance and the soil water regime. The value of SUM to sustainable soil fertility is well recognised but little is known about the processes that determine these three key roles in tropical soils. Recent research has postulated the existence of distinct SUM fractions, which differ with respect to their roles in fertility. Research under the TSBF SUM theme seeks to identify the size and properties of the functional SUM pools, their variation in relations to climate, soil type and land use practice, and their relevance to soil fertility. This research is essentially strategic and is unlikely to produce improved technologies in the short-term. It constitutes nonetheless one of the most critical research areas in agricultural and environmental science for the future.
4. Soil Biota: Soil biota can be manipulated to enhance nutrient cycling, improve the physical properties of soil and regulate decomposition processes
Key soil biotic groups such as N-fixing bacteria, mycorrhiza, earthworms and termites are important as regulators of nutrient cycling, decomposition, soil organic matter formation and soil structure maintenance. TSBF research under the Soil Biota Theme seeks to define these roles in a quantitative fashion and to develop practical means of manipulating soil biota to improve soil fertility.
5 TSBF 1994 TSBF RESEARCH THEMES: SOME CASE STUDIES
SYNCHRONY: Synchronisation between soil N mineralisation and maize N uptake through management of maize stover. Stephen M Nandwa, Kenya Agricultural Research Institute, Nairobi.
Maize stover is a commonly available crop residue in the farming systems of East and Southern Africa. Longer-term trials indicate that retention of stover assists soil fertility but it is not a favoured management practice because stover has a direct market value as livestock feed and its application may result in supressed yields due to short-term N-immobilisation of nutrients. Research was conducted to evaluate the effects of stover placement on nitrogen mineralisation in maize based upon the hypothesis "N recovery efficiency by maize can be improved through ,nicrobial iminobilisation of N on decaying maize stover and subsequent mineralisation in synchrony with crop demand"
Experiments were conducted in two highland agroecological zones of Kenya: Kabete in the sub- humid zone and Katumani, a semi-arid site. Maize stover was applied at the rate of four Tiha either as surface mulch or incorpQrated with and without N fertilizer (50 kg N ha1) over four successive seasons. Stover decay, soil N mineralisation and crop N uptake were measured at four week intervals over 16 weeks.
During this experiment, a complicated series of N release patterns were observed. In the first cropping season, mulching resulted in the greatest N uptake (Figure 3). Following incorporation, N mineralisation was less than when stover was removed, resulting in a suppression of N uptake and N use efficiency. During the second season, this trend was reversed with the surface mulch resulting in N iniinobilisation and a suppression of N uptake, and incorporation resulting in more efficient mineralisation of N. The immobilisation due to the mulch in the second season was likely influenced by the incorporation during land preparation of the stover remaining from the first season. For some treatments, total N uptake exceeds net mineralisation, a situation difficult to explain. The discrepancy may be attributed to the litter bag technique itself, which prevents the soil drying during incubation periods because mineralisation is promoted through a series of wetting and drying events.
mineralisation uptake 100 Removed Mulch Incorporated 80 1991 60 -c
Z 20
0
(20) 4 81216 481216 481216 4 81216 481216 4 81216 Time (weeks) Time (weeks)
Figure 3. Effect of stover placement on soil nitrogen mineralisation and maize uptake during two successive cropping seasons at Kabete in the Eastern Kenyan Highlands.
6 TSBF Report: 1994
Figure 4. Stover placement influences the efficiency of N recovery by maize.
The effects of maize stover placement on Apparent N Recovery Efficiency (ANRE) in the presence of N fertilizer measured at crop harvest over the first two seasons Kabete are shown in Figure 4. Since stover contains a significant quantity of N (18 and 26 kg N ha1 for the first two seasons respectively), ANRE was calculated using the combined input of fertilizer (50 kg N had) plus stover N.
In conclusion, incorporation resulted in an initial decrease in ANRE followed by an increase when compared to stover removal during the first and second growing seasons, respectively, while mulching resulting in a depression of ANRE in the second season only. In subsequent seasons, N uptake and dry matter accumulation tended to be enhanced by incorporation, and suppressed by surface mulching. It is clear from these results that maize stover is best used as an organic resource in i wit" U
Maize productivity and nitrogen dynamics are effected by stover placement in the Kenyan Highlands.
7 TSBF Repo#: 1994
SOIL ORGANIC MATTER: Organic nwtterfractions in tropical forest soils. Peter Motavalli, Cheryl Palm, Ted Elliott, Bill Parton and Serita Frey, Colorado State University.
The search for controls on the content and fractions of soil organic matter in tropical soils and for biologically meaningful fractions of SOM has been the focus of a three year study conducted at the Natural Resources Ecology Laboratory at Colorado State University. Funded by the National Science Foundation of the US, the study has compared the soil organic matter content and composition of tropical soils with varying texture and mineralogy. The idea for this study was a direct result of hypotheses generated at the third TSBF meeting held in 1986 in Yurimaguas, Peru. The hypothesis most relevant to this study was stated: Soils with high clay content accumulate more SOM. Clay type (mineralogy) and type of cations present mod?fy the SOM stabilization. In general, it is hypothesized that allophanic and oxidic minerals stabilize more C than do other minerals.
Surface soils were sampled from undisturbed tropical forest ecosystems (Table 1). The soils represented allophanic (volcanic), smectitic, kaolinitic, and oxidic mineralogies and included loamy (< %40 clay) and clayey (>40%) textures. A suite of soil measurements was taken to determine the proportion of the various soil organic matter fractions and their relative nitrogen supplying capacity and how these relate to the physical and chemical properties of the soils. Carbon fractionation measurements included light fraction C and microbial biomass C, which represent the more labile SOM constituents, mineral associated C, which is a more stabilised fraction and total organic C.
Total C ranged from 1.43 to 12.0%, with allophanic soils containing significantly higher C contents than soils with other mineralogies (Table 1). In addition, allophanic soils contained more light fraction C and mineral associated C than the othersoils. There was an increase in %C with an increase in clay content for the kaolinitic and oxidic soils but not for the smectitic soils.
Stabilization should be reflected by a higher proportion of the total C being in the mineral associated C fraction and by lower CO2 evolution relative to total C. Figure 5 does not confirm
Table 1. Organic matter contents and other site parameters (from Motavalli et al., 1994).
Soil Mineralogy Clay pH Organic C (%) (H20) (%)
Burriga (BU) Smectitic 26 6.7 2.76 Rio Paila (RP) Smectitic 22 6.5 2.88 Santa Ana (SA) Smectitic 60 6.5 3.37 Yurimaguas(YU) Kaolinitic 14 3.9 1.43 Manaus (MA) Kaolinitic 75 4.2 3.33 Colonia (CO) Kaolinitic 43 4.4 4.53 Valenga (VA) Oxidic 23 4.9 2.23 Ouro Preto (UP) Oxidic 15 5.7 1.24 Una (UN) Oxidic 58 4.3 3.23 Birrisito (BI) Allophanic TNA* 4.8 5.38 Tierra Blanca (TB) Allophanic TNA 5.7 4.82 Popayan (P0) Allophanic TNA 5.0 12.00
* Texture Not Applicable to allophanic minerals.
8 TSBF Report: 1994
microbial biomass light fraction mineral associated
1 00 — — — — — = — — — — 90- 0
- -
70- - 0 60- - - -
= 50- - -
0 - Cl) j 40-
0 - I • • • • • •
- BI TB P0 RP BU SA YU CO MA OP VA UN Forest soil
- Allophanic - Smectitic - Kaolinitic -- Oxidic --
Figure 5. The proportion of soil organic carbon residing in different SUM fractions of several South American forest soils (site codes from Table 1). these predictions. Although oxidic soils do show a high percentage of mineral associated C, it is not higher than that of smectitic soils, and allophanic soils show the lowest percentage of mineral associated C. Carbon dioxide release from the different soils also did not support the hypothesis that SOM stabilization will depend on mineralogy, in fact, there was no significant difference among the minerals in the amount of CO2 released as a percentage of the total carbon. Carbon dioxide release, however, was inversely related to the clay content of the soils indicating that stabilization may simply be related to the amount of clay in the soil. Further study with the same set of soils, using additions of 14C labelled glucose and plant materials, indicate that pH is an important factor in C stabilization. Obviously, a complex set of physical, chemical and biological factors control C stabilisation.
These results may be representative but there is also reason to suspect that the current methodologies for measuring the different soil C fractions are not applicable for all minerals. For example, the allophanic soils show a much higher percentage of the soil C in the light fraction. This could be a reflection of the low density minerals in allophanic soils floating and being included in the light fraction. The higher than expected mineral associated C in the smectitic soils may be an artefact of the difficulty in dispersing these soils to separate the light fraction. Some of the light fraction was trapped in aggregates and therefore included in the mineral associated fraction. Additional work is required to develop techniques for separating soil organic matter fractions and care must be taken in interpreting results among soil types.
9 TSBF 1994
SOIL BIOTA: Earthworms as a multipurpose resource in tropical cropping systems. B. Pashanasi, P. Lavelle, J. Alegre, F. Charpentier, H. Ydrogo, Soil Macrofauna Network.
After many years of field experimentation by TSBF researchers with expertise in soil biota throughout the world, additional insights into the effects and management of earthworms have been achieved. Some examples follow.
Earthworm activities can increase plant productivity. A significant correlation was observed in field experiments between earthworm biomass and production of maize and rice (Figure 6). Legume crops did not respond to earthworm inoculation. A biomass of 40 g m2 was necessary to achieve a significant increase of plant production. Factors that determine the carrying capacity for earthworms in a given soil remain poorly understood, the availability of suitable organic substrate is likely to be most important. Experiments on inoculation of earthworms in cultivated fields have shown that some soils cannot sustain earthworm biomass at a level that is sufficient to have an impact on plant growth. In that case it may be interesting to supplement the soil with an organic substrate that feeds the worm but does not have negative effects on plants.
Earthworm activity improves mycorrhizal infection of tree seedlings in the nursery. In a 7-month experiment, growth of tree seedlings of three different species (Bixa orellana, Eugenia stipitata and Bactris gasipaes) responded to inoculation of Pontoscolex corethrurus by increased growth and improved rates of mycorrhizal infection. Bixa orellana grew more rapidly than the other two species. After 120 days, biomass was increased by respectively 107 and 177% in treatments inoculated with 350 and 700 mg of earthworms in each culture bag, and significant increases in N, Ca and Mg contents of leaves were observed. Lower increases were observed with Eugenia stipitata (+ 35.4% and +42.4% respectively) and Bactris gasipaes (+ 32.1 and 29.2 respectively). In the last case, however, differences were not significant.
Losses in C in cropped systems are magnified by earthworm activities. At Yurimaguas, the inoculation of earthworms did not prevent cultivated soils from losing organic matter and nutrients. Nutrient contents rapidly decreased in both inoculated and uninoculated systems. At the 6th harvest, however, all nutrient contents tended to be stabilised in inoculated treatments but only K contents were significantly higher in the presence of earthworms. After 3 harvests, C-contents
140- A r=O.53
0 20 100 2 Increase in earthworm biomass (gim )
Figure 6. Relationship between the increase of earthworm biomass and the increase of grain production in experiments conducted at Yurimaguas (Peru), Lamto (Cote dIvoire) and La Mancha (Mexico).
10 TSBF Report: 1994
800 Cacoons
:::::::::•: Immatures C Adults
Introduction of 20 adults 200
0 • I — 0 20 40 60 80 100 120 Days following initial introduction
Figure 7. Production of P. corethrurus in a mixture of 1:3 soil and sawdust at Yurimaguas. in the upper 10 cm of soil started to be lower in treatments inoculated with earthworms but the difference was only significant at harvest 5. Comparable results were obtained with N-contents. These results suggest that, in spite of an increase of organic inputs to the soil resulting from increased plant production, earthworm activities have a cost in tenns of total C. Preliminary results indicate that losses are especially important in coarse (>50 and fine (<2 fractions. Based on results obtained from a natural African savanna (Lamto, Cote d'Ivoire), the annual amount of C directly mineralised through earthworm respiration may be estimated at 1-2 t ha1. During the three years that the experiment lasted, 3-6 t C have been thus utilised. The net loss of C observed in the presence of earthworms in the 0-10 cm layer where most of this activity occurs is not greater than 0.20 to 0.30% which is equivalent to 2.4-3.6 T ha1 after three years. An average 30 % increase of production of shoot and root production has been observed during the 6 cropping cycles; they represent an overall C input of 3.8 t organic matter i.e., 2.2 1 carbon. This preliminary balance indicates that in spite of an increased C input to the system estimated at 2.2 1 carbon ha', earthworm activities have resulted in a loss of 2.4-3.6 T carbon ha1 that is explained by the mineralisation of 3-6 T carbon by earthworm activities. The overall loss seems to be simply explained by the difference between earthworm consumption and the excess of C captured by the system in the presence of earthworms. There is, however, evidence that earthworms do not only have a quantitative effect on C stocks. They also affect the distribution of C among pools and the turnover time of different fractions. These very preliminary calculations emphasise the need to establish accurate balances of C and nutrients to understand the effect of earthworms on SOM dynamics, and design agricultural practices that meet the demand for food of earthworms.
Sawdust residues may be used to cuLture P. corethrurus. Inoculation of earthworms in fields that do not have them, or in nursery bags, requires the production of high numbers of individuals. At Yurimaguas, experiments have shown that a 1:3 mixture of sawdust and soil is a suitable substrate for the production of P. corethrurus (Figure 7). In 50 x 50 x 15 cm wooden frames, 600 earthworm were recovered 60 days after inoculation of 50 adults. In 5x1 m field designs, average density was 680 individuals per m2 120 days after inoculation of 20 adults, and a second addition of 20 adults at day 40. These experiments demonstrate that production of P. corethrurus is feasible, and that the number of adults initially inoculated is an important parameter.
11 TSBF Repoil: 1994
RESOURCE INFEGRATION: Resource allocation in the Mutoko CommunalArea, Zimbabwe. Saskia van Oosterhout, Department of Research and Specialist Services, Ministry of Lands Agriculture and Water Development and Simon Carter, TSBF.
Work within TSBF 's Resource Integration Theme has continued to focus on communal areas in Zimbabwe. An initial survey in Mutoko in Northeast Zimbabwe, reported in TSBF Report 1992, has been followed with more detailed exploration of the way farmers manage soil fertility, and the timing of management practices in relation to key events throughout the season.
Farmers strategies for managing on-farm variability. Visits to Mutoko and elsewhere during the growing seasons of 1992/3 and 1993/4 have shown that farmers face a diverse range of ecological conditions within their farms, and that management varies for specific niches depending upon their clay and organic matter contents, and the degree of human intervention (Table 2). Nutrient rich "niches" such as termite mounds and old cattle pen sites received few inputs yet were highly productive in the relatively wet 1992/3 season. Dambo soils were more heavily manured than other soils. These soils (Dambos) and the poor sands received the highest rates of chemical fertilizer application. Whilst these rates were low per hectare, farmers applied fertilizer carefully to individual plants. Time of application was carefully selected: in the 1993/4 season, very little fertilizer was applied until farmers were sure that application would have a beneficial effect on maize yield (Figure 8). Most fertilizer and manure is applied to maize; small grains and other subsistence crops rarely benefit from addition of nutrients.
Monitoring of farmers response to changing resource availability and opportunities. Given the diversity in edaphic conditions and the high inter-seasonal variability in rainfall in Zimbabwe's Communal Areas, farmers' strategies in allocating land and labour and in reacting to changes in resource availability are of vital importance. These include changes in labour availability due to migration, social obligations, and sickness, changes in prices and policies such as free fertilizer distribution, and other unpredictable events. A monitoring project was begun at the beginning of the 1993/4 season to increase understanding of these resource management strategies, as well as to provide a set of long term observations of on-farm activities (Figure 8). The data generated will help to understand the limitations and opportunities of a range of households with different resource endowments to enhance soil fertility through improved use of organic and inorganic nutrient sources.
A farm in Mutoko during the 1993-1994 growing season. The patchy appearance is typical and crop response is best under trees, on termite mounds, at old cattle pen sites and in manured areas.
12 TSBF Report: 1994
Table 2. Fertiliser use and manuring in the Motoko communal farm area of Zimbabwe.
Soil Type Fertilizer application rate (Kg ha') % Manuring Ammonium Nitrate Compound D (34:0:0) (8:14:7)
Jecha (poor, eroded, 36.4 37.9 8.9 infertile sands) Musapa (undifferentiated 23.3 31.5 12.3 sands of moderate fertility) Doro, Barebare (fertile 45.3 40.1 42.2 "dambo" clay-barns) Niches (termite mounds, 2.2 2.2 1.3 old homestead and cattle pens)
Moves towards on-farm experimentation. Monitoring of resource management is being accompanied by the establishment of simple farmer-managed experiments. In 1994, farmers were given seed of Crotalaria juncea and sorghum and millet grain varieties. The objective of these experiments is to see in which crop combinations and when during the cropping cycle, farmers are best able to grow and utilise Crotalaria as a green manure
Future activities. On-farm research will expand to two more communal areas, Mangwende and Chivi, during 1995 and 1996. These are respectively wetter and drier than Mutoko, and have contrasting socio-economic environments. The three sites also need to be placed within a broader national context, in order to facilitate comparisons with other parts of the country and generalization of research findings. A first step will be the production of a typology of communal areas using available statistics on crops, livestock, population, soils and rainfall. These data have been collated as layers in a Geographic Information System for a number of different years, allowing the analysis of spatial and temporal changes in land use, population and livestock densities and the interrelations between these factors, broad soil conditions and rainfall variability.
60 100
50
40 c0 E E
C 30 C CO 0) 20 0::
0) 0 10
0 09-Oct-93 09-Dec.93 06-Feb-94 07-Apr-94 Date Apphcation of manure — Planting maize Application of fertilizer Rainfall
Figure 8. Use of fertilizers and cattle manure on 16 farms monitored during the 1993/4 season. Rainfall was very sporadic, only farmers who planted maize between mid-October and mid- November harvested a reasonable crop.
13 TSBF Repo4: 1994 AFNET RESEARCH HIGHLIGHTS
The TSBF African Network is now active in nine East and Southern African countries. The research topics include investigations into the four TSBF themes and generally address the dtfjlculties of smalihold far,ners in maintaining soil fertility. Many of the research objectives identWed at the onset of AJNet activities have been realised, particularly the evaluation of farmer-available organic resources in smaliholder cropping systems. At the same time, additional proposals have become funded. A new development in the organisation of AJNet is the selection of a Liaison Officer by network participants to oversee AJNet developments and assist the Network Coordinator. In the period 1993-1995, the Liaison Officer has been Dr Mary Okwakol of Makerere University, Uganda.
Research sites of the TSBF African Network
14 TSBF Reporl: 1994
KENYA: The Kenyan Litter Decay Network. John Lekasi and Fritz Schnier, a 1.0 collaboration between the Kenya Agricultural Research Institute, the Fertiliser Use Research C) 08 Project (FURP) and TSBF. C
It is essential to better understand the rates of 0.6 mass loss and nutrient mineralisation from farmer-available organic resources before our attempts to better link nutrient supply with a) crop demands can become realised. Litter 02 decay processes are being studied across seven sites along an elevational transect in Eastern Kenya. By conducting identical 00 0.0 02 0.4 0.6 0.8 1.0 studies at different sites that are representative of major agroecological zones, scientists are Time (years) better able to understand and predict the effects of climate, soil properties and Figure 9. The effects of soil fauna and macrofauna on decomposition. placement on the decomposition of maize stover in the Kenyan Highlands. The Kenyan Litter Decay Network was initiated in March 1993 at the request of FURP which sought to quantify the amounts of nutrients released by decaying maize stover in fertiliser use experiments established across Kenya. TSBF supplied litter bags and methods to KARl personnel who conducted litter decay experiments which identify the separate roles of litter placement, quality, soil N status and macrofaunal activity on decomposition in agricultural settings (Figure 9). The results of this study indicate that the placement and nutrient qualities of organic resources control decomposition across all sites with the most rapid decay occurring in mid-elevation, sub-humid environments. Soil macrofauna, particularly termites, greatly influence the mass loss of litter in environments where these organisms are present. Litter decay was reduced at the highest elevation site, due in part to cool temperature and its influence on microbial and faunal populations. Slower rates of decomposition were associated with higher soil organic matter contents. The rates of litter decay and nutrient mineralisation fitted to mathematical equations which allow researchers and extensionists to predict the amounts of nutrients made available to subsequent crops when crop residues and tree prunings are applied to soils.
The deployment of litter bags in the field in the Highlands of Kenya (left) and a closeup of a litterbag containing maize stover and termite-resistant steel mesh inserts (right).
15 TSBF 1994
KENYA: Imp roved use of crop residues in maize-based cropping systems. Robert Okalebo and John Lekasi, Kenya Agricultural Research Institute, Muguga.
At present, many farmers in Kenya find fertilisers too expensive for utilisation in fertility maintenance programmes. At the same time, many organic resources are available to farmers but the benefits resulting from their use are not sufficiently understood. This condition provides the basis for current on-farm trials at Malaya in Crop roots being collected and washed in the crop residue Western Kenya where maize experiment at Malaya Farm in Western Kenya. and groundnuts are major crops. The soils in this area are highly weathered (Ultisols) and extremely deficient in both N and P. The experiments at Malaya farm explore the nutrient release from farmer-available organic resources and the uptake pattern of the maize crop. Also under study are the longer-term effects on soil properties resulting from the regular addition of organic inputs of different qualities.
Maize stover, groundnut trash and farmyard manure were incorporated into the soil with and without mineral nitrogen and the soil sampled after 33, 119 and 174 days. The most rapid mineralisation was observed with groundnut trash. The nutrient demand of maize extended over four months following planting. A litter decay experiment containing the different organic materials was installed concurrently with the maize productivity trial and the decline in litter mass and total nutrients calculated. The decomposition constants of maize stover, farmyard manure and groundnut trash were -11.1, -22.9 and -32.5 yf', respectively. Most of the maize stover had mineralised after four months.
Current activities at Malaya include studies on the incorporation of crop residues, farmyard () and chicken manure to soils and their effects on soil nutrient profiles and a) crop productivity (Figure 10). One impact on neighbouring farms is increased frequency of groundnut cultivation coupled with greater awareness of the indirect benefits of using Figure 10. Soil mineral N within soils receiving different residue groundnut residues. inputs 33, 119 and 174 days following residue incorporation.
16 = == TSBF 1994
KENYA: The Nutrient Monitoring (NUTMON) Project. Stephen Nandwa, Kenya Agricultural Research Institute, Nairobi.
Calculations of the nutrient balance at a national scale show that the sum of nutrient outputs exceeds inputs in most countries in sub-Saharan Africa. Kenya was recently described by E. Smaling as having one of the highest rates of nutrient depletion from soils that are being mined at the rate of 42 kg N, 3 kg P and 30 kg K/ha/year, respectively. Estimates for the densely populated District of Kisii reveal even greater nutrient deficits, with outputs on average exceeding inputs by 112 kg N, 3 kg P and 70 kg K/ha/year. This rate of nutrient depletion, especially in a District of important agricultural potential is unacceptable, but how accurate are these estimates?
With funding from the Rockefeller Foundation, an intensive nutrient monitoring programme has commenced in four Districts in Kenya to quantify the extent of nutrient depletion at the farm- level, and to identify driving forces influencing nutrient management in the agricultural sector at different scale levels. Embu, Kakamega, Kisii, and Kilifi districts were selected on account of their different agro-ecological environments and ethnic backgrounds, encompassing a broad range of agricultural priorities and opportunities. Initially, the districts were stratified using satellite images into a series of land use zones, which were then modified to form land use systems combining soil and climate data. A Rapid Rural Appraisal was then conducted in order to fine tune these land use systems into groups of "homogeneous farm types". A selection will subsequently be made of 3-4 farms per "farm type" zone, at which with the participation of the farmer, the major nutrient flows into, within and out of the farm will be identified and quantified. Important socioeconomic factors which affect nutrient flows, such as off-fann income, land ownership, labour and capital input and risk management will also be determined.
The collated data will provide a framework for policy makers and researchers to investigate options to mitigate nutrient depletion, and to design strategies for improving nutrient use efficiency through the integrated management of nutrients from organic and inorganic resources. The project is a collaborative venture involving staff at KARl's National Agricultural Research Laboratories, Embu, Kakamega, Kisii, and Mtwapa Regional Research Centres, scientists from Wageningen in The Netherlands and TSBF.
Planned changes to farming systems require an understanding of farmers' decision-making and knowledge of under-exploited resources and opportunities. Improvement in nutrient use efficiency using available organic resources is one such opportunity.
17 TSBF Repoii: 1994 - =
MOZAMBIQUE: Soil organic matter dynamics during slash and burn agriculture and secondary recovery in coastal dune forests. Alexandra Serra King and John Hatton, Department of Biological Sciences, Universidade Eduardo Mondlane, Maputo.
The coastal dune forests of Mozambique represent a fragile environment because these occupy soils of low inherent fertility. Until recently, conditions were such in Mozambique that these lands were placed into cultivation because more fertile lands were not readily available to farmers and, to some extent, populations had become displaced Many crops perform poorly in the slash and burn toward the coastal zone. Complicating systems practiced on Inhaca Island. this situation was the lack of strong markets for agricultural products and inaccessibility to external inputs. As a result, the farmers who clear the coastal dune forests on Ithaca Island in Maputo Bay cultivate mixtures of subsistence crops consisting of maize, sorghum, groundnut, cowpea, cassava and cucurbits. Yields decline rapidly in these soils and forest succession is often arrested. Researchers in Mozambique sought to relate this fertility decline to a loss of soil organic matter in sandy soils subject to slash and burn agriculture at Ponta Torres, and to secondary forest recovery near the Marine Biology Station on Inhaca Island.
The sample sites consisted of climax dune forests at Ponta Torres and the Marine Biology Station, three, four and five year-old mixed cultivation fields cleared from climax forest at Ponta Torres and slowly recovering secondary vegetation near the Marine Biology Station which had been abandoned by farmers seven and 15 years previously. When combined, these sites represent a
Farmers cultivate cucurbits as a means of risk avoidance in marginal mixed cropping systems following the clearing of dune forest in coastal Mozambique.
18 TSBF Report: 1994 chronosequence of slash and burn agriculture followed by forest regrowth although the Ponta Torres and Marine Biology Station are approximately 8 km apart. Soil measurements included total soil organic carbon, nitrogen and phosphorous, and microbial biomass C.
Soil organic carbon and total nitrogen are rapidly lost from the forest soil during cultivation and are extremely slow to reaccumulate during secondary forest establishment (Figure 11). The soil organic carbon contents across the Ponta Torres chronosequence were significantly different from one another. Microbial biomass was significantly greater in the Ponta Torres forest than in adjacent agricultural fields. Total phosphorus contents of soil became more concentrated due to clearing and burning, presumably because this nutrient is not volatilised during burning. Soil moisture contents and cation retention were diminished following forest disturbance. Total carbon, microbial biomass C and total nitrogen contents of the slowly- recovering fallows differed significantly from those of the well-established forest adjacent to the Marine Biology Station, suggesting that the fallow interval necessary to reaccumulate nutrients extends far beyond 15 years.
While the existing farmer conditions and soil fertility exhaustion in the coastal forest zone are bleak, the opportunities for improvement are great. These 0 5 10 15 farmers are practising traditional Years following clearing or land abandonment cultivation in absence of all external inputs including advice, improved crop forest IS&B cropsi arrested succession forest varieties and nutrient inputs. One viable alternative to mixed annual cropping is Figure 11. The dynamics of soil organic C (top), total the establishment of multistrata N (centre) and total P (bottom) along a slash & burn agroforests but these must be established chronosequence on Inhaca Island, Mozambique. soon after forest clearance rather than into the nutrient depleted soils resulting from annual cropping. An example of such a system occurs near the Ponta Tones study site and consists of coconut, mango and guava as tree crops with an understorey of sugar cane, sweet potato and goat forage. This system produces large amounts of organic materials, particularly coconut husks, peelings and goat manure, which could be used as organic inputs to annual crops. At the same time, local markets are strengthening as political stability is restored in Mozambique and Inhaca Island emerges as a tourist destination.
19 ___
TSBF 1994
RWANDA: Laboratory culture of Eminoscolex lavellei (Eudrilidae) in Kanyonyo ka Kajondo, Department of Biology, University of Rwanda, Butare.
A new earthworm which ingests soil organic matter was discovered in Rwanda and designated Eminoscolex lavellei (Eudrilidae). This species is commonly found in the pastures and agricultural systems of Rwanda. Initial attempts to culture this species in the laboratory as a research tool for further ecological studies met with difficulty in part because this relatively small species is not well suited to clayey soils. Modifications of the culture technique commonly employed within the Macrofauna Network were therefore necessary and have since been undertaken. The results presented here were obtained with earthworms born from cocoons that were laid and hatched in the laboratory at Butaré.
Growth of E. lavellei was initially slow during the first 135 days (Figure 12). After that time, average earthworm mass increased rapidly achieving 195 mg, which is half the maximum weight of adults recovered in the field, by day 210. The newly hatched worms weighed 4.8 mg on average and the first cocoon was produced by adults weighing an average of 51 mg. Maturity was reached after 105 days, but the highest rate of cocoon production was observed between days 180 and 195 before declining (data not shown). Fecundity was thus concentrated in a 40 days period, between days 180 and 205 after hatching, an average number of 5.6 cocoons/adult (SE = 0.08) was produced during this period. Soil ingestion rate was almost constant (4 g dry soil g1 fresh weight during all of the growth period, except during the first two weeks where a higher value was measured (8 g). This may be the result os smaller individuals being unable to ingest larger soil particles that contain more nutritious substrate because older, more decomposed SOM is generally smaller in size.
The TSBF research site in Butare is no longer operational following the civil strife in Rwanda during 1994. Prior to this, eleven species belonging to five different trophic groups and four families of earthworms were documented to occur in Rwanda. Dr. Kajondo is presently safe in Zaire and efforts are being made to continue his research activities within the region.
250 A mass 'J CD 0) • ingestion Cl) g 200
150 CD 4 .- O _•- 100 0C', .c 50 3 ci) Cl) 0 30 60 90 120 150 180 210 days of earthworm culture
Figure 12. Growth and injestion rates of E. lavellei cultured under laboratory conditions.
20 TSBF Report: 1994
SOUTH AFRICA: Trace gas fluxes between savanna ecosystems and the atmosphere. Mary and Bob Scholes, University of Witwatersrand, Johannesburg and CSIR, Pretoria.
Work at the Nylsvley site has concentrated on the role of soil biology in controlling the fluxes of trace gases between the terrestrial ecosystem and the atmosphere. The trace gases of interest are those with 'greenhouse gas' warming potentials (such as C02, CH4 and N20), or those that participate in the formation of tropospheric ozone (such as NO and CO), which also gives them an indirect greenhouse potential. Our hypothesis is that the flux from biogenic soil emission processes are at least of the same magnitude, when integrated over the year, as the pyrogenic processes, which have been the focus of attention to date. Further, we consider all these processes to be directly or indirectly associated with the nitrogen and carbon cycle of the ecosystem (and especially the parts which take place in the soil). The detailed understanding of these cycles at Nylsvley, developed during the TSBF 'Minimum Experiment', has been invaluable in understanding the emission process, and will be used for modelling the emissions in the future.
The soils of Nylsvley, like most other well-drained, infertile soils, are weak CH4 sinks. Although there is a well-developed termite fauna (twenty-two species), and the soils in the vicinity of the mounds are methane sources, the termite emissions are insufficient to make the landscape as a whole a net source. The emissions of NO, on the other hand, are among the highest measured in the world, with a mean of about 30 ng N-NO m2 No measurable quantities of N2O are emitted. Carbon monoxide appears to be emitted mainly from the photolysis of plant litter when exposed to the bright African sun.
The TSBF KILLSOM experiment which has been running at Nylsvley for five years was originally designed to deliver information on the stability of soil carbon, but has yielded an unexpected dividend to the trace gas work. The diffences in NO emission between the treatments (a control with full litter inputs, a treatment with all inputs prevented, and a treatment with zero inputs and monthly tillage) are clear and strong, decreasing in that order (Table 3). We interpret this as confiming our hypothesis that the NO emissions are directly linked to the nitrification process, which is in turn driven by the availability of readily-decomposible organic substrates.
Table 3. Nitrous oxide emissions from a South African savanna resulting from different land managements.
Treatment NO emissions (ppb)
Nutrient poor site Control 100.9 No organic inputs 10.0 No organic inputs with tillage 6.4
Nutrient rich site Control 42.1 No organic inputs 7.4 No organic inputs with tillage 2.8
21 TSBF 1994
TANZANIA: Nutrient mineralisa lion and immobilisation by incorporated prunings of Lantana camara and Sesbania sesban. Nancy Wangari and Gottfried Msu,nali, Sokoine University of Agriculture.
One use of organic amendments for soil fertility improvement relates to the ability of the organic inputs to supply nutrients for plant growth. This in turn requires decomposition and mineralisation rates that match the plant demand for those nutrients. Nutrient release within a given environment is controlled by many factors, including the chemical composition, placement and rate of application of the resource. A glass-house experiment was conducted to determine the decomposition rate and nutrient release patterns of Sesbania sesban (sesbania) and Lantana camara (lantana) green manures. Fine branches and leaves were placed into litter bags and buried at 10 cm depth in wooden troughs containing a sandy clay loam. Litter bags were recovered at three week intervals over 12 weeks. Dry matter, organic C, total N and P were measured. The data were fitted to exponential models. Soil microorganisms were counted on soil extract agar.
For both sesbania and lantana, the most rapid decline in dry matter occurred during the first three weeks with less change in mass observed over each additional sampling interval (Figure 13). The mineralisation of nitrogen from decomposing leaves of sesbania demonstrated a similar pattern to the changes in dry weight, expressing a mineralisation pattern well described by the exponential model. However, an initially rapid and persistent immobilisation of nitrogen by lantana was measured throughout the experiment. Similar immobilisation was also observed when phosphorus contents were measured. The net inimobilisation of nutrients resulting from the addition of lantana incorporated as a green manure has several important implications. The less rapid decomposition of lantana when compared to sesbania within the same environment suggests that the tissue chemistry of lantana renders it more resistant to microbial decay. This conclusion is supported by two additional observations. Lantana leaves contain higher levels of polyphenolics than sesbania (6.0% vs 2.0%) and soil microbial populations were lower in the soils when lantana, rather than sesbania, was applied. Inconsistent with this argument is the relatively high N content of lantana (2.03%, C:N = 19). Our results suggest that lantana not be applied as a green manure to annual crops, but could rather be mixed with other materials and composted prior to use. Certainly, the mechanisms responsible for the anomalous immobilisation by lantana warrant further investigation.
Sesban/a sesbaa Lantana camara — '— drv matter - - A-- diy matter —.—nifrogen ...o... nitrogen
0.2 mineralisation 0 immobilisationjJ 0 -0.2 N. \••\ a -0.4 o ..,
0 0.1 0.2 0.3 Time (year)
Figure 13. The comparison of dry weight loss and N mineralisation of Sesbania sesban and Lantana camara indicates that N mineralisation of L. camara is subject to still unknown regulatory mechanisms.
22 TSBF Report: 1994
UGANDA: Use offariner-avaikible organic resources in banana-based cropping bean trash systems. Mateete Bekunda, Department of •1 Soil Science, Makerere Universily. maize stayer cow manure Banana cultivation in humid areas of Uganda continues to grow in importance as rural compost population densities increase and as demand other manure from urban areas intensifies. Scientists and students of Makerere University interviewed groundnut trash 510 farm families practising banana-based cassava peels 11 cultivation in six Districts along the Lake Victoria Basin of Southwestern Uganda to potatoes peels 11 determine which resource management grass II strategies are undertaken to mitigate limitations to banana cultivation and the sorghum stover I importance of livestock and intercropping other vegetation ] within those systems (Figure 14). Of the farmers interviewed, 97 % reapply banana kitchen wastes I stalks and leaves to the banana mats upon coffee husks harvest, a practice that may contribute — I 5 —J I I to 0102030405060 7080 attack by banana weevils and stem (%) nematodes. Figure 15 illustrates that stalks frequency of use were also used as mulches of cash (4%) and field crops (2%) and as livestock feed Figure 14. The frequency of farmers applying different organic (10%). Farmers applied a wide range of residues within banana-based additional resources to bananas including cropping systems in six Districts of South-eastern Uganda. field crop residues (81 %), manures (31 %), compost (16%) and chemical (4%) inputs. To depict banana farmers as depleting soil fertility in pursuit of continued yet steadily declining banana production is an over-generalisation. Farmers practice a range of soil fertility management strategies suggesting that many farmers are able to move between those strategies as conditions warrant. A developed understanding of the optimal usefulness of banana and other supplementary litters is necessary as a means of offsetting the present disopportunities of fertiliser unavailability and nutrient depletion. Future research will focus upon the comparative advantages of banana litter and peels as either a mulch or animal feed and the nutrient use efficiency of farmer-available resources.
Figure 15. Farmer resource management strategies among 510 banana-based cropping systems in south-eastern Uganda. Note the frequency of manure, compost and external organic input use.
23 1SBF Repoit: 1994
UGANDA: Banana root distribution and density. David Bwarniki and Julius Zake, Department of Soil no Science, Makerere University. 4.0
5.0 One option for the maintenance of soil fertility is the 3.0 addition of nutrient-rich organic inputs originating beyond the farm boundaries. One such organic U, den&ty C 3.0 2.0 resource for bananas in Uganda is coffee husks. 8, / mass Effective use of these organic Inputs is necessarily 2.0 influenced by the rooting density and distribution of 1.0 101 bananas. Yet, the depth of rooting and extension of banana roots had not been documented previously, and 00 00 011 0.55 0.99 1 43 1.87 2.31 2.75 the of rooting behaviour to the addition of decomposing organic resources was unknown TSBF Distance from (cm) scientists in Uganda established an on-station + coffee husks experiment examining the rooting pattern of bananas 4.0 and the response of that pattern to the application of mass —i 50 massive amounts of coffee husks. Root hioniass of the 3.0 bananas not receiving coffee husks was 780 kg/ha and increased 3.3 and 6.6-fold when incorporated and 30 surface mulched, respectively 16). (Figure That V .,.,.,.., \ surface mulching resulted in greater root productivity 2.0 (8 \ than incorporation is useful information from the soil management perspective, hut somewhat perplexing 10 scientifically. Bananas demonstrate shallow rooting, 0.11 0 99 1.43 1.87 2,31 2.75 and it is possible that physical soil disturbance Distance from (cm) accompanying incorporation may have killed a significant proportion of the roots. Alternatively, the Figure 16. The effects of coffee husk massive application rate (144 T/ha) may have resulted addition to banana root distribution and in microbial or nutrient imbalances adjacent to the productivity based upon root-ingrowth roots. Husk incorporation resulted in two-fold measurements. increases in maximum rooting depth (70 vs 140 cm), despite lower total biomass, again suggesting that the roots have become displaced from the surface horizon. The use of coffee husks as external inputs to bananas grown as a monoculture resulted in increased banana productivity and that increase was related to root productivity and behaviour. The abilities of additional, more readily available organic resources at more realistic rates are the planned topics of future research efforts on the nutrient management of banana.
,
1, ) 5? I 'I
4 L?4
Use of surface mulches on smalihold, banana-based cropping systems in Uganda.
24 ______
TSBF 1994
UGANDA: Banana root distribution and density. David Bwamiki and Julius Zake, Department of Soil no mulch Science, Makerere University. 0 One option for the maintenance of soil fertility is the 3.0 addition of nutrient-rich organic inputs originating 4.0 8 beyond the farm boundaries. One such organic density 3.0 20 resource for bananas in Uganda is coffee husks. Effective use of these organic inputs is necessarily 2.0 influenced by the rooting density and distribution of 1.0 bananas. Yet, the depth of rooting and extension of .. banana roots had not been documented previously, and 1.43 1.87231 2.75 the plasticity of rooting behaviour to the addition of from decomposing organic resources was unknown. TSBF Distance stool (cm) scientists in Uganda established an on-station + coffee husks experiment examining the rooting pattern of bananas 6.0 4.0 and the response of that pattern to the application of density mass 50 / massive amounts of coffee husks. Root biomass of the -. 3.0 bananas not receiving coffee husks was 780 kg/ha and 4.0 "S 8 increased 3.3 and 6.6-fold when incorporated and 30 20 surface mulched, respectively (Figure 16). That B surface mulching resulted in greater root productivity than incorporation is useful information from the soil 1.0 management perspective, but somewhat perplexing
scientifically. Bananas demonstrate shallow rooting, 0.0 and it is possible that physical soil disturbance Distance from stool (cm) accompanying incorporation may have killed a significant proportion of the roots. Alternatively, the Figure 16. The effects of coffee husk massive application rate (144 T/ha) may have resulted addition to banana root distribution and in microbial or nutrient imbalances adjacent to the productivity based upon root-ingrowth roots. Husk incorporation resulted in two-fold measurements. increases in maximum rooting depth (70 vs 140 cm), despite lower total biomass, again suggesting that the roots have become displaced from the surface horizon. The use of coffee husks as external inputs to bananas grown as a monoculture resulted in increased banana productivity and that increase was related to root productivity and behaviour. The abilities of additional, more readily available organic resources at more realistic rates are the planned topics of future research efforts on the nutrient management of banana.
Use of surface mulches on smallhold, banana-based cropping systems in Uganda.
24 TSBF Report: 1994
UGANDA: Changes in earthworm populations due to land 200 preparation. Maiy Okwakol, Department of Zoology, Makerere Isd 0 05 University, Kampala. ('1
One important component of environmentally-friendly methods of 150 land conversion is the effect upon E soil macrofaunal communities + Earthworms promote soil physical properties such as aggregation and water infiltration recycle soils from C) 100 lower depths and mobilise nutrients These benefits may only E be realised when the earthworm communities are not devastated by C.) land management practices The objective of this research is to 50 E determine land management practices that promote macrofaunal U_I LL activity and productivity of soil in Uganda The study is being undertaken at the Makerere — Jnisity 0 Land Preparation collaboration with The International Board for Soils Research and Figure 17. Earthworm populations in response to various Management (IBSRAM). The land preparation methods at Kabanyolo, Uganda. study site is situated 20 km north of Kampala and at an altitude of 120 m. It lies in the higher rainfall zone with mean rainfall of 1160 mm, most of which comes in March-May and September-November. The soils are medium acidic red to reddish brown sand clay barns. The previous vegetation was bush and the land had not been cultivated for 15 years.
The following land management practices were studied:
* Traditional method where vegetation is cut, residues dried and burned and the is tilled by hand using a hoe. * Semi-mechanized without burning where the forest and understorey is felled by hand, tractors used to remove large trees and the soil is tilled by hand with a hoe. * Semi- mechanized with burning where the forest and understorey is felled by hand, tractors used to remove large trees, the remaining vegetation burned arid the soil is tilled by hand with a hoe. * Fully mechanized where the land is cleared with a bulldozer and tilled with a tractor.
Burning does not appear to reduce earthworm populations because populations are greatest under the Semi—mechanised/buming regime (Figure 17). Hand clearing may have suppressed earthworm populations because this practice results in more complete litter removal than semi-mechanised means. Clear cutting and mechanised tillage clearly has a severe impact on earthworm populations. We conclude that the more deleterious impact on earthworms arises during tillage as opposed to clearing and that the transition from traditional methods of clearing to machine assisted ones will not severely influence total population sizes of earthworms.
25 TSBF RepotI: 1994
Measuring understorey biomass and standing litter in a humid forest of Equatorial Africa.
ZAIRE: Carbon and nutrient dynamics resulting from slash & burn agriculture. Jean Nyangeko, Institut Facultaire des Sciences Agronomiques, Kisingani.
The success of farming systems in the humid tropics is closely related to the dynamics of organic matter and soil biological processes. Plant nutrients are accumulated by natural forest vegetation over decades or centuries and then utilised by shifting cultivators in slash and burn agriculture. Once felled, the forest biomass is too great for incorporation into the soil, so the vegetation is left to dry, then burned. Tillage is accomplished by hand and a series of intercrops are established until soil fertility becomes diminished. Then lands are abandoned and a natural forest fallow re- accumulates nutrients. A research project was recently established that seeks to characterise the carbon and nutrient dynamics of slash and burn agriculture in Kisangani, Zaire. The specific objectives include:
* To characterise the vegetation and soil organic matter dynamics during shifting cultivation in an Equatorial Rainforest in Zaire.
* To measure the total system carbon lost to the atmosphere from a rainforest during the clearing and burning phase of shifting cultivation.
* To measure vegetation regrowth and soil carbon sequestration during the fallow interval of shifting cultivation in a rainforest.
* To identify candidate land management practices that result in improved crop productivity and increased cropping interval of lands cleared by shifting cultivators.
A forest-cultivation-fallow sequence along a rainforest margin was identified 12 km to the NE of Kisangani. The forest area scheduled for clearing is being characterised in terms of standing forest tree and understorey biomass, standing litter and soil organic matter fractions. After clearing and burning by farmers, the measurements will be repeated. This approach measures the magnitude of carbon loss resulting from the clearing and burning event. At each farm, nearby land that had been previously cleared and continuously cropped, or cropped and abandoned (recovering fallow) has been dated and identified. The rates of plant productivity and organic matter dynamics are being measured at six month intervals at each of these sites over an 18 month period. These combined measurements provide a chronological sequence of total system carbon.
26 TSBF Report: 1994 0.8 0) ZAMBIA: Litter 0.7 decay studies on candidate agroforestry species. Bright Mwakalombe, Misamfu Agricultural Research Station, Kasama, Zambia.
The agriculture of Northern Zambia is dominated by slash-and-bum and rotational fallow cultivation systems. In the chitemene system, a larger area of miombo forest is cleared than is eventually cultivated because 0 the vegetation is concentrated in the middle of the clearing prior to burning. The chitemene 0 system has led to widespread day9 33 933 933 forest destruction but continues for lack of Cal//ana'ra Fleming/a Uapaka viable alternatives. One alternative under ca/othyrsus macrophyla kirk/ana investigation by TSBF scientists at the Figure 18. The effects of soil fauna on establishment of litter banks which consist of decomposition of organic inputs. fast growing tree species that are acclimatized to the extremely acidic soil of Northern Zambia. It is hoped that the use of tree prunings as green manures will result in greater permanency of agriculture and, hence, reduced need to clear additional miombo woodlands.
Over the past several years, three tree species have been identified through research efforts at Misamfu that have special promise as agroforestry litter bank systems. These species are Calliandra calothyrsus and Flemingia 'nacrophylla, two nitrogen-fixing legumes that have been introduced to the area, and Uapaka kirkiana, an indigenous fruit tree. An experiment was installed to investigate the role of macrofauna in the decomposition of tree prunings by comparing the mass loss of the three tree species (Figure 18). The prunings were placed in litter bags of different sized meshes, and collected periodically over 90 days. Soil macrofauna, particularly termites that are nearly ubiquitous at the experimental site, are excluded from the litters by the finer sized mesh (0. 1 mm) but not the coarser (5 mm).
The exclusion of soil fauna resulted in significantly reduced mass loss in all three species. This suggests that mound-building termites, among other organisms, may be transporting large amounts of tree pruning beyond the root zones of cultivated crops thus reducing the direct nutrient contribution of those prunings to the soil. This observation is supported by field experiments with a bean (Phaseolus vulgaris) and maize (Zea tnays) rotation where prunings applied at the rate of four tons per ha did not result in significant increases in crop productivity. To date, the search continues for plant species that are able to provide nutrient-rich prunings and readily decompose during a cropping cycle but are not an attraction to elements of the soil fauna! community that transport litter away Surface mulching of beans with Flemingia from the cropping system. macrophylla at the Misamfu Research Station.
27 TSBF 1994
ZIMBABWE: Benefits from cereal/legume rotations. Linus Mukurumbira, Soil Productivity Research Laboratory, Department of Research and Specialist Seri'ices, Marondera.
One option for the maintenance of soil fertility in cereal-based cropping systems is through the introduction of cereal/legume rotations. Legumes are able to maintain soil fertility within the rotation because of their deep rooting, different nutrient requirements and ability to procure atmospheric nitrogen through symbiotic N-fixation. TSBF scientists at the Grasslands Research Station, Marondera have conducted field experiments which examine the effects of introducing legumes into continuous maize cropping systems. These experiments are located on-station and in nearby communal farming areas, and include the introduction of TSBF Network scientists, boara members and soyabeans, groundnut, cowpea and bambara staff viewing the Marondera legume rotation groundnut. One such on-going experiment to trials at harvest maturity during the 1993 study the effects of grain legumes to maize season. yields was initiated in 1985.
In the on-station experiment at Marondera, cowpea, groundnut, bambara groundnut and soyabean were grown in a three-year legume/maize/maize rotation between 1991 and 1993. The rotations are studied at several levels of applied chemical nitrogen. The control plot is planted in a short season maize variety during the legume seasons. The residual effects of legumes were greatest with soyabean and bambara groundnut and more reduced in the groundnut treatments (Figure 19). Maize yields following rotation with cowpea were often less than those of the maize monocrop, suggesting that the growth of cowpea depleted the soil to a greater extent than the short season maize variety. The addition of 60 kg chemical nitrogen/ha increased maize yields from 2.9 to 4.6 T/ha but the maize grain yield in the bambara and soya rotations not receiving N yielded almost as well (4.0 and 4.2 T/ha, respectively).
While the yield benefits of legume rotation with continuous maize Cowpea rotation maize have been demonstrated, the economic 7 gains are subject to the prices of the various EJ Bambara rotation commodities. Seed oil legumes had in the past L.. 6 EJ Soyabean rotation been subsidised in Zimbabwe as a means of I LSD 0.01 for N effect securing domestic cooking oil production. Without these subsidies, the higher yield potential of maize offsets its lower commodity price and for the time being maize monocrops remain more profitable. The greater significance of legume rotations lie in two areas, the rotation with certain legumes is a likely path to restoring lost soil fertility and, among the communal farmers, legumes have been J' identified as a woman's crop, so the individuals No applied N + 60 kg N/ha responsible for the cultivation of annual field crops stand to benefit more from "less Figure 19. Maize grain yield at Marondera, profitable" legume rotation. Zimbabwe in the third season of a legume/maize/maize rotation.
28 TSBF Report: 1994
ZIMBABWE: Decomposition of Brachystegia spiciformis and Leucaena leucocephala leaves in litter bags buried in sandy soil. Petros Nyathi and Bruce M. Campbell, Department of Research and Specialist Services, Ministry of Lands Agriculture and Water Development and Department of Biological Sciences, University of Zimbabwe, Harare.
Smalihold farmers find themselves in a dilemma when they recognise I A that soil fertility can only be S maintained through the replacement k = -0.42 of nutrients removed or lost from — — the cropping system and no readily- . s available sources of those nutrients E are identified. Plant biomass from .... k = -1 .24 agroforestry is one possible source, - but the nutrient concentrations and U) — release patterns during decay must be suited to crop demands for • k = 4.74 benefits from their application to be Z a realised. Researchers in Zimbabwe k = -7.65 are exploring the possibility of • £ using the senescent leaves from o.o 02 08 native and exotic tree species as Time (year) organic inputs. An experiment was established on sandy soil cleared of Figure 20. Nitrogen release from decaying Leuceana all vegetation to study the leucoceophala and Brachystegia during two decomposition patterns of senescent growing seasons with different amounts of precipitation. leaves of Brachystegia a dominant tree species of the miombo woodland, and Leucaena leucocephala, an exotic N-fixing multipurpose tree from Central America. Differences in decay rates were related to chemical composition and climate.
Significant difference in mass loss between the two species were observed during the early stages of decomposition. L. leucocephala decayed more rapidly than B. spicjfor.'nis during both seasons illustrating that the greater initial N and lower lignin contents of L. leucocephala prime decomposition processes (Figure 20). The higher N content and faster decay of L. leucocephala leaves are indications of greater capacity to contribute nutrients to the soil system (Table 4). Litter decay patterns of the two species were more similar during the second, wetter season, suggesting that climate occupies a dominant role in mass loss. Total rainfall during the experimental period was 263.3 mm and 597.5 mm in the first and second seasons, respectively. The effects of leaf composition were most pronounced during the first, drier, season when L. leucocephala released N much more rapidly than did B. spiqformis. During that season, L. leucocephala leaf mass declines in a non-linear fashion while B. spic?formis decay in a more linear maimer which suggests that different mechanisms may be operative.
Table 4. Lignin and nitrogen contents of decaying Leucaena leucocephala and Bra chystegia during the 1992/1993 growing season in Zimbabwe.
Parameter retrieva 1 week 3 8 16 30 Lignin(%) L. leucocephala 23.1 18.3 20.7 27.9 B. spic?formis 30.5 23.4 29.4 34.7 LSD 0.05 5.2 4.6 ns 1.5 Nitrogen (%) L. leucocephala 1.3 1.5 1.6 2.3 B. 1.1 1.1 1.6 1.3 LSD 0.05 ns 0.3 0.3 0.6
29 TSBF Repoil: 1994
ZIMBABWE:Nitrogen dynamics _ • • a sandy Zimbabwean in soil soil + 40 T manure/ha under manure fertilisation. 1< N h * 0 Herbert Murwira, Chemistry and - - - Soil Research Institute, Harare 0 •80 Among the low cost management options that conmiunal area farmers can use for the 02 improvement of soil fertility is the unamended soil application of manure in E conjunction with supplemental N Q fertilisers. The effects of 0.1 fertilizer-N addition on the decomposition of a nitrogen-poor 5 cattle manure was studied. 0.0 Fertilizer-N was added to manure C.) 0 .05 .10 .15 .20 amended soils (40 t/ha) at rates equivalent to 0, 20, 40, 80 and Cumulative N mineralisation (mglg soil) 100 kg N ha1. The research objectives were to determine the Figure 21. Cumulative carbon and nitrogen mineralisation relative efficiency of nitrogen following the addition of manure and inorganic N during a release from manure and to five month laboratory incubation. develop a basis for manure management systems involving the manipulation of quality, quantity and timing of inorganic inputs so as to synchronise nutrient release from the inputs with uptake by plants. The soil at the site was a Haplustalf at the Grasslands Research Station, Marondera, with a surface horizon containing 90% sand.
Carbon and nitrogen mineralisation from manure. The addition of manure resulted in increased C mineralisation (Figure 21). N mineralisation was reduced by manuring at higher rates of applied fertiliser-N. Addition of fertiliser-N stimulated C mineralisation in unamended soil except at an application rate of 100 kg N ha1. The stimulation of C mineralisation which occurred in unamended soil may be explained through the inherent N limitations within the soil and the accumulation of readily decomposable C once that limitation was overcome. In soils receiving manure and increasing rates of inorganic N, an overall declining trend in C mineralisation was noted. The reduction of C mineralisation may be due to microbial assimilative activities becoming more efficient as N availability increases. The reduction in net N mineralisation at higher levels of applied fertiliser when manured and unamended soils are compared. The effects of N addition on N mineralisation from the soil and manure are illustrated in Figure 22. High mineral N values were measured in the 80 and 100 kg N hat application rates. There was an immobilisation of N due to manure application during the first two weeks of the incubation. Small amounts of N were mineralised over the longer-term. Addition of manure and 20 kg N ha1 also immobilised N but this effect was of shorter duration. A minimum of 40 kg N ha1 was required to establish a consistent net mineralisation (data not shown). Where then is the N applied as manure, an external N source that far exceeds that applied as fertiliser? Clearly soil N is being immobilised through the stimulation of microbial activity following manure addition and at later stages mineralisation and immobilisation are nearly offsetting. Rather than directly increasing mineralisation of manure N, the first increment of fertiliser N addition had the indirect effect of shortening the net immobilisation interval. It can be speculated from this study that N release from livestock manures in the communal farming areas is similarly reduced and poorly timed with crop demands. Therefore, the addition of supplemental fertilizer N may be a direct means to better match nutrient availability and crop demand in these soils.
30 TSBF Report: 1994
Partitioning of N in manure amended soils in 200 the field. Given the immobilisation of nitrogen kg N/ha observed in laboratory incubations following ..*.. 0 manuring, a field experiment was established to U) determine the effect of timing of N application 20 on N release and plant uptake. Manure was —.— 80 applied at planting at a more realistic rate of 10 T ha1 and 100 kg fertiliser N ha' applied at o 100 planting or six weeks afterwards. Nitrogen 100 mineralisation and leaching was estimated by in- situ incubation. Addition of manure resulted in a >50% reduction of yield when compared to the complete control (Table 5). The application E of pre-plant fertiliser N greatly improved maize yield, but post-plant applications were most effective in conjunction with manure addition. 0 The manure treatment demonstrated immobilisation of N during the first 8 weeks. Early application of fertilizer N resulted in significantly more available N compared to 5 fertiliser addition 6 weeks after planting. E Nitrogen recovery, calculated as the difference between the manure and fertiliser N treatments and the complete control divided by the total external N applied, ranged between <0% to 0 20 40 60 80 69% of and was poorest in the manure treatment Period of incubation (days) and greatest when fertiliser N was applied. Synchrony between N release and uptake was Figure 22. The effects of inorganic N maximised through the use of fertilizer N addition on net nitrogen mineralisation in a applied six weeks after planting. As a sandy Alfisol amended with 40 T hat of low management strategy, application of inorganic N quality manure. should be delayed so as to reduce N losses and increase synchrony of N availability and uptake by the crop. Another conclusion that may be drawn is that the addition of high amounts of low quality manures under N-limiting growth conditions should be discouraged in communal farming areas unless fertiliser N is applied.
Table 5. Grain yields and N uptake by maize grown in an Alfisol amended with manure (10 T ha1) and fertiliser N (100 kg ha1) applied at pre- and post-planting.
Treatment Grain yield Grain N Total N uptake kgha1
Control 2640 33 50 Manure 1255 17 48 Manure + N (pre-planting) 3938 60 131 Manure + N (post-planting) 4731 69 115 N (pre-planting) 4394 82 114 N (post-planting) 3691 64 119
31 TSBF Repoit: 1994 AFRICAN NETWORK SUMMARY
The last two years of AfNet has seen both consolidation of initial experimental findings and continued network expansion. Most of the projects funded during the network s inception are now completed, have yielded valuable information on the biological management of soils and as a result been extended through donor support. The AfNet results presented in the preceding country reports speak for themselves. AfNet has emerged as a contributor to the scientific state- of-the-art while at the same time addressing serious problems encountered by the smallholder farming sector. AfNet has become well represented throughout East and Southern Africa. The map of AfNet cooperators presented at the beginning of this section is superimposed upon the natural vegetation zones of the sub-region and the land areas that are cleared for agriculture. Research projects are under way in the humid forest, woodland and savanna zones and are located in almost all of the major areas that are converted to agriculture including the East African Highlands, the Lake Victoria Basin, the Indian Ocean Coastal Basin, traditional slash & burn areas of Zaire and Zambia and more intensive annual cropping of the drier Miombo Woodlands.
Of equal importance is the more complete distribution of AfNet research projects within the four TSBF Themes; Synchrony, SOM, Soil Biota and Resource Integration (Table 6). Prior to 1993, AfNet could have been viewed as an extension of the Synchrony Theme, as the majority of research activities were evaluating the feasibility of various organic resources as additions to soils. This was an important exercise, as evidenced by the preceding country reports, because many significant understandings emerged; maize stover, Lantana and low quality livestock manures are not, in and of themselves, suitable amendments to soils from the farmers perspective because short-term benefits are not realised. Cereal/legume rotations, mixed placement of residues and use of N-fixing plants as soil amendments were identified as opportunities for farmers and certainly warrant further investigation. Another important finding by many AfNet scientists is the strong relationship between litter decay and soil faunal activity. The realisation that the addition of organic resources may serve to feed faunal communities, rather than provide substrate to better understood and more predictable microbial processes, deserves further investigation.
The network has not only produced valuable results but also expanded into new geographical and subject areas. The Rhizobium Ecology Network of East and Southern Africa pioneered TSBF activities into new countries as well as served as stimulus to redefine the former Soil Fauna Theme into new Soil Biota Theme, which studies beneficial organisms in a wider context. Scientists who were formerly studying "litter decay" have now learned the importance of various
Table 6. The distribution of AfNet activities within the TSBF Research Themes.
Country Activities Themes Synchrony SOM Biota Integration
Kenya 5 + + +
Mozambique 1 +
Rwanda 1 - + South Africa 1 + + +
Tanzania 1 + - + Uganda + + +
Zaire 1 — + Zambia I + + Zimbabwe 3 + + +
32 TSBF Report: 1994
AfNet scientist are broading their base among the TSBF Research Themes and pioneering the inter-relationships between those Themes.
"agents of litter decay" and in so doing have irreversibly linked the Synchrony and Soil Biota Themes. The Soil Organic Matter Theme, until recently, had lesser importance within the network but is now being directly addressed in several funded projects, and perhaps more importantly, SOM fractionation is being practised in laboratories that had little interest in doing so in the past. The winds of change have brought the former Programme Centre in South Africa into AfNet, a move that serves to strengthen overall network scientific capabilities. The newly- developed Resource Integration Theme was readily adopted within the network. This adoption is due in large part to that theme's evolution and the important inputs to its development by AfNet scientists during meetings in Kenya (1992) and Zimbabwe (1993). But more importantly, AfNet has embraced the Resource Integration Theme because of its potential relevance. Farmers become more immediate clients when the findings which emerge from other themes are evaluated on-farm and placed within a decision-making context.
AfNet successes have extended beyond publication of scientific articles. For example members have been invited to deliver papers at international meetings and become reviewers and editors of international journals. AfNet thrives through the insights and commitment of its individual network scientists, and, by all indications, will continue to do so in the future.
The rapid adoption and advance of the Resource Integration Theme is due to its immediate relevence to the problems encountered by smaliholder farmers.
33 TSBF 1994
SOUTH ASIA REGIONAL NETWORK
The South Asian Regional Network (SARNET) was initiated in April 1992 at a workshop held in Kausani, Uttar Pradesh, India. Subsequently, a Network Coordination Unit was established with the Jawaharlal Nehru University, New Delhi and G.B. Pant Institute of Himalayan Environment and Development, Almora. SARNET is coordinated by Ashes/i Das through funding from IDRC (Canada). SARNET was initiated in India, but plans to develop into a regional programme over the coming years.
The major focus of TSBF research in South Asia is resource poor farmers where organically- based agriculture is still practised. TSBF will conduct research to devise new options for sustainable soil fertility management based on indigenous technical knowledge. In mountainous areas, the traditional farming community considers cropland not as a discrete independent system but as a subsystem of a complex ecosystem consisting of croplands, animal husbandry, forests, and human beings. TSBF research will target research methods which may be applied to crop residue management, organic-inorganic interactions, root turnover and soil organic matter dynamics within these systems.
Biodiversity, soil fertility and ecosystem function. Farmers maintain a wide variety of crops, crop genotypes, trees and other plants in their ecosystems to serve a range of productive and social purposes and also conserve fallow and forest areas that are necessary to the continued functioning of the agricultural lands. TSBF has a particular advantage in studying the role of key groups of the soil fauna and microflora in agricultural productivity and sustainability and can draw on the wide range of expertise among Indian scientists in the fields of ecology, botany, zoology and microbiology to investigate the relationship between biodiversity, agricultural change and agroecosystem function.
SARNET development. The proceedings of the workshop held in Kausani in 1992 was published and widely distributed to South Asian Scientists. Currently, SARNET is restricting research to zones identified as high priority areas at the inaugural workshop. These zones include the Himalayan, Northern Plains and Western Ohats (Southern India). In each zone, key collaborators were identified and research proposals are being developed within the TSBF research themes.
SARNET research priorities. The research components emphasized above are critical to land-use planning for sustainable development for three reasons:
* the evolution of agricultural practices that are both sustainable and profitable is essential to the alleviation of rural poverty; * the establishment of such practices in the margins of conservation areas is an important of conservation policy; * such agroecosystems can in themselves be important sources of biodiversity maintenance.
The targets chosen for initiation of research in the SARNET are, in order of priority:
1. The integrated management of soil fertility in montane agroecosystems of the Central, Western and Eastern Himalayas. 2. A thematic network on soil biota research with emphasis on utilization and conservation of biodiversity under agricultural intensification and rehabilitation of degraded lands at forest margins in India. 3. The integrated management of soil fertility in small scale farming systems and plantation agricultural in the Western Ghats. 4. Organic matter management in small scale and intensive agricultural systems in the semiarid zone of northern India with a particular focus on agroforestry.
34 - 1994
GLOBAL NETWORK REPORT: FOCUS ON LATIN AMERICA
TSBF does not have a as such in Latin America but maintains close linkages with scientists in the Caribbean, Central and South America. Some of the research sites such as Martinique, Yurimaguas and Ticoporo began their association with TSBF as Programme Centres and have since served as a nucleus to attract additional scientists to the programme.
BRAZIL: Forest litter contributions to soil organic matter. Joao Matos and Erick Fernandez, EMBRAPA, Manaus.
Soil organic matter decline and fertility depletion are associated changes following forest clearing. Understanding the relative importance of above- and below-ground inputs and tillage practices in the maintenance of SOM and its various fractions will guide the future management of tropical soil fertility. A modified KJLLSOM experiment, where the changes in SOM pools are measured over time, established on an Oxisol in an undisturbed forest near Manaus, Brazil, was designed to look at some of these issues. EMBRAPA (Empresa Brasileira de Pesquisa Agropecuaria) scientists in collaboration with scientists from Colorado State University are monitoring organic matter content and fractions in plots where above and below ground inputs are controlled. This study is part of a larger study at Colorado State University, funded by the National Science Foundation of the US, that is looking at the controls on soil organic matter content and fractions. The following treatments were established in four replicates in October 1992.
1. Above and below ground inputs: Undisturbed tropical rainforest. 2. Aboveground inputs only: Trenched plots to 50 cm (no roots), aboveground inputs remain. 3. Below ground inputs only: No trenching, aboveground inputs removed biweekly. 4. No inputs: Trenched plots, aboveground inputs removed biweekly. 5. No inputs with tillage: Same as Treatment 4 and tilled monthly.
The soils are sampled annually to 20 cm and monitored for total soil carbon and nitrogen, microbial C and N, light fraction C and N, anaerobic N mineralisation and CO2 evolution. In addition, litter fall is collected biweekly in the surrounding forest to give an estimate of aboveground inputs. These parameters will give an indication of the change in various soil organic matter fractions and the activity associated with those fractions. These changes can then be correlated to the type and amount of input and the tillage management. Data from this type of experiment are also important for validating the CENTURY model for the tropics. The experiment is now in its third year and the results are being prepared for publication.
A KILLSOM experiment established in Manaus, Brazil which partitions the contribution of different forest system inputs to SOM.
35 TSBF Repoil: 1994
COLOMBIA: Biological process studies in, pasture systems. R.J. Thomas, N. Asakawa, P. Lavelle and T. Decaëns, CT, Cali, Colombia and ORSTOM, Bondy, France.
Decomposition of forages and crop residues. The recycling of nutrients via litter and crop residues is of major importance for farmers with limited resources and there is much interest in the efficient combination of the use of organic and inorganic nutrient sources for sustainable agricultural production. As part of a wider study on nutrient cycling employing TSBF methodology, litter bags were used to compare decomposition rates of grass and legume forages and crop residues including different size mesh bags and mixtures of grass and legume leaf litters on a sandy loam (Alegria) and a clay loam soil (Intro II). Legume and crop residues decomposed faster than grass litter (Table 7). Nutrient concentrations were also greater in legumes and crop residues than grasses. From an analysis of the relationships between initial composition and decay rates, the strongest linear relationship was obtained between the lignin:N ratios and half-lives (R2 = 0.62). The best mathematical fit to the decomposition data was obtained with a single exponential equation containing a residual function. Data from the use of litter bags of
Table 7. Decomposition parameters for the decay of pasture grasses, legumes and crop residues.
Species k coefficient1 Half-life2 (day') (day)
Site: Alegria Bracharia dictyoneura 0.0014 ± 0.0002 179
B. dictyoneura , 0.0017 ± 0.0002 148 B. dictyoneura 0.0018 ± 0.0002 144 Centrosema 0.0022 ± 0.0003 113 B. dictyoneura/C. 0.0020 ± 0.0003 118 Stylosanthes capitata 0.0025 ± 0.0001 109 B. dictyoneura/S. capitata 0.0020 ± 0.0002 127
Site: Intro II Bracharia dictyoneura 0.0014 ± 0.0003 161 B. dictyoneura 0.0020 ± 0.0002 129 B. dictyoneura 0.0014 ± 0.0003 159 C. 0.0014 ± 0.0003 164 B. dictyoneura/C. 0.0016 ± 0.0002 153 Arachis pintoi 0.0024 ± 0.0006 68 B. dictyoneura/A. pintoi 0.0020 ± 0.0005 86 Cassava leaves 0.0023 ± 0.0006 68 Maize stover 0.0021 ± 0.0005 79 Rice straw 0.0027 ± 0.0005 71
1 based on first order exponential decline where remaining litter/initial litter = 2 based on the first order exponential equation when remaining litter/initial litter = 0.5
36 TSBF Report: 1994 mesh size 1, 2 or 4 mm did not result in significant differences in the decomposition of four forage legumes and one grass. Similarly cutting the litter in pieces 5-10 mm length did not result in greater rates of decomposition compared with intact litter deposited on the soil surface. Mixtures of grass and legume litter (50:50) decomposed at rates equivalent to the values estimated from the mean parameters of each individual species. For example, there was no synergistic nor inhibitory effect of one species on another.
Effect of introduced forage grasses and legwnes on soil fauna. The encouragement of beneficial soil organisms is a goal for the more benign use of the land for agricultural production and yet this area is probably one of the most neglected areas in tropical agriculture. A long-term Bra chiaria decumbens/Puerariaphaseoloides pasture was compared with a native savanna, gallery forest and cropped land on similar Oxisol soils for macrofauna populations at the Carimagua experimental station in the eastern plains of Colombia. The improved pasture containing a forage legume was supporting an earthworm population between 4 to 5 times that of the native vegetation. Fauna were virtually eliminated after rice or cassava monocropping (Figure 23). Further, the number of species under the pasture was the same as that under native vegetation. The results demonstrate that it is possible to build up large populations of fauna, mainly earthworms, with introduced plant species using limited amounts of inputs.
60 others
I 50 termites earthworms CI 40
30
20
10 C',
ii •1 0 Savannas Pastures Field crops
Figure 23. Effect of land management on soil macrofauna in a Colombian Oxisol.
37 TSBF 1994
CUBA: TSBF Experimentation. Rafael Villegas, Manuel lzquierdo, Nelson Pina, Emma Ruiz, Mario de Leon, Eugenio Garcia, Ramon Blanco (Sugar Cane Research Institute) and Francisco Martinez, Angelica Martinez, Theresa Bach and Maria Gonzelez Perez (Institute of Soils).
Cuba is currently in a transition from high-input agriculture to an integrated, low-input agriculture due to the current economic crisis in the country. This transition is occurring at a large scale and national scientists are keenly aware of the relevance of TSBF themes in making the change. Cuban involvement with TSBF began in 1991 as a request from scientists at the Sugar Cane Research Institute for TSBF literature. Since then, they have translated the Handbook of Methods into Spanish and have initiated KILLSOM field experiments on soil organic matter decline, litter decomposition studies and in situ mineralization. The KJLLSOM experiment has been installed in sugar cane fields in three sites; Cienfuegos, Camaguey, and Jovellanos. The first two sites are on smectitic soils, while the third is a eutrophic, kaolinitic/oxidic soil. All three sites had high levels of inherent soil fertility but the soil organic matter has been depleted due to 50 years of continuous cultivation in sugar cane. In the past sugar cane was heavy fertilized and residues were removed. Burning has recently been banned and residues are now incorporated. In the KILLSOM plots, changes in total soil organic matter, microbial biomass and particulate organic matter in bare soil plots are being compared to changes in plots receiving external inputs. At the Cienfuegos site there are paired forest and sugar cane plots where soil fauna measurements have been conducted. This is also an excellent site to make comparisons of C12/C13 ratios in the soil organic matter fractions because a C4 plant (sugar cane) replaced a predominantly C3 forest. The scientists are looking for collaborators for both the fauna and isotope work.
The Institute of Soils in Cuba also has ongoing research that readily fits into testing hypotheses in the SYNCHRONY and SOM Themes. In an experiment with paddy rice under different levels of fertilization, they compared decomposition of residues and showed significantly higher rates of decomposition in the presence of higher fertility levels. There is concomitant decrease in SOM with higher rates of fertilization. Other measurements indicate that the SOM which remains is more recalcitrant. In another experiment they are comparing soil organic matter fractions in the natural system, 10 years, and 30 years of rice cultivation. We look forward to seeing several TSBF hypotheses tested through their research. Exciting results from Cuba may be expected in the next TSBF report.
A KILLSOM experiment at Cienfuegos. Note the extensive root bamers that exclude roots.
38 TSBF Report: 1994
AUSTRALIAN PROGRAMME CENTRE FINDINGS: GOOD SOIL IN A DRY SEASON
This summary was prepared from articles sent to TSBF Headquarters by Ram Dalal, Queensland Wheat Research Institute, Toowoomba, Australia. TSBF Programme Centre research was established at the institute in 1986 to evaluate the effects of soil conservation and regenerative rotations and fallows on the soils of sub-tropical Queensland. During the winter season of 1994, wheat planted into a full soil water profile received only 18 mm offurther precipitation prior to wheat maturity. Nonetheless, wheat yields after lucerne, grass-legume pasture and chickpea averaged 1.6 T ha' and exceeded that of continuously cropped wheat by 60%. Wheat growers in the area better realise that soil restoration offers returns during poorer growing seasons.
The TSBF research agenda at Warra has always had a strongly applied focus. After an average of 30 years continuous wheat cropping, soil fertility is in serious decline, grain protein contents are reduced and soil organic matter contents are 30% of their original level. The researchers at Warra sought to identify more sustainable land use strategies and to elaborate upon the mechanisms which underlie these conservation practices (Table 8). Zero tillage improved water infiltration and storage while reducing salts in the root zone by almost 250 kg ha1 yf1. Establishment of grass-legume pastures greatly increased earthworm populations and doubled microbial biomass. Four year-old grass-legume pastures accrued 650 kg of soil organic carbon ha1 Rotation of wheat with chickpea did not increase soil organic matter or microbial biomass, but rather its benefits arose from the chickpea N-fixing symbiosis. Not only has this research generated numerous scientific findings, at the same time it has served as a continuous demonstration of diversified land management options to surrounding farmers.
Table 8. Land management options for restoring soil fertility in wheat-based cropping systems of sub-tropical Queensland.
Continuous cropping with N-fertiliser applied Advantages: Nitrogen is immediately available to the crop, most profitable when rainfall is sufficient and the soil is not degraded. Disadvantages: Does not regenerate degraded soils, higher N application rates offer poorer economic return during drier years. Continuous cropping with Zero Tillage Advantages: Reduces run-off and soil erosion, improves water storage during drier years, conserves soil organic matter, offers a more reliable response to applied fertilisers. Disadvantage: Higher levels of fertiliser-N are required to achieve yields than from conventional tillage during wetter years. Wheat/short-term legume ley rotation Advantages: Supplies 60-80 kg N ha1 to the following wheat crop, improves wheat protein content, legumes are self regenerating. Disadvantages: Legumes are incomplete livestock rations which may develop bloat, offers lower overall economic return. Wheat/longer-term grass-legume ley Advantages: Supplies up to 80 kg N ha1 to the following wheat crop, provides quality livestock feed, rapidly replenishes soil organic matter. Disadvantage: May reduce soil water storage for the subsequent wheat crop. Chickpea/chickpea/wheat rotation Advantages: Chickpeas supply 40 kg N ha' to the subsequent wheat crop and provide greater returns than wheat/ley rotations because chickpeas are a cash crop, disruption of wheat disease cycles. Disadvantages: Nitrogen contribution may be insufficient to produce high-protein wheat, chickpea stubble offers incomplete erosion control.
39 TSBF 1994
Tree diameter measurements are a component of total system biomass measurements in the TSBF approach to characterisation of humid forests.
ALTERNATIVES TO SLASH & BURN
As many as 17 million hectares of tropical forest are cleared and burned annually. This scale of forest clearing is accompanied by impacts at the local, regional, and even global levels, including erosion and silting of watersheds, loss of plant and animal biodiversity, and climatic change. Although some of the area is cleared by large companies for logging and ranching, much is cut and burned by farmers to provide food for their families. If the rate of deforestation is to be curtailed then the needs of these subsistence farmers must be addressed.
The Alternatives to Slash and Burn Agriculture (ASB) Initiative brings together scientists from international centres, national research organizations, universities, and NGOs devoted to finding farming and forestry practices that provide sustainable use of presently deforested lands and at the same time improve the livelihood of slash and bum farmers. The socioeconomic underpinnings of the problem of slash and burn combined with its environmental consequences and the various agronomic and political solutions to the problem necessitate a multidisciplinary and interdisciplinary approach.
Conceived in 1990, the Slash and Burn Consortium currently consists of fifteen institutions covering a range of expertise from international policy and marketing, participatory research, soil fertility and greenhouse gas emissions. Activities in the first years of ASB consisted of selection of membership countries, definition of objectives and activities, and acquisition of funds. Eight countries, accounting for the major areas of rapid deforestation and covering a range of biophysical and socioeconomic enviroments, comprise the Benchmark Areas where case studies will be conducted. Extrapolation will be based on results arising from these sites. Field activites began in 1994 in Brazil, Cameroon, and Indonesia with funding from the Global Environment Facility (GEF), a funding mechanism that arose during planning for the United Nations Conference on Environment and Development in 1992.
The primary activity of 1994 was to develop an integrated and multiscalar characterisation and diagnosis guideline that identifies key processes underlying slash & burn. It also allows for identification of research priorities, cross site comparisons and extrapolation to other sites. TSBF has been involved in the development and testing of these guidelines. A qualitative model integrating the biophysical, socioeconomic and political dimensions of slash & burn environments and predicting land use patterns is shown in Figure 24.
40 ______
TSBF Report: 1994
TSBF has taken the lead in establishing parameters and methods for characterising carbon and nutrient stocks and dynamics in tropical forests cleared for slash and burn agriculture. The large reduction in carbon stocks upon tropical forest clearing may account for 28% of the build up of CO2 in the atomosphere. What is not known is the amount of carbon taken up by and sequestered in regrowing vegetation and soils / I Increased and under different land use I I • loss of resourcesl ISustained Production practices that follow slash and I • poverty I I • alleviate poverty i • unsustainable I I • conserve resources burn. TSBF has held or • deforestation I arid-use I I reduce participated in workshops at the three benchmark sites focusing Figure 24. Conceptual framework for development of the on field methods for measuring Alternatives to Slash & Burn. above- and belowground carbon stocks in forest and different land-use practices, laboratory methods for analyzing soil carbon fractions, and model simulations of changes in carbon stocks. The CENTURY model was installed at each of the three benchmark sites, scientists trained in use of the model and site data files developed that simulate the predominant forms of slash & burn (Figure 25).
TSBF has also developed in collaboration with the Global Change in Terrestrial Ecosystems Programme (GCTE) and Indonesian partners a simple protocol for measuring greenhouse gas emissions, C02, N20, and CR4, from the forest and shifting cultivation fields. The method is currently being tested and samples are analyzed at the University of Copenhagen by GCTE scientists. Once validated, the protocol will be used to compare gas fluxes among the sites and different land uses.
Losses of soil carbon following slash and burn are also generally associated with a decline in crop production. Shifting cultivation and other low-input forms of agriculture depend on the maintenance of soil organic matter through the use of -13 organic inputs and recycling of 12 forest biomass C -12 crop residues. TSBF plans to total soil organic c assess the organic and inorganic 9 rice biomass (1/ha) -9 resources available to farmers 8 -8 — and the opportunities and * constraints related to their use. a * "S - - -' This activity involves c '---- characterization of the chemical 2 :.. . . constituents of the organic i -1 inputs and an assessment of 0 0 ...... ,. 0 10 20 30 40 50 60 70 80 90 100 their potential in improving soil time (years) fertility. When a wider range forest slash fallow permanent manure of soil management options are growth & burn growth rice ap lied available to farmers, land abandonment will be reduced. Figure 25. A CENTURY model simulation of soil and biomass carbon pools of a slash and burn system in Jambi, Sumatra.
41 1SBF Repoit 1994
RHIZOBJIJM ECOLOGY NETWORK OF EAST AND SOUTHERN AFRICA
Indigenous rhizobial populations control inoculation strategies. The need for the application of rhizobial inoculants and the magnitude of the response to applied rhizobia are determined by the species diversity and population sizes of indigenous soil rhizobia and the availability of mineral nitrogen within the soil system. Soil rhizobia were enumerated using plant infection counts and the most-probable-number (MPN) technique. The legume/Rhizobium symbiosis is characterised by specificity between the host and microsymbiont, which is identified as cross inoculation groups. The selection of a range of legumes, characteristic of individual cross-inoculation groups, as hosts for MPN assays allows for the species composition and population sizes to be characterised. The lack of rhizobia within a soil allows for the comparison of inoculated and uninoculated treatments as a direct measure of biological nitrogen fixation.
The nature and size of indigenous rhizobial populations in soils often influences the symbiotic capacity of host legumes and determines the need for and response to applied rhizobial inoculants. Rhizobial populations were determined by TSBF scientists at 46 sites in 8 African countries (Ethiopia, Kenya, Mozambique, Rwanda, Tanzania, Uganda, Zambia and Zimbabwe). The sites include semi-arid and moist tropical lowlands and highlands with annual precipitation ranging from 209-1400 mm/yr and annual temperatures of 15-29.1°C. The populations were determined by plant infection counts on host legumes that are representative of different cross-inoculation groups. These population data were expressed as log10 g and combined with additional site characteristic which included vegetation type, ecological zone (Figure 26), legume coverage (%), mean annual temperature and moisture, soil total C (%), total N, CEC, pH and sum of the extractable bases (cmol/kg). Total population sizes (log10 cells g soif 1) were greatest in highland soils (mean 3.31 sem = 0.28) followed by humid and sub-humid lowlands (mean = 2.41 sem = 0.27) and semi-arid lowlands (mean = 2.19 sem = 0.42) and covaried significantly with mean annual temperature (R2 = -0.64) and soil clay content (R2 = 0.60). Bradyrhizobium species were the most frequently observed species in the wet and semi-arid lowlands (2.37 and 1.84 log10 cells g respectively), and were consistently high in the humid areas of Uganda. Rhizobium phaseoli were most numerous in highland soils (3.01 log10 cells g particularly in the Kenyan and Rwandan Highlands. Total rhizobia, Bradyrhizobium species and R. phaseoli 07' all rhizobia n=174 strain 0 use of effective 0.5 improved canler/select stress tolerant strain improved delivery system/select competitive strain/response unlikely inoculation response extremely unlikely 0 03
0.1A.-______0 6-10 51-100 501-1000 >5000 1-5 11-50 101-500 1001-5000 rhizobial population/g soil
Figure 26. The distribution of population sizes of rhizobia measured by RENEASA scientists. The population size catagories correspond to those that require different strategies of rhizobial inoculation.
42 TSBF Report: 1994
population sizes differed significantly between ecological zones but B. japonicum and R. loti did not. The results of this investigation suggest that rhizobial species that are associated with host legumes not native to the region are nonetheless widespread throughout the subregion, particularly R. phaseoli, and to a lesser extent, B. japonicum in Zambia and Zimbabwe. At the same time, the presence of effective rhizobia in sufficient numbers to meet the nodulation requirements of crop legumes must not be taken for granted. In Preparation of growth pouches containing host legumes by a several natural ecosystems, RENEASA scientist in Mozambique. no or extremely few rhizobia were recovered, as was the case with sandy soils in coastal Mozambique. The activities of the RENEASA Network has had a wide range of outputs and impacts ranging from methodology development, training and advancement of the scientific state-of-the-arts. Specific examples follow.
Methodology development in plant infection counts. The use of plant infection counts as a rapid, reliable whole soil/plant bioassay has been reinforced within universities, ministries and at international centres. Many institutes were required to develop or refurbish aseptic plant growing facilities in order to conduct their participation in the network. The technique was used for the first time at ICRAF, Kawanda Research Centre (Uganda) and Eduardo Mondlane University (Mozambique). The University of Nairobi MIRCEN developed the capacity to produce growth pouches locally rather than to import them. Approximately 13,000 growth pouches were fabricated in Nairobi for distribution throughout the region.
Training in Rhizobiuin ecology. A training workshop was conducted in collaboration with UNESCO MIRCEN and the Soil Productivity Research Laboratory in Marondera, Zimbabwe on the use of serology in Rhizobium ecology studies. Participants from Uganda, Kenya, Rwanda, Zambia and Zimbabwe were instructed in the use of antibiotic resistant markers, immunodiffusion and agglutination as tools in following the fate of rhizobia on a strain-specific basis. Individual training in basic Rhizobiology was provided to the cooperators from Mozambique who had been previously unfamiliar with Rhizobium ecology studies.
Advancement of the scientific state-of-the-arts in Rhizobiology. Scientists at many research institutes within East and Southern Africa have developed a more mechanistic understanding of the importance of indigenous rhizobial populations on legume responses to inoculation. Presentations on the goals, approaches and results of RENEASA were given at the TSBF Afnet workshop (Harare, July 1993), the UNEP-SCOPE Soil Biodiversity Workshop (London, July 1993), the ISSS Soil Biodiversity Symposium (Mexico, July 1994) and the AABNF meeting (Harare, September 1994).
43 TSBF 1994 GLOBAL CHANGE AND TERRESTRIAL ECOSYSTEMS
The world's land-use systems are in the process of major change. Investigation of the response of terrestrial ecosystems (natural and managed) to global change is the task that has been taken on by GCTE (Global Change and Terrestrial Ecosystems) a core project of the International Geosphere-Biosphere Programme (IGBP). The objective of GCTE is "to predict the effects of changes in climate, atmospheric composition and land use on terrestrial ecosystems, including agricultural and production forestry systems" and "to determine how these effects lead to feedbacks to the atmosphere and the physical climate system". The definition of Global Change used by GCTE includes climate change, land-use changes driven by physical, demographic, economic, social and technological pressures as well as atmospheric changes such as rise in CO2 and other greenhouse gases which have both direct effects on vegetation and ecosystem function and also indirect influences through their relationship with climate. One of the major foci of the GCTE Project is on the response of agriculture and forestry to global change. TSBF scientists are beginning to play an significant role in GCTE research activities.
Response of multispecies agroecosystems to global change. The successful implementation of recommended management practices, whether for soil fertility, pest control or other ecosystem components, is dependent on the overall maintenance of integrated ecosystem function. This concern with sustainability as well as productivity has become a major focus for agricultural research and development in the last decade. TSBF has been taking the lead in promoting a GCTE activity to investigate the factors determining the capacity of agroecosystems to respond to global change, with a emphasis on land-use change and climatic uncertainty. The Programme hosted a workshop on this theme funded by IDRC (Canada) in Kenya in May 1994. The main focus was on multi-species agroecosystems which are characteristic of so much of tropical agriculture.
The effects of global change on natural ecosystems and on the intensive monocultures typical of the Northern hemisphere are being researched in many countries. Most of the world's farmers, however, depend for their food and income on so-called "multi-species" or "complex" farming systems such as multiple cropping systems, complex crop and fallow rotational systems, agroforestry systems, and mixed livestock and arable systems. The social and economic circumstances under which multi-species farming systems are managed is in most cases quite different from the "agribusiness" context of intensive monocultures. For most of the farming communities dependent on multi-species agriculture, the whole family livelihood and culture are embedded in the farming practice and its environment rather than being determined by the externalities of the market economy.
At the same time, current concerns with the sustainability of agricultural practices has led to an increased interest in these types of system as a means of stabilising food production and conserving natural resources and environments, particularly in the tropics. A new dimension is added to this goal by the accelerating rate of global change in climate, land degradation, and atmospheric composition.
The workshop came up with recommendations for four areas of research:
* Experimental studies on the relationship between agroecosystem complexity, productivity and sustainability. * Long-term agroecological experiments and on-farm monitoring for global change research * Modelling complex agricultural systems. * Collaborative studies with the Human Dimensions Programme on farmers' strategies for combating change.
44 TSBF Report: 1994
Soil biodiversity and agricultural change. 4 SOM Fraction Following the Shaba workshop TSBF has o \ obtained funds from UNEP to develop a labile component project within the first of these supply areas. TSBF scientists from across the nutrient stable buffering " globe are planning a collaborative project to investigate the relationships between water \ stable buffering agricultural intensification, soil biodiversity \ and agroecosystem function. soil structure \ labile + maintenance stable Soil organic matter management. miscellaneous \ many One of the major concerns of global change > (sorption, pest reduction, etc.) research is to diminish the rate of carbon — level of land use intensification emissions, in the form of carbon dioxide or nutrient + nutrient + liming + artificial hydrop- methane, in order to limit the 'greenhouse loss inputs + Irrigation media poriics effect' on the world's climate. A major lost value of C resource functions source of carbon emission is the oxidation of soil organic matter. The net loss of carbon Figure 27. The functional role of soil organic through this pathway also has a negative matter within a system depends on the intensity effect on soil fertility an issue addressed by with which that system is managed. TSBF's SOM Theme (Figure 27).
TSBF has therefore joined with other scientists to participate in GCTE activities concerned with investigating the mechanisma which promote sequestration of carbon in soil. As part of this activity TSBF organised and co-hosted, with GCTE, ICRAF, ISSS, and UNEP a workshop in Nairobi on the topic of 'Management of carbon in tropical soils under global change: science' practise and policy'. The output of the meeting will be published in a series of papers in a special issue of Geoderma. More importantly the workshop was able to provide good guidelines for future research in SOM dynamics, the most strategic area of TSBF's research.
There is an increasing awareness that the maintenence of soil fertility occupies a central role in global and atmospheric changes.
45 TSBF 1994 THE MACROFAUNA NETWORK
The Macrofauna network obtained a three-year renewal in funding from the EC/STD Programme for 1 994-1 996, and was expanded to include three more research teams in India, Martinique, and The Netherlands. In the additional network countries of Brazil, Cuba, Congo and Senegal, funding is provided through other means but the research continues to be coordinated through the network.
The main objectives of the network are to research the improvement of plant production and conservation of soil fertility through the introduction of selected earthworm species; to extend experimental results to farmer s fields and check for social acceptability and economic feasibility; and to form an international group able to face the increasing need for research in tropical soil biology. Six research activities are ongoing within the network: the development of databases of earthworm species and communities to allow a better knowledge of the existing fauna; the basic ecological studies of species with large environmental tolerance; the effects of selected earthworm species on soil processes at different scales of time and space; experimentation on earthworm introduction in farmer s fields at Yurimaguas, Peru; the regeneration of degraded soils in intensive tea plantations in India and degraded Vertisols in Martinique; and the description and quantification of the socio-economic value of earthworms in low-input agricultural systems (Figure 28). Some of the results of network research to date may be summarised as follows:
* All types of managed land use result in decreased soil biodiversity, however, systems that include a mixture of trees and grasses tend to be more resilient. * Annual cropping has negative impacts on soilfauna communities. * The bio,nass of endogeic earthworms in pastures is as great as 3 TIha but when the pasture was established in cleared forest , the earthworm communities were not diverse. This is not the case when pastures were developed from natural savannas.
The function of biodiversity in soil function is becoming an important theme for research in the MACROFAUNA network. The recognition that soil organisms having opposite effects may regulate soil aggregation has opened new research avenues. For example, recent studies of processes of soil physical degradation in Amazonian pastures show that soil compaction might result from the dominance of a single "compacting" earthworm species over "decompacting" species.
70 E.J Totonacs 60 Nahuas cJ Popolucs 0 50 0 40 C 0 30 0 I- ci) 20 a) E 10 'I- 0 - yes no uncertain yes no uncertain Do earthworms provide benefits? Do earthworms have harmfuL effects?
Figure 28. Farmer perception of the beneficial and detrimental effects of earthworms in cropped soils in three localities of Veracruz, Mexico.
46 TSBF 1994
AtNet scientists assemi led ar Egerton University in Kenya during September 1994 participate to in the Data Analysis, Interpretation and Scientific Writing Workshop.
TRAINING BY TSBF
Training in TSBF research approaches and scient(fic methods continues to be an important component of Headquarters supportfor the regional networks and other collaborators. During the past two years, TSBF has conducted training in laboratory methods, data interpretation and use of the CENTURY Model. Training in Laboratory Methods in Soil and Plant Analysis, Kawanda Agricultural Research Station, Uganda, 2-14 February 1993. This workshop was funded by the Rockefeller Foundation through the IITA component of the Uganda Banana Project in order to offer training to technicians and professional staff from Kawanda Station and Makerere University in standardised, time-efficient analytical methodologies. An additional objective was to identify research bottlenecks within those laboratories. J. Robert Okalebo and Kenneth Gathua from the Soil Chemistry Laboratory, Kenya Agricultural Research Institute, Muguga conducted this training workshop along with Dr. Mateete Bekunda of the Soil Science Department, Makerere University. Paul Woomer assisted through presentations on quality control and data management. AfNet Data Analysis, Interpretation and Scientific Writing Workshop, conducted at CIMMYT/KARI/Egerton University CMIRT Unit, Egerton University during September 15- 23, 1994. During previous AfNet meetings, participants had asked that a training activity be organised to provide training in the use of computer software packages to analyze and interpret data and to assist TSBF scientists prepare scientific papers from their analyses. Fourteen network scientists from six African nations assembled for the eight day workshop which covered topics ranging from the use of spreadsheet, statistical and graphics software packages, approaches to transforming and analyzing litter decay results, the manuscript drafting and editorial process and journal instructions to submitting authors. Several manuscripts were drafted and refined during the workshop and course materials assembled into a manual for use in curriculum development. Application of Simulation Models to Shifting Cultivation Systems, Bogor, Indonesia; Nkolbison, Cameroon and Puerto Vehlo, Brazil between August and November, 1994. A contribution by TSBF to the Alternatives to Slash & Burn Consortium is the application of simulation modelling to shifting cultivation systems. The model selected for this purpose is CENTURY ver 3.0 and during the later months of 1994, training workshops were conducted in which the model was installed, site data files developed and longer-term projections run based on current and alternative farmer practices. Through the use of simulation models, it is hoped that the impacts of current shifting agricultural and alternative practices may be predicted.
47 TSBF 1994
Recent publications by TSBF include The TSBF Handbook of Methods (2nd Edition), The Biological Management of Tropical Soil Fertility and Methods of Soil and Plant Analysis.
RECENT TSBF PUBLICATIONS
An important TSBF Headquarters staff activity is the compilation, synthesis and publication of experimental methods and research findings of network scientists.
Tropical Soil Biology and Fertility: A Handbook of Methods (2nd Edition). Edited by Jo Anderson and John Ingram, published by CAB International (Wallingford, UK), 221 pp. The TSBF Handbook of Methods was first published in 1989 as a means of assisting network cooperators in standardised site characterisation. Subsequently, these methods were tested in a wide range of field and laboratory environments which resulted in revision of TSBF standardised methods. Presently, this book consists of 7 chapters and 15 appendices prepared by 38 contributors on TSBF philosophy, site characterisation, field measurements, laboratory practice and quality control. A must for any soils, ecology or natural resource laboratory.
The Biological Management of Tropical Soil Fertility. Edited by Paul Woomer and Mike Swift, published by J. Wiley & Sons (Chichester, UK), 243 pp. This book reports on the first five years of research by TSBF scientists, containing nine multi-author chapters produced by a total of 34 contributors. Topics coved in this book include an overview of soil biological processes, state-of-the-arts reviews of the TSBF research themes, use of models and the integration of process research with farm practice. The book is intended as a basic text on sustainable soil management for the disciplines of soil science, agronomy, forestry and ecology.
Laboratory Methods of Soil and Plant Analysis: A Working Manual. Written by Robert Okalebo, Kenneth Gathua and Paul Woomer, published by TSBF Nairobi, 88 pp. During February 1993, TSBF was asked to conduct a workshop on analytical methods at the Kawanda Research Station, Uganda in support of the Banana Programme. This book is based upon the manual prepared for that workshop and is intended for use by technicians and undergraduate students. The topics covered in the manual include laboratory safety, quality control, sample preparation, soil physical and chemical properties, organic matter fractionation.
Tropical Soil Biology and Fertility Research: South Asian Context. Edited by P.S. Ramakrishnan, K.G. Saxena, Mike Swift and Paul Seward, published by G.B. Pant Institute of Himalayan Studies and Development, Kosi, India, 147 pp. This book resulted from the Inaugural TSBF Programme-South Asian Workshop held in India during April 1992. The book consists of two sections, the first being an explanation of the TSBF Research Themes within the South Asian context and the second section describing two case studies from India.
48 TSBF Repoil: 1994 SELECTED PUBLICATIONS BY TSBF SCIENTISTS
Publication in the international literature is an essential component of all research programmes. TSBF encourages all scientific staff and participating network scientists to disseminate their work through the highest quality journals and books. TSBF Headquarters maintains a bibliographic data base of TSBF and other contributions to the scientific state-of-the-arts and periodically distributes updates of this data base throughout the networks.
JOURNAL ARTICLES
Anderson, J.M. 1991. The effects of climate change on decomposition processes in grassland and coniferous forests. Ecological Applications 1:326-347. Barois, I. 1992. Mucus production and microbial activity in the gut of two species of Amynthas from cold and warm tropical climates. Soil Biology and Biochemistry, 24:1507-1510. Barois, I., Blanchart, E., Lavelle, P., Toutain, F. and Villemin, G. 1992. Transformation of the soil structure through Pontoscolex corethrurus (Oligochaeta) intestinal tract. Geoderma 56:57-66. Barrios, E. and Herrera, R. 1994. Nitrogen cycling in a Venezuelan tropical seasonally flooded forest: Soil nitrogen mineralization and nitrification. Journal of Tropical Ecology 10:399- 416. Bekunda, M.A., Smethurst, P.J., Khanna, P.K. and Willett, I.R. 1990. Effects of post-harvest residue management on labile soil phosphorus in a Pinus radiata plantation. Forest Ecology and Manage,nent 38:13-25. Blanchart, E. 1992. Restoration by earthworms (Megascolecidae) of the macroaggregate structure of a destructured savanna soil under field conditions. Soil Biology and Biochemistry 24:1587-1594. Blanchart, E., Bruand, A. and Lavelle, P. 1993. The physical structure of casts of Milisonia anomala (Oligochaeta:Megascolecidae) in shrub savanna soils (Côte d' Ivoire). Geoderma 56: 119-132. Brown, S., Hall, C.A.S., Knabe, W., Raich, J., Trexler, M.C. and Woomer, P. 1993. Tropical forests: their past, present and potential future roles in the world's carbon budget. Water Air and Soil Pollution 70:71-94. Carter, M.R., Parton, W.J., Rowland, I.C., Schultz, J.E. and Steed, GR. 1993. Simulation of Soil Organic Carbon and Nitrogen Changes in Cereal and Pasture Systems of Southern Australia. Australian Journal of Soil Research 31:481-491. Carter, S.E. and Jones, P.G. 1993. A model of the distribution of Cassava in Africa. Applied Geography 13:353-371. Cuevas, E., Brown, S. and Lugo, A. E. 1991. Above- and below-ground organic matter storage and production in a tropical pine plantation and a paired broadleaf secondary forest. Plant and Soil 135:257-268. Dalal, RC. 1992. Long-term trends in total nitrogen of a Vertisol subjected to zero-tillage, nitrogen application and stuble retention. Australian Journal of Soil Research 30:233- 231. Fragoso, C. and Lavelle, P. 1992. Earthworm communities of tropical rain forests. Soil Biology and Biochemistry 24:1397-1408. Izac, A-M.N. and Swift, M.J. 1994. On agricultural sustainability and its measurement in small- scale farming in sub-Saharan Africa. Ecological Economics 11:105-125. Lauenrotb, W.K., Urban, D.L., Coffin, D.P., Parton, W.J. Shugart, H.H., Kirchner, T.B. and Smith, TM. 1993. Modeling vegetation structure-ecosystem process interactions across sites and ecosystems. Ecological Modelling 67:49-80.
49 TSBF 1994
Lavelle, P., Blanchart E, Martin, A., Martin, S., Barois, I., Toutain, F., Spain, A. and Schaefer, R. 1993. A hierarchical model for decomposition in terrestrial ecosystems. Application to soils in the humid tropics. Biotropica 25:130-150. Lavelle, P., Melendez, G., Pashanasi, B. and Schaefer, R. 1992. Nitrogen mineralization and reorganization in casts of the geophagous tropical earthwonn Pontoscole,x corethurus (Glossoscolecidae). Biology and Fertility of Soils 14:49-53. Motavalli, P.P., Palm, C.A., Parton, W.J., Elliot, E.T. and Frey, S.D. 1994. Comparison of laboratory and modelling simulation methods for estimating soil carbon pools in tropical forest soils Soil Biology and Biochemisry 26:935-944. Murwira, H.K. and Kirchmann, H. 1993. Nitrogen dynamics and maize growth in a Zimbabwean sandy soil under manure fertilization. Communications in Soil Science and Plant Analysis 24:2343-2359. Parton, W.J., Scurlock, J.M., Ojima, S.D., Gilmanov, T.G., Scholes, R.J., Schimel, D.S., Kirchner, T., Menaut, J.C., Seastedt, T., Garcia Moya, E., Kamnalrut, A. and Kinyamario, J. 1. 1993. Observations and modelling of biomass and soil organic matter dynamics for the grassland biome worldwide. Global Biogeochemical Cycles 7:785-809. Pashanasi, B. 1992. Effect of inoculation with the endogeic earthworm Pontoscolex corethrurus (Glossoscolecidae) on N availability, soil microbial biomass and the growth of three tropical fruit tree seedlings in a pot experiment Soil Biology and Biochemistry 24: 1655- 1659. Reddy, V.R. and Pasha, M. 1993. Influence of rainfall, temperature and some soil physico- chemical variables on seasonal population structure and vertical distribution of earthworms in two semi-arid tropical grassland soils. International Journal of Biometeorology 37:19-26. Sanginga, N., Mulongoy, K. and Swift, M.J. 1992 Contribution of soil organisms to the sustainability and productivity of cropping systems in the tropics. Agriculture, Ecosystems and Environment 41:135-152. Spain, A.V., Lavelle, P. and Mariott, A. 1992. Stimulation of plant growth by tropical earthworms. Soil Biology and Biochemistry 24:1629-1633. Szott, L.T., Palm, C.A. and Davey, C.B. 1994. Biomass and litter accumulation under managed and natural tropical fallows. Forest Ecology and Management 67:177-190. Tiessen, H., Cuevas, E. and Chacon, P. 1994. The role of soil organic matter in sustaining soil fertility. Nature 371:783-785. Vermeulen, S.J., Woomer, P,, Campbell, B.M., Kamukondiwa, W., Swift, M.J., Frost, P.G,H., Chivaura, C., Murwira, H.K., Mutambanengwe, F. and Nyathi, P. 1q93. Use of SCUAF model to simulate natural miombo woodland and maize monoculture ecosystems in Zimbambwe. Agroforestry Systems 22:259-27 1. Woomer, P.L. 1993. The impact of cultivation on carbon fluxes in woody savannas of Southern Africa. Water Air and Soil Pollution 70:403-412.
BOOKS, BOOK CHAPTERS AND PROCEEDINGS
Campbell, B.M., Bradley, P.N. and Carter, S.E. 1994. Sustainability and peasant farming systems; Some observations from Zimbabwe. Stockholm Environment Institute, Stockholm. 13 pp. Carter, SE., Bradley, P.N., Franzel, S. and Lynam, J.K. 1994. Spatial variation as a factor in natural resource management research. Stockholm Environment Institute, Stockholm. 16 pp. Lavelle, P., Spain, A.V., Blanchart, E., Martin, A. and Martin, S. 1992. The impact of soil fauna on the properties of soils in the humid tropics. In: (P.A. Sanchez and R. Lal, eds) Myths and Science of Soils of the Tropics, SSSA Special Publication, Madison, Wisconsin, pp.157-185. Lavelle, P., Gilot, C., Fragoso, C. and Pashanasi, B. 1994. Soil fauna and sustainable land use
50 TSBF Report: 1994
in the humid tropics. In: (D.J. Greenland & I. Szabolcs, eds) Soil Resilience and Sustainable Land Use. CAB International, Wallingford, U K. pp.291-308. Okalebo, J.R., Gathua, K.W. and Woomer, P.L. 1993. Laboratory Methods of Plant and Soil Analysis: A Working Manual. TSBF Programme, Nairobi, Kenya. 88 pp. Palm, C.A., Swift, M.J. and Woomer, P.L. 1994. Biological dynamics in slash-and-bum agriculture. In: (P.A. Sanchez and H. Houten, eds) Alternatives to Slash and Burn Agriculture. International Soil Science Society Symposium iD-6, Mexico. pp.78-92. Ramakrishnan, P.S. 1992. Agriculture and Sustainable Development. MAB Series Volume 10, UNESCO, Paris. 424 pp. Ramakrishnan, P.S. 1992. Ecology of shifting agriculture and ecosystem restoration. In: (M.K. Wali, ed) Ecosystem Rehabiltation. Volume 2. SPB Academic Publishing, The Hague, The Netherlands. pp. 19-35 Ramakrishnan, P.S., Saxena K.G., Swift M.J. and Seward P.D. 1993. Tropical Soil Biology and Fertility: South Asian Context. G. B. Pant Institute of Himalayan Environment and Development, Kosi, India. 147 pp. Sanchez, P.A., Woomer, P.L. and Palm, C.A. 1994. Agroforestry approaches for rehabilitating degraded lands after tropical deforestation. JIRCAS international Symposium Series 1:108-119. Saxena, K.G, Woomer, P.L. and Seward, P. D. 1993. Potential application of research in South Asian Regional Network. In: (P.S. Ramakrishnan et at., eds) Tropical Soil Biology and Fertility: South Asian Context. G.B. Pant Institute of Himalayan Environment and Development, Kosi, India. pp.61-76. Swift, M.J. 1993. Maintaining the biological status of soil:a key to sustainable land management? In: (D.J. Greenland & I. Szabolcs, eds) Soil Resilience and Sustainable Land Use. CAB International, Wallingford, UK. pp.235-248. Swift, M,J. and Anderson, J.M. 1992. Biodiversity and ecosystem function in agricultural systems. In: (E. D. Schultze and H. Mooney, eds) Biodiversity and ecosystem function. Springer-Verlag, Berlin. pp. 15-42. Woomer, P.L. 1994. Most probable number counts of soil microorganisms. in: (R. Weaver, ed.) Methods of Soil Analysis, Part 2. Biochemical and Microbiological Properties. American Society of Agronomy, Madison, USA. pp.59-79. Woomer, P.L. and M.J. Swift. 1994. The Biological Management of Tropical Soil Fertility. John Wiley & Sons, Chichester, UK. 243 pp. Woomer, P.L., Lekasi, J., Okelabo, R. and Palm, C.A. 1993. Principles and methods of soil fertility research in maize-bean cropping systems of the Eastern African Highlands. In (C. Wortmann & J.K. Ransom, eds.) Soil Fertility Research for Maize and Bean Production Systems in Eastern African Highlands. Network on Bean Research in Africa, Workshop Series No. 21, dAT, Dar es Salaam, Tanzania. pp.21-34.
THESES FOR UNIVERSITY DEGREES
Fragoso, C. 1993. Les Vers de Terre de 1 'Est et du Sud-Est Mexicains. Doctorate Thesis. Universite Paris VI, France. Gilot, C. 1994. Effets de l'introduction du Ver Geophage Tropical Milisonia anomala (Omodeo) en Systemes Cult ives sur les Caracteristiques des Sols et la Production Vegetate en Moyenne Cote d 'Ivoire. Doctorate Thesis. INAPG-Paris, France. King, A. S. 1994. Dinamica da Materia Organica em Foresta e Machambasde D?ferentes Idades apos Corte e Queima, na lisa da inhaca. Honours Thesis. Universade Eduardo Mondlane, Maputo, Mozambique. Murwira, H. 1993. Manure as a Resource in Communal Area Farming Systems. Doctorate Thesis. University of Zimbabwe, Harare, Zimbabwe. Wangari, N. 1994. Decomposition and Nutrient Release Patterns of Sesbania sesban and Lantana camara and use ofLantana as a Green Manure Source in Vegetable Production. M.Sc. Thesis, Sokoine University of Agriculture, Morogoro, Tanzania.
51 TSBFRepoit: 1994 TSBF BOARD OF MANAGEMENT AND IDRC CR01 HEADQUARTERS STAFF
11111111101111 1111 111 273868 TSBF Board of Management
Prof. M.P. Salema (Chairman), FAO/IAEA Joint Division, Vienna, Austria. Prof. P.S. Ramakrishnan (Vice-Chairman), Jawaharlal Nehru University, New Delhi, India. Prof. M.J. Swift (Director, officio), TSBF, Nairobi, Kenya. Prof. J.M. Anderson, Rothamsted International, Harpenden, UK. Dr. E. Cuevas, Centro de Ecologia, IVIC, Caracas, Venezuela. Dr. M. Hadley (er officio), Division of Ecological Sciences, UNESCO, Paris, France. Prof. R. Harwood, Michigan State University, USA Prof. O.W. Heal, Institute of Terrestrial Ecology, Edinburgh, UK. Mr. J.S.I. Ingram, IGBP/GCTE, Oxford, UK. Prof. P. Lavelle, Laboratoire d'Ecologie des Sols Tropicaux, ORSTOM, Bondy, France. Dr. R.J.K. Myers, International Board for Soils Research and Management, Thailand. Dr. F.N. Muchena, National Agricultural Research Laboratories, KARl, Kenya. Prof. H. Scharpenseel officio), ISSS, University of Hamburg, Germany. Dr. T. Younes officio), IUBS, Paris, France.
The Nairobi Headquarters Staff of TSBF
TSBF Headquarters are located at UNESCO's Regional Office for Science and Technology in Africa (ROSTA) which is located at the United Nations Regional Office complex, Gigiri, Kenya. Current staff (above) include Mike J. Swift (Director), Paul D. Seward (Executive Officer), Simon E. Carter (Resource Integration), Eve Crowley (Rockefeller Fellow), Cheryl A. Palm (Synchrony), Paul L. Woomer (Soil Organic Matter), Charles Ngutu (Finance Officer), Alice Ndung'u, Mary Kinyanjui, Juliet Ogala (Secretaries), Alan Kwabiah (PhD student), Gerald Gacheru and Nancy Wangari (Research Assistants).
52 HQ core activities are supported primarily by the Rockefeller Foundation and IDRC (Canada). Grants are also received from UNESCO-Man and the Biosphere Programme, UNESCO-ROSTA, UNDP, UNEP, ODA, SAREC (Sweden) and the International Union of Biological Sciences (hUBS). TSBF is hosted at the UNESCO Regional Office for Science and Technology for Africa (ROSTA) in Nairobi.
Further information about the TSBF Progranune can be obtained from:
The Programme Director Tropical Soil Biology and Fertility Programme do UNESCO-ROSTA P0 Box 30592 Nairobi Kenya
Telephone: +254 2 622584 / 622659 Telex: 22275 UNESCO KE FAX: +254 2 521159 E-mail: [email protected]
Back cover photographs: Livestock manure applied in rows prior to incorporation into the soil by communal farmers in Motoko, Zimbabwe (left). Computer training of Indonesian scientists in the use of the CENTURY model in conjunction with the Alternatives to Slash & Burn (right). TSBF: THE TROPICAL SOIL BIOLOGY AND FERTILITY PROGRAMME
The TSBF Programme aims to contribute to human welfare and the conservation of environments in the tropics by developing adoptable and sustainable soil management practices that integrate the biological, chemical, physical and socioeconomic processes that regulate soil fertility and optimise the use of organic and inorganic resources available to the land-users. TSBF is a voluntary participatory international research programme whose members are committed to the concept that the fertility of tropical soils is controlled by biological processes and can be managed by the manipulation of these processes. Membership of TSBF is open to any scientist conducting research in the tropics within the framework of the TSBF research strategy. TSBF was initiated in 1984 under the patronage of the Man and Biosphere programme of UNESCO and the Decade of the Tropics initiative of the International Union of Biological Sciences (LUBS). The programme was founded with the aim of promoting the biological management of soil fertility as an essential component of sustainable agricultural development.
ISBN 9966-9892-1-9