id5736109 pdfMachine by Broadgun Software - a great PDF writer! - a great PDF creator! - http://www.pdfmachine.com http://www.broadgun.com
ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES
FACULTY OF SCIENCE ENVIRONMENTAL SCIENCES PROGRAM
Assessment of Soil Acidity in Different Land Use Types: The Case of Ankesha Woreda, Awi Zone, Northwestern Ethiopia
By
Tessema Genanew
A Thesis Submitted to School of Graduate Studies of Addis Ababa University in the Partial Fulfillment of the Requirements for Degree of Master of Science in Environmental Science
Addis Ababa November 2008
i ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES FACULTY OF SCIENCE ENVIRONMENTAL SCIENCES PROGRAM
Assessment of Soil Acidity in Different Land Use Types: The Case of Ankesha Woreda, Awi Zone, Northwestern Ethiopia
By
Tessema Genanew
A Thesis Presented to School of Graduate Studies of Addis Ababa University in the Partial Fulfillment of the Requirements for Degree of Master of Science in Environmental Science
Advisor: Dr. Mekuria Argaw Environmental Sciences Program, Faculty of Science Addis Ababa University
Co- Advisor: Dr. Enyew Adgo Agriculture and Environmental Sciences Department Bahir Dar University
Addis Ababa November 2008
ii ACKNOWLEDGEMENTS
I want to express my sincere thanks to my advisor Dr. Mekuria Argaw for his guidance as well as persistent support in different aspects through out my study. I have benefited a lot from his wealth of experience. I am very grateful to my second advisor Dr. Enyew Adgo his continuous support and constructive comments on the proposal and on the final thesis. I am also greatly indebted to Mr. Alayu Yalew for his industrious support by providing camera, flash, transport service and logical suggestions during the fieldwork.
Special thanks go to Mr.Tamiru Misganaw and Mr. Kehali Jembere for assistance they offered during soil sample analysis. I am very grateful to the Horn of Africa Regional Environmental Centre Demand Driven Action Research and Network, and Addis Ababa University, which made this study possible by financing all the expenses required for the study. The kind collaboration from Awi Zone Environmental Protection, Land Use and Land Administration Department and Ankesha Woreda Agriculture and Rural Development office staff members during my fieldwork is also very much appreciated.
I am thankful to my families, especially my brothers Abebe Genanew, Michael Genanew and Abraham Bekele, and all my friends for supporting me in all means they could. Last but not least, my special thanks are reserved for my mother, w/o Zabishwork Akalu, for her strong moral support and good wish to my achievement. Above all, I admire God for making everything possible.
i TABLE OF CONTENTS
ACKNOWLEDGEMENTS...... I TABLE OF CONTENTS...... II LIST OF TABLES...... IV LIST OF FIGURES ...... V LIST OF APPENDICES...... VI LIST OF ACRONYMS ...... VII ABSTRACT...... VIII 1. INTRODUCTION ...... 1 1.1 Background and Justification...... 1 1.2 Statement of the Problem...... 2 1.3 Objectives...... 3 1.3.1 General Objective ...... 3 1.3.2 Specific Objectives ...... 3 1.4 Significance and Scope of the Study...... 3 2. LITERATURE REVIEW ...... 5 2.1 Overview of Soil Acidification ...... 5 2.2 Status and Distribution of Acid Soils in Ethiopia...... 7 2.3 Main Causes of Soil Acidity...... 8 2.3.1 Rain fall and Leaching...... 8 2.3.2 Acidic Parent Materials...... 9 2.3.3 Organic Matter Decay /Dissociation/...... 9 2.3.4 Nutrient Removal by Crop Residue from Farm Land ...... 10 2.3.5 Inappropriate Use of Nitrogenous Fertilizers ...... 11 2.4 Impact of Land Use and Management Practice on Soil Acidification...... 11 2.5 Soil Acidity and Nutrient Availability to Plants...... 12 2.6 Effect of Soil Acidity on Soil Fauna anda ...... 15 2.7 Management Options of Soil Acidity Problems ...... 16 2.7.1 Agricultural Lime Application...... 17 2.7.2 Selection of Acidity Tolerant Crop Variety...... 18 3. MATERIALS AND METHODS...... 19 3.1 The Study Area ...... 19 3.1.1 Location and Description...... 19 3.1.2 Climate...... 20
ii 3.1.3 Soil and Geology...... 21 3.1.4. Land Use and Farming Systems ...... 22 3.2 Methodology ...... 24
3.2.1 Study Design...... 24 3.2.1.1 Soil Survey...... 25 3.2.1.2 Socioeconomic Survey...... 29 3. 3 Data Analysis and Statistical Procedures ...... 31 4. RESULTS AND DISCUSSION...... 32 4.1 Soil Acidity Status of Different Land Uses...... 32 4.1.1 Soil pH Level ...... 32 4.1.2 Exchangeable Acidity and Acid Saturation ...... 34 4.1.3 Exchangeable Bases and CEC ...... 37 4.1.4 Soil Fertility Parameters ...... 39 4.1.4.1 Available Phosphorous and Available Potassium...... 40 4.1.4.2 Organic Matter and Nitrogen...... 41 4.2 Soil Acidity and Soil Property Relationships in Different Land Uses...... 42 4.3 Farmers’ Perception of Soil Acidity and Their Management Practices...... 45 4.3.1 Socioeconomic Characteristics of Households...... 45 4.3.2 Perceived Causes and Indicators of Soil Acidification...... 46 4.3.3 Farmers’ Response to Soil Acidity Problems and Their Coping Mechanisms...... 50 4.3.4. Farmers'Perception on Eucalyptus Plantation and Soil Acidity ...... 53 5. CONCLUSIONS AND RECOMMENDATIONS ...... 55 5.1 Conclusions...... 55 5.2 Recommendations...... 56 REFERENCES ...... 58 APPENDICES ...... 66
iii
LIST OF TABLES
Table 1. Approximate amount of calcite and dolomites removed from the soil by crops...... 10 Table 2. Aailable forms of essential plant nutrients...... 13 Table 3.Optimum pH requirement of some crop plants...... 13 Table 4. Descriptive terms for various pH ranges...... 15 Table 5. Crop tolerance for permissible acid saturation...... 18
Table 6 .Values of pH (KCl) and pH (H20) (1:2.5 soil-liquid ratio) in different land uses...... 33 Table 7.Values of exchangeable acidity and acid saturation in different land uses ...... 36 Table 8. Values of exchangeable bases,effective cation exchange capacity (ECEC) and cation exchange capacity (CEC) in different land uses ...... 39 Table 9.Values of available phosphorus and available potassium in different land uses...... 40 Table 10.Value of organic matter and total nitrogen of soils different land uses...... 42 Table 11. Correlation coefficients(r) between soil acidity and soil property ...... 44 Table 12 . Characteristics of respondents in Hateta and Denzuria Kebeles...... 45 Table 13. Perception of farmers on existence of soil acidity problem ...... 46 Table 14. Farmers’ response for probable causes of crop yield reduction ...... 49 Table 15. Comparison of crop yield in quintal per hectare /qt/ha/ in 1980s and 2007...... 49 Table 16. Farmers’ response for dominant plantation tree in surveyed households ...... 54
iv LIST OF FIGURES
Figure 1. The relation between soil pH and plant nutrient availability...... 14 Figure 2. Map and location of the study area in Amhara Regional State ...... 19 Figure 3. Mean annual rainfall of the study area based on nearby rain fall stations...... 21 Figure 4. Flow chart of the study design...... 24 Figure 5. Soil sampling sites in different land use types...... 26 Figure 6. Level of acid saturation in different land use types at two locations...... 37 Figure 7. Farmers’ response for causes of soil acidity ...... 47 Figure 8. Pie chart for response of farmers towards the use of crop residues...... 48 Figure 9. Farmers’ coping mechanisms of soil acidity ...... 50 Figure 10. Farmers’ opinion for the purpose of acidic soil “Gibiz Merate” ...... 53
v
LIST OF APPENDICES
Appendix 1. Mean annual rainfall of three stations in Gojjam ...... 66 Appendix 2. Brief description of the sampling sites ...... 67 Appendix 3. Laboratory analysis results for soil properties at Hateta Kebele ...... 68 Appendix 4 . Laboratory analysis results for soil properties at Denzuria Kebele ...... 69 Appendix 5. Analysis of variance of soil properties at Hateta Kebele ...... 70 Appendix 6. Analysis of variance of soil properties at Denzuria Kebele ...... 72 Appendix 7. Analysis of farmers’ perception ...... 74 Appendix 8. Household survey questionnaires ...... 75
vi
LIST OF ACRONYMS
ANOVA Analysis of Variance ASP Acid Saturation Percentage CEC Cation Exchange Capacity C: N Carbon to Nitrogen Ratio cm centimeter cmol (+)/kg centimole of cations per kilogram of soil DAP Diammonium Phosphate Fertilizer EDTA Ethylene diamine tetra acetic acid EMA Ethiopian Mapping Agency FAO Food and Agriculture Organization in United Nation EFAP Ethiopian Forestry Action Program EIAR Ethiopian Institute of Agriculture Research EMS Environmental Management System ENRC Environment and Natural Resource Committee GIS Goegraphic Information System Kg Kilogram Km Kilometer LSD Least Significant Difference m.a.s.l meter above sea level MoARD Ministry of Agriculture and Rural Development OC Organic carbon oC Degree Celsius pH Power of Hydrogen PA Peasant Association RELMA Regional Land Management Unit SE Standard Error of the Mean SNNP Southern Nation Nationality and People SOM Soil Organic Matter
vii ABSTRACT
The aim of this study was to assess the status of soil acidity levels, probable causes and to understand farmer’s practices at Ankesha Woreda. Soil samples were collected from four different land use types: cultivated fields, backyard fields, Eucalyptus plantation and grazing lands. Composite samples were taken from a depth of 0-20cm representing different land uses at two peasant associations and analyzed in laboratory for a range of soil properties. Socioeconomic survey was conducted in order to understand farmers’ perception on soil acidity problem and their copping mechanisms. The results revealed that the soils in all land uses are strongly acidic (pH<5.5) at both sites except backyard soils. The backyard soils had a statistically significant (p<0.01) higher soil pH and lower acid saturation than soils under the other three land uses. Furthermore, highly significantly higher (p<0.01) exchangeable bases (Ca2+, Mg2+, K+, Na+), effective cation exchange capacity, available phosphorous and available potassium was obtained from backyard fields than soils of other land uses. Texture analysis revealed that all the soils lie in texture classes between loams to clay loam. A highly significant strong negative (p<0.01) correlation of acid saturation with exchangeable bases, soil pH, CEC and available macronutrients, imply that acidity affects major soil fertility parameters. Local farmers have understood the problem of soil acidity on their farmland, locally; they called such land ‘Gibiz Merate,’ meaning ‘inactive’. They perceived that acidic parent material, high rainfall followed by erosion and intensively continuous cultivation are the probable causes for soil acidity. The status of soil acidity in cultivated field is beyond (>40%) acidity tolerance limit of locally produced crops in the area. In general, the difference in level of acidity in different land uses is more likely due to the differences in the intrinsic management systems. Thus, their action to cope up with the problem focused on use of farmyard manure around the homestead garden, shift the cropland to Eucalyptus plantation otherwise left for grazing. The study underscores that soil acidity problem is critical in Awi zone, and calls the need for immediate intervention to amend the soil for crop production. Moreover, special attention should be given to improvements on land management practices for sustainable productivity of soils in different land use types.
Keywords: Ankesha Woreda, Land uses, Management practices, Perception, Soil acidity
viii 1. INTRODUCTION
1.1 Background and Justification
Ethiopia has one of the oldest agrarian cultures in the Sub-Saharan Africa with large agriculture potential. Agriculture is not only the backbone of the economy but also a major occupation for nearly 85% of the population. Furthermore, long-term economic development and poverty alleviation programs in Ethiopia are designed to be based on development in the agricultural economy (EFAP, 1994; Gete Zelleke, 2003).
The survival and wellbeing of human beings in countries with subsistence agriculture and centuries old farming practices such as Ethiopia depend on the extent of maintaining soil fertility and other soil quality parameters (Heluf Gebrekidan and Wakene Negassa, 2006). In most parts of the country, the dependency on farming is extremely high, with 90% of population being entirely dependent on agriculture. However, farm productivity is low as the result of lack of agricultural inputs, outdated farming methods, widespread of land degradation, overgrazing, soil erosion, uncertain land tenure, and recurrent droughts, all in combination with high population pressure (RELMA, 2005).
The rate of soil quality degradation depends on land use systems, soil types, topography, and climatic conditions. Land uses have significant influences on soil quality indicators, particularly at the surface horizon. Soil pH, CEC, total N and OC, different forms of P, exchangeable bases, and available micronutrients were affected due to intensive cultivation and use of acid forming inorganic fertilizers for the past three decades in western Ethiopia (Wakene Negassa and Heluf Gebrekidan, 2003).
Soil acidification is, among the important environmental factors, emerging as an important land degradation issue. It is significant ecological process and one of the world’s major soil management problems. In natural process, soil acidity is advanced weathering-stage of soils and/or depletion of primary minerals in soils on geomorphologically stable landforms in humid environments (Richter and Markewitz, 2001). It is a process by which soil pH decreases over time. Soils can be acidified under natural conditions over thousands of years especially in high rainfall areas. Moreover, they can also acidify rapidly over a few years under intensive agricultural practices (Wakene Negassa and Heluf Gebrekidan, 2003).
1
Research interest in soil acidity increased in the 1970s because of the problems associated with acid rain (Reuss and Johnson, 1986). Currently there is a renewed interest in soil acidity because of the set-aside policy where by agricultural land is taken out of production. In tropical regions, soil acidity is major problem, which can have pedogenic or anthropogenic causes. The upland soils are nevertheless considered the largest remaining potential for future agricultural development (Spark, 2002).
The western and southern parts of Ethiopia, are dominantly covered by soils with pH<5.5 (Schlede, 1989). In this area, the annual rainfall exceeds to potential evaporation/ET/. Similarly, the soils in areas such as Nedjo, Diga, Gimibi and Bedi in Oromiya, Chencha and Sodo in SNNP, and Gozamin and Senan Woreda in Eastern Gojjam and Awi zone in West Amhara region have acidic problems in the soil (MoARD, 2006). Particularly, the highly weathered and leached Acrisols of Injibara area (Awi Zone) have strong acid reaction (4.81) (Yihenew Gebreselassie, 2002).
1.2 Statement of the Problem
The extent of soil acidity and rates of acidification are receiving interest in Awi zone. Even though soil acidity is identified as an issue requiring urgent attention in the western part of Ethiopia, information on the effect of land use type and management practices on soil fertility parameters in the country, particularly, Awi zone is very limited. The causes and extents of the problem in that specific area has not been identified and quantified.
As the result of this knowledge gap, farmers remain with one or two relatively acid tolerant crops to sustain their life and the problem is continuing. Productivity of most cereals is low and yield reduction becomes frequent. The low productivity of crops in that area exposes the farmers to food scarcity and indebtedness with credits as well as seasonal labor. The reasons for the yield reduction associated with soil acidity and management practices that help to overcome soil acidity and/or aggravate acidity problems are not clearly identified and described.
Farmers and development agents didn’t know of existence of acidic soil in the area until recent years, because there is no visible specific symptom on the crop, except reduction in
2 yield. Moreover, no one identifies which land use type is more acidic. Likewise, soil properties, such as exchangeable acidity, acid saturations, pH, exchangeable bases, CEC, texture, available P, available K, total N and organic matter of the soil and their relationships to soil acidity have not been analyzed and quantified. This study tries to fill the gap of knowledge in soil acidity problems in the study area.
1.3 Objectives
1.3.1 General Objective
The overall aim of this study is to examine the status of soil acidity problems in different land uses and the same time to analyze the possible associated causes; and thereby to evaluate and understand the farmers’ soil management practices as well as their perceptions of the problem. Finally, based on the findings, the study will try to put forward possible soil management options to minimize soil acidification in the different land uses in the study area.
1.3.2 Specific Objectives
. To evaluate the extent of soil acidity problems in different land use types . To understand farmers’ practices and to assess if these practices overcome soil acidity and /or aggravate acidity problems . To suggest possible soil management options to improve soil acidity problem in the different land uses of the study area
1.4 Significance and Scope of the Study
As the problems of soil acidity have not been paid due attention in Awi Zone so far, this study will provide first-hand information on the impact of land use and management practices on soil acidification. Since the study addresses the status of soil acidity and the farmers’ management aspect of the problem, the results will be of crucial importance for the government to formulate appropriate policies for soil acidity amendments in the region. Agricultural research centers and extension workers will benefit from the outputs. Moreover, the results will be of use to concerned stakeholders (e.g., Development Agencies, Lime Industry Agencies), who try to initiate soil acidity amendments for
3 sustainable land use and soil productivity in the region. Overall, the study will strengthen public awareness on the status of soil acidification in different land uses in the region and bring about early protection measures. However, due to time constraints, this research work focused on status of soil acidity in different land uses at two Kebeles and might not represent the whole Woreda. Similarly, not all soil quality indicators were analyzed in laboratory.
This study addresses the acidity problems in different land uses in Ankesha Woreda and the thesis is organized into five chapters. The existing knowledge assessed in the literature review in chapter two, the conditions of the study area and the methodological framework of the research is described in chapter three. Results on soil acidity status and farmers’ perception on soil acidity problems presented and discussed in chapter four. Chapter five concludes from the major findings of the research and provides relevant recommendations for further research.
4 2. LITERATURE REVIEW
2.1 Overview of Soil Acidification
Acid soils are soils that have a pH of less than 7.0. Acidity is due to hydrogen (H+) ion concentrations in the soil. The higher the H+ concentration, the lower the pH will be. Soil acidification is a natural process whereby natural ecosystems operate over many thousands of years. However, under agricultural management, acidification can accelerate with the rate of change being detectable over decades. The rate of soil acidification depends on the rate of acid added to the soil and broadly related to soil type, rainfall and land use (Helyar, 1991). He also explained that soil acidity develops more rapidly on lighter-textured soils than on heavier clay soils; the lighter textured soils have a lower buffering capacity to changes in soil pH and often may be naturally acidic.
According to Schlede (1989) explanations, the most essential unfavorable fertility features of acid soils are: . Presence of greater quantities of exchangeable and soluble Al3+ and pH value less than 4.5 to 5.5. . Increased amount of soluble Mn2+ and Al3+ have toxicity effect on cultivated plants and correlated with lower K+, Ca2+ and Mg2+ consumption . Acid soils frequently are ‘inactive’ with fertilization; that is why the added fertilizers /NPK/ in spite of the nutrient deficiency of the soils do not effect yield increase or even decrease the yields. . As a rule, acid soils are poor in available Ca and Mg ion due to leaching in humid climate. Generally, the soil acidity can have impacts on agriculture, biodiversity, environment and the wider community in general due to the following reason: . Helpful soil microorganisms may be prevented from recycling nutrients (e.g. nitrogen supply may be reduced). . Phosphorus in the soil may become less available to plants, deficiencies of calcium, magnesium and molybdenum may occur. . The ability of plants to use subsoil moisture may be limited, Aluminium, which is toxic to plants and microorganisms, may be released from the soil, levels of manganese may reach toxic levels.
5 . Uptake by crops and pastures of the heavy metal contaminant, cadmium level may increase and increased nitrate contamination of groundwater. All these lead to reduction of water quality, reduced agricultural yields, and farm income and domestic/export earnings. Moreover, reduced options for agriculture and vegetative cover are leading to accelerated run-off and erosion, and irreversible clay structure damage (or hard setting), declining pH of streams, increased infrastructure costs, and decreased land values.
Mesfin Abebe (1998) reported that Acrisols/Oxisol, Nitosols/Ultisols and Alfisols, as moderately to intensively weathered soils, have limited in basic rocks that usually contain more easily weathered potassium. They have high level of exchangeable acidity. Schlede (1989) also reported that Acrisols and Nitosols, together comprising about 85% of the area covered by acid soils with pH <5.5 are the dominant soils units in Ethiopia. He explained that high rainfall areas increased leaching of basic cation nutrients and higher levels of plant production leading to increased acidification.
In accordance with the results of the technical report, Ethiopia Geomorphology and soils (1984), Acrisols are soils with usually weakly developed commonly pale topsoil horizons, having significant features of illuvial clay translocation in the subsoil horizons. Base saturation is generally low. Its pH value is usually below neutrality. It is formed under significant precipitation conditions /semi humid to humid / never under arid conditions. It is the results of strong weathering and depletion of bases by leaching.
The exchangeable acidity refers to the amount of H+ ions and Al3+ ion in cation exchange sites of negatively charged clay and organic matter fractions of the soil. Soil exchangeable acidity determines the amount of lime necessary to increase the soil pH (McLaren and Cameron, 1996). Al in soil solution reacts with water to produce H+ ion, thereby causing + 3+ acidity. Here Al acts as a “exchangeable acidity” bound H and Al that is not displaced or slowly displaced is called “non-exchangeable acidity’’. Example: Organically complexed Al, Al-hydroxyl cations, weathering of soil, bound Al3+
Hydrogen ion in soil solution is termed active acidity and is the acidity measured by common pH tests. Hydrogen and aluminum ions adsorbed on soil colloids are termed exchangeable acidity. Active acidity is due to the hydrogen ion concentration of soil
6 solution where as exchangeable acidity, refers to those hydrogen and aluminium ions adsorbed on soil colloids (Brady, 1984; Summer, 1992). Adsorbed H+ (Al3+) ions soil solution H+ (and Al3+) ions (Exchange acidity) (Active acidity)
The exchange acidity sometimes referred as ‘reserve’ acidity (Kolay, 1993). The main source of soil acidity includes; Hydrolysis of aluminum, Alumino-silicate clay dissociations, Organic matter dissociations, Carbonation, Nitrification, Sulfur oxidation and soil amendments. All these processes produce H+ ions, which causes soil acidity. Example:
Hydrolysis of aluminum 3+ 2+ + Al (soln.) + H20Al (OH) + H 2+ 2+ + Al (OH) + H20 Al (OH) + H 2+ + Al (OH) + H20 Al (OH) 3 + H Precipitate Each hydrolysis reaction librates H+ and lowers soil pH unless a source of OH- ion + + 2- represent with which the H ion react. Oxidation of NH 4 and S in soils by microorganisms also causes soil acidity: + - + NH4 + 3O2 2NO2 + 4 H + H2O (Bacteria involved is nitrosomonas). This reaction goes to nitrification process. - - 2NO2 + O2 2NO3 (A bacterium involved here is nitrobacter).
2.2 Status and Distribution of Acid Soils in Ethiopia
Geologically, Ethiopia lies at the northern end of the continental part of the Eastern Rift. Voluminous piles of mainly tertiary volcanic rocks occupy large parts of the country along the Rift Valley. Proterozoic marbles occur in the Western (Gojjam, Wollega, Illubabor, Kaffa) and Southern (Omo, Sidamo) parts of Ethiopia (Schlede, 1989). A general observation is that these resources occur in areas where strong to moderately acid soils (pH< 5.5) are dominant and marble deposits are well distributed over the area of acid soils that require liming materials to improve soil productivity (Schlede, 1989).
About 40.9% of Ethiopia is covered by strong to weak acid soils. From these 27.7% moderate to weak acids with pH 5.5-6.7 and 13.2% covered by strong to moderate acidic soils with pH <5.5 (Schlede, 1989). The western and southern parts of Ethiopia are
7 dominantly covered by soils with pH<5.5. Here leaching of cations in soils is most responsible for increased soil acidity (Schlede, 1989).
In moving from central (West Shoa) to Western Ethiopia (West Wellega), the degree of soil acidity that is measured in terms of acid saturation percentage is increased(ASP> 60). . In Western and Eastern Wellega zones, the large proportion exchangeable acidity was due to exchangeable aluminum while at West Shoa zone it was due to exchangeable hydrogen. The acidity problem in East and West Wellega zones of Oromiya region is critical (Abdenna Deressa et al., 2007).
2.3 Main Causes of Soil Acidity
Soil acidification is a naturally occurring process but escalated by human activity. Initially, each type of soil has a certain level of acidity depending upon its composition, native vegetation, and rainfall amounts; however, various factors over time cause changes in soil pH. Leaching, erosion, and crop uptake of basic cations (Ca2+, Mg2+, K+), decay of plant residues, and plant root exudates are all means by which the soil acidity is increased. However, a common source of acidity comes from H+ ions that are released when high levels of aluminum (Al3+) in the soil react with water molecules.
2.3.1 Rain fall and Leaching
Soil acidity is really a high rainfall problem (Slattery and Hollier, 2002). Excessive rainfall is an effective agent for removing basic cations over a long period. When water passing through the soil, it leaches basic nutrients (Ca and Mg). Here acidic cations replace basic cations. Leaching of basic cations (Ca, Mg, K and Na) from the soil, by heavy rainfall leaves acidic cations (Al3+, Fe2+) to remain in the soil. This is the reason for the occurrence of acidic soils in humid regions and alkaline or neutral soils in arid regions.
In general, the increase of rainfall decreases pH and increases leaching of basic ions as well as movement of clay in the soil, which is responsible for soil acidification. Sandy soils are often the first to become acidic because water percolates rapidly, and sandy soils contain only a small reservoir of bases (buffer capacity) due to low clay and organic
8 matter contents (Helyar, 1991). In humid climates, leaching losses outpace nutrient inputs by mineral decomposition and atmospheric deposition for along period of time (Richter and Markewitz, 2001).
2.3.2 Acidic Parent Materials
The kind of parent materials from which the soil is formed influences the pH value of the soil. Soils developed from basic rocks generally have higher pH values than those formed from acidic rocks. Due to differences in chemical composition of parent materials, soils will become acidic after different lengths of time. Thus, soils that developed from granite material are likely to be more acidic than soils developed from calcareous shale or limestone (Getaneh Assefa, 1975). The western part of the Blue Nile basin has been more maturely eroded; nearly all volcanic rocks have been eroded, exposing mostly pre- Cambrian metamorphic and granite rocks. The later rocks are acidic, i.e. trachyte and rhyolites, than the plateau basalts (Getaneh Assefa, 1975). Tertiary and quaternary basalt and rhyolites occurring in topographic positions from gently undulating to dissected hills are the main rock types in Wellega (Heluf Gebrekidan and Wakene Negassa, 2006).
In warm humid climate, it is likely to be thoroughly oxidized, well leached, and comparably low calcium because of leached out (Brady, 1984). Thus together with climate, the nature and properties of parent materials are the most significant factors affecting the kind and quality of the soils. The rock compositions, which have more than 66% silica, are grouped under acidic soil and the lighter color alkali-alumino-silicates are predominant acidic rocks (Getaneh Assefa, 1984).
2.3.3 Organic Matter Decay /Dissociation/
Soil organic matter is derived from the decayed tissue of plants and from animal excreta; particularly urine (Ngugi et al., 1978). Organic matter consists of numerous compounds that vary greatly in their ease of decomposition. Microbes rapidly decompose sugars, starches and proteins while lignin, fats and wax are resistant to this process. Fresh organic residues consist mostly of easily decomposed compounds that break down rapidly under favorable conditions. The result is a rapid reduction of in the volume of SOM. Slattery and Hollier (2002) stated that adding organic material to soils increases their capacity to withstand a decreased pH in the short term. However, a build up of organic material may
9 make soil more acidic since decomposition of organic matter adds to soil acidity. Decaying organic matter produces H+ that is responsible for acidity. The carbon dioxide
(CO2) produced by decaying organic matter reacts with water in the soil to form a weak
acid called carbonic acid. The same acid develops when CO2 in the atmosphere acts with rain to form acid rain naturally. The contribution to acid soil development by decaying organic matter is generally very small, and it would only be the accumulated effects of many years (Slattery and Hollier, 2002).
2.3.4 Nutrient Removals by Crop Residue from Farm Land
Large quantities of mineral nutrients are removed from soils as the result of plant growth and development and the harvesting of the crop (Bezdicek et al., 1998). He elaborated as nutrient removals by crop as an effect on soil acidity development because crops absorb the lime-like elements, as cations, for their nutrition. When these crops are harvested and the yield is removed from the field, then some of the basic material responsible for counteracting the acidity developed by other processes is lost. The net effect is increased soil acidity. Thus, increasing crop yields will cause greater amounts of basic material to be removed.
The major acidification processes in intensively cultivated soils are due to removal of basic cations (Na+, Ca2+, Mg2+and K+) and acidity developed from continuous application of inorganic fertilizer (Kang, 1993). High yielding forages, such as Bermuda grass or alfalfa, can cause soil acidity to develop faster than with other crops (Dolling, 2001). Most agricultural products are slightly alkaline so their removal from the farm leaves soils slightly acidic. The alkalinity of different agricultural products, and therefore the impact of their removal vary, as indicated Table 2. Soil acidification is often expressed in terms of the amount of lime required to neutralize the input of acids into the soil.
Table 1. Approximate amount of calcite and dolomite removed by crops Product Yield Lime requirement Wheat 2 t/ha 18 kg/ha Lupines 2 t/ha 40kg/ha Grass hay 5 t/ha 125 kg/ha Clover hay 5 t/ha 200 kg/ha Lucerne hay 5 t/ha 350 kg/ha Source: Dolling (2001)
10
Clover and Lucerne hay remove more basic cations from the soil (Table 1). Thus removing their crop residue aggravates soil acidity development.
2.3.5 Inappropriate Use of Nitrogenous Fertilizers
The acidification from use of nitrogen fertilizer has the most serious effect in weakly buffered soils. This is because of the leaching of small reserve exchangeable cations and the increase aluminum concentration in the soil solution and reduction of soil buffering capacity (Wild, 2003). The use of fertilizers, especially those supplying nitrogen, has often been blamed as a cause of soil acidity. Although acidity is produced when ammonium-containing materials are transformed to nitrate in the soil, this is countered by other reactions and the final crop removal of nitrogen in a form similar to that in the + - fertilizer. In the soil solution, the nitrogen present in ionic form as NH4 , NO 3 or
CO(NH2)2 (Urea), all of which can be adsorbed by plant roots. Being positively charged, + 2+ 2+ NH4 is adsorbed in soil by exchange with Ca , Mg and other cation on the negatively charged clay and organic matter. Nitrate ion usually remains in the soil solution. Urea rapidly hydrolyzed by the enzyme to release ammonia (Wild, 2003).
Application of such fertilizers before a plant is at a suitable stage of growth to absorb the available nitrogen is an example of inappropriate use that causes soil acidity. The amount of nitrate that leaches will depend on the amount of nitrogen in the soil and the amount of water draining below the root zone. Generally, the impact of nitrogen fertilizers on acidification depends on the type of fertilizer and what happens to the nitrogen.
2.4 Impact of Land Use and Management Practice on Soil Acidification
Ethiopian’s ancient and highly weathered soils and current systems of agricultural land use are particularly vulnerable to soil acidification process. It is emerging land degradation problem in western Ethiopia. However, information on the effect of land use and management practices on soil chemical properties in the country is very little (Heluf Gebrekidan and Wakene Negassa, 2006). In the highlands, due to intensive land use and high population pressure, the land is severely degraded, eroded and the nutrient status of most soils is decreasing. Between 70 and 75% of the agricultural soils of the highland plateau area of Ethiopia are phosphorus deficient (Duffera and Robarge, 1999). Animal
11 manure and crop residues, instead of being returned to the land, are largely used as fuel and livestock feed respectively (Mulugeta Lemenih, 2004).
Continuous cultivation and inorganic fertilizer application resulted in decline of soil pH and caused loss in basic cations especially under intensive cropping on inherently poor soils (Mokwunye, 1978). Thus, agricultural production increases the rate of acidification through the addition of acidifying fertilizers, increased nitrate leaching and the export of produce. Alemayehu Tafesse (1990) also observed the occurrence of K deficiency on crops in the Alfisols at state farms of Wellega in Western Ethiopia that were subjected to intensive cultivation.
Planting trees such as Pinus and Eucalyptus species invariably alters many soil properties. Soils under plantations typically become more acidic, the effect usually being attributed to the uptake of basic cations into the forest biomass. Pine needle litter contains acidic organic compounds that are released into the soil during decomposition (Mills and Fey, 2003). Coniferous forests can produce an acid litter because the tissues of such vegetation contain considerable concentration of soluble organic acids. Dilute acids together with the soluble organic acids from vegetation can readily leach fulvic acids, in soil humic material. This can produce strong acidification and weathering of soils leading to podosol formation and low base saturation (Harrison and DeMora, 1995). Plantation forestry has resulted in an increase in soil nitrate in many areas, possibly due to greater mineralization under forests than grasslands (Mills and Fey, 2003). Thus, land use can lead to subtle changes in soil chemistry.
2.5 Soil Acidity and Nutrient Availability to Plants
The major impact that an extreme pH has on plant growth is related to the bioavailability of plant nutrients or the soil concentration of plant toxic minerals (McLaren and Cameron, 1996). In highly acidic soils, aluminium and manganese can become more available and more toxic to the plant where as at lower pH values calcium, phosphorous and magnesium are less available to the plant (Richter and Markewitz, 2001). Nutrients are ready for uptake by plant when they are present in their available form (Table 2). The availability of phosphorus is strongly influenced by soil pH.
12 Table 2. Available forms of essential plant nutrients Macro nutrients Micro nutrients Element Symbol Forms take-up Element symbol Forms take-up the plant the plant - 2+ Carbon C CO2, HCO3 Iron Fe Fe 2+ Hydrogen H H2O Manganese Mn Mn 2+ Oxygen O O2, H2O Cupper Cu Cu - + 2+ Nitrogen N NO3 , NH4 Zinc Zn Zn - - 2- Phosphorus P H2PO4 , HPO4 Molybdenum Mo MoO4 + Potassium K K Boron B H3BO3 2- - Sulphur S SO2, SO4 Chlorine Cl Cl Calcium Ca Ca2+ Magnesium Mg Mg2+ Source: McLaren and Cameron (1996)
The impact of soil acidity on plant varies according to the tolerance of different species but can indicate stunted root growth, decreased quality and bulk of pasture and susceptibility to disease. Plants thrive best in different soil pH ranges. The pH tolerance range for various crop species can vary (Table 3). Soil pH values above or below these ranges may result in less vigorous growth and nutrient deficiencies. Most of secondary and micronutrients deficiencies are easily corrected by keeping at the optimum pH value.
Table 3. Optimum pH requirement of some crop plants Crop types pH range Crop types Ph range Wheat 5.5-6.5 Cabbage 6.0-7.5 Barley 5.8-6.5 Carrot 5.5-7.0 Field beans 6.0-7.5 Cauliflower 6.0-7.5 Field pea 6.0-7.5 Potato 4.8-6.5 Corn/maize/ 6.0-7.0 Tomato 5.5-7.5 Oats 5.0-6.5 Lettuce 6.0-7.0 Soybean 6.5-7.0 Straw berry 5.0-6.5 Red clover 5.6-7.0 Alfalfa 6.5-7.0 Asparagus 6.0-7.5 Apple 5.5-6.5 Source: McLaren and Cameron (1996)
As indicated in Table 3, Potatoes are often thought of as "acid loving" plants. They are acid tolerant and will grow reasonably well at soil pH levels down to about 4.8. A nutrient that is necessary for healthy plants need to be dissolved before uptake by plants. Dissolution of these nutrients usually takes place in neutral to slightly acidic pH values. Under acidic condition, the presence of high levels of soluble iron, aluminium and manganese leads to the precipitation insoluble phosphate compounds. Besides, phosphate can be ‘fixed’ hydrous oxides of Al and Fe and by certain silicate clays, which can also
13 reduce by availability (McLaren and Cameron, 1996). The amount of available phosphorus in an environment, therefore; can drastically affect productivity. The availability of micronutrient (Fe2+, Mn2+,Cu2+, Zn2+) increases as soil pH decreases, except for molybdenum (Figure 1). Since the plants in only minute quantities need micronutrients, plant toxicity in addition to other detrimental effects occurs with excess amounts.
Figure 1. The relation between soil pH and plant nutrient availability (Source: ENRC, 2004)
According to Jones (2001), description soils with a pH (H2O) of less than seven are acidic. Moderately acidic soils have a pH range of 5.6 to 6.0. Strongly acidic soils have a pH range of 5.1 to 5.5. Very strongly acidic soils have a pH range of 4.5 to 5.0 and soils with a pH or 4.5 or lower are regarded as extremely acidic (Table 4).This pH value used to aid to diagnosis of plant nutrient deficiencies. As the pH decreases below 5.5, the availability of Al and Mn increase and may reach a point of toxicity to the plant. Excess Al3+ in the soil solution interferes with root growth and function, as well as restricting plant uptake of certain nutrients, namely, Ca2+ and Mg2+ (McLaren and Cameron, 1996).
14 Table 4. Descriptive terms for various pH ranges Descriptive Terms pH Range Extremely acid < 4.5 Very strongly acid 4.5 -5.0 Strongly acid 5.1-5.5 Moderately acid 5.6-6.0 Slightly acid to Neutral 6.1-7.3 Slightly alkaline 7.4-7.8 Source: Jones (2001)
2.6. Effect of Soil Acidity on Soil Fauna and Flora
Soil acidification has an impact on soil biodiversity. It reduces the numbers of most macro fauna including, for example, earthworm numbers and affected is rhizobium survival and persistence. Decomposition and nitrogen fixation may be reduced which affects the survival of native vegetation; biodiversity may further decline as certain weeds proliferate under declining native vegetation (Slattery and Hollier, 2002). In strongly acid soils, the associated toxicity may lead to decreased plant cover and reduced microorganisms. This brings a susceptibility to erosion under high rainfall events, and agricultural disturbances (Slattery and Hollier, 2002). The correlation of soil and biodiversity can be observed spatially both natural and agricultural vegetation boundaries correspond closely to soil boundaries (Young and Young, 2001).
Soil organic matter supplies energy and body-building constituents for soil organisms, increases microbial populations and their activities, source and sink for nutrients, ecosystem resilience, and affects soil enzymes where as microorganisms are the driving force for nutrient release to plants (Baskin, 1997). Microbes break down SOM as they consume it for food. Any factor that affects soil microbial activity also affects SOM break down (Bardgett, 2005). Thus, the relationship of soils to biodiversity is intimate and complex. Soil can be managed to optimize its fertility and health under natural and agricultural land uses, to benefit biodiversity.
Mesofauna (mites, acarids and springtails) are intermediate in size and in combination with the micro flora (bacteria and fungi) play a dominant role in the soil food web fauna in recycling nutrients and carbon. Soil pH influences soil microbes. In most cases,
15 however, bacteria are responsible for most of the decomposition of SOM, and as a rule this process is markedly slowed if pH levels drop below 6.0 (Sanchez, 1976). Since soil acidity reduces populations of soil bacteria, then those organisms feeding on bacterial (protozoa and beneficial nematodes) would logically decrease in population. However, there is limited information on the effects of soil acidity on the soil fauna in general (Graham, 1998).
Microorganisms associated with nitrification, require a certain soil pH range to function efficiently. Since these organisms require large amounts of Ca to perform the conversion, a pH of 5.5 to 6.5 is necessary for Ca to be available (Buerkert et al, 1990). In addition, the activity of bacteria (Rhizobia species) which are responsible for nitrogen fixation in legume crops decreases when the pH drops below 6.0. Soil acidity affects microbes that are responsible for the breakdown of crop residues and soil organic matter (Coyne, 1999).
2.7. Management Options of Soil Acidity Problems
The management of acid soils should aim at improving the production potential by addition of amendment to correct the acidity and manipulate the agricultural practices to obtain optimum crop yields under acid condition. It is most important that soil acidity should be treated at an early stage. If acidity spreads into the sub-soil, serious yield reduction may occur. The first step in managing soil acidity is to diagnose any increase in acidity. Farming practices recommended for minimizing acidification include: . Matching nitrogen fertilizer inputs to crop demand. . Using forms of nitrogen fertilizers that cause less acidification. . Efficient irrigation management to minimize leaching. . Early sowing after fallow to ensure more rapid utilization of available nitrogen. . Growing deep-rooting perennial species to take-up nitrogen from greater depths. . Regular applications of lime to counter the acidification inherent in the agricultural system based on soil pH, soil type and land use type. . Growing acid tolerant crops or crop varieties that are relatively more tolerant of acid soils such as sugarcane, coffee, papaya and bananas in conjugation with row crops make an important ecosystem on acid soils in Ethiopia. All these are a short-term option to mitigate the soil acidity and associated consequences.
16 . Land use change could be a long-term management strategy for soil acidity (ENRC, 2004).
2.7.1 Agricultural Lime Application
Soil acidity is corrected by the application of lime material (Adams and Evans, 1962). Lime is the cheapest and most effective cure for soil acidity. The carbonate component of lime consumes hydrogen ions present in the soil and reducing their concentration in soil solution and so that raising soil pH. The lime material has to be a calcium or magnesium salt of a weak acid such as limestone (CaCO3), dolomite (Ca Mg (CO3)2), quicklime
(CaO), hydrated lime or slaked lime (Ca (OH)2). In correcting acidity, enough lime should be added to neutralize not only the active acidity but also the reserve or potential acidity. Acidity is normally corrected to increase pH to about 5.9 (Boyd, 1979). From the initial pH of the soil and reduction of pH of the buffer solution, the lime requirement could be calculated using standard tables (Adams and Evans, 1962).The liming of acid soils is regarded as the major solution to soil acidification at present in the western part of Ethiopia. Currently, determination of lime requirement has been done based on acid saturation.
If the crop to be sown is tef, then, permissible acid saturation could be 40% (table 6). Therefore, sufficient lime is needed to bring the acid saturation from 50% to 40%. If it is assumed that, the neutralizing value of the available lime is 75% that of the pure CaCO3 and that incorporation depth is 15cm the lime requirement factor will be approximately 3000kg lime/ha/cmol of acidity to be eliminated (Farina and Chanon, 1991). If the neutralizing value is lower or higher than 75%, the lime requirement factor is adjusted accordingly. Similarly, if incorporation depth is greater than 15cm, as it is likely, to be when tractor drawn implements are used the requirement factor is increased accordingly.
Moreover, crops vary in their acid saturation tolerance limit. Relatively, tef and potatoes are more tolerant to soil acidity and followed haricot bean, maize and finger millet whereas most vegetables like, cabbage, carrot and tomatoes are very susceptible to soil acidity (Table 5). In general, crops with low acid saturation tolerance limit need more lime to raise soil pH.
17 Table 5. Crop tolerance for permissible acid saturation Crop type Acid saturation Crop type Acid saturation tolerance tolerance limit (%) limit (%) Cabbage 1 Sorghum 10 Carrot 1 Barley 10 Tomato 1 Wheat 10 Field bean 5 Sweet potato 10 Sunflower 5 Haricot Bean 20 Pepper 5 Maize 20 Cotton 5 Groundnut 20 Kale/rapeseed 5 Potato 30 Onion 5 Tef 40 Source: MoARD (2007)
Liming improves base saturation and availability of Ca and Mg. Fixation of P and Mo is reduced by inactivating the reactive constituents. Toxicity arising from excess soluble Al, Fe and Mn is corrected and there by root growth is promoted and uptake of nutrients is
improved. It also stimulates microbial activity and encourages N2 fixation and nitrogen mineralization, and hence, legumes are highly benefited from liming.
2.7.2 Selection of Acidity Tolerant Crop Variety
Different plants had different strategies to adapt the acid soil (Ren Fang Shen and Rong Fu Chen, 2006). Plants those are more tolerant of acid (Al3+) stress (more adaptive to acid soils) should be developed for maintaining and increasing productivity on acid soils. The emerging era of adapting the plant to the natural environment is paramount to stabilizing crop yields and world food security for the future. The key to this effort will be breeding cultivars with high nutrient use efficiency and tolerant to abiotic stresses. Recent findings have shown the existence of inter-intra specific differences in acidity tolerance and nutrient use efficiency in many crops cultivars and genotypes. Genotypes that have high nutrient use efficiency genetic and physiological components of plants have profound effects on the ability of plants to acquire, transport, and utilize absorbed nutrients under various environmental and ecological conditions (Baligar and Fageria, 2006).
18 3. MATERIALS AND METHODS
3.1 The Study Area
3.1.1 Location and Description
The study was conducted at Awi Zone, which is located in the Amhara Region of Northwestern Ethiopia, roughly mid between Debre Markos and Bahir Dar. In the current administrative structure, the Zone has seven main administrative‘Woredas’: Banja, Ankesha, Fagtalekoma, Dangila, Guangua, Guagusashekuadad and Jawi (Figure 2). The last two Woredas are not indicated on the map, because they are partitioned in recent years. This zone is known by its richness in water resources and high rainfall. Figure 2. Map and location of the study area in Amhara National Regional State
(Source: ArcMap version 9.1, Gis by ESRI, 2005) The selected Woreda for study, Ankesha Woreda, lies within range of latitudes 10°23'N and 10° 85'N, and longitudes 36°35'E and 36°57'E (EMA, 2008). It is located about 452 km Northwest of Addis Ababa, 133 km Southwest of Bahirdar and 17 km South of
19 Injibara town with an altitude range between 1000 and 2800 m.a.s.l. The specified area is 10 km south of the main road of Addis Ababa to Bahirdar at the upper source of Blue Nile Basin. Undulating slope, seasonal and intermittent streams, and steep slopes are characteristics of the topography of the site. This Woreda was selected for the fact that: soil acidification is critical and burning issue requiring urgent attention in the area but probable causes, acidity levels and impact of land use change not yet assessed and evaluated.
Population
According to population and housing Census of Ethiopian Central Statistic Authority projection, the total population of the Ankesha Woreda is about 226,004 in twenty nine Peasant associations (Administrative Kebeles) and two towns (Gimjabet and Ayehu town) in which the total male population comprises 49% and remaining are females (CSA, 1998). Population density of the area is very high on the average 283 per square kilometer and the average family size is six people per household. Among these 94.5 % of the pupation lives on in the rural area, which is totally, derives their livelihoods directly or indirectly from agriculture. The agricultural sector is predominantly subsistence in nature, in which the major part of farm production is for household consumption. Small-scale subsistence farms, with an average land holding of less than one hectare, and food crop production is predominantly rain-fed and small scale traditional irrigation.
3.1.2 Climate
The study area belongs to Northwestern highlands of Ethiopia. Similar to other parts of the region, the rainfall of Ankesha area is erratic. The rainfall mostly extended unimodal, one growing periods, with mean annual value of 2057.5mm (National Meteorological Agency, 2008). The main rainy season (meher) extends from Mid-May to the Mid- October. The months of July and August receives the highest amount of rainfall that reaches above 450mm at the peak periods (Figure 3). Annual mean rainfall data collected from three stations, for three consecutive years at Injibara and Kessa in Dega part and Azena in Woina Dega, indicated that all stations receive very high annual rainfall reaching up to 2173mm, 2357.6 mm and 2057.5 mm (National Meteorological Agency, 2008) respectively (Appendix 1). Here Azena station is found at the study site.
20 600 Injibara station 500 Kessa Station Azena Station 400
300
200 Rainfall amount in mm in amount Rainfall 100
0 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Months (2003-2005)
Figure 3. Mean monthly rainfall of the study area based on nearby rainfall stations (Source: National Metereolological Agency, 2008)
Temperature varies between the mean annual of minimum 110c and mean annual maximum of 25oc across the elevation gradient respectively. The Woreda spans three agroclimatic zones; Dega (10%), Woina Dega (80%) and Kolla (10%) (Office of Agriculture and Rural Development, 2007). The study concentrates in the Dega area where soil acidity becomes critical problem.
3.1.3 Geology and Soil
Geology The western part of the Abay river basin has been more maturely eroded, nearly all volcanic rocks have been eroded, exposing mostly pre-Cambrian metamorphic and granite rocks (Getaneh Assefa, 1975). The volcanic rocks forming the plateaus are mostly basalts that flowed out on a flat low land surface. The granite rocks are acidic, i.e. trachyte and rhyolites, than the plateau basalts (Getaneh Assefa, 1975). Several peaks are dramatic stone columns, most likely volcano cones, which are probably made of rhyolites (Mac Lachlan, 2001). The Awi area, the previous Agew Mider, (about N10°and E37°) is also included in this plateau.
21 Soil The soils of the Northwestern highlands of the country are largely developed from parent materials of volcanic origin. However, in certain parts, there are soils that were developed from basement materials, limestone, alluvial materials and sandstone (Physical Planning Department, 1985).The soils of the area are closely related to their parent materials and their degree of weathering. The main parent materials are basalt, granite, lava, gneiss, volcanic ash and pumice (Getaneh Assefa, 1975). The dominant soils in the Amhara National Regional State in their respective order are Luvisol (15.1%), Cambisols (14.3%), and Leptosols (14.3%). Nitosols (13.7%), Vertisol (10.8%), Acrisols (2.6%) and Regosols (2.1%) (Bureau of Agriculture, 1999).
According to Ankesha Woreda Office of Agriculture and Rural Development report (2006), the soil types by color involves brown (75%), red (15%) and Black (10%) and with respect to soil groups Nitosol, Acrisols, Chromic Vertisol, Cambisols and Leptosols are dominant soils in the area. According to Yihenew Gebreselassie (2002) the soil of Injibara area are Acrisols.
3.1.4. Land Use and Farming Systems
Land use
At present, cultivated lands cover about 77%, including annual and perennial crops, of the total geographical area of the Woreda (i.e. 79881.75ha). The problem of cultivated lands is not only being on steeper slopes but also they are losing their depth and fertility due mismanagement. Some of the farms seem to have been reached a level of no return.
The vegetation cover in the Woreda constitutes 13.2% of the total geographical area, including, homestead plantation, natural forest, boundary and patches of woodlots, bushes and shrubs (Office of Agriculture and Rural Development, 2007). The natural vegetation is shrunk around the Churches, near the bottom of high mountains and course of rivers. Especially around the Churches, they are not damaged due to religious considerations. According to the report compiled by Agriculture and Rural development office experts (2007), the dominant tree species in the area includes Eucalyptus globulus, Croton macrostachyus, Cupressus lusitanica, Acacia decurrens, Albizzia gummifera, Cordia
22 africana, Ficus sycomorus, Erythrina abyssinica and Syzygium guieense. In the mountains and high altitude zones, especially around the churches, the most commonly seen tree species include Juniperus procera, Podocarps fulctatus, Olea spp. etc. while the lower altitude zones mainly represented by Acacia, Albizzia gummifera, Cordia africana, etc. Especially, Eucalyptus globulus, Acacia decurrens, Cupressus lusitanica and Arundinaria alpina/ Bamboo/ is economically the main source of income for the residents.
The grazing land is limited to 7.85% of the total geographical area as per the present land use dynamics. Infrastructures covers 2.2% of the geographical area and remaining 0.02% under water bodies, seasonal swamp, rocky surfaces and other unarable lands ( Office of Agriculture and Rural Development, 2007). The forest and pasture lands are under constant pressure due to the expansion of agriculture lands (IDWSDD, 2006).
Farming System
The farming system of the area is predominantly subsistence farming based on mixed crop-livestock production. Cattle and equine (horse) provide inexpensive and easily accessible inputs required for crop production such as draft and threshing power in the agricultural production system, while crop production supports the livestock by providing crop residues that supplement the feeds required by the livestock. After crop harvest, cattle and equine are allowed to graze on the weeds and remaining crop stalks on the croplands. However, most of the main grazing is carried out in the forest and on communal grazing lands. Manure from the cattle is mainly used for homestead gardens, while those farm fields away from the home garden, often receive little or no manure. Tillage involves both a simple oxen-plough and horse-plough that cultivates the soils to a shallow depth (observation and oral communication with the farmers). Major crops grown in the area are maize, tef, potato, wheat, barley and other vegetables, mainly with one harvest per year. In addition, barley, wheat, potatoes and other vegetables also produced twice per year with traditional irrigation system in which the farmers using indigenous knowledge.
The farming system is a traditional parkland agroforestry system with scattered trees on farms. The trees are preserved from the original forest during clearance, which are
23 indicator of previously existing forest in that area (Office Woreda Agriculture and Rural Development, 2007).
3.2. Methodology
3.2.1. Study Design
In order to evaluate status of soil acidity in different land uses and understand farmers’ perception, two types of survey have been carried out. These are soil survey and socio economic survey (Figure 4). Sampling Strategy and Data Collection Procedures
Study Design
Soil Survey Socioeconomic Survey
Soil sampling and Analysis of Farmers Soil Laboratory Analysis perception to soil acidity
Evaluation of Status Correlation Identification of Soil of soil acidity in Analysis among Acidity Causes and different land uses Soil Properties Copping Mechanisms
Determination of Understand Farmers Identification of More Relationships Soil Practices to overcome Acidified Property & Soil Acidity Soil Acidity problem Land Use Type
Discussion on Status of Soil Acidity in Different Land Uses and Propose Management Options for sustainable Land use and Soil Productivity
Figure 4. Flow chart of the study design
24 3.2.1.1 Soil Survey
Before soil sample collection, field observation and a reconnaissance soil survey was carried out during March 2008 and a purposive sampling method was employed to identify representative land use types. Based on information collected from a reconnaissance survey of the prevailing areas, farmers’ interviews, agricultural experts and development agents, two representative soil-sampling sites were selected. In selecting the site, differences in geologic, topographic and climatic conditions were minimized by selecting closely located sites.
A. Soil Sampling
Soil samples were taken from four land use types with three replication of each at two Kebeles. The land use types were cultivated fields, backyard fields, Eucalyptus plantation and grazing lands. Composite soil samples were collected at a soil depth of 0- 20 cm from the respective land uses by transect walk on the field in the following manner. First, replications in each land uses were made based on a natural slope break with a minimum allowable slope difference of 1-2 % relative to the preceding position. Then, a square of 20 m by 20 m plot size was established in each replication. Here pits were dug with auger at the four corners and in the centre of the square plots. Soil samples were removed from a soil depth of 0-20 cm uniformly along each depth at five spots and held on the plastic tray.
The soils were mixed, quartered and reduced to 1kg and sealed with plastic bags together with a tag, which holds proper labeling of land use type, geographical position, altitude, slope, name of landowner, name of peasant association, field history, date of collection and field code of the sample. This referred as one composite soil sample. By doing so, twenty-four composite soil samples were collected for all land use types at two Kebeles (Figure 5). In each step brief description of the sampling sites were recorded by using GPS and clinometer (Appendix 2). Finally, the composite soil samples were brought to Gondar Soil Testing Laboratory for analysis of soil property parameters.
25
Figure 5. Soil sampling sites in different land use types
N.B: I= the first site/Hateta Kebele/; II= the second site/Denzuria Kebele
26 B. Soil Laboratory Analysis
Soil pH
Soil pH is a measure of the hydrogen ion (H+) activity in the soil solution (Jones, 2001). The pH of the soil potentiometrically measured by using two different liquids namely distilled water and 1M KCl solution. It was determined in the supernatant suspension of soil solution ratio of 1:2.5 soils: liquid mixture by using pH meter. This value of a solution is the negative logarism (base 10) of hydrogen ion activity (mole per liter) in the soil solution (Jones, 2001).
Exchangeable acidity, Effective CEC and Acid Saturation
The total exchangeable acidity was measured according to McLean (1965) as described by National Soil Research Centre (Sahlemedhin Serstu and Taye Bekele, 2000). A neutral 1N potassium chloride solution is used to leach exchangeable hydrogen and aluminium ions from the soil samples. The acidity brought into solution from various sources in the soil is measured by titration with standard solution of an alkali. The amount of alkali used being equivalent to the sum of the hydrogen and aluminium ions known as exchangeable acidity. Effective CEC and Acid saturation were calculated as follows:
Effective CEC (cmol (+)/kg) = Exchangeable Bases [Ca+Mg+K+Na] + Exchangeable acidity
Acid saturation %= Exchangeable acidity (cmol. (+)/kg) x100 Effective CEC (cmol. (+)/kg
Exchangeable base cations and CEC
The exchangeable cations were determined by measuring the total amount of a given cation needed to replace all the cation from a soil exchange site and it is expressed in centimoles per kg of soil (cmol/kg of soil). The ammonium acetate method is suitable for acid to neutral soils. Exchangeable base cations (Ca2+,Mg2+, K+, Na+) and cation exchange capacity (CEC) of the soils were determined by the 1M ammonium acetate (pH 7) method according to the percolation tube procedure (Van Reeuwijk, 1993). Five gram of soil
27 mixed with five gram of acid washed sand was leached by 200 mL of 1M ammonium acetate, pH 7 solution. EDTA titrimetric method and exchangeable K and Na measure exchangeable Ca and Mg in the ammonium acetate leachate by flame photometer (Van Reeuwijk, 1993).
Available phosphorous Available phosphorous content of the soils was determined by 0.5M sodium bicarbonate extraction solution /pH 8.5/ method of Olsen as outlined by Van Reeuwijk (1993). The sample is extracted with a sodium bicarbonate solution at pH 8.5. Phosphate extract is determined colorimetrically after treating it with ammonium Molbdate, Sulphuric acid reagent with ascorbic acid as reducing agent. Five grams of soil were shaken with 100 mL of 0.5 M sodium bicarbonate extracting solutions for 30 minutes and filtered. Three millilitres of the filtrate was mixed with 3 ml of mixed reagent and the amount of phosphorous was determined by spectrophotometer at 882nm (Van Reeuwijk, 1993).
Available potassium The Morgan method was primarily used for the determination of potassium in acid soils with cation exchange capacity of less than 20 meq/100g, which was initially proposed by Morgan (1941). Under this procedure, the sample extracted with Morgan’s solution and K in the extract was measured by flame photometer as outlined by Sahlemedhin Sertsu and Taye Bekele (2000).
Total Nitrogen The total nitrogen content of the soil was determined by wet-oxidation procedure of the Kjeldahl method (Bremner and Mulvaney, 1982). One gram of soil to pass 0.5mm sieve was digested in 3 ml concentrated H2SO4 containing 1.1g of K2SO4 catalyst mixture + (K2SO4,CuSO4.5H2O:Se in 100:10:1weight ratio) to convert organic N to NH4 _N. The digest was distilled with 20ml of 10M NaOH and the librated NH3 was trapped in 5mL + H3BO3-indicator solution. The NH4 -N in the distillate was determined by titrating with 0.01MHCl. Potassium sulphate is added to raise the boiling point of the mixture during digestion, copper sulphate and Selenium powder mixture is added as a catalyst. The + procedure determines all soil nitrogen (including adsorbed NH4 except that nitrate form).
28 Soil Organic Matter Organic carbon content of the soil was determined by the wet combustion procedure of Walkley and black 1934). One gram of soil, previously ground to pass a 0.5 mm sieve was reacted with a mixture of 10 ml of 0.17M K2Cr2O7 and 20 ml of 96% Sulphuric acid. The excess dichromate solution was titrated against 1mL ferrous sulphate after addition of about 150 ml distilled water, 10 ml of 85% of phosphoric acid and 1 ml indicator solution (0.16% Barium diphenylamine sulphate). Then organic carbon content of the soil could be calculated as:
%C = NxV1-V2x0.39 x mcf S Where: N=Normality of ferrous solution (from blank titration)
N = N (K2Cr2O7) x V (K2Cr2O7) V (FeSO4)
V1= ml ferrous sulphate solution used for blank V2= ml ferrous sulphate solution used for sample S= weight of air dry sample gram 0.39= 3x10-3 x 100% x 1.3 (3= Equivalent weight of carbon) mcf= moisture correction factor
In this method, about 77% of carbon is oxidized by potassium dichromate. The correction factor 100/77(1.3) is used in the calculation. The value of 77% is approximation since the ineffectiveness of combustion varies with the type of organic matter present. Organic matter contains 58% C conversion of % carbon to % organic matter (Sahlemhidin Sertsu and Taye Bekele, 2000). Therefore, 100/58 (1.724) is the empirical factor.
Soil Texture
Soil texture was determined by the hydrometer method (Bouyoucos, 1951) as described by National Soil Research Center in Ethiopian Agricultural Research Institute (Sahlemedhin Sertsu and Taye Bekele, 2000).
3.2.1.2 Socioeconomic Survey
Socioeconomic survey was conducted in order to understand farmers’ perception to soil acidity problem and their coping mechanisms. Thus, open and closed ended semi structured questionnaires were prepared to substantiate and augment the qualitative results. The procedure of household selection was carried out as described below.
29
A. Household Selection Firstly, a purposive sampling method was employed to identify representative peasant associations (PAs) from twenty-nine Kebeles of Ankesha Woreda. Representative PAs were selected based on information collected from a reconnaissance survey of the prevailing areas, farmers interviews, agricultural experts, development agents and PAs administration offices as described before in soil sampling. Accordingly, Denzuria and Hateta Kebele PAs were selected. The reason why these two Kebeles were chosen is that, they are representative of other ten Kebeles that have soil acidity problems in the Woreda. Since their most agro ecological, biophysical, geological origin and the socio economic aspects of the area are more or less similar with other nearby Kebeles (observation). Thus, they represent a good example for the perception analysis. Besides, there were no previous attempts of assessing any soil acidity causes, problems and coping mechanisms in different land use system in the area.
Secondly, sample households were purposively selected from a list of registered peasants obtained from the respective PAs administration offices based on criteria. The criteria includes those farmers whose age greater than 32 years, their proximity to the sampling sites and who have their own land. This is to know land use history.
B. Questionnaire Survey The questionnaire was prepared in English (Appendix 8). In order to facilitate the survey and to collect appropriate information by the enumerators, the questionnaire was translated into the local language (Amharic). After translating the language, pre- questionnaire test was carried out to make the interview understandable for enumerators. From the households of 1056 in Hateta and 1332 Denzuria PAs population respectively, 60 farm households were selected for each Kebele. Totally 120 farm households were surveyed. Data on household characteristics, farm attributes or variables related with soil acidity and its management, characteristic and coping mechanisms of soil acidity, crop production systems, field history, Eucalyptus plantation and grazing land managements aspects were collected by administering a semi-structured questionnaire survey. Informal discussion with elders and agricultural experts were also employed to understand the extent and severity of soil acidity problems in the study area.
30
3. 3 Data Analysis and Statistical Procedures
The data generated from soil laboratory analysis were analyzed by comparing the four land use type’s analytically using descriptive statistics and ANOVA to detect whether differences in the soil attributes studied differed significantly (at p<0.05) between and within the lands uses types or not. One-way analysis of variance (ANOVA) was used to assess variations in soil properties among different land uses and management systems. The LSD (Fisher’s protected mean separation) method was employed to distinguish the means that were significantly different. A correlation analysis was carried out to determine the relationships between other soil property and soil acidity. Sample means and variations were calculated for attributes that are parametric, and sample proportion was calculated for the attributes that are categorical. The qualitative data generated by semi-structured questionnaires and informal discussion with respect to land management practices were used to substantiate and augment the quantitative results. The data were edited, coded and analyzed using the Statistical Package for Social Sciences (SPSS) release 15 (Bryman and Cramer, 2006).
31 4. RESULTS AND DISCUSSION
4.1 Soil Acidity Status of Different Land Uses
Changes in land use and management practices often modify most soil morphological, physical and chemical properties to the extent reflected in agricultural productivity. Different land use systems have significant influence on most important soil quality indicators. At the sampling site, the soil texture analysis, based on hydrometer method, indicated that, in most of the soils, the proportion of sand fraction was high (38.61 to 41.28 %) followed the silt fraction (35.28 to 36.61%) and the clay fraction (23.44 to 24.77%) in all land use types at Hateta Kebele. Thus, the textural class of the soils in all land uses was loam. Where as, in Denzuria Kebele, the proportion of particle size ranged from 32.61 to 39.28% for sand, 35.28 to 38.61% for silt and 26.11% to 30.11% for clay (Appendices 3, 4) in all land use systems. Hence, the textural class of soils was lie on clay loam in texture. Relatively, the sand fraction was the largest proportion in all land use systems in the two sampled kebeles.
The status of soil acidity in different land uses, in terms of soil pH, level of exchangeable acidity, acid saturation, amount of exchangeable base cations, status of major soil fertility parameters and their relationships to soil acidity, explained briefly in the subsequent topics.
4.1.1 Soil pH Level
The pH value of soil is indicator of intensity of its acidity. Measuring soil pH is the most widely used and simplest method of assessing soil acidification. The actual acidity of a soil is readily determined by measuring the pH of the soil solution (Batjes, 1995). The pH values measured in water were higher by about 1.00 to 1.50 units than their respective values measured in KCl solution under different land uses of the topsoil (depth of 0- 20cm) at both sites (Table 6). The decrease in soil pH when measured in KCl solution indicates that appreciable quantity of exchangeable hydrogen (H) had been released into the soil solution through exchangeable reaction with potassium (K) in the KCl solution. This is related to the presence of weatherable minerals in the soil that indicated high potential acidity (Heluf Gebrekidan and Wakene Negassa, 2006). They also observed that
32 the pH value measured in water were higher by about 1.00 to 2.7 units than their respective values measured in KCl solution. Similarly, Murray et al. (1992) explained that the soil: liquid ratio and the composition of the equilibrating solution affects the pH value of the soil.
As a result, the pH (KCl) values are strongly acidic (pH<5.0) in all land use systems. The mean value of soil pH (KCl) increased at backyard fields (pH ≥4.55) but decreased at other three land use types (pH ≤3.95) at both sites (Table 6). The backyard soils had significantly higher (p<0.01) pH of KCl than soils under the other three land use types at
both sites. Correspondingly, the mean value of pH H2O was significantly (p<0.05) differed between cultivated and backyard fields in Hateta kebele and highly significantly (p<0.01) differed on backyard fields than other three land use types in Denzuria Kebele (Appendices 5, 6).
Regardless of the methods, soil pH was lowest on the top soil of cultivated fields while,
relatively, higher soil pH (H2O) (5.54 and 5.80) and pH (KCl) (4.55 and 4.75) were recorded on backyard fields at Hateta and Denzuria Kebeles respectively. Generally, the backyard soils were moderately acidic where as soils of cultivated fields, eucalyptus plantation and grazing lands were strongly acidic (pH<5.5) soil at both sites (Table 6).
Table 6. Values of pH (KCl) and pH (H2O) by soil-liquid ratio in different land use (Mean±SE)
Hateta Denzuria
Soil pH (1:2.5) Soil pH (1:2.5)
Land Use Types KCl H2O ÄpH KCl H2O ÄpH
a a a a Cultivated field 3.85 ±0.012 5.12±0.076 -1.27 3.76±0.01 4.86±0.071 -1.10
Backyard field 4.55±0.17b** 5.54±0.098b* -0.99 4.75±0.13b** 5.80± 0.16b** -1.50 Eucalyptus a ab a a Plantation 3.86 ±0.03 5.26±0.032 -1.40 3.84±0.03 5.00±0.05 -1.16
a ab a a Grazing land 3.95 ±0.026 5.29±0.031 -1.39 3.85±0.01 5.01±0.04 -1.16
Mean values with different superscript letters in columns indicate significant differences at á=0.05; á= 0.01, Where *p<0.05, **P<0.01
33 The low soil pH in cultivated fields was probably due to continuous removal of basic cations by crops, intensive cultivation that enhanced leaching of basic cations and washed away of exchangeable bases by rill and sheet erosion. On the contrary, relatively higher soil pH in backyard fields attributed due to application of manure, wood ashes and other easily decomposable garbage around the homestead gardens. Urine and ash are normally high pH materials and good for formation of complex bonding Al with organic matter. This finding is in agreement with Heluf Gebrekidan and Wakene Negassa (2006) who reported that land use and management practices have markedly influenced all of the soil chemical properties. Eck and Stewart (1995) also observed that, though the composition and amount of nutrients in manure are variable depending on the type of animal, ration fed, amount and type of bedding material, collection system, and management between production and use; manure contains all the essential chemical elements needed by plants and its potential nutrient contribution is quite considerable.
4.1.2 Exchangeable Acidity and Acid Saturation
There was great variation on exchangeable acidity and acid saturation of the soils under the different land use types in both sites at the soil depth of (0-20 cm) topsoil. The highest exchangeable acidity value obtained from soils of cultivated fields [(5.29 cmol (+) kg-1 and 7.88cml (+) kg-1)] and followed by eucalyptus plantation [(4.93 cmol (+) kg-1and 7.35cmol (+) kg-1)]. Where as the lowest exchangeable acidity were registered on backyard soils [(0.55cmol (+) kg-1 and 0.39 cmol (+) kg-1)] at Hateta and Denzuria kebeles respectively (Table 7). The backyard soils had highly significantly lower (p<0.01) exchangeable acidity than soils under the other three land use types (Appendices 5, 6). Similar trends were observed in acid saturation percentage. It is significantly lower (p<0.01) on soils of backyard fields than other three land use types. Relatively, the highest acid saturation were recorded in cultivated fields (40.27% and 57.72%) and followed other two land use types where as the lowest were on soils of backyard fields (2.62% and 1.58%) on the former and later kebeles (Table 7). The significance difference in acid saturation between backyard fields and cultivated fields were probably due to the difference in agronomic management practice and application of farmyard manure.
34 Hence, cultivated fields, Eucalyptus plantation and grazing lands had very high level of soil acidity. As described in soil acidity management and lime application principle guideline prepared by Ministry of Agriculture and Rural development (2007), the permissible acid saturation tolerance limit of crops listed by order as cabbage, carrot and tomatoes (1%), onion, field bean and rape seed (5%), wheat and barely (10%), and maize, potatoes and tef (20%, 30% and 40%) respectively. However, the acid saturation recorded in cultivated field is beyond (>40%) acid saturation tolerance limit of locally produced crops in the study area.
In general, the highest status of acidity on cultivated fields indicate the marked influence of continuous cultivation and removal of basic cations by crop uptake where as the better soil condition on backyard soils signify the importance of manure and wood ash application. In addition, the higher status of soil acidity in Eucalyptus plantation indicates the acidifying effect of eucalyptus tree; however, it has no significant impact on the tree itself as one can see good growth of the trees. This indicates deep-rooted plants are more tolerant to soil acidity encountered with they can catch up the leached base cations in the subsoil. Where as the existence of high level of acidity on the plantation is being attributed to the uptake of more basic cations into the tree biomass and low return through its leaf drop.
On the other hand, the higher acidity on grazing land entails that pasture species such as grasses / legumes aggravate soil acidity development by taking more basic cations during harvest and livestock feed. The reason could be less return of grass/legume biomass to the soil except the underground plant parts. Moreover, the development of soil acidity also attributed poor livestock distribution on grazing lands due to exposure of sheet and rill erosion. As farmers explained most grazing lands were infertile and acidified by nature, otherwise they were converted when the cultivated field is exhausted. Beecher and Lake (2004) also explained that major causes for acidification of grazing lands could be nitrate leaching and build up of soil organic matter. Helyar (1991) also reported that the rate of soil acidification depends on the rate of acid added to the soil and broadly related to soil type, rainfall and land use.
35 Table 7.Values of exchangeable acidity and acid saturation in different land uses (Mean±SE)
Hateta Denzuria Acid Acid Ex. Acidity Saturation Ex. Acidity Saturation Land use Types In cmol. (+) kg-1) (%) In cmol.(+) kg-1) (%) a a a a Cultivated Field 5.29±0.147 40.27±1.35 7.88±0.54 57.72±6.03 Backyard Field 0.55±0.166b** 2.62±1.21b** 0.39±0.06b** 1.58±0.39b** Eucalyptus a ac a a Plantation 4.93±0.69 36.04±5.50 7.35±0.37 48.36±4.03
a c a a Grazing Land 3.96±0.129 27.45±0.97 * 6.84±0.31 49.43±2.04 Mean values with different superscript letters in columns indicate significant differences at á=0.05; á= 0.01, Where *p<0.05, **P<0.01
Soils of location two (Denzuria) are in most of the cases more acidic than location one (Hateta) in all land use types except the backyard fields (Figure 6). This is more likely due to biophysical condition of the area and land management practices. Location two found slightly higher in altitude (2408 masl) than location one (2390 masl) (Appendix 2). According to local farmers’ explanation, there was also a difference in year of plantation in case of Eucalyptus plantation. It was planted before thirty years in Denzuria where as twelve years old in Hateta Kebele. In the same way, the establishments of the communal grazing land in Denzuria is unknown by elders. It existed since before the Derge regime. However, the grazing land in Hateta kebele was allotted at the end of 1970s. In general the differences in level of acid saturation at two locations more probably due to the topographic condition, the management factor and the intrinsic character of the soils. However, the soil acidity differences between Kebeles at different land uses were not statistically significant.
36 70 AS% in Hateta Kebele 60 AS% in Denzuria Kebele
50
40
30
20 Acid saturation (%) saturation Acid 10
0 Cultivated field Backyard field Eucalyptus Grazing land plantation Land use types
Figure 6. Level of acid saturation in different land use types at two locations
4.1.3 Exchangeable Bases and CEC
Depletion of base cations by leaching aggravates extent and rate of soil acidification process. These exchangeable cations varied markedly due to differences in land use systems. The highest concentrations of exchangeable bases viz., Ca2+ (11.29 cmol(+)kg-1), Mg2+ (9.20 cmol(+)kg-1), K+ (2.49 cmol(+)kg-1) and Na+ (0.12 cmol(+)kg-1) at Hateta kebele and Ca2+ (12.41 cmol(+)kg-1)), Mg2+ (11.22 cmol(+)kg-1)), K+ (1.83 cmol(+)kg-1) and Na+ ( 0.16 cmol(+)kg-1) at Denzuria Kebeles were registered for the top soil backyard fields. Where as the lowest exchangeable bases (Ca2+, Mg2+, K+ and Na+) were registered for the top soil cultivated fields (Table 9).
In general the highest total exchangeable bases ((23.10 and 25.61) in cmol (+) kg-1)) were recorded on backyard soils whereas the lowest total exchangeable bases was obtained from cultivated fields (7.89cmol (+)/kg and 5.90cmol (+) kg-1) followed by other two land use types in Hateta and Denzuria kebeles respectively (Table 8). Backyard soils had significantly higher exchangeable bases (p<0.01) than soils under the other three land use types (Appendices 5, 6).
37 The highest exchangeable K recorded for backyard fields and the lowest at cultivated fields. Particularly, in cultivated fields of Hateta kebele, it is deficient (0.35 cmol (+) kg-1) when compared to 0.38 cmol (+) kg-1 which is established to be critical level of exchangeable K for most crops (Barber, 1984). The result was in agreement with the findings of Alemayehu Tafesse (1990) and Heluf Gebrekidan and Wakene Negassa (2006) who reported the prevalence of K deficiency on Alfisols in Wollega State farm and Bako research fields respectively. The higher exchangeable K in backyard soils was probably related to application of manure and wood ashes. Wakene Negassa et al. (2001) observed that the chemical composition of applied farmyard manure supplied to the crop that had considerable amounts of different essential macronutrients and small amounts of micronutrients usually deficient in acid soils.
The lower value of exchangeable K in cultivated soil may be related to intensive cultivation and removal of base cations during crop harvest that enhanced its depletion. Many research results from different areas of tropics supported the findings of the present study. According to Baker et al. (1997), Saikh, et al. (1998), Heluf Gebrekidan and Wakene Negassa (2006) who observed that intensive cultivation and use of acid forming inorganic fertilizers affected the distribution of K in the soil and enhanced its depletion. Exchangeable Calcium was also very low (<5cmol (+)/kg) in all land uses except backyard soils as compared to the critical level calibrated by Marx et al (1996). Similarly, exchangeable sodium was almost negligible in all land use types. Kang (1993) stated that the major acidification processes in intensively cultivated soils are due to removal of basic cations (Na, Ca, Mg, and K) by crop uptake, leaching and erosion.
There was great variation in effective cation exchange capacity (ECEC) of the soils under the different land use systems. The highest ECEC (23.98 cmol (+) kg-1) and 26.00 cmol (+) kg-1) was recorded in the backyard fields whilst the lowest (13.18 cmol (+) kg-1) and 13.78 cmol (+) kg-1) was registered in the cultivated field at Hateta and Denzuria kebele respectively (Table 8). Backyard soils had a statistically significant higher ECEC, (p<0.05) in Hateta and (p<0.01) in Denzuria Kebele respectively, than soils under the other three land use types. In line with ECEC, the highest value of CEC (27.36 cmol (+) kg-1 and 30.16 cmol (+) kg-1) was observed in backyard soils and the lowest recorded on Eucalyptus soil and grazing land at both former and later kebeles. The decrease in CEC was not consistent showing that there was no significance difference among different land
38 use systems (Table 8). High CEC for clay minerals in general indicated the presence of high weatherable minerals in the soil (Yerima, 1993).
Table 8. Values of exchangeable bases, effective cation exchange capacity (ECEC) and cation exchange capacity (CEC) in different land uses (Mean ± SE) Soil properties parameter in cmol (+)/kg Land use types
2+ 2+ + + Hateta Ca Mg K Na TEB* ECEC CEC
a a a a a a a Cultivated field 3.55±1.19 3.97±0.55 0.35±0.03 0.02±0.00 7.89±0.67 13.18±0.81 21.70±0.81
Backyard field 11.29±1.36b** 9.20±1.97b* 2.49±0.57b** 0.12±0.04a 23.10±3.82b** 23.98±3.34b** 27.36±4.11a Eucalyptus a a a a a a a plantation 4.46±0.505 3.62±0.54 0.68±0.08 0.05±0.02 8.82±0.93 13.75±0.33 16.36±1.54
a a a a a a a Grazing land 4.53±1.12 4.88±1.39 1.04±0.07 0.06±0.07 10.50±0.54 14.45±0.61 21.22±1.00 Denzuria
a a a a a a a Cultivated field 3.14±1.19 2.23±0.35 0.47±0.06 0.06±0.01 5.90±1.10 13.78±0.78 25.82±2.46
Backyard field 12.41±1.72b** 11.22±1.52b** 1.83±0.33b** 0.16±0.02b* 25.61±3.27b** 26.00±3.22b** 30.16±3.80a Eucalyptus a a a ab a a a plantation 3.35±0.96 4.04±1.23 0.44±0.04 0.12±0.02 7.96±0.95 15.31±0.82 21.57±3.98
a a a a a a a Grazing land 3.35±0.43 2.86±0.19 0.73±0.04 0.08±0.01 7.02±0.48 13.86±0.57 16.96±4.33
Mean values with different superscript letters in columns indicate significant differences at á=0.05, á= 0.01, Where *p<0.05, **P<0.01
4.1.4 Soil Fertility Parameters
Soil acidity is one property associated with decline in soil fertility and low productivity. The success of soil management in maintaining soil fertility attributes depends on understanding the soils response to land use and management practices over time. Since soil, fertility and productivity are easily affected by land use and management practices, depletion of nutrients such as P, N, Ca, K etc., in acidic soil leads to an increasing threat to agricultural and natural ecosystems. The major impact of soil acidity on plant growth is related to the bioavailability of plant nutrients or the soil concentration of plant toxic minerals (McLaren and Cameron, 1996). In highly acidic soils, Aluminium and Manganese can become more available and more toxic to the plant in addition, at lower pH values Calcium, Phosphorous and Magnesium is less available to the plant (Richter and Markewitz, 2001). Thus, apart from taking measures to minimize the impact of
39 human activities on acidification, it is important for us to understand the processes that cause soil acidification and to adopt techniques to neutralize the acidity.
4.1.4.1 Available Phosphorous and Available Potassium
The highest concentrations of available P (25.01 ppm and 36.36 ppm) by the Olsen method were registered on the backyard fields at Hateta and Denzuria Kebeles respectively. Where as lowest values were recorded in Eucalyptus soil (6.94ppm) at the former and in cultivated field (9.52 ppm) in later Kebeles (Table 9).
The critical values for Olsen, P were established to be 8.5ppm by Tekalign Mamo and Haque (1991) for some Ethiopian soils accordingly. However, the available P contents of the soils in the present study were below the critical level at Hateta Kebele on cultivated and Eucalyptus soils. Tisdale et al. (1997) also calibrated available phosphorous by Olsen method as very low (<3.00ppm), low (4.00 to 8.00ppm), medium (8.00-11.00ppm) and rich (>12.00ppm). Hence, available P in cultivated field was generally low (<10ppm). It is also better to consider that the amount of P extracted by Olsen method depends on the pH of the soil, it extracts more in acid soils, and the opposite is true for higher pH. The low available phosphorus content in acid soils is due to not only the inherently low available content of acid soils but also the high fixation capacity of the soil.
Table 9. Values of available phosphorus and potassium in different land use (Mean± SE)
Hateta Denzuria
Land use types Avail. P in ppm Avail. K in ppm Avail. P in ppm Avail. K in ppm
a a a a Cultivated field 7.99±0.724 23.19±3.21 9.52±1.24 33.89±9.30
Backyard field 25.01±3.20b** 427.11±87.83b** 36.36±3.12b** 264.82±53.59b**
a a a a Eucalyptus plantation 6.94±0.19 82.92±10.81 9.66±1.47 32.99±4.46
a a a a Grazing land 8.90±0.26 145.34±18.42 11.87±2.61 90.95±16.98
Mean values with different superscript letters in columns indicate significant differences at á=0.05; á= 0.01, Where *p<0.05, **P<0.01
40 However, backyard soils had a statistically significant higher available P (p<0.01) than soils under the other three land use types. This is most probably due to existence of optimum soil pH and application of phosphorous fertilizer in addition to farmyard manure. Phosphous is readily available at pH ranges 5.5 to 6.5 (McLaren and Cameron, 1996). Similar trends were obtained on available Potassium. A highly significant higher (p<0.01) available potassium were obtained in backyard fields (427.11ppm and 264.82ppm) than other land use types (Table 10). Relatively, the lowest available Potassium was registered on cultivated fields and Eucalyptus plantation at both locations which are below the critical level (<150 ppm) as described by Marx et al (1996).
4.1.4.2 Organic Matter and Nitrogen
Most cultivated soils of Ethiopia are poor in their organic matter content due to low amount of organic materials applied to the soil and complete removal of the biomass from the field (Yihenew Gebreselassie, 2002). However, generally, higher organic carbon content, ranged from 2.95% in Eucalyptus soil to 6.97% in grazing land, were recorded from Acrisols of Ankesha Woreda which is unusual in acid soils (Table 11). In the same way, Yihenew Gebreselassie (2002) also obtained 3.5% organic carbon content from Acrisols of Injibara. Sanchez (1976) indicated that absence of a direct relationship between color and organic matter, and he elaborated that many Oxisol (Acrisols) and Ultisols (Nitosols) have higher organic carbon content than Vertisol. Anda et al. (2008) also observed that Oxisol have a positive impact on soil carbon sequestration and stabilization. The organic matter content also ranged from 7.82 to 8.56% in cultivated field, 5.08 to 11.38 % in Eucalyptus soil and 10.61 to 12.02 % in grazing land for both locations. Nevertheless, the increase in organic matter was not consistent showing that there were no significance (>0.05) differences among different land use types (Table 10). There was a significantly higher (p<0.05) total nitrogen content on grazing land than in cultivated and eucalyptus plantation (Appendices 5, 6). Such differences attributed to continuous cultivation that increased organic carbon oxidation. In most, case the C: N ratio ranges from 20 to 30 considered as normal soil. However, the C: N ratio registered at both sites ranges about 10 to 13 which are below the normal (Table 11). This indicates the existence of enough N to meet microbial needs. Foth and Ellis (1997) reported that soils with C: N ratios in the range of to 12 provide N in excess of microbial needs. Whereas soils with C: N ratios above 35 not likely to contain enough N to meet microbial needs.
41 Table 10.Value of organic matter, total nitrogen and C: N ratio of soils in different land uses (Mean ±SE) Hateta Denzuria Land use types O.M% TN% C:N O.M% TN% C:N
a a a a Cultivated field 8.56±0.49 0.41±0.03 12 7.82±0.48 0.42±0.02 * 10.81
a b a b Backyard field 10.20±0.56 0.56±0.45 10.57 8.07±1.82 0.52±0.04 9.0
b a bc b Eucalyptus plantation 5.08±0.31 ** 0.30±0.02 * 9.8 11.38±0.51 0.54±0.04 12.22
a b c b Grazing land 10.61±0.86 0.56±0.41 10.98 12.02±0.48 * 0.54±0.01 12.91 Mean values with different superscript letters in columns indicate significant differences at á=0.05; á= 0.01, Where *p<0.05, **P<0.01
4.2. Soil Acidity and Soil Property Relationships in Different Land Uses
There is a strong relationship between soil acidity and other soil properties from soils of
different land uses. The correlation analysis indicated that soil pH (H2O; KCl) is highly significantly (p<0.01) and positively correlated with total exchangeable bases (Ca2+, Mg2+, K+ and Na+) (r=0.903**; r=0.979**), and CEC (r=0.457*; r=0.622**) but negatively correlated with exchangeable acidity (r=-0.902**; r=-0.901**) and acid saturation (r=-0.918**; r=-0.889**) for water and KCl respectively (Table 12). This result is in agreement with the findings of Yihenew Gebreselassie (2002) at Injibara area who observed that pH is highly significantly (p<0.01) and positively correlated with Ca (r=0.886**) and Mg (r=0.775**) whereas highly significantly and negatively correlated with exchangeable acidity (r=-0.612**). McLaren and Cameron (1996) elaborated that basic cations (Ca2+, Mg2+, K+ and Na+) are usually found only in low amounts in acidic soil; because they have been displaced from cation exchange sites by H+ and Al3+ ions and subsequently leached from the soil. The rate of removal of these cations normally exceeds their rate of release by mineral weathering and deficiencies may occur in acid soils where as the micronutrients cations are highly soluble at low pH and toxic to plant. Schlede (1989) explained that increased amount of soluble Mn2+ and Al3+ have toxicity effect on cultivated plants and correlated with lower K+, Ca2+ and Mg2+ consumption.
Correspondingly, available phosphorous and available potassium were highly significantly (p<0.01) and negatively correlated with level of acid saturation (r=-0.786** and r=-0.814**) respectively (Table 11). However, they are strongly (p<0.01) and
positively (r=0.799**, r=0.784**) correlated with soil pH (H2O) respectively (Table 12)
42 and the same is true for pH of KCl. The availability of phosphorus is strongly influenced by soil pH. The form of phosphate ion present in the soil changes with pH. According to McLaren and Cameron (1996) under acidic condition, the presence of high levels of soluble iron, aluminium and manganese leads to the precipitation insoluble phosphate compounds. Moreover, phosphate can be ‘fixed’ hydrous oxides of Al and Fe and by certain silicate clays, which can also reduce its availability.
There was also highly significant (p<0.01) positive correlation (r=0.834**) between organic mater and total nitrogen content under different land use systems (Table 11). Fisseha Itanna (1992) reported similar observations at Vertisol of Shoa Robit (r=0.90), Debre Ziet (r=0.96) and Sheno (r=0.99). Nevertheless, weakly correlations were registered with soil acidity, soil pH and exchangeable bases (Table 11).
In general the results of the correlation analysis showed that acid saturation and exchangeable acidity have strong correlation with soil pH, exchangeable bases, CEC, available Phosphorus and available Potassium where as there was a weak correlation with Nitrogen and organic matter content of the soil in the study area (Table 11).
43
Table 11.Correlation coefficients(r) between soil acidity and other soil property (n=24)
Pearson product moment correlations between soil property and soil acidity Soil pH pH in cmol(+)kg-1 Ex. AV.P AV.K OM 2+ 2+ + + Parameters ( H2O) (KCl) Acidity Ca Mg K Na TEB* ECEC CEC AS% (ppm) (ppm) % pH KCl 0.916** EX. Acidity -0.902** -0.901** 2+ Ca 0.912** 0.956** -0.879** 2+ Mg 0.804** 0.900** -0.828** 0.820** + K 0.807** 0.905** -0.837** 0.863** 0.817** + Na 0.526** 0.684** -0.427* 0.649** 0.598** 0.567** TEB* 0.903** 0.979** -0.899** 0.961** 0.944** 0.903** 0.657** ECEC 0.828** 0.947** -0.790** 0.931** 0.930** 0.877** 0.717** 0.976** CEC 0.457* 0.622** -0.469* 0.645** 0.583** 0.528** 0.461* 0.641** 0.684** AS% -0.918** -0.889** 0.976** -0.889** -0.842** -0.815** -0.477** -0.908** -0.804** -0.441* AV.P 0.799** 0.936** -0.804** 0.883** 0.887** 0.796** 0.672** 0.924** 0.926** 0.602** -0.786** AV.K 0.784** 0.872** -0.831** 0.833** 0.791** 0.990** 0.498** 0.875** 0.841** 0.495** -0.814** 0.763** OM -0.183 -0.023 0.048 -0.038 0.097 0.076 0.228 0.033 0.099 0.111 0.048 0.060 0.091 TN 0.190 0.353* -0.292 0.286 0.437* 0.427* 0.430* 0.384* 0.434* 0.315 -0.277 0.400* 0.433* 0.834**
(**) = correlation is significant at the 0.01 level (p<0.01), (*) = correlation is significant at the 0.05 level (p<0.05), and numbers without asterisks indicate there was no significant differences at 0.05 level, n=24 Ex. acidity= Exchangeable Acidity, TEB*= Total Exchangeable bases, Av.P= Available Phosphorous, Av.K =Available Potassium, AS%=Acid Saturation Percentage, ECEC=Effective Cation Exchange capacity, CEC= Cation Exchange Capacity, OM= Organic matter, TN= Total Nitrogen
44 4.3 Farmers’ Perception of Soil Acidity and Their Management Practices
The significance of acid soils is not well understood by farmers, the community, state and local government. Raising the awareness of acid soils is a precursor to the effective management of the problem. Environmental management systems have the potential to deliver management solutions to soil acidity issues (ENRC, 2004). However, there is a large gap between the concepts of EMS and land use change; and the day-to-day reality of farming, Awi zone in general and Ankesha in particular. Basic issues such as improving indigenous soil management practices by farmers experience and awareness of acid soils need to be addressed. Thus, understanding the socioeconomic aspect and practices are an essential prerequisite to the uptake of acidic soil management and amendment principles.
4.3.1 Socioeconomic Characteristics of Households
The majorities (> 97%) of the surveyed households were male-headed and the mean age of respondents (household head) was 46 in the Hateta Kebele and 49 in Denzuria Kebele. Most of the respondents in Hateta Kebele were literate either with formal or informal education and only 37% of them were illiterate. However, in Denzuria Kebele, more than 42% of the respondents were illiterate. The average family sizes of the household were 6 and 7 in Hateta and Denzuria PAs respectively. Beside, more than 95% respondents were married in both peasant associations (Table 12). Farmers in the Hateta Kebele had a mean land holding of 1.625 ha per household. Whereas in Denzuria Kebele PAs mean land holding is 1.575 ha. Furthermore, ninety-two percent in Hateta and 95% in Denzuria of the surveyed households have their own land (Table 12).These households obtained land through a system of land redistribution/land allotment. In spite of low farm productivity, all of the surveyed households are being entirely dependent on agriculture.
Table 12. Characteristics of respondents in Hateta and Denzuria Kebeles Educational Status Sex (%) (%) Average Marital status (%) Average Own Peasant Average Family Land Land Association Male Female Age Literate Illiterate Size Married Divorce (ha) (%) Hateta PAS(n=60) 98 2 46 63 37 6 97 3 1.625 92 Denzuria PAS(n=60) 97 3 49 58 42 7 95 5 1.575 95 Source: Own survey (2008)
45 4.3.2 Perceived Causes and Indicators of Soil Acidification
Farmers in the study areas have a wealth of knowledge about their land resources, its characteristics, limitations, potentials and management options. About 80% and 85 % of surveyed households in Hateta and Denzuria PAs respectively, were aware of the existence of soil acidity problems on their farm since 2006 (Table 13).
Table 13. Perception of farmers on existence of soil acidity problem
Hateta Peasant Association/PA/ Frequency Percent Valid Yes 48 80.0* NO 12 20.0 Total 60 100.0 Denzuria PA Valid Yes 51 85.0 NO 9 15.0 Total 60 100.0 (*) Indicate higher proportion of respondents for respective questions Source: Own survey (2008)
Their awareness may be due to the promotion activity of the government for lime application on farm demonstration trial. In fact, they didn’t know the name “acidic soil” before the stated year but locally, they call such farmland “Gibiz Merate”; meaning ‘inactive’. They explained as, the name “Gibiz” is given to it due to lack of response for fertilizer and poor performance of the crop to be sown. These lands are not suitable for any crop except some grass species and relatively acid tolerant crops like, tef and potatoes with good agronomic management. This is in agreement with Schlede (1989) who explained that acid soils frequently are ‘inactive’ with fertilization; that is why the added fertilizers /NPK/ in spite of the nutrient deficiency of the soils does not affect yield increase or even decrease the yields. Local farmers have experiences of changing ‘Gibiz’ to ‘non Gibiz’ by frequent application of farmyard manure and good agronomic managements as means of reclamation.
The perception of farmers on the causes and indicators of soil acidity reflects if farmers have rightly understood the problem and helps to evaluate if their actions are focused in mitigating the right causes. Thus, those farmers who assured soil acidity are a key
46 problem were asked to list and rank the main causes of soil acidity. In both peasant associations, more than 51% of the surveyed households perceive that soil acidity is not due to a single factor but it is the combining effect of inherent acidic parent material, high rainfall followed by erosion and leaching, continuous cultivation and inappropriate use of nitrogenous fertilizers (Figure 7).
60 Inherent acidic parent material
High rainfall followed by leaching & 50 erosion Continuous cultivation 40 Inappropriate use of nitrogen fertilizer combination of all 30
20
10 % of house hold respondents hold house of %
0 Hateta PA Denzuria PA Kebeles /PAs/ Figure 7. Farmers’ response for probable causes of soil acidity problem
Removing produce from the farmland can be thought of as equivalent to removing lime, leaving the soil more acid. The way that plants take up nutrients results in a partitioning of acidity into the soil and alkalinity into the plant as dry matter. As agriculture removes plant material from as grain or pasture, less alkalinity is returned to the soil, and the soil becomes more acidic. Above 70% of the surveyed households reply that, the majority of crop residues are used for livestock feed at both peasant associations (Figure 8). This has an agreement with the observation by Mulugeta Lemenih (2004). He noted that in the highlands, animal manure and crop residues, instead of being returned to the land, are largely used as fuel and livestock feed. Generally, production of all agricultural products causes soil acidification. Continuous and intensive cultivation of the same land and use of crop residue for fuel wood and livestock feed speed up nutrient removals from the field.
47 Figure 8. Pie chart for response of farmers towards the use of crop residues (n=60)
purpose of crop residue in Hateta kebele Purpose of crop residue in Denzuria Kebele
income income source source, 6% 5% Fuel source Fuel source, 20% 24%
livestock feed livestock 75% feed, 70%
Farmers’ explanations for chactoristics, indicators, crops grown and Management of “Gibiz Merate’’ Unique property of “Gibiz Merate” . The following symptoms tend to indicate The soils of this land have: problem of ‘Gibiz Merate’ (soil acidity) . High workability in dry season /easy for . Falling yields, leaf discolorations ploughing/ and susceptible to stress . Limited grass and crop species and only tef . Crops lack response to fertilizers, reduced and potatoes are grow together with good . Yields, poor plant vigor,increased incidence agronomic of disease, uneven pasture and crop growth . Low water holding capacity, High seepage . poor establishment and persistence of pasture . The soil is reddish to black in color . Poor nodulation of legumes, stunted root . Yield of Barley, wheat and legumes are growth. highly reduced time to time and in some plot, . High annual weeds infestation, persistence of they are not produced at all. acid-tolerant weeds’ such as locally called:
. Arebakash (Spergula arvensis)
. Yeweftef (Eragrostis cilianensis)
Crop yield decline Agricultural experts and farmers thought the opinion that crop production has been declining year to year since the last fifteen years. About 88.3% of the surveyed households also perceived that soil acidity and soil erosion were the main reasons for crop yield decline (Table 14). Some of the crops such as field pea, field bean, wheat, linseed, barley and others
48 become out of production due to soil acidity problems unless special management is employed. Table 14. Farmers’ response for probable causes of crop yield reduction (n=120) Cumulative Hateta Peasant Association Frequency Percent Percent Valid Soil Acidity 27 45.0 45.0 Soil Erosion 26 43.3 88.3* Snow and Pests 3 5.0 93.3 I don’t realize 4 6.7 100.0 Total 60 100.0 Denzuria Peasant Association Valid Soil Acidity 30 50.0 50.0 Soil Erosion 23 38.3 88.3 Snow and Pests 4 6.7 95.0* I don’t realize 3 5.0 100.0 Total 60 100.0 (*) Indicate higher proportion of respondents for respective questions. Source: Own survey (2008)
Most crops have poor performance in acidic soil, and others are disappearing in the surrounding since two to three decades. Based on farmers and experts explanation, productivity, crop diversity and yield drastically had been reduced since 1980s (Table 15). Legumes and wheat become out of production. This could be important indictor for severity of soil acidity at the study area. Even though new varieties were not introduced in the cropping system, the existing once like potatoes and tef relatively covers large proportion of the cultivated area by now.
Table 15. Comparison of crop yield in quintal per hectare /Qt/ha/ in 1980s and 2007 Average yield Qt/ha in % of 1980s Average yield Qt/ha in 2007 Yield yield S/N crop type Min. Max. Average Min. Max. average difference Reduction 1 Tef 11 18 14.5 4 8 6 8.5 58 2 Barley 20 31 25.5 8 12 10 15.5 61 3 Noug 4 6 5 1 2 1.5 3.5 70 4 Linseed 3 4 3.5 * * * - 100 5 Wheat 16 28 22 * * * - 100 6 Potato 60 90 70 30 52 41 29 41 7 field pea 8 14 11 * * * - 100 8 Field bean 9 15 12 * * * - 100 (*) Indicate where the crop is not produced by now in the specified area. min. = Minimum, Max. = maximum, Source: Office of Agriculture and Rural Development (2008)
49 4.3.3 Farmers’ Response to Soil Acidity Problems and Their Coping Mechanisms
According to Teklu Erkossa and Gezahegn Ayele (2003), indigenous knowledge refers to the perception that farmers have about their natural and social environment, which they use to adopt, adapt and develop technologies to their local context. The rationale for undertaking certain traditional practices among others is recognition of problems by the local people. Indigenous practices are aimed at arresting the local priority problems.
Hence, the farmers’ understanding and response to soil acidity problem was based on their observations of indicators mainly associated workability, yield decline and similar weed species infestation like Arebakash (Spergula arvensis) and Yeweftef (Eragrostis cilianensis), poor response of barley, wheat, field pea and other similar crop species. Their responses were also focused on improving these problems. Nearly all the farmers who perceived soil acidity problem in their farm responded by applying either one or more of the soil management practices (coping mechanisms soil acidity problem) described as follows (Figure 10).
35 Good agronomic practice 30 Farm yard manure application Fallowing 25 Liming and proper use of fertilizer Crop rotation 20 Use of acid tolerant species Soil conservation structure 15
10
5 % of household respondents household of % 0 Hateta PA Denzuria PA Kebeles/ PAs/
Figure 9. Farmers’ coping mechanisms of soil acidity problem
Agronomic practices Agronomists attempt to develop techniques that will increase the yield of field crops, improve
50 their quality, and enhance production efficiency and profitability while conserving the fertility of the soil. Farmers’ perceived as agronomic practice is making the farmland suitable to the crop to be sown by adjusting ploughing time, sowing date and critical weeding periods. As indicated in Figure 9, more than 55% of the surveyed households at both kebeles employed good agronomic practices and use of farmyard manure on their farm to tackle soil acidity problems partially. But, the problem is there. Moreover, lime application and use of acid tolerant species is an early stage and not clearly innovated. More than 95% of the respondents didn’t know about lime amendments and acid tolerant varieties unless the environment selects the tolerant one. Crop residues are gathered for livestock feed and remaining grazed by livestock. Nevertheless, there is no experience of mulching; rather crop residues are mostly used for livestock feed.
Manure Farmyard manure is very good to improve organic matter content of soil, increase moisture retention and reduce soil acidity problems. However, the application is limited to backyard fields due to inadequate availability and labor requirement for transportation. More than 30% of the farmers, on surveyed households, agreed that organic fertilizers improve crop yields and soil fertility, while half of them also noted that they enhance the structure of the soil and increase its organic matter content (Figure 9). Farmers said that the disadvantages of using mineral fertilizers were that they are expensive and need to be applied every year, while the main constraints on producing and applying organic inputs were the high labor and transport requirements. Many farmers could not get enough manure to make a significant difference to their soils. They also reported that it was not always possible to get sufficient material to make compost. That is why manure application is limited to backyard fields.
Fallowing Land is left fallow one to maximum of two years when yields of most crops become very poor. Soil fertility could be improved by fallow vegetation. Only about 10% of the surveyed households have experience of using fallow for nutrient recovery (Figure 9). Nevertheless, usually unaffordable due to scarcity of land. The farmers explained that early sowing after fallowing is better practice to reduce severity of soil acidity.
51
Crop rotation Rotating cultivation of various crops in space and time without any fixed sequence, often depending on the yield response. If a decline in yield is observed for cereals, legumes will be replaced in the cycle. Crop rotation increases soil workability and soil nutrient recovery. Mostly the surveyed households rotate the crops as teff-noug-teff in the cultivated field faraway from home and barley- potato- maize and then barley in the backyard fields. Some farmers employed intercropping. Potatoes are intercropped with maize mainly to improve ‘exhausted’ soils. Even though more than 10% of the surveyed households practiced crop rotation as copping mechanism, but it is not effective as compare to farmyard manure.
In addition to the stated management practices, the farmers shift their cropland to Eucalyptus plantation and grazing land. About 42 % and 36 % of the respondents in Hateta and Denzuria peasant associations respectively change their cropland to grazing pasture (Figure 10). However, the grass species grew on acidic soils are unpalatable and poor in performance to support the livestock feed. Most farmers engaged and intended to expand Eucalyptus plantation by realizing its economic importance and compatibility to their farmland. Others tried to produce crops by using farmyard manure as reclamation (Figure 10). According to Daba Wirtu and Gong (2000) observation at Chancho area, the financial return from Eucalyptus globulus is more than ten times higher than the financial return from agricultural crops at a discount rate of 10%. Thus, plantation of eucalyptus globulus is economically more profitable than agricultural use of land where by transport access and fertility of the farmland is considered.
52 45 Eucalyptus plantation 40 Left for grazing land 35 producing crops with agronomic management 30 25 20 15 10 5 % of household respondents household of % 0 Hateta PA Denzuria PA Kebeles/PAs/ Figure 10. Farmers’ opinion for the purpose of acidic soil “Gibiz Merate”
4.3.4. Farmers’ Perception on Eucalyptus Plantation and Soil Acidity
Respondents claim that forest cover in former days was more than one third of the zone area. However, due to growing population numbers and heavy utilization the indigenous trees are disappearing. About 65% and 66% of the surveyed households in Hateta and Denzuria PAs respectively perceived that natural forest has decreased drastically which existed before 15 years and exotic plantation forest has been increased (Appendix 7).
Diminishing natural forest resources are being compensated by rapid expansion of the use of planted exotic trees. The majority (>58%) of surveyed households explained that among the exotic trees, Eucalyptus tree become the most dominant tree species around the area (Table 16). They have an average of 185 trees per households. Almost all of the farmers prefer Bahr zaf/eucalyptus tree/ to other species encounter with its comparative economic advantage. Among Eucalyptus species the most commonly found species in Awi area/Dega region/ is Eucalyptus globulus also known as Nech Bahr Zaf in Amharic, Fuchi Bahr Zaf in Awigni, and Tasmanian blue gum in English (MacLachlan, 2001). Bahr zaf/ Eucalyptus/ is preferred over other species, because of its fast growing, environmentally compatible for acidic soil, drought resistant, has a straight form for construction, split easily, easy for propagation, wide spread ability in the nursery and its bark makes rope. As well, its leaves burn easily and it is a cash crop/source of income/.
53 Table 16. Farmers’ response for dominant plantation tree in surveyed households Cumulative Hateta Peasant Association Frequency Percent Percent Valid Eucalyptus globulus 35 58.3 58.3 Acacia decurrens 12 20.0 78.3 Cupresus lusitanica 8 13.3 91.7 Other indigenous trees 5 8.3 100.0 Total 60 100.0 Denzuria Peasant Association Valid Eucalyptus globulus 36 60.0 60.0 Acacia decurrens 12 20.0 80.0 Cupresus lusitanica 7 11.7 91.7 Other indigenous trees 5 8.3 100.0 Total 60 100.0 (*) Indicate higher proportion of respondents for respective questions Source: Own survey (2008)
Though Eucalyptus trees that have replaced the indigenous species have proven themselves valuable and useful to farmers, there are disadvantages to the high level of use currently employed. The farmers themselves say that the tree is not good for the soil. This is verified by Lisanework Nigatu and Michelson (1994) who compared Cupressus lusitanica and Eucalyptus globulus (exotics) and natural forest effects on nutrient cycling in forested areas. They reported that “the annual nutrient input by litter of the two exotics generally was much lower than that of the Juniperus procera and, in particular, that of the natural forest. Besides, more than 61% the surveyed households perceived as Eucalyptus tree has a negative impact. There is an impact on stream flow decrement or dried in the surrounding /deplete underground H2O /, leaves are not decomposable, no more organic matter return to the soil, shading effect and harbor birds .This is in agreement with the observations by MacLachlan (2001) in Banjashikudad and Fagta Lekoma Woreda of Awi zone. He noted that a major drawback that farmers believe is that Eucalyptus tree hurts the soil and limited in usefulness for furniture and lumber. Nevertheless, their responses were also focused on continuing expanding the plantation regardless of associated problems. This is mainly due to its economic feasibility for local and regional purposes as well as growing ability on acidic soil.
54
5. CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions
From the results of the present study, it is possible to conclude that, the soils in all land use types are strongly acidic at both sites except backyard soils. Higher soil pH and lower acid saturation in backyard soils indicate its suitability for crop production and have a better status of available nutrients. Whereas significantly lower soil pH and higher acid saturation in cultivated fields show that, the soil is not suitable for crop production and poor in available nutrients. Moreover, exchangeable bases (Ca, Mg, K, and Na) and available phosphorous are significantly lower and below the critical level in all land use types except backyard soils. A strong negative correlation of acid saturation with exchangeable bases, soil pH, CEC, available phosphorus and potassium, imply that acidity affects major soil fertility parameters. Thus, land use systems can lead to subtle changes in soil chemistry.
Local farmers have understood the problem of soil acidity, which is explained by irresponsiveness of the farmland to inorganic fertilizer and poor performance of their crops. Such farmland is locally known as ‘Gibiz Merate’, meaning ‘inactive’. Moreover, their understanding to soil acidity problem is based on their observations of indicators mainly associated with workability, yield decline, annual weeds infestation like Arebakash (Spergula arvensis) and Yeweftef (Eragrostis cilianensis). They perceived that acidic parent material, high rainfall followed by erosion and intensively continuous cultivation are the probable causes for soil acidity. Their action to cope up with the problem focused on use of farmyard manure around the homestead garden, shift the cropland to Eucalyptus plantation otherwise left for grazing. Lime application as soil acidity reclamation is limited on farm demonstration trail and clear yield differences not yet evaluated. Most farmers engaged and intended to expand Eucalyptus plantation by realizing its economic importance and compatibility to their farmland.
Generally, the difference in level of acidity in different land use types is more likely due to the differences in intrinsic management systems. The highest status of acidity on cultivated
55 fields indicates the marked influence of continuous cultivation and removal of basic cations by crop uptake where as the better soil condition on backyard soils signify the importance of manure and wood ash application. In addition, the higher status of soil acidity in Eucalyptus plantation indicates the acidifying effect of Eucalyptus; however, it has no significant impact on the tree itself as one can see good growth of the trees. This shows deep-rooted plants are more tolerant to soil acidity encountered with they can catch up the leached cations in the sub soil by their long roots. Where as the existence of high level of acidity on plantation is being attributed to the uptake of more basic cations into the tree biomass and low return through its leaf drop.
On the other hand, the higher acidity on grazing land entails that pasture species such as grass/legumes hay aggravates soil acidity development by taking basic cations during harvest and livestock feed. The reason could be less return of grass/legume biomass to the soil except the under ground plant parts. This acidification process and depletion of base cations lead to an increasing threat to agricultural productivity and natural ecosystems in the study area. Thus, the study emphasize that soil acidity problem is critical in Awi zone, and calls the need for immediate intervention to amend the soil for crop production and sustainability of soil productivity.
5.2 Recommendations
Beyond taking measures to minimize the impact of human activities that cause soil acidification:
It is important to add organic materials in the form of farmyard manure/compost on farmland and adopt techniques by applying lime to neutralize the acidity.
Integration of government agencies, lime industry agencies and the agricultural community should involve seeking for soil acidity amendments and management options.
Support and incentives by the government and non-government organizations are required to address the problem immediately. Moreover, subsidized soil testing at reduced cost to farmers should have been used effectively to increase community awareness about soil acidity.
56 Furthermore, special attention should be given to improvements on land management practices for sustainable productivity of soils.
In general, land use change has to be implemented as a long-term management strategy to improve soil acidity problem.
Further work on micronutrient status, microbial population, botanical composition, soil-plant analysis, field experiments and detailed soil profile studies should be made to give a clear picture regarding the study area.
57 REFERENCES
Abdenna Deressa, Negassa Chewaka and Tilahun Geleto. 2007. Utilization of diversity in land use systems. Sustainable and organic approaches to meet human needs. Inventory of soil acidity status in croplands of Central and Western Ethiopia. Oromiya Agricultural Research Institute, Natural Resources Management, Ethiopia. Adams, F. and Evans, C.E. 1962. A Rapid method of measuring lime requirement of red- yellow podzolic soils. Soil Science Society of America. Proceedings 26: 355-357. Alemayehu Tafesse. 1990. Soil and irrigation management in the state farms. In: Proceedings of the First Natural Resource Conservation Conference Natural Resource Degradation: A Challenge to Ethiopia. Pp. 47-52. Institute of Agricultural Research, 7-8 Feb. 1989. Addis Ababa, Ethiopia. Anda, M., Shamshuddin, J., Fauziah, I. C., Syed Omar, S. R. 2008. Pore space and specific surface area of heavy clay Oxisol as affected by their mineralogy and organic matter. Technical articles: Soil Science. 173 (8): 560-574, August 2008. Aplin, G. 1998. Australians and their environment: An introduction to environmental studies. Oxford University Press, Melbourne. Baligar, V.C. and Fageria, N.K. 2006. Yield sustainability of crops. Soil acidity impact on nutrient use efficiency. World Congress of Soil Science (WCSS), Embrapa, Brazil. Barber, S. 1984. Soil nutrient bioavailability mechanistic approach. John Wiley and Sons, Inc. New York 398p. Bardgett, R.D. 2005. The biology of soil. A community and ecosystem approach. Oxford University Press Inc, New York. Baskin, Y. 1997. The Work of Nature. The scientific community on problems of the environment. Island Press, Washington, DC. Batjes, N.H. 1995. A Global data set of Soil pH properties. Technical paper 27: International Soil Reference and Information Centre (ISRIC), Wageningen. Beecher, H.G. and Lake, B.A. 2004. Rural Industries Research and Development Corporation. Identification and management of soil acidity in irrigated lands of Southern NSW: Publication No. 04/007; Project No. DAN 161A.
58 Bezdicek, D., John, H., Mary, F., Dennis, R. and Jon, M. 1998. Effects of long-term direct seeding on soil properties on Northwest farms. Proceedings, PNW direct seed cropping systems conference, January 7-8, Pasco WA, 1998. Boyd, C.E. 1979. Water quality in warm water fishponds. Craft Master Printers Inc., Opelika, Alabama. 359 p. Bouyoucos, G.H. 1951. A recalibration of the hydrometer for making mechanical analysis of soils. Agronomy Journal 43: 434-438. Brady, N.C. 1984. The nature and properties of soil. 8thed. Eurasia Publishing House. Ltd. New Delhi, India. Bremner, J.M. and Mulvaney, C.J. 1982. Nitrogen-total, pp. 595-624. In: A.L. Page R.H Miller and D.R Keeney (eds.) Methods of Soil Analysis. Part II. Chemical and microbiological properties. Agronomy 9. American Society of Agronomy Inc. Madison, Wisconsin. Bryman, A. and Cramer, D. 2006. Quantitative data analysis with SPSS release 15 for windows: A Guide for Social Scientists. Routledge, London. Buerkert, A., Cassman, K. G. de la Piedra,R., and Munns, D. N. 1990. Soil acidity and liming effects on stand, nodulation, and yield of common bean. Agronomy Journal 82: 749- 754. Bureau of Agriculture. 1999. Agricultural Master Plan of the Amhara National Regional State. Technical report on soil and water management, Bahir Dar, Ethiopia. Coyne, Mark. 1999. Soil microbiology an exploratory approach. Delmar publishers, Albany, New York. CSA. 1998. Federal Democratic Republic of Ethiopian Office of Population and Housing Census Commission Central Statistical Authority: The 1994 Population and Housing Census of Ethiopia Results for Amhara Region, Vol. II Analytical Report: June.1998. Addis Ababa, Ethiopia. Daba Wirtu and Gong, P. 2000. The economics of growing Eucalyptus globulus labill. On the highlands of Oromiya, Ethiopia with special reference to Intoto and Chancho areas. Ethiopian Journal of Natural Resources 2(2): 203-225. Dolling, P. 2001. National Land and Water Resources Audit, Project 5.4C. Soil acidity and acidification, 15 P.
59 Doran, J. W. and T. B. Parkin. 1994. Defining and assessing soil quality. Pp. 1-21. In: J.W. Joran, D.C. Coleman, D.F. Bezdicek and B.A. Stewart (eds.). Defining soil quality for sustainable environment, SSSA. Special Publ. No. 35, Madison, Wisconsin, USA. Duffera, M. and W.P, Robarge. 1999. Soil characteristics and management effects on phosphorus sorption by High land Plateau Soils of Ethiopia. Soil Sci. Soc. Am. J. 63: 1455-1462. Eck, H.V. and Stewart, B.A. 1995. Manure. In: J.E. Rechcigl (ed.), Soil amendments and environmental quality, Pp. 169-199. Lewis Publ., Boca Raton. EFAP. 1994. Ethiopian Forestry Action Program. The Challenge for development. Vol. II. Final Report. Ministry of Natural Resource Development and Environmental Protection. Addis Ababa, Ethiopia. EMA. 2008. Ethiopian Mapping Authority, top sheet NC 37_1 and NC-37_5. ENRC. 2004. Report of the Environment and Natural Resource Committee. Victoria, Parliament. Inquiry on the impact and trends in soil acidity. Parliamentary paper No. 59 of Session 2003-2004. Farina, M.P.W. and Chanon, P. 1991. A field comparison of lime requirement indices for maize. Plant and soil 134: 127-135. Foth, H. and B. Ellis. 1997. Soil fertility. CRC Press. Inc., USA. Getaneh Assefa. 1975. Stratigraphy and sedimentlogy of Mesozoic sequences in the Upper Abay (Blue Nile) River Valley Region. Ethiopia. Ph.D. Thesis. University of Minneota, London, England. Getaneh Assefa. 1984. Fundamentals of geology. Addis Ababa University, Addis Ababa, Ethiopia. Gete Zelleke. 2003. State of natural resource base in Ethiopia: Challenges and Opportunities. Rural Development in the Ethiopian Highlands, pp. 36-41, (FAO). FAO Corporate Documents Repository, Rome. GIS by ESRI. 2005. Working with a Mixed ArcGIS Version Environment (ArcMap version 9.1). An ESRI White Paper. December 2005. ESRI-380, Network, St., Redlands, USA Graham, P.H. 1998. Biological dinitrogen fixation. Pp 322-345. In: David M. Sylvia, Jeffery F. Fuhrman, Peter G. Hartel, and David A. Zuberer (ed). Principles and application of soil microbiology. Prentice Hall, New Jersey.
60 Heluf Grebrekidan and Wakene Negassa. 2006. Impact of land use and management practices on chemical properties of some soils of Bako Area, Western Ethiopia. Ethiopian Journal of Natural Resource 8(2): 177-197. Helyar, K.R. 1991. ‘The management of acid soils’, in RJ Wright, VC Baligar and RP Murrmann (eds), Plant-soil interactions at low pH, Kluwer Academic Publishers, Netherlands. Harrison, R.M. and DeMora, S.J. 1995. Introductory Chemistry for Environmental Science. 2nd ed. Cambridge University Press. Pp. 326-338. IDWSDD. 2006. Bureau of water resources development irrigation and watershed study and design department feasibility report on Fettam watershed January 2006. Bahirdar, Ethiopia. Jones, J.B., Jr. 2001. Laboratory guide for conducting soil tests and plant analysis. CRC Press, Boca Raton London New York, Washington, D.C. Kang, B.T. 1993. Changes in soil chemical properties and crop performance with continuous cropping on Entisols in the humid tropics. Proceedings of International Symposium Organized by the Laboratory of Soil Fertility and Biology, Katholieke Universities and International Institute for Tropical Agriculture, 4-6Novembet,1991. Leuven, Belgium. Pp 297-306. Kolay, A.K. 1993. Basic concepts of soil science. School of agricultural science and rural development. North Eastern Hill University, Madziphema Nagaland, Willey Eastern Limited. New Delhi India. Pp. 129. Lisanework Nigatu and Michelson, A. 1994. Litter fall and nutrient release by decomposition in three plantations compared with natural forest in the Ethiopian highland. Forest Ecology and management 65: 149_164. Mahler, R. L. and R. E. Mcdole,R.E. 1987. Effect of soil pH on crop yield in Northern Idaho. Agron. J. 79:751-755. Maclachlan, M. 2001. Manual of Highland Ethiopian Trees. Prepared for development agents of ‘Dega’ Areas in Region 3. SIM Forestry Project. Pp. 279-280. Marx, E.S., Hart, J. and Stevens, R.G. 1996. Soil testing interpretations guide. Oregon State University Extension Service, US Department of Agriculture, USA.
61 Mclaren, R.G and Cameron, K.C. 1996. Soil Science. Sustainable production and environmental protection. 2nd ed. Oxford University Press. Auckland, Oxford, New York. McLean, E.O. 1965. Part II. Chemical and microbial properties, including measurement and sampling of Aluminium. In: C.A. Black (eds.) Methods of soil analysis. Agronomy 9: 978-998. American Society of Agronomy Inc. Madison, Wisconsin. Mesfin Abebe. 1998. Nature and management of Ethiopian soils. Alemaya University of Agriculture. Alemaya, Ethiopia. 272p. Mills, A.J. and Fey M.V. 2003. Declining soil quality in South Africa. Effects of land use on soil organic matter and surface crusting. Review article; South African Journal of Science 99, September/October 2003. MoARD. 2006. Ministry of Agriculture and Rural Development. Conference report on March 2006, Amharic version (Unpublished). Addis Ababa, Ethiopia. MoARD. 2007. Ministry of Agriculture and Rural Development: Soil acidity management and lime application principle. Guideline for development agents. Amharic Version P. 6, Addis Ababa, Ethiopia. Mokwunye. A.U. 1978. The role of inorganic fertilizers in the chemical degradation of Nigerian Savanah soils Samaru Conference Paper 14. Expert evaluation on methodology for assessing soil degradation. FAO, Rome. Morgan, G.H. 1941. Chemical diagnosis by the Universal Soil Testing System. Conn. Agr. Exp. Sta. (New Haven), Bull.450. Mulugeta Lemenih. 2004. Effects of land use changes on soil quality and native flora degradation and restoration in the Highlands of Ethiopia: Implications for sustainable land management. Doctoral Dissertation. Uppsala, Sweden. Murray. D., alter, C.C and Andereg J.C. 1992. Control of cephalosporium stripe of winter wheat by liming. Plant Dis. 76: 282-286. National Meteorological Agency. 2008. Monthly total rainfall in mm 2003-2005. Injibara, Kessa and Azena stations at Gojjam Region, Addis Ababa, Ethiopia. Ngugi, D., Karau, P., and Nguyo, W. 1978. East African Agriculture. A textbook for secondary school. Mcmillan Education Limited, Hong Kong.
62 Nyborg, M. and. Hoyt P.B,. 1978. Effects of soil acidity and liming on mineralization of soil nitrogen. Can. J. Soil Sci. 58: 331. Office of agriculture and rural development. 2007. Compiled Report7. Amharic version, Ankesha. Olsen, S.R., Cole, C.V., Watanabe, F.S. and L.A. Dean, L.A. 1954. Estimation of available P in soil by extraction with sodium bicarbonate. USDA Circular 939: 15-19. Physical Planning Department. 1985. A regional atlas of northern Ethiopia. Bahir Dar, 95p. Rayment, G.E. and Higginson, F.R. 1992. Soil pH. Australian laboratory handbook of soil and water chemical methods, Inkata Press, Melbourne. pp. 17–23. RELMA. 2005. Regional land management Unit/World Agro forestry Centre; Managing land. Practical guide for Development agent. Technical handbook No. 36: Eastern and Central Africa regional programme, Nairobi, Kenya, Ministry of Agriculture and Rural Development; Addis Ababa, Ethiopia. Ren Fang Shen and Rong Fu Chen. 2006. General status of soil acidity in south china and plant adaptation to acid soil. State key laboratory of soil and sustainable agriculture. Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China. Reuss, J.O, and Johnson, D.W. 1986. Acid deposition and the acidification of soils and waters. Springer-Verlag, New York. Richter, D.D and Markewitz, D. 2001. Understanding Soil Change. Soil sustainability over millennia, centuries and decades, Cambridge University Press. Pp 182-184. Sahlemedhin Sertsu and Taye Bekele. 2000. Procedures for soil and plant analysis. Technical paper 74, National Soil Research Center, Ethiopian Agricultural Research Organization (EARO), Addis Ababa. Saikh, H., Varadachari, C. and Ghosh,K. 1998. Effects of deforestation cultivation on soil CEC and contents of exchangeable bases. A case study in Simplipal National Park, India. Plant and Soil 204: 67-75. Sanchez, P.A. 1976. Properties and management of soils in the tropics. John Wiley and Sons, New York. 618p. Schlede, H. 1989. Distribution of acid soils and liming materials in Ethiopia: Note. No.326. Peoples Democratic Republic of Ethiopia. Ministry of Mines and Energy Ethiopian Institute of Geological Surveys: Industrial Mineral Division. Addis Ababa, Ethiopia.
63 Slattery, B and Hollier, C. 2002. Impacts of acid soils in Victoria, A Report for Department of Natural Resources and Environment, Goulburn Broken Catchment Management Authority and North East Catchment Management Authority. Sparks, D.L. 2002. Department of Plant and Soil Science University of Delaware, Advance in Agronomy Vol. 77 p. 283. Academic Press, Newark Delaware. Summer, M.E. 1992. Determination of exchangeable acidity and exchangeable aluminium using 1nkcl, In S.I Donohue, ed., Reference soil media diagnostic procedures for the Southern Region of United States, Southern Cooperative Series Bulletin Number 374. Virginia Agricultural Experiment Station, VPI and SU, Blacksburg, 41-42. Technical Report on Ethiopia, Geomorphology and Soils. 1984. FAO, UNDP, the Provisional Military Government of Socialist Ethiopia, Ministry of Agriculture. Land use planning and Regulatory Department, Rome. Tekalign Mamo and Haque, I. 1991. Phosphorous Status of some Ethiopian soils. Evaluation of soil test methods for available phosphorus. Tropical Agriculture (Trinidad) 68: 61-66 Teklu Erkossa and Gezahegn Ayele. 2003. Indigenous knowledge and practices for soil and water management in East Wollega, Ethiopia: Universitaet Hohenheim, Soil Science and Site Ecology, Germany/Debre Zeit Agricultural Research Centre (DZARC), Ethiopia. Tisdale, S.L., Nelson, W.L., Beaxon, J D. and. Havlin, J.L. 1997. Soil fertility and fertilizers. 5thed. Macmill publishing company, U.S.A. Van Reeuwijk, L. P. 1993. Procedure for soil analysis. 4thed. .International soil reference and information center.Wageningen, The Netherlands. Wakene Negassa and Heluf Gebrekidan. 2003. The impact of different land use systems on soil quality of Western Ethiopian Alfisols: Bako Agricultural Research Center; West Shoa, Alemaya University, Ethiopia. Wakene Negassa, Kefyalew Negisho, Friesen, D.K., Ransom,J., Abebe Yadessa. 2001. Determination of optimum farmyard manure and NP fertilizers for maize on farmers’ field: Seventh Eastern and Southern Africa Regional Maize Conference 11th-12th. February 2001. Pp. 387-393.
64 Walkey, A. and. Black, C.A. 1934. An examination of degtjareff method for determining soil organic matter and proposed modification of the proposed modification of the chromic acid titration method. Soil Science 37: 29-38. Wild, A. 2003. Soil, land and food: Managing the land during 21st century. Cambridge University press. Pp. 106-107. Yihenew Gebreselassie. 2002. Selected chemical and physical characteristics of soils of Adet Research Center and its testing sites in Northwestern Ethiopia; Ethiopian Journal of Natural Resources. Ethiopian Society of Soil Science, Vol. 4(2):199-215. Addis Ababa, Ethiopia. Yerima, B.P.K. 1993. Manuals for good laboratory practice. Improvement of soil services for agricultural development (Eth/87/010). Field document no. 52. Land use planning and regulatory department, Ministry of natural Resources development and Environmental protection /FAO/ Addis Ababa, Ethiopia. Young, A. and Young R. 2001. Soils in the Australian landscape, Oxford University Press, Melbourne.
Internet Sources/web sites
URL1: http://www.soils.wisc.edu/extension/FAPM/proceedings/2A.barak.pdf. Accessed, 2005
URL2: http://www.tropentag.de/2004/abstracts/full/265.pdf.Accessed, December2004
URL3: http://www.nrw.qld.gov.au/factsheets/pdf/land/l45.pdf. Accessed, March 2006
ULR4: http://www.agric.wa.gov.au/content/lwe/land/acid/bulletin4505.pdf. Accessed, 2008
URL5: http://www.agric.wa.gov.au/content/past/op/cp/bull4538.pdf. Accessed, December 2004
URL6: http://www.metla.fi/silvafennica/full/sf40/sf403417.pdf.Accessed, December 2004
65 APPENDICES Appendix 1. Mean annual rainfall of three stations at Gojjam
Injibara Stations Distance from Ankesha Ju Year Jan Feb Mar Apr May n Jul Aug Sept Oct Nov Dec Total km Dir 2003 0 18.1 61.8 15 75 375.3 570.9 397 422.1 85.4 81.4 4.3 2106.5 17 N 2004 18.8 9.1 21.6 103 55.4 320.2 626.2 388 411.4 133.3 71.3 44.1 2202.8 2005 1.2 6.6 51 74 76.8 385.2 490 510 459 116.8 39.3 0 2210.1 Mean R.F 6.67 11.27 44.8 64 69.1 360.2 562.4 432 430.8 111.8 64 16.1 2173.1 Kessa Station 10 E 2003 0 24.2 101.5 6 27.6 423.3 608 489 569 49 26 38 2360.9 2004 24 10.1 18.3 150 37.5 318 533 513 573 171 63 27 2437.3 2005 4 32.1 55.3 53 112.5 329.9 542 437 486 190 32 0 2274.7 Mean RF 9.4 22.1 58.37 70 59.2 357.1 561 480 543 137 40 22 2357.6 Sw Azena station 13 2003 0 51.5 108.1 0 26 338 518 436 567 176 102 33 2355.4 2004 2.5 3.1 25.4 105 72.9 291 268 632 386 143 108 56 2092.6 2005 0 5.5 103.7 22 91.4 341 296 269 350 179 67.5 0 1724.6 Mean 63.4 RF 0.8 20 79.07 42 3 323 361 446 434 166 92.4 30 2057.5 N.B. Dir. =Direction=North, E=East, SW=South West
66
Appendix 2. Brief description of the sampling sites
Land use Geographical position Altitude slope Land use history or Type Rep E/Longitude/ N/Latitude/ (m.a.s.l.) (%) Vegetation
Hateta Kebele tef, Noug, Cultivated HCU-01 36°53'34.34'' 10°51'58.93'' 2362 2 Finger millet Field HCU-02 36°53'33.40'' 10°51'59.04'' 2360 1 low level arable HCU-03 36°53'32.11'' 10°51'59.09'' 2359 4 farming Backyard HB-01 36°53'56.56'' 10°52'23.27'' 2388 5 Potato,Barley,Maize Field HB-02 36°53'55.26'' 10°52'21.99'' 2383 2 " HB-03 36°52'37.63'' 10°50'57.76'' 2385 3 "
Eucalyptus HEU-01 36°53'56.44'' 10°53'18.58'' 2432 1 Cover with Plantation HEU-02 36°53'57.37'' 10°53'17.22'' 2429 3 Eucalyptus tree HEU-03 36°53'58.73'' 10°53'16.18'' 2426 4 since 15 years ago Grazing HGR-01 36°53'52.67'' 10°52'25.92'' 2389 6 Communal Land HGR-02 36°53'52.67'' 10°52'25.92'' 2391 5 grazing Land HGR-03 36°53'52.46'' 10°52'26.43'' 2386 1 since 1970s ago Average(masl) 2390 Denzuria Kebele
Cultivated DCU-11 36°55’41.97½ 10°51’30.88’’ 2401 1 tef, Noug Field DCU-12 36°55’39.88½ 10°51’33.31’’ 2400 3 low level arable DCU-13 36°55’39.40½ 10°51’37.14’’ 2406 4 farming Backyard DB-11 36°55’26.94’’ 10°53’19.75’’ 2409 4 Potato, Barley, Maize Field DB-12 36°54’35.86’’ 10°51’57.85’’ 2413 5 " DB-13 36°51’37.79’’ 10°50’28.50’’ 2405 1 " Eucalyptus DEU-11 36°55’58.15’’ 10°52’11.27’’ 2428 5 Cover with Plantation DEU-12 36°55’48.82’’ 10°51’54.81’’ 2423 4 Eucalyptus tree DEU-13 36°55’47.96’’ 10°51’54.68’’ 2426 2 since 15 years ago Grazing DGR-11 36°51’34.25’’ 10°51’34.42’’ 2398 5 Communal Land DGR-12 36°55’28.50’’ 10°51’31.44’’ 2395 3 grazing Land DGR-13 36°55’22.58’’ 10°51’26.23’’ 2392 2 since 1970s ago Average(masl) 2408 N.B: °=Degree,’ =minute; ’’ =seconds (Source: Own survey Data, 2008)
67 Appendix 3. Laboratory analysis results for soil properties at Hateta Kebele Hateta AV.P -1 kebele pH(1:2.5 )Liquid Ratio Exchangeable cations in cmol(+)kg (ppm) Av. K silt 2+ 2+ + + Land use Rep H2O KCl EA Ca Mg K Na TEB* ECEC AS% CEC OM% TN% (Olsen) (ppm) sand% % Clay% class HCU_01 5.6 3.87 5.54 5.85 2.93 0.40 0.02 9.20 14.70 37.60 23.30 8.91 0.37 6.68 29.43 43.28 33.28 23.44 Loam HCU_02 5.9 3.86 5.29 2.93 4.18 0.33 0.02 7.46 12.80 41.50 21.00 9.18 0.40 8.11 21.4 35.28 39.28 25.44 Loam Cultivated HCU_03 5.00 3.83 5.03 1.88 4.81 0.31 0.02 7.02 12.10 41.70 20.80 7.60 0.46 9.18 18.73 37.28 37.28 25.44 Loam field Mean 5.12 3.85 5.29 3.553 3.97 0.35 0.02 7.89 13.20 40.30 21.70 8.56 0.41 7.99 23.19 38.61 36.61 24.77 Loam SD 0.13 0.02 0.26 2.057 0.96 0.05 0.00 1.15 1.40 2.33 1.41 0.85 0.01 1.25 5.57 4.16 3.06 1.55 SE 0.076 0.012 0.147 1.187 0.554 0.03 0.00 0.67 0.81 1.35 0.81 O.49 0.03 0.724 3.21 2.40 1.76 0.67 HB_01 5.67 4.72 0.41 12.75 12.10 3.01 0.09 27.98 28.40 1.44 34.80 11.10 0.65 30.63 556.4 43.28 35.28 21.44 Loam Backyard HB_02 5.61 4.72 0.36 12.55 10.04 2.97 0.19 25.75 26.10 1.38 26.80 10.40 0.54 24.85 465.5 41.28 37.28 21.44 Loam Field HB_03 5.35 4.22 0.88 8.57 5.44 1.48 0.07 15.56 17.40 5.05 20.60 9.15 0.50 19.55 259.5 35.28 37.28 27,4 Clay Loam Mean 5.54 4.55 0.55 11.29 9.20 2.49 0.12 23.10 23.98 2.62 27.36 10.20 0.56 25.01 427.1 39.95 36.61 23.44 Loam SD 0.17 0.29 0.29 2.358 3.42 0.87 0.06 6.62 5.78 2.10 7.12 0.97 0.10 5.54. 152.1 4.16 1.15 3.46 SE 0.098 0.17 0.166 1.36 1.97 0.51 0.04 3.82. 3.34 1.21 4.11 0.56 0.45 3.20 87.83 2.40 0.67 2.00 HFEU_01 5.26 3.84 5.39 4.18 2.72 0.77 0.05 7.72 13.10 41.10 17.80 4.70 0.29 7.32 96.3 41.28 35.28 23.44 Loam HFEU_02 5.21 3.82 5.84 3.76 3.55 0.74 0.02 8.07 13.90 42.00 13.60 5.70 0.34 6.82 90.95 39.28 35.28 25.44 Loam Eucalyptus HFEU_03 5.32 3.92 3.56 5.44 4.60 0.53 0.09 10.66 14.20 25.00 18.50 4.85 0.26 6.68 61.52 39.28 39.28 21.44 Loam Plantation Mean 5.26 3.86 4.93 4.46 3.62 0.68 0.05 8.82 13.70 36.04 16.36 5.08 0.30 6.94 82.92 39.95 36.61 23.44 SD 0.06 0.05 1.21 0.874 0.94 0.13 0.04 1.61 0.57 9.54 2.67 0.54 0.04 0.34 18.73 1.15 2.31 2.00 SE 0.032 0.03 0.69 0.505 0.54 0.08 0.02 0.93 0.33 5.50 1.54 0.31 0.02 0.19 10.81 0.67 1.33 1.15 HGR_01 5.33 3.99 3.86 5.44 4.81 0.92 0.07 11.24 15.10 25.60 19.50 10.80 0.57 8.54 123.1 37.28 35.28 27.44 ClayLoam HGR_02 5.23 3.90 4.22 2.30 7.32 1.16 0.05 10.83 15.10 28.01 22.97 11.97 0.59 9.40 181.9 43.28 35.28 21.44 Loam Grazing HGR_03 5.31 3.95 3.81 5.85 2.51 1.03 0.05 9.44 13.30 28.80 21.20 9.03 0.55 8.75 131.1 43.28 35.28 21.44 Loam Land Mean 5.29 3.95 3.96 4.53 4.88 1.04 0.06 10.50 14.45 27.45 21.20 10.60 0.56 8.90 145.3 41.28 35.28 23.44 Loam SD 0.05 0.05 0.22 1.942 2.41 0.12 0.01 0.94 1.05 1.67 1.74 1.48 0.1O 0.45 31.91 3.46 0.00 3.46 SE 0.031 0.026 0.129 1.12 1.39 0.07 0.07 0.54. 0.61 0.97 1.00 0.86 0.41 0.26 18.82 2.00 0.00 2.00 *TEB=Total exchangeable base; ECEC=Effective cation exchange capacity, As%=acid saturation percentage EA=exchangeable acidity’s TN= Total nitrogen, OM= Organic Matter; Avp=available phosphorous
68
Appendix 4 . Laboratory analysis results for soil properties at Denzuria kebele Denzuria AV.P -1 Kebele PH:1:2.5 Liquid Ratio Exchangeable cations in cmol(+)kg (ppm) AV.K silt 2+ 2+ + + Land uses Code-Rep H2O KCl EA Ca Mg K Na TEB* ECEC AS% CEC OM% TN% Olsen (ppm) sand% % Clay% Class Cultivated DCU_11 4.96 3.78 6.81 5.44 1.88 0.42 0.05 7.79 14.6 46.60 27.14 8.46 0.42 11.40 32.1 41.28 35.28 23.44 Loam Field DCU_12 4.90 3.76 8.59 2.51 2.93 0.41 0.09 5.94 14.5 59.10 21.06 6.89 0.45 7.18 18.73 39.28 35.28 25.44 Loam Clay DCU_13 4.72 3.75 8.23 1.46 1.88 0.59 0.05 3.98 12.2 67.40 29.26 8.11 0.38 9.97 50.83 31.28 39.28 29.44 Loam Mean 4.86 3.76 7.88 3.14 2.23 0.47 0.06 5.90 13.78 57.72 25.82 7.82 0.42 9.52 33.89 37.28 36.61 26.11 SD 0.12 0.02 0.94 2.06 0.61 0.10 0.02 1.91 1,4 10.50 4,26 0.82 0.04 2.15 16.12 5.29 2.31 3.06 SE 0.07 0.01 0.54 1.19 0.35 0.06 0.01 1.10 0.78 6.03 2.46 0.48 0.02 1.24 9.30 3.05 1.33 1.76 Backyard DB_11 5.95 4.94 0.30 15.68 14.01 2.27 0.19 32.15 32.50 0.92 37.60 9.41 0.59 42.60 312.97 29.28 39.28 31.44 ClayLoam Field DB_12 5.48 4.50 0.51 9.83 10.87 1.18 0.14 22.02 22.50 2.26 27.60 10.30 0.52 33.20 157.8 37.28 35.28 27.44 ClayLoam DB_13 5.98 4.82 0.36 11.71 8.78 2.04 0.14 22.67 23.00 1.56 25.20 4.48 0.44 33.28 323.7 31.28 41.28 27.44 ClayLoam Mean 5.80 4.75 0.39 12.41 11.22 1.83 0.16 25.61 26.00 1.58 30.16 8.07 0.52 36.36 264.8 32.61 38.61 28.80 SD 0.23 0.19 0.09 2.44 2.15 0.47 0.02 4.63 4.56 0.55 5.37 2.57 0.06 4.41 92.82 4.16 3.06 2.31 SE 0.16 0.13 0.06 1.72 1.52 0.33 0.02 3.27 3.22 0.39 3.80 1.82 0.04 3.12 53.59 2.40 1.76 1.33 Eucalyptus DFEU_11 5.10 3.88 6.61 5.23 2.93 0.37 0.14 8.67 15.3 43.30 29.50 12.40 0.61 7.25 24.07 43.28 35.28 21.44 Loam plantation DFEU_13 4.93 3.79 7.62 2.09 6.48 0.47 0.09 9.13 16.8 45.50 16.80 10.93 0.52 12.33 37.45 35.28 37.28 27.44 Clay loam DFEU_12 4.99 3.84 7,83 2.72 2.72 0.49 0.14 6..7 13.90 56.30 18.50 10.81 0.48 9.40 37.45 39.28 35.28 25.44 Loam Mean 5.01 3.84 7.35 3.35 4,04 0.44 0.12 7.96 15.30 48.40 21.60 11.40 0,54 9.66 32.99 39.28 35.90 24.80 SD 0.09 0.05 0.65 1.66 2.11 0.06 0.03 1.65 1.43 6.99 6.90 0.89 0.07 2.55 7.73 4.00 1.15 3.06 SE 0.05 0.03 0.37 0.96 1.23 0.04 0.02 0.95 0.82 4.03 3.98 0.51 0.04 1.47 4.46 2.31 0.67 1.76 Grazing DGR_11 5.09 3.86 6.96 4.18 2.93 0.75 0.09 7.95 14.90 46.70 15.70 12.97 0,57 16.48 120.4 35.28 35.28 29.44 ClayLoam land DGR_12 5.00 3.84 6.25 2.72 3.14 0.79 0.07 6.72 13.00 48.20 10.20 11.69 0,59 11.68 90.95 31.28 37.28 31.44 ClayLoam DGR_13 4.94 3.85 7.32 3.14 2.51 0.64 0.09 6.38 13.70 53.40 25.23 11.40 0,55 7.46 61.52 37.28 33.28 29.44 ClayLoam Mean 5.01 3.85 6.84 3.35 2.86 0.73 0.08 7.02 13.90 49.40 16.75 12.02 0,57 11.87 90.95 34.61 35.28 30.11 SD 0.08 0.01 0.54 0.75 0.32 0.08 0.01 0.83 0.98 3.54 7.50 0.84 0,02 4.51 29.43 3.06 2.00 1.15 SE 0.04 0.01 0.31 0.43 0.19 0.04 0.01 0.48 0.57 2.04 4.33 0.48 0.01 2.61 6.99 1.76 1.15 0.67 *TEB=Total exchangeable base; ECEC=Effective cation exchange capacity, AS% = Acid saturation percentage, EA=exchangeable acidity’s TN= Total nitrogen, OM= Organic Matter; Av. P = Available phosphorous
69 Appendix 5. Analysis of variance of soil properties at Hateta kebele (Location-1) ANOVA for pH of Water Sum of Source of variation Squares df Mean Square F Sig. Between Groups .283 3 .094 7.220 .012 Within Groups .104 8 .013 Total .387 11 ANOVA for pH of KCl Sum of Source of variation Squares df Mean Square F Sig. Between Groups 1.016 3 .339 15.294 .001 Within Groups .177 8 .022 Total 1.193 11 ANOVA for Exchangeable Acidity Sum of Source of variation Squares df Mean Square F Sig. Between Groups 48.053 3 16.018 257.312 .000 Within Groups .498 8 .062 Total 48.551 11 ANOVA for Exchangeable Calcium Sum of Squares df Mean Square F Sig. Between Groups 115.488 3 38.496 10.748 .004 Within Groups 28.653 8 3.582 Total 144.141 11 ANOVA for Exchangeable Magnesium Sum of Source of variation Squares df Mean Square F Sig. Between Groups 59.778 3 19.926 4.129 .048 Within Groups 38.610 8 4.826 Total 98.388 11 ANOVA for Exchangeable Potassium Sum of Source of variation Squares df Mean Square F Sig. Between Groups 7.995 3 2.665 13.423 .002 Within Groups 1.588 8 .199 Total 9.584 11 ANOVA for Exchangeable Sodium Sum of Source of variation Squares df Mean Square F Sig. Between Groups .015 3 .005 3.531 .068 Within Groups .011 8 .001 Total .026 11 ANOVA for Exchangeable Bases Sum of Source of variation Squares df Mean Square F Sig. Between Groups 453.121 3 151.040 12.421 .002 Within Groups 97.284 8 12.161 Total 550.05 11
70 ANOVA for Effective CEC Sum of Source of variation Squares df Mean Square F Sig. Between Groups 235.770 3 78.590 8.551 .007 Within Groups 73.530 8 9.191 Total 309.299 11 ANOVA for Acid Saturation Percentage Sum of Source of variation Squares df Mean Square F Sig. Between Groups 2554.945 3 851.648 32.863 .000 Within Groups 207.319 8 25.915 Total 2762.264 11 ANOVA for Cation Exchange Capacity Sum of Source of variation Squares df Mean Square F Sig. Between Groups 173,894 3 57.965 3.687 .062 Within Groups 125,767 8 15.721 Total 299,661 11 ANOVA for Available Phosphorous Sum of Source of variation Squares df Mean Square F Sig. Between Groups 661.198 3 220.399 27.044 .000 Within Groups 65.197 8 8.150 Total 726.395 11 ANOVA for Available Potassium Source of variation Sum of Squares df Mean Square F Sig. Between Groups 287548.64 3 95849.488 15.621 .001 Within Groups 49086.000 8 6135.750 Total 336634.464 11 ANOVA for Organic Matter Sum of Source of variation Squares df Mean Square F Sig. Between Groups 56.935 3 18.978 18.351 .001 Within Groups 8.274 8 1.034 Total 65.208 11
ANONA for Total Nitrogen Sum of Source of variation Squares df Mean Square F Sig. Between Groups .147 3 .049 13.285 .002 Within Groups .030 8 .004 Total .177 11
71 Appendix 6. Analysis of variance of soil properties at Denzuria kebele (Location 2) ANOVA for pH of Water Sum of Source of variation Squares df Mean Square F Sig. Between Groups 1,648 3 ,549 20,471 ,000 Within Groups ,215 8 ,027 Total 1,863 11 ANOVA for pH of KCl Sum of Source of variation Squares df Mean Square F Sig. Between Groups 1.987 3 .662 48,973 ,000 Within Groups .108 8 .014 Total 2.095 11 ANOVA for Exchangeable Acidity Sum of Source of variation Squares df Mean Square F Sig. Between Groups 110.839 3 36.946 91.265 .000 Within Groups 3.239 8 .405 Total 114.078 11 ANOVA for Exchangeable Calcium Sum of Source of variation Squares df Mean Square F Sig. Between Groups 187.641 3 62.547 15.164 .001 Within Groups 32.997 8 4.125 Total 220.638 11 ANOVA for Exchangeable Magnesium Sum of Source of variation Squares df Mean Square F Sig. Between Groups 155.475 3 51.825 17.472 .001 Within Groups 23.729 8 2.966 Total 179.204 11 ANOVA for Exchangeable Potassium Sum of Source of variation Squares df Mean Square F Sig. Between Groups 3.845 3 1282 14.625 .001 Within Groups .701 8 .088 Total 4.46 11 ANOVA for Exchangeable Sodium Sum of Source of variation Squares df Mean Square F Sig. Between Groups .016 3 .005 8.914 .006 Within Groups .005 8 .001 Total .020 11 ANOVA for Total Exchangeable Bases Sum of Source of variation Squares df Mean Square F Sig. Between Groups 789.313 3 263104 26.857 .000 Within Groups 78.373 8 9.797 Total 867.86 11
72 ANOVA for Effective cation exchange capacity Sum of Source of variation Squares df Mean Square F Sig. Between Groups 311.751 3 103.917 11.523 .003 Within Groups 72.147 8 9.018 Total 383.898 11 ANOVA for acid saturation Sum of Source of variation Squares df Mean Square F Sig. Between Groups 5840.580 3 1946.860 45.515 .000 Within Groups 342.195 8 42.774 Total 6182.775 11 ANOVA for cation exchange capacity Sum of Source of variation Squares df Mean Square F Sig. Between Groups 288.416 3 96.139 2.327 .151 Within Groups 330.526 8 41.316 Total 618.943 11 ANOVA for available phosphorous Sum of Source of variation Squares df Mean Square F Sig. Between Groups 1532.643 3 510.881 33.676 .000 Within Groups 121.363 8 15.170 Total 1654.006 11 ANOVA for Available Potassium Sum of Source of variation Squares df Mean Square F Sig. Between Groups 107942.184 3 35980,.28 14.685 .001 Within Groups 19601.749 8 2450.219 Total 127543.933 11 ANOVA for organic matter
Sum of Source of variation Squares df Mean Square F Sig. Between Groups 42.973 3 14.324 4.752 .035 Within Groups 24.113 8 3.014 Total 67.087 11 ANOVA for Total Nitrogen Sum of Source of variation Squares df Mean Square F Sig. Between Groups .039 3 .013 4.467 .040 Within Groups .023 8 .003 Total .063 11
73 Appendix 7. Analysis of farmers’ perception
Farmers’ Response for Probable Causes of Soil Acidity Problems (n=60) Cumulative Hateta Peasant Association Frequency Percent Percent Valid Inherent acidic Parent Material 11 18.3 18.3 High Rainfall Followed By leaching & 6 10.0 28.3 erosion Continuous Cultivation 5 8.3 36.7 Inappropriate use of nitrogen 6 10.0 46.7 fertilizers Combination of all 32 53.3 100.0 Total 60 100.0 Denzuria Peasant association Valid Inherent acidic Parent Material 11 18.3 18.3 High Rainfall Followed By leaching & 6 10.0 28.3 erosion Continuous Cultivation 5 8.3 36.7 Inappropriate use of nitrogen fertilizer 7 11.7 48.4 Combination of all 31 51.7 100.0 Total 60 100.0
Farmers’ Response to Soil Acidity Problem Coping Mechanisms (n= 60)
Hateta Peasant Association Frequency Percent Cumulative Percent Valid Good Agronomic Practices 18 30.0 30.0 Use Of Farmyard Manure 15 25.0 55.0 Fallowing 7 11.7 66.7 Liming And Fertilizer 5 8.3 75.0 Crop Rotation 9 15.0 90.0 Acid Tolerant Varieties 2 3.3 93.3 Soil Conservation Structure 4 6.7 100.0 Total 60 100.0 Denzuria Peasant Association Valid Good Agronomic Practices 19 31.7 31.7 Use of Farmyard Manure 17 28.3 60.0 Fallowing 6 10.0 70.0 Liming And Fertilizer 3 5.0 75.0 Crop Rotation 7 5.0 90.0 Acid Tolerant species /Varieties 2 11.7 86.7 Soil Conservation Structure 6 10.0 100.0 Total 60 100.0
74
Farmers Response for the Purpose of ‘Gibiz Merate’ Cumulative Hateta Peasant Association Frequency Percent Percent Valid Eucalyptus Plantation 19 31.7 31.7 Left For Grazing 27 45.0 76.7 Crop Production With Manure& Good management 14 23.3 100.0 Total 60 100.0 Denzuria Peasant Association Valid Eucalyptus Plantation 25 41.7 41.7 Left For Grazing 22 36.70 78.4 Crop Production With Manure and good 13 21.6 100.0 management Total 60 100.0
Farmers’ Response for Forest Covers Change(n= 60)
Cumulative Hateta Peasant association Frequency Percent Percent Valid Natural Forest Has Disappear 39 65.0 65.0 Plantation Forest Has Increased 5 8.3 73.3 Natural Forest Has Increased 4 6.7 80.0 Natural Forest Has Decreased 5 8.3 90.0 Plantation Forest Has Decreased 6 10.0 100.0 Total 60 100.0 Denzuria peasant Association Valid Natural Forest Has Disappear 40 66.7 66.7 Plantation Forest Has Increased 6 10.0 76.7 Natural Forest Has Increased 3 5.0 81.7 Natural Forest Has Decreased 5 8.3 90.0 Plantation Forest Has Decreased 6 10.0 100.0 Total 60 100.0
Appendix 8. Household survey questionnaires
Dear respondent this research has the following aims: . To identify land use and management practices that maintain soil quality without compromising crop net returns to farmers
75 . To understand farmers’ practices that helps to overcome soil acidity and /or aggravate acidity problems . To suggest possible options to improve farmers’ practices of managing acidity problems The information you provide has the sole purpose of achieving the targets mentioned above. Thus, you are humbly requested to respond to questions responsibly. In responding to a given question, you should take into account the history of your farmland.
Questionnaire No: ______Survey Area: Region______Zone ______Woreda ______PA/kebele/ ______Village ______Date of interview: ______Name of interviewer ______Name of head of Household: ______Age ______Sex ______Marital status: ______Academic status: ______Family size: ______
PART I. Land holding, Soil acidification and land management practices
Section A: Soil acidity and its management practices I would like to ask you about soil acidity problems on your farm and how you manage it. 1. Do you possess your own land? Yes----1/No---2 2. If yes, how many ‘Timad/qada’ of land do you possess? A. 0.25 ha_0.75 ---1 B. 0.75ha-1.5 ha ---2 C. 1.5 ha _2 ha---3 D. > 2 ha ---4 3. Do you have fallow lands? Yes---1/No---2, If No, why? 4. Are there crops sown to fertilize the farmland? Yes----1/N----2 If yes, what are they? ------5. Do you observe yield decline from year to year? Yes---1/No----2 6. If yes, what are the causes for yield decline? A. Soil acidity problem--1, B. Soil erosion, ---2 C. Snow & Pest-----3, D. I don‘t realize-- 4 7. Is there soil acidity problem in your plot land? Yes---1/No---2
76 If yes, what is the local name of acid soils?------8. What are the characteristics of acid soils that distinguish it from other soil types? ------9. What are the main causes of soil acidification by perception in your plot? A. Inherent acidic parent material-----1 B. High rainfall followed by leaching& erosion---2 C. Continuous cultivation and removal of crop residue from the farm---3 D. All -----5 10. How do you overcome soil acidity? A. Good agronomic practice/ early and late sowing in Main rainy season/-1 B. Farm yard manure application----2, C. Fallowing ----3 D. Liming and proper use of fertilizer---4, E. Crop rotation---5 F. Use of acid tolerant improved seeds/plants----6, G. Soil conservation structure----7, If you have others Specify ------11. Do you mulch your farmland with crop residue? Yes---1/No----2 12.If no, what are the uses of crop residue?A.Feed for livestock¨--1,B.Fuel source--2 C.Income source-----3, D.All -----4 13. For what purpose do you use this soil type? A. Growing plants----1, B. for grazing 2. C. producing crop by using farmyard manure if the area is nearby the home garden ----3 14. In which land use type is soil acidity problematic in you opinion? Why? ------
PART II. Crop production 1. Would you tell me which crop have poor performance yield in acid soils? ------2. Is there any shift in crop types grown in the area since 15 years? Yes---1/no--2
77 3. If yes, which crops disappeared? ------4. Which one become new introduction in the cropping system of the area? ------5. Do you use the correct fertilizer rate according to recommendation of Ministry of agriculture? Yes----1/no---2 6. If no, why? ------7. Would you tell me the productivity of cereal crops? ------Which crop type show relatively better performance in acidic soil? S Crop type Yield per ha in 1980s Average yield / /ha in 2007 difference Remark N Potential Actual Potential Actual Yield av.yield yield av.yield
8. In which land use type do you get better yield? ------9. Why you did n’t use manure on cultivated fields far away from home? ------
Part III. Plantation Forest and grazing lands 1. Is there a natural undisturbed forest currently in this village? Yes---1 / No--2 2. If No, was there a forest 15 years ago? Yes---1/ No---2 3. What changes have you observed in the forest cover since the last15 years? A. Natural forest has decreased -& plantation forest has increased----1
78 B. Natural forest has increased--2, C. Natural forest has no change--3 D. plantation forest has decreased---4, E. I did n’t realze it----5 4. If your answer is A, which plantation forest is become dominant by now in your village? A. Eucalyptus globulus ---1, B. Acacia decurrens---2 C. Cupressus lusitanica---3, D. Other indigenous trees---4 5. If your answer is A, why is it widely spread? Reason:------6. What are the main problems to Eucalyptus globulus in your farmland? ------7. Do you have eucalyptus trees in your farmland? Yes---1/No---2 If yes, how many tree stands do you have? 8. Is there a natural indigenous forest trees plantation currently in this village? Yes---1/No---2 If no, was there before 15 years? Yes---1/no---2 If yes, which type disappeared------and which one become new introduction in area? ------9. Do you have your own grazing land? Yes---1/No---2 How many hectares? And how do you manage it?------10. What type of land leave for communal grazing land in your village? ------11. Do you use control-grazing system in communal grazing lands? Yes---1/no---2 If no, Why? ------
79
DECLARATION
I, the undersigned, declare that this thesis is my own work and all materials used for this thesis have been duly acknowledged.
Name: Tessema Genanew Jember
Signature: ------
Date of Submission: November 2008
This thesis has been submitted for examination with my approval as research advisor
Mekuria Argaw (Ph. D.) Enyew Adgo (Ph.D)
Signature ------Signature------
80