LAND USE ANALYSIS FOR AGROFORESTRY RESEARCH AND DEVELOPMENT: A CASE STUDY FOR LUWERO DISTRICT IN UGANDA. Joyce N Muwanga

Transcription

1 LAND USE ANALYSIS FOR AGROFORESTRY RESEARCH AND DEVELOPMENT: A CASE STUDY FOR LUWERO DISTRICT IN UGANDA by Joyce N Muwanga B.Sc. University of Nairobi, 1972 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Plant Science) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA September, 1993 Joyce Namazzi Muwanga, 1993

2 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. (Signature) Department of The University of British Columbia Vancouver, Canada Date^CD-1 ED DE-6 (2/88)

3 ii ABSTRACT A land use evaluation in Luwero district of Uganda was undertaken as the primary stage in planning for appropriate agroforestry research and development. Published information sources, personal interviews, discussions with key informants and a survey of 50 randomly selected households across the banana-coffee farming system were used in the study. The biophysical environment at altitudes of m a.s.l is characterised by undulating topography intersected with river valleys. The climate is characterised by a mean temperature range of 15 C (minimum) to 30 C (maximum) with pronounced wet and dry seasons; the bimodally distributed annual rainfall is mm. Soils are predominantly ferralsols (Oxisols) supporting a forest-savanna mosaic vegetation type. The socio-economic environment is characterised by an aging population (>50 years), widespread temporary land ownership, and a predominance of family labour. Shortages of cash, lack of credit facilities and external inputs, poor marketing and transportation infrastructure, and inadequate extension services are identified constraints. The banana-coffee production system is organised on a subsistance level with crop production carried out on gentle slopes, in homegardens and in plots on the outer edges of the homegardens; cooking bananas are the main

4 iii staple. Cash crops (cotton and coffee) are neglected. Soil fertility management is inadequate. Livestock production is a minor component of the system; various livestock are kept for home consumption and cash income. Trees occupy traditional niches in homegardens and compounds for provision of shade and fruits. Secondary roles include fuelwood, building materials, raw materials, fencing and windbreaks. Ficus natalensis, Albizia spp., Markhamia lutea and a range of fruit trees are grown. Production is constrained by socio-economic problems which are exacerbated by declining soil fertility, lack of external inputs, poor farm management, and low quality fodder. Improved production would require attention to: (i) cash availability, (ii) cash, food crops and livestock production, (iii) tree cultivation and (iv) land tenure. These areas may be addressed by: (i) re-settlement assistance to farmers, (ii) provision of credit facilities and secure land tenure, (iii) improvement in service infrastructure and extension services, (iv) agroforestry education, and (v) intensified soil fertility management. Agroforestry practices to address production constraints should involve implementation of strategies which are readily adoptable and include: (i) use of upperstorey trees in homegardens and/or coffee plots, (ii) expansion of fruit tree cultivation, (iii) development of

5 iv fodder banks, and (iv) boundary tree planting. Additional agroforestry practices, such as alley cropping, will require further research and education via institutional demonstration trials.

6 V TABLE OF CONTENTS Page ABSTRACT ^ ii TABLE OF CONTENTS ^ v LIST OF TABLES ^ viii LIST OF FIGURES ^ xi ACKNOWLEDGEMENTS^ xii DEDICATION ^ xiiia CHAPTER 1. INTRODUCTION ^ Background ^ The Research Problem ^ Study Rationale ^ Study Objectives^ 9 CHAPTER 2. LITERATURE REVIEW ^ Agroforestry Defined ^ Agroforestry and Sustainable Land Use ^ Nitrogen-fixing Trees (NFTs) ^ Agroforestry for Soil Fertility Maintenance and Food Production ^ Agroforestry and Soil Erosion ^ Agroforestry for Livestock Production and Rangeland Conservation ^ Agroforestry for Wood Products and Forest Conservation ^ Case Studies in Agroforestry Development Project Planning^ 30

7 vi CHAPTER 3. RESEARCH DESIGN AND METHODOLOGY ^ The Study Area ^ Location^ Rationale for the Research Method ^ Data Collection ^ Land Use Description Worksheets ^ Diagnostic Survey ^ Sampling for Respondents and the Survey Area^ Data Analysis^ Limitations to the Study ^ 44 CHAPTER 4. RESULTS AND DISCUSSION ^ The Biophysical Environment^ Climate ^ Topography and Soils ^ Vegetation ^ Socio-economic Environment ^ Population and Settlement ^ Transport and Communications ^ Land Tenure ^ Labour ^ Marketing, Farm-inputs and Credit Facilities^ Development Policy for Luwero District ^ Description of the Farming System ^ The Homestead and Settlement History ^ 68

8 vii The Household Production Resources ^ The Production System ^ Crop Production ^ Livestock Production ^ Tree Production ^ 112 CHAPTER 5. INTERVENTIONS ^ Summary of Production Characteristics of the Banana-Coffee Farming System^ Future Development and Sustainability of the Banana-Coffee Farming System^ Potential Interventions ^ Non-agroforestry Interventions ^ Agroforestry Interventions^ Research Needs^ 148 CHAPTER 6. SUMMARY AND CONCLUSIONS ^ 153 REFERENCES ^ 160 APPENDIX 1. Basic Procedures of the Diagnostic and Design (D&D) Methodology ^ 168 APPENDIX 2. Land Use Description Worksheets ^ 169 APPENDIX 3. Questionnaire for the Diagnostic Survey of the Household Production System ^ 188 APPENDIX 4. Chi-Square Statistical Analysis ^ 224

9 viii LIST OF TABLES Table 1. Selected villages in counties and sub-counties for the diagnostic survey Page ^45 Table 2. Population distribution in Luwero district by country Table 3. Gender status of heads of surveyed households in the banana-coffee farming system Table 4. Age structure of heads of surveyed households in the banana-coffee farming system ^52 ^70 ^70 Table 5. Period of residency and farming activity by farmers on their plots, in the banana-coffee farming system ^71 Table 6. Original land use on surveyed farms in the banana-coffee farming system Table 7. Farmers' evaluation of original soil condition on their farms in the banana-coffee farming system ^72 ^72 Table 8. Farmers' estimation of their plot size in the banana-coffee farming system 74 Table 9. Ownership status of additional plots of land among the surveyed farmers in the banana-coffee farming system Table 10. Water sources available to the surveyed farmers in the banana-coffee farming system Table 11. Sources of labour for the surveyed farmers in the banana-coffee farming system Table 12. Availability of full and part-time labour among the surveyed farmers of the banana-coffee farming system ^76 ^78 ^81 ^82 Table 13. Main sources of cash income among the surveyed farmers of the banana-coffee farming system 84

10 ix Table 14. Production units identified on surveyed farmers' plots in the banana-coffee farming system Table 15. Summary of crops produced on the surveyed farms in the banana-coffee farming system Table 16. Cropping calender for the surveyed farmers in the banana-coffee farming system Table 17. Crops planted and hecterage for March- June 1992 growing season in Luwero district Table 18. Fertility management practices used by the surveyed farmers in the banana-coffee farming system Table 19. Crop production constraints expressed by farmers of the banana-coffee farming system ^86 ^88 ^89 ^90 ^95 ^99 Table 20. Herd size and distribution of cattle among the surveyed farmers in the banana-coffee farming system ^103 Table 21. Herd size and distribution of goats, sheep, and pigs among the surveyed farmers in the banana-coffee farming system^104 Table 22. The distribution and size of poultry flocks among the surveyed farmers in the bananacoffee farming system ^106 Table 23. Methods of livestock feeding used by farmers in the banana-coffee farming system 107 Table 24. Livestock production constraints experienced by farmers in the banana-coffee farming system ^ Table 25. Functional role of trees incorporated on farms in the banana-coffee farming system... Table 26. Energy sources used by farmers in the bananacoffee farming system ^ Table 27. Sources of tree seedlings used by the farmers of the banana-coffee farming system ^118

11 Table 28. Tree management practices used by farmers of the banana-coffee farming system x ^119 Table 29. Tree production constraints experienced by farmers in the banana-coffee farming system 120 Table 30. Preferred functional role of trees indicated by farmers of the banana-coffee farming system ^122 Table 31. Preferred tree species for planting indicated by farmers of the banana-coffee farming system ^124 Table 32. Preferred niches for tree planting indicated by farmers of the banana-coffee farming system ^125

12 xi LIST OF FIGURES Figure 1. Figure 2. Location of Luwero district Map of Luwero district showing the surveyed area ^ Page Figure 3. A generalized topographic section of the surveyed area 48 Figure 4. Figure 5. A schematic layout of the settlement pattern in the banana-coffee system Political map of Luwero district showing urban centres and transportation network ^ Figure 6. Figure 7. A typical household production layout in the banana-coffee farming ^ 69 A typical vertical zonation of a homegarden surveyed in Nyimbwa subcounty 94

13 xii ACKNOWLEDGEMENTS The completion of this study would not have been possible without the participation of several parties. I would like to thank the farmers of Luwero district and the district government officials for administration (DAO), agriculture (DAO), forestry (DFO), and veterinary services (DVO) for their cooperation in the lengthy interviews and discussions during the survey exercise. Ruth Sebbowa is especially acknowledged for her assistance with the survey work. My special thanks go to my academic and thesis advisor, Dr. F.B.Holl, for his untiring support and encouragement during the entire course of my study programme and thesis preparation. Dr. Holl took a keen interest in my work and spent lengthy hours reading, making constructive comments and editing the manuscript. I am further indebted to him and his wife Ruth for their physical and moral support during the time I was hospitalised. I would also like to thank members of my supervisory committee, Dr. M.Garland, Dr.A.A.Bomke and Dr.M.D.Pitt for their support and enlightment on pertinent issues during the preparation of the thesis. Furthermore, I would like to thank Dr. J.W.R.Aluma of Makerere University, Kampala for his support and constructive ideas during the survey work in Uganda. I am also grateful to Mesfin Tesfaye and Karen Golinski for their timely input in the preparation of the thesis.

14 My deep thanks go to all my relatives and friends in Uganda and Canada for their physical and moral support in one way or another during the course of my study. It is not possible to thank each one of them individually. However, my special thanks go to my children, Angella, Sheilla, Denis and Veronica for enduring my long absence while they encouraged me through prayer and letter writing to persevere and complete my programme. In the same vein, I extend my deepest thanks to my loving husband, Jim, for his support and encouragement while he patiently waited for my return home; for "behind every successful woman, there is always a successful man". Lastly, I would like to thank the following who made this study programme possible. I.D.R.C., Ottawa, financed the entire study programme. ICRAF, Nairobi, facilitated the training programme. AFRENA project (Uganda) provided logistical support for field work in Uganda. The Government of the Republic of Uganda gave me study leave for two years to pursue graduate studies.

15 To My Beloved Parents, Florence and Ezerah K Sebbowa

16 1 CHAPTER 1 INTRODUCTION 1.1 Background World population growth is steadily increasing. At the present growth rate of 80 million a year, (85% in developing countries), it is estimated that 4.85 billion people will be living in developing countries by the year 2000 (World Resources Institute et al., 1989 cit. by ICRAF, 1990). These changes are being accompanied by increased urbanization, industrialization and increased use of natural resources to meet the needs of the growing population. While this situation provides farmers with opportunities for marketing their agricultural produce, it is likely to be associated with significant problems. The world's arable land is limited. FAO (1988) reported the decline in arable land per head of population in the tropics from 0.28 ha to 0.22 ha between 1971 and Farms have become smaller with increased fragmentation as families expand. Increased production through extension of the agricultural land base has been accomplished using lands marginally suitable for arable farming with a resulting decline in crop yields. In tropical Africa, the search for fodder, fuelwood and additional agricultural land for the growing population has led to the disappearance of natural forests and woody savanna. This trend has led to the destruction of natural resources and the

17 2 resultant decline in productivity through (i) soil degradation, compaction, and decline in fertility, (ii) deforestation, (iii) pasture degradation and (iv) loss of biological resources (ICRAF, 1990). Uganda, a land-locked country lying between latitudes 1 3' S and 4 4'N and longitudes 29 33' E and 35 20' E, has been no exception to the effects of population growth on the natural resource base. Uganda has a population of about 16,000,000 with an annual growth rate of 2.5% (MPED, 1991). Uganda has a predominantly agricultural economy which contributes well over 90% of export earnings and employs 80% of the total population (MPED, 1989). The small-scale family holding is the basic unit of production. Fuelwood and charcoal are the major sources of energy for cooking for over 80% of the urban and rural population. Livestock production is a major economic activity with open range dominating in the vast areas of the natural savanna forests. Continuous cultivation of arable land with minimal fertilizer input has led to a decline in soil fertility and productivity (Djimde et al., 1988). The World Commission on Environment and Development (WCED) in its report "Our Common Future" observed the need for sustainable development as the only pathway to prevent the negative effects of population and economic growth on the natural resource base (WCED, 1987). Sustainable development aims at meeting the needs of the present without compromising

18 3 the ability of future generations to meet their needs (WCED, 1987). Such an approach requires the organization of every economic activity on a sustainable basis. The need for effective integrated land use is, therefore, of primary importance to agriculture. In this context, therefore, agroforestry is a promising land use given the important role of trees in the lives of many rural-based farmers for provision of their basic needs (food, fodder, fuelwood, building materials, cloth, medicine). The use of nitrogenfixing trees in agroforestry systems may contribute to the improvement and maintenance of soil fertility, thus facilitating long-term production in the absence of expensive external inputs. 1.2 The Research Problem "The nutritional value of any food that is not eaten is zero, regardless of its chemical composition." (Raintree, 1983). Agroforestry has great potential to improve the general socio-economic well-being of small-scale resource-poor farmers, through better, more sustainable production of goods to fulfil their basic needs (Vergara and MacDicken, 1990). However, like any other technology intended to improve the socio-economic well-being of people, agroforestry will have no impact if it is not relevant to the high priority needs and production problems of the users. In the absence of such relevance, it will neither be adopted nor applied by those for

19 4 whom the benefits are intended. Pearse (1980) described the unanticipated negative effects of the "green revolution" technology which had low adoption rates among the less advantaged majority of intended users. In another development project, Hoskins (1982) cited by Raintree (1983) reported the destruction of a eucalyptus woodlot introduced for fuelwood production by the women residents of Burkina Faso (West Africa) who did not view fuelwood as their priority need. The need to plan for agroforestry technology development, therefore, is necessary to (i) develop appropriate problem-oriented research and extension projects, and (ii) ensure that the scarce resources available for development projects in developing countries are used efficiently. This is particularly important given the time lag associated with agroforestry systems development before the positive attributes may be realized. The development of appropriate agroforestry research and extension projects requires a thorough understanding of existing land use systems, including the role of the tree component, as well as the needs and production constraints of the farmers. Such understanding focuses development efforts on making improvements within the existing land use systems. In this respect, farmer participation in the planning phase is indispensable. Farmers understand their needs, their production constraints, and the biophysical and socio-economic environment in which they operate. Such a consultative

20 5 approach ensures incorporation of the attributes of adoptability (perceived advantages, compatibility, low technical complexity) right from the planning stage, thus avoiding design errors which may result in technically and environmentally feasible, but often non-adoptable, agroforestry technologies (Raintree, 1990). In order to develop the most appropriate agroforestry strategy for a target area, it is desirable to implement a diagnostic survey and analysis of land use in the area, with specific focus on the farm household where management decisions are made. Four factors influence the choice and design of agroforestry technologies for specific production systems according to Scherr (1987). (i) The biophysical environment The biophysical environment of a locality will influence the choice and potential performance of trees, arable crops and pasture grasses. Altitude will affect temperature, evaporation and length of the growing season and hence the choice of crops that can be grown. Rainfall amount and distribution will not only influence crop selection, and cropping patterns, but will also determine production gaps, such as shortages of fodder for animal feed. Soil fertility, erodibility, and other characteristics are factors in appropriate land use, as well as defining problems that may require specific management attention (Djimde et al., 1988). Information on topography, hydrology, vegetation, geology,

21 6 fauna and indigenous diseases is also useful to the planning process. (ii) Organization of the production system Characteristics of the current production systems for crops, livestock and trees will also be important factors in the choice and design of agroforestry technologies. Land use intensity of the system is an important aspect; different land use intensities under identical environmental conditions will require different agroforestry interventions. For example, alley cropping may be appropriately practiced with most grain production systems, while rotation fallow may be preferred for tobacco production. Similarly, existing farm management practices will provide a framework for determination of the most suitable new technologies. Traditional tree planting activities including agroforestry practices, tree niches (locations), economic goals and farmer-designed preferences are important components of planning. Such information helps to identify strategies which address improvement of existing practices, as well as new technologies. (iii) Specific sub-system constraints Within the household production system, needs and production constraints will determine the agroforestry strategies which are required to address priority problems. Declining crop yields, declining soil fertility, declining

22 7 livestock production and fuelwood shortages require planting of different trees and use of different management practices to meet production goals. (iv) The socio-economic environment "Agroforestry is a human and therefore a social activity. It is the farmer and not the technocrat who knows what he/she wants. It is largely social factors, which the farmer uses to determine whether agroforestry is an opportunity, a burden or an impossibility." (Fortmann, 1990). What often appears to be good technology to the scientist may be totally unattractive to the farmer because of the social and economic implications. The successful introduction of agroforestry technologies in a given locality should, therefore, be preceded by a clear understanding of not only the production needs, but also the socio-economic environment in which farmers operate. Key variables in this respect include (i) property rights as they relate to land and tree tenure rights, (ii) labour availability, (iii) capital, (iv) markets and transportation, (v) government/institutional support services and policies. 1.3 Study Rationale Agriculture is the backbone of Uganda's economy. Luwero district was renowned for its agricultural production of the country's traditional export cash crops (cotton and coffee) as well as a wide range of food crops. Animal production was

23 8 also pronounced in the north, east and western parts of the district. The 1970's and early 1980's, however, were characterized by a sharp decline in agricultural production (MPED,1989). This decline was a result of the prevailing political uncertainty which disrupted all economic activity. Luwero district was severely affected, leading to an outmigration of the population and an almost total collapse of agricultural production and associated support services. Since restoration of peace in the late 1980's, Luwero district has undergone an aggressive rehabilitation and development process. The revival of the agricultural sector is a major focus of development policy to increase production for both domestic consumption and export. The introduction of sustainable land use practices to address existing problems and to exploit the agricultural potential of the district is both opportune and necessary. Agroforestry strategies will contribute towards the revival of agriculture through increased and diversified production on a sustained basis, thus enhancing the socio-economic welfare of the people of Luwero and the country at large.

24 9 1.4 Study Objectives. This study was developed to analyze agroforestry research needs and development for Luwero district. The specific objectives are: i) to describe the physical and social-economic environment of Luwero district; ii) iii) to describe the farming system; to analyse and diagnose the farming system for production constraints; iv) to recommend agroforestry and non-agroforestry interventions to address diagnosed problems; and v)^to identify research needs to develop the recommended agroforestry interventions.

25 10 CHAPTER 2 LITERATURE REVIEW This chapter reviews literature relevant to the potential attributes of agroforestry as a sustainable form of land use, and as a means of improving the socio-economic well-being of resource-poor farmers. 2.1 Agroforestry Defined. Agroforestry is a new word for a set of old practices involving the management of woody plants with agricultural crops and/or livestock on the same unit of land. Traditional agroforestry systems have been practiced for decades under different names throughout tropical Asia, Latin America and Africa. The traditional homegardens of Asia and Africa; the garden of Eden in the Biblical story of creation; the ancient mixed tree gardens in Central America; shifting cultivation and the slash and burn agriculture practiced in the humid tropics of Asia, Africa, Central and South America up to the end of the nineteenth century are historical examples (MacDicken and Vergara, 1990). Agroforestry, as a science of land use was institutionalized in 1977 following a recommendation by the Canadian International Development Research Centre (IDRC) (King, 1989). It had been observed from a study commissioned by IDRC that there was a great inter-dependence of agriculture

26 11 and forestry among the small-holder farmers of the low-income tropical countries. The need to develop scientificallymanaged, integrated agriculture and forestry production systems was deemed urgent in order to optimize land use and improve the living conditions of the low-income small-holder farmers. The International Council for Research in Agroforestry (ICRAF) was established to spearhead research in combined land management systems for agriculture and forestry. Agroforestry has been defined by ICRAF as a "form of land use where woody perennials (trees, shrubs, palms, bamboos) are deliberately grown on the same land management unit as agricultural crops and/or animals in some form of spatial or temporal sequence; there must be, however, ecological and/or economic interactions between the woody and non-woody components" (Lundgren, 1982). Agroforestry is intended to build upon and improve the sustained production of traditional agricultural systems through application of scientifically developed and managed technologies. It attempts to optimize the positive ecological and economic interactions of the system components. The definition of agroforestry reflects three elements managed by people: the tree, the food or forage crop, and the animal. Three classes of agroforestry systems based on the structural and functional characteristics of the species components have emerged. The agrosilvicultural system incorporates trees or shrubs with crops; the silvopastoral

27 12 systems include trees or shrubs with crops or pastures; and the agrosilvopastoral systems incorporate trees/shrubs and crops or pastures with or without animals. Agroforestry encompasses a wide range of practices within each system. The arrangement of species components in time or space gives rise to different cropping patterns. Nair (1989) and Young (1989) have described and reviewed over twenty agroforestry practices. The potential for designing these agroforestry practices provides an opportunity for researchers and extension personnel to contribute towards solving many of the subsistence farming problems which may relate to sustainability of resources or production output shortages (Wood, 1990). 2.2 Agroforestry and Sustainable Land Use The use of agroforestry systems has been proposed as a means of developing sustainable land use (Wiersum, 1990). Sustainable land use is characterized by conservation of the natural resource base on which production depends as well as maintenance of adequate levels of agricultural production and acceptable living conditions for present and future generations (Young, 1989; Wiersum, 1990). The role of agroforestry in sustainable land use is attributed to its ability (i) to increase and diversify production, especially under conditions of land shortage, (ii) to contribute to sustained production of crops and

28 13 livestock on fragile lands and in areas where there is minimal accessibility to external inputs, and (iii) to contribute to rehabilitation of degraded lands (Wiersum, 1990). 2.3 Nitrogen - fixing Trees (NFTs) The success of agroforestry systems is largely due to the inclusion of nitrogen-fixing trees (Nair, 1989). By virtue of their ability to fix atmospheric nitrogen, these trees may contribute significant amounts of nitrogen to the soil via plant litter and root debris, helping to maintain soil fertility through nutrient and organic matter cycling (Brewbaker, 1987; Sanchez, 1987). Brewbaker et al. (1990) reported a total of 650 woody species, mostly tropical and sub-tropical, with the ability to fix atmospheric nitrogen. Nine families, dominated by the Leguminosae are represented (Brewbaker, 1987). The nonleguminous families include the Betulaceae, Casuarinaceae, Coriariaceae, Cycadaceae, Elaeagnaceae, Myriacaceae, Rhamnaceae, Rosaceae and Ulmaceae, each with fewer than 40 species currently known to nodulate (Brewbaker et al., 1990). The majority of nitrogen-fixing trees are shrubs or small trees of secondary forests and grasslands, and are already components of traditional agroforestry systems in the humid and sub-humid tropical countries. Examples include tropical Asian farming systems and many African farming systems which display a high level of integration of such trees to provide a

29 14 variety of products (Fonzen and Oberholzer, 1984; Fernandes et al., 1984; Odwol and Aluma, 1990) Among the significant nitrogen-fixing trees and shrubs commonly incorporated in agroforestry systems are members of the genera, Acacia, Casuarina, Coriaria, Erythrina, Gliricidia, Inga, Leucaena, Prosopis and Sesbania (Dommergues, 1987; Nair, 1984; Young, 1989). Leucaena leucocephala has been reported to fix up to 500 kg N/ha/yr as compared to Casuarina equisetifolia, a non-legume capable of fixing up to 110 kg N/ha/yr (Dommergues, 1987). The deep rooting system of nitrogen-fixing trees and shrubs, with their associated mycorrhizal infection, facilitates the absorption of the less mobile soil nutrients required for plant growth, such as P, K, Zn, Mo, as well as the easily leached nitrates (Young, 1989). Recycling of these nutrients is promoted through litter-fall, thus providing usually unavailable soil nutrients to the associated agricultural crop (Young, 1989). Increased soil organic matter levels and the consequent improved cation exchange capacity (CEC), together with the improved soil physical properties and water retention capacity, also contribute to improved soil fertility (Young, 1989). 2.4 Agroforestry for Soil Fertility Maintenance and Food Crop Production. Soil fertility is the capacity of soil to support plant growth on a sustained basis within given ecological conditions (Young, 1989). Declining soil fertility is a result of the

30 15 various effects of decreasing nutrient and organic matter levels, deteriorating soil physical properties, acidification, salinization, compaction and erosion. In the developed countries of North America and Europe, soil fertility and crop production are maintained primarily by external mineral fertilizer inputs. In the developing countries, however, soil fertility and food production are primarily maintained by the use of organic sources of fertilizers. The attraction of properly managed agroforestry systems lies in their potential to maintain and improve soil fertility and food yields as well as provide other tree products such as fuelwood, fruits, fodder and poles. Among the most promising technologies for soil fertility maintenance and food production are alley cropping (hedgerow intercropping) and mixed inter-cropping, including homegardens (Young, 1989). Alley cropping is one of the agroforestry practices which has received wide research attention for development in sustainable land use (Kang and Wilson, 1987). Alley cropping involves the growing of food crops between hedgerows of trees and shrubs, preferably nitrogen-fixing species. The hedgerows are cut back at the planting of the associated food crop and periodically pruned during the growing season to prevent shading. The prunings provide green manure to the associated crop through incorporation in the soil or mulching. This green manure is a major source of nitrogen and other

31 16 nutrients. Kang and VanDenBeldt (1990) compared the suitability of alley cropping for soil fertility and maize production on an Alfisol in the humid tropics of Nigeria using shrub species of Leucaena leucocephala and Gliricidia sepium. Five annual prunings of Leucaena hedgerows yielded 7.4 tons of dry matter per hectare with nutrient yields of 247 kg N, 19 kg P, 185 kg K, 948 kg Ca and 16 kg Mg per hectare per year while Gliricidia sepium gave 5.5 tons of dry matter with 169 kg N, 11 kg P, 149 kg K, 66 kg Ca and 17 kg Mg/ha/year. Kang et al.(1990) also reported the maintenance of maize yields at high levels with addition of prunings of Leucaena leucocephala over a period of six years, with and without addition of nitrogen fertilizers, giving mean yields for maize of 4.1 t/ha and 3.2 t/ha respectively. The high yields of maize were attributed to nitrogen from the prunings, improved soil physical properties, increased soil organic matter levels, and improved soil moisture availability. By-products from this system included fuelwood and occasionally fodder. Although alley cropping is a popular agroforestry recommendation, testing and adoption by farmers is still in its early stages in many developing countries. In the Philippines, alley cropping has been notable in increasing food production in sloping areas (Tacio, 1991). In Nigeria, the practice has been accepted in some parts of the country but land tenure systems tend to be an obstruction to extensive development (Kang et al., 1990). In Eastern Africa, the

32 17 technology is in its early stages of development. Current research under the Agroforestry Research Networks for Africa (AFRENA) programme involve testing of suitable nitrogen-fixing trees for incorporation into alley cropping systems (Hoekstra and Beniest, 1991). Preliminary results indicate Calliandra, Gliricidia and Leucaena are promising species for soil fertility and food production enhancement (Hoekstra and Beniest, 1991) Mixed intercropping is characteristic of many of the traditional agroforestry systems in tropical countries. The emphasis in such systems is on food production together with the associated tree products including poles, fuelwood, fruits and occasionally fodder. The accumulation of plant litter over time contributes to soil fertility through addition of organic matter and control of soil erosion. The sustainable attributes of traditional homegardens in many tropical countries have been documented; the Chagga homegardens of Tanzania and the homegardens of the Lakeshore region in Uganda have been described (Fernandes et al., 1984; Odwol and Aluma, 1990). Such homegardens are ecologically and economically sound, and biologically sustainable (Nair, 1989). Boundary planting around food crop plots is productive in itself through provision of tree products (poles, fuelwood) while also providing benefit to the associated crop. Living fences and shelterbelts are good examples of this technology. The windbreaks project of the Majjia Valley in Niger provides

33 18 a vivid example of an agroforestry strategy with direct impact on food production (Foley and Barnard, 1990). The planted windbreaks provide protection to farmers and their fields from the strong dry winds which sweep down from the Sahara. Food crop yield increases resulting from these shelterbelt effects are significant (Foley and Barnard, 1990). 2.5 Agroforestry and Soil Erosion Control The major adverse effects of wind and water erosion include loss of soil nutrients, declining soil fertility and siltation of water reservoirs (Young, 1989). Soil erosion is one of the worst forms of resource degradation and its effects are usually not reversible within a short time-frame. An estimated average of 5 million hectares of arable land is lost annually (McLaren and Skinner, 1987 cited by ICRAF, 1990). Properly managed agroforestry systems have the potential to reduce soil erosion. The benefits are more discernible in marginal uplands (rather than the productive lowlands) where problems of soil erosion and soil fertility are more prevalent (Young, 1989; MacDicken and Vergara, 1990). Young (1989) has discussed both the direct and indirect mechanisms through which agroforestry practices can control soil erosion; the creation of semi-permeable hedgerow barriers, the provision of a soil cover by litter and prunings, and the increase in soil resistance to erosional forces through high levels of organic matter are direct mechanisms. In addition, the stabilization

34 19 of conventional erosion control structures (earth structures) by the tree root system is an example of indirect mechanism. There is a growing body of experimental results to demonstrate the role of agroforestry systems in erosion control. Recent extension projects as well as observations of traditional agroforestry practices demonstrate the erosion control impact of these practices (Young, 1989). Alley cropping has shown great potential for soil erosion control through the creation of semi-permeable barriers consisting of hedges of trees and shrubs planted along contours as well as the soil cover provided by the prunings. Effective soil erosion reductions of up to 8 t/ha/yr on a 7% slope in the sub-humid climate of Africa were reported under hedgerows of Leucaena leucocephala and Gliricidia sepium at 2-m row spacing compared to 4-m spacing (Lal, 1989). The Sloping Agricultural Land Technology (SALT) agroforestry project in the Philippines has used hedgerows of Leucaena leucocephala to control erosion, improve soil fertility and improve food crop yields on steep slopes (Tacio, 1991). Wiersum (1984) compared erosion rates among traditional agroforestry systems of the tropics. Low rates of erosion (< 2 t/ha/yr) were observed under multi-storey tree gardens with a thick litter cover, moderate rates (2-10 t/ha/yr) under the cropping periods of shifting cultivation and taungya systems, and high rates (>10 t/ha/yr) in clean-weeded tree plantation crops. Trees on erosion control structures, on a slope of 54% under an annual

35 20 rainfall of 1700 mm in Thailand, have reduced soil loss significantly to 13 t/ha/yr as compared to 52 t/ha/yr under conventional conservation structures without trees (Hurni and Nuntapong, 1983 cited by Young, 1989). The Agroforestry Research Network for Africa (AFRENA) in Uganda is currently testing tree species of the genera Alnus and Calliandra in the management of conventional soil erosion structures (terraces) on the steep agricultural slopes of Western Uganda (Hoekstra, 1991). A high tree canopy may also contribute to significant increases in soil erosion. Wiersum (1985) reported that while an Acacia tree canopy decreased rainfall reaching the soil by 11.8%, the erosive power of the water was increased by 24.2%; this effect was a result of the concentration of water into larger drops. Tropical homegardens, therefore, owe their soil erosion control attributes not so much to their multi-layer canopy structures but to the thick litter cover which accumulates over time (Fernandes et al., 1984; Odwol and Aluma, 1990; Wiersum, 1985). Experimental data on the mechanisms of action of agroforestry practices contributing to soil erosion control are still scarce, given recent attention to the science of agroforestry, and the long time-frame of the tree component. A synthesis of available information would likely suggest that the cover aspect is more effective than the barrier effect. In designing agroforestry practices for soil erosion control,

36 21 maintenance of a plant cover throughout the rainy season should be the primary objective. 2.6 Agroforestry for Livestock Production and Rangeland Conservation. Successful livestock production depends on the availability of high quality feeds, including protein rich fodder. Trees and shrubs (usually nitrogen-fixing), have provided basic fodder in the form of browse to a large and diverse livestock population in the natural rangelands of tropical Africa. A total of 165 million tropical livestock units (TLU) 1 depend on natural silvopastoral systems (Le Houdron, 1987 cit FAO, 1985). Besides their use as fodder, these multipurpose trees and shrubs play a major role in fulfilling other basic needs of many small-holder farmers, such as fuelwood, fibre for clothing and handicrafts, wood for construction, tools, human food and medicine. Their diverse role also includes shelter for the animals and soil fertility maintenance through biological nitrogen fixation (Le Houdron, 1987). Grass pastures provide fodder for livestock which is relatively low in protein content and dries out during prolonged drought; these factors contribute to lower liveweight gains in animals and reduced milk yields. Rose- Innes (1964) has reported a crude protein content of 18.1% for nitrogen-fixing trees as opposed to 5.8% for the grasses in 1 1 TLU = approx. 250 kg. liveweight of animals.

37 22 the tropical savanna of West Africa. Pratchett et al. (1977), in his study in Botswana on browse quality and animal response, established that protein level in browse was the most limiting factor in liveweight gain in beef cattle on natural rangelands. Up to 54% of liveweight variation was due to the crude protein content of the herbage selected by animals, while digestibility of the same samples accounted for a further 32%. They concluded that research efforts should be directed towards increasing the crude protein content of the diet available to beef cattle. In a similar study, Zimmerman (1980), experimenting with steers in the mixed tree savanna of the Transvaal in South Africa, estimated that the intake of digestible crude protein accounted for 79% of the variation in daily liveweight change in cattle. Studies conducted in summer in the semi-arid areas of Kenya and in the rangelands of Arizona gave supportive results (McKay and Frandsen, 1969; Ward, 1975). These observations, particularly in summer, are related to the low crude protein content of grasses (Torres, 1983). Increased availability of crude protein to the grazing or browsing ruminant could be attained through the introduction of fodder 'trubs' (trees and shrubs) which are known for their high protein content. Nitrogen fixing trees have the potential to fulfil this objective. Eighty (80) nitrogen-fixing tree species have been reported as significant fodder trees in tropical countries. Brewbaker and Macklin (1990) discussed the most prominent ones

38 23 found in the genera Acacia, Desmanthus, Ca'anus, Gliricidia, Leucaena, Sesbania and Chamaecytisus. The quality of their fodder varies depending on protein and mineral content, as well as dry matter digestibility and palatability. The genus Leucaena comprises some of the highest quality fodder trees in the tropics. Its peak quality values have shown dry matter digestibility (DMD) of 55-70%, crude protein content of 20-25%, mimosin content of 4.5% and a tannin content of % (Brewbaker, 1987). The presence of mimosin is reported to cause loss of appetite in animals, thus resulting in weight losses (Jones, 1979; Brewbaker, 1987). Attempts to eliminate this effect have included the administering of Leucaena fodder as part of balanced rations to animals. Mineral supplementation is currently recommended, while breeding for low-toxicity cultivars is viewed as a longterm solution. Leucaena fodder is reported to increase milk production but, at the same time, to taint both the colour and odour (Jones, 1979; Torres, 1989). This problem is commonly overcome by preventing animals from browsing Leucaena several hours before milking. Leucaena is the subject of extensive research; the Indian Grassland and Fodder Research Institute, Tamil Nadu Agricultural University (India), the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria and the Agroforestry Research Networks for Africa (AFRENA) programme are involved in extensive research into fodder production and the quality of different species of Leucaena

39 24 (Brewbaker, 1987; Hoekstra and Beniest, 1991; Kang and VanDenBeldt, 1990). The genus Acacia also provides important protein-rich fodder in most of the dry savanna of tropical Africa. Brewbaker and Macklin (1990) have described a total of 1200 species, of which over 800 are found in the tropics. It is one of the largest and most ecologically diverse nitrogenfixing tree species. Its fodder is, however, unpalatable because of its thorniness (Brewbaker et al., 1990). The genus Gliricidia provides some high quality fodder. Gliricidia maculata given as a supplement in equal proportion with Brachiaria grass in the diet of milking cows produced liveweight gains of 14 kg cow -1 month-1 and milk yield increases of 6.6 L cow -1 day-1 compared to a loss of 12 kg month-1 in liveweight and milk production of 5.8 L day -1 when cows were given grass alone (Chadhokar and Lecamwasam, 1980 cited by Torres, 1983). No significant weight increase was observed when fodder of Gliricidia sepium was fed to sheep and goats over a four month period; liveweight gains were, however, observed after a period of 9 months, suggesting the requirement for presence of an adaptation period (Carew, 1980 cited by Torres, 1983). The slow rates of liveweight gain were attributed to the possible presence of a mineral deficiency in the feed. Although there is a considerable body of information on the chemical composition of fodder from trees and shrubs, few

40 25 of them have been evaluated in terms of animal response. Available information suggests that (i) tree/shrub fodder is mainly considered as a source of protein, (ii) fruits and, in particular, pods from legume trubs could be used as both energy and protein supplements, (iii) although dry matter productivity from the foliage of trubs appears to be rather low, it nevertheless provides a major source of feed during the dry seasons when grasses are normally scorched, while podproducing trubs can be a rich source of energy and protein concentrate, and (iv) low trub intake could result in a low protein supply for the animal. In addition to the provision of fodder, trees and shrubs may play additional roles affecting the general productivity of livestock (Torres, 1983). Microclimate improvements under shade trees result in increased pasture growth with a higher protein content. Improvements in pasture production of up to 287% have been reported for grasses under canopies of leguminous trees (Shanker et al., 1976 cited by Torres, 1983). Shelter to animals in the form of shade has also been described as an important aspect of animal production under grazing conditions. With shade, animals tend to eat and graze for longer periods, water requirements are reduced, growth rates and milk yields are enhanced, and reproductive rates and survival rates of offspring are improved (Robinson, 1982). Trees and shrubs play an important role in paddocking animals by providing poles on which barbed wire may be

41 26 fastened or through living fences which do not require wiring. The availability of living fences may be a significant limiting factor under grazing or browsing systems in arid or semi-arid conditions where the cost of fencing increases as carrying capacity decreases, or in the more humid regions where poles have to be replaced more often. ILCA (1981) cited by Torres (1983) reported high investment in wire fences as being limiting to the economic viability of browse trub plantations. Fast-growing, shrubby plants, easily propagated by cuttings and unpalatable to animals are preferred. Torres (1983) described the use of Euphorbia spp. as living fences in the highlands of East Africa. Brewbaker and Macklin (1990) have discussed silvopastoral practices which could be developed to address farm fodder needs. Alley cropping with a fodder component, fodder or protein banks, living fences along plot boundaries, plantation crops with pastures or trees on rangelands are among the most significant examples. The incorporation into these systems of trees and shrubs which are known for their high protein content could contribute to increased availability of high quality fodder for improved production. A cut-and-carry system dominates where herd sizes are small, and feeding occurs in stalls. Kang and Wilson (1987) have discussed the development of alley farming incorporating a fodder production component at the International Livestock Centre for Africa (ILCA) in Nigeria.

42 27 Pasture degradation of natural rangelands is a major problem in the humid and sub-humid tropics as well as in the arid and semi-arid zones. Tree planting to meet fodder needs will also make a significant contribution to releasing pressure on the natural rangelands. 2.7 Agroforestry for Wood Products and Forest Conservation Wood products, including fuelwood, charcoal and building materials are important components of the everyday life of many peoples of the developing world. The consumption of these products has resulted in severe deforestation with associated flooding and soil erosion, loss of biological resources, and adverse climatic change. Repetto (1987) reported a drop of 24% in closed forests and woodlands in Africa between The World Resources Institute et al. (1989) cited by ICRAF (1990) contributed to this observation by reporting a clearing of 11 million hectares of tropical forests and woodlands per year. It should be noted, however, that in spite of these levels of deforestation, small-holder farmers in developing countries will not go out of their way to plant trees for such products; this is particularly the case with respect to fuelwood production. Foley and Barnard (1984) cited by Torres (1989), described the problem: