Abstracts on erosion and desertification control[edit | edit source]

Acknowledgements[edit | edit source]

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Erosion and desertification control

Review, Africa, indigenous methods, soil and water conservation, ethno-engineering, maintenance, project interventions, research needs, policy requirements, IIED


1. Indigenous soil and water conservation in Africa.[edit | edit source]

Gatekeeper Series Nr. 27; Int. Inst. for Environment and Development

(IIED), London, 1991, 32 pp.; price £2.50 inc. p and p

The objective of this paper is to assess the current knowledge of indigenous Soil and Water Conservation (SWC) in Africa and to identify research needs and policy requirements in the field of African indigenous SWC.

Many parts of Africa are experiencing annual population growth rates between 2 and 4%, degradation of the natural resource base, recurrent droughts and a growing dependence on food aid as well as the import of cereals to cover food deficits. During the last two decades increasing financial outlays for agricultural research in Africa have neither produced significant breakthroughs nor led to agricultural growth.

Numerous reports have warned against the disastrous effects of increasing erosion, land degradation, desertification, mismanagement of natural resources due to increasing demographic pressure, and as a result, soil conservation emerged as a central concern in East Africa.

In many African countries considerable efforts have been made during and since colonial times to conserve soil and water resources. Yet most soil and water conservation projects in sub-Saharan Africa have failed. A major argument is that what has been constructed - often at great expense - has seldom been maintained by the "benficiaries".

The most important reasons for these failures in African soil and water conservation (SWC) include a dominant top-down approach, the use of techniques which are complicated to design and expensive to maintain both in terms of labour and capital, and therefore are not replicable by farmers, a neglect of farmer training, a heavy reliance on machinery for the construction of conservation works and an indiscriminate use of food-for-work.

Partly as a reaction to the disappointing results of integrated rural development programmes (IRDP's) with their strong emphasis on "transfer of technology", the 1980's have seen a growing awareness of the importance of indigenous environmental knowledge.

As part of this trend, the awareness of the importance of indigenous SWC techniques has also increased.

Three major issues are explored in this paper:

- The first demonstrates that despite a growing awareness of its importance, African indigenous SWC continues to be neglected.

  • The second analyses present trends in indigenous SWC. Are indigenous techniques increasingly abandoned and if so, why?
  • The third briefly examines the effect of project interventions. Some examples will be given of project interventions damaging indigenous

SWC and of others improving the efficiency of indigenous SWC techniques.

Concluding, the author states amongst other that slowly but surely, a certain consensus is emerging that indigenous SWC techniques could be used and have a role to play. This trend reflects a feeling of disappointment with or even despair about the failure to narrow the gap between food needs and food production in Africa and the inability to create conditions for sustainable rural development.

A marriage between indigenous and modern techniques may be required to increase the technical efficiency (coping with degradation) as well as the returns to labour (higher incomes).

Indigenous SWC techniques are not well known and require some research.

Experiments should be designed to improve their technical efficiency, and several techniques should be tested at village level and evaluated by technicians and villagers. It may take 3-5 years before the best and most acceptable technical package is identified, hence tangible results can rarely be obtained before 5-10 years have elapsed. It is essential that donor agencies and governments accept these time frames for projects.

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Latin America, Ecuador, proceedings, workshop, DESFIL, USAID, sustainability, slopes, agriculture, methods, strategic planning institutions, incentives, DESFIL, USAID


2. Sustainable uses for steep slopes.[edit | edit source]

Workshop Proceedings "Sustainable Uses for Steep Slopes", Vol. II; DESFIL in coop. with USAID, USA; 1987, 47 pp. + annex

During the Inca period, the Andean highlands were home to 20 million persons, and sustained an efficient agriculture, evidently sufficient to support this population, indeed with excess production to trade with lower areas. The historical record left by these peoples attests that it is possible to practice efficient and sustainable agriculture in the region.

Therefore, a workshop for applied development practitioners, was held 1987. The workshop had two general purposes:

- To report experience in implementation and applied research on the development and the intensified but sustainable uses of fragile, steeply sloped areas; and

  • To draw conclusions and lessons learned from past experience for the design and management of future development on fragile, steeply sloped areas.

Presentations were made by persons and institutions that had attempted project implementation or had concluded applied research projects based on steep slopes, could document what happened, and could draw lessons learned, implications for policy, and recommendations for the design and management of future projects from these experiences.

The working groups emphasized sociocultural themes and community participation. Those present, most of whom were not social scientists, were overwhelmingly of the opinion that effective technical measures for degradation control - such as terraces, windbreaks, living barriers, diversion or infiltration ditches, mulching techniques, crop rotation, cross-slope farming, and so on - proved under on-farm conditions, existed.

Farmers, however, and many personnel in public sector institutions and donor agencies were unaware that degradation was a problem, did not immediately perceive or pay for its effects, and were thus reluctant to apply or continue to apply the efficacious, available control measures.

The sociocultural deficiencies that the working groups identified in development projects and programs in fragile areas are, in general, that local participation was not included in development efforts and that the talent, leadership, and traditions of the native communities and of the national-regional technicians community were not called upon. In addition, projects are usually designed to cover relatively short time spans, and so do not provide for postproject continuity of degradation-control programs.

In the design and management of natural resources projects, the working groups signaled a need for an interdisciplinary focus on the multiple phases and effects of the degradation problem.

Workshop participants noted the existence of certain problem-prone areas, such as p�ramos, dormant volcano craters, and very high cloud forests, which nevertheless offer development potential. The key to the development of these areas is multiple, non-intensive, non-agriculturally based uses (such as a combination of forestry, tourism, and public education programs, or the non-intensive exploitation of indigenous species). Basic data on the identification and sustainable uses of such zones are lacking.

1255 92 - 13/53

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Africa, review, land restoration, revegetation, agro-silvicultural methods, shelterbelts, plantations, rangeland, forests, woodlands, case studies strategies, constraints, control measures, intervention methods, knowledge gaps


3. Land restoration and revegetation.[edit | edit source]

In: FAO Conservation Guide No. 21, "Role of Forestry in Combating

Desertification"; FAO, Rome, 1989, pp. 253-265

This paper deals with the objectives of land restoration and revegetation, the strategies and practices carried out to realize the objectives within the context of the constraints, and arrives at recommendations of lines of action to deal with the problem.

The broad objectives of land restoration and revegetation are:

- to restore the land and vegetation for increased food production.

  • to enhance food production and also to generate income and to improve the quality of life through resource conservation and development.

The specific goals are:

- Protection of the soil from wind and water erosion and maintenance of its fertility.

  • Protection of catchment areas and perennial and seasonal water courses to assure regulated flow of water both in quantity and quality. Also efficient and wise use of the scarce resource of water.
  • Enhancement of the productive role of the vegetation to realize maximum production of fodder, wood, fibers, medicinal products, tannins, perfumes, gums and other products.

Land restoration and revegetation is carried out through execution of corrective measures on land where the degradation has occured. The current measures usually executed are summarized in this paper such as:

- On cultivated land:
- Agro-silvicultural methods
- Shelterbelts
- Plantations on seriously degraded irrigated or rainfed crop land
- On rangeland
- On forests and woodlands
- On bare land: sand and sand-dune fixation

The case studies discussed illustrate what happens when vegetation is destroyed by imbalanced use of land.

The following conclusions and recommendations are drawn:

Land and vegetation degradation is essentially a land use problem and the key to success for restoration and revegetation centres on:

- Integration of land use within ecological context.

  • Active peoples' participation, through various means, as no government can cope with these problems.
  • Building and strengthening the staff base at all levels to execute these programmes, and filling the present gaps in knowledge.
  • Integration of all available knowledge into working practical models that can solve the problems.

No effort on land restoration and revegetation can achieve its objectives without the active participation of the people. This cannot be done without motivation. That coercion through laws alone has largely failed needs no illustration. There is a need for studies to evolve methods of motivation, coercion and others that can lead to sound practices of efficient utilization and conservation.

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Erosion and desertification control

Africa, Nigeria, study, IITA, land-use, shifting cultivation, soil erosion, alley cropping, bush fallow system, no-tillage system, economic analysis

EHUI, S.K. et al.

4. Economic analysis of soil erosion effects in alley cropping, no-till, and bush fallow systems in southwestern Nigeria.[edit | edit source]

IITA Research No. 3, 1991, pp. 1-5

Based on a simulation model, this paper uses a capital budgeting approach to determine how land-management technologies are compared with each other and with traditional bush fallow systems in southwestern

Nigeria, taking into account both the short-term and long-run impact of soil erosion on agricultural productivity and profitability.

The analysis is also conducted under two population density scenarios (high and low), which permits to verify the hypothesis that there exists a positive correlation between population density and agricultural intensification. This study thus differs from previous economic analyses in that the productivity effects of soil erosion and population growth rate are assessed.

Five land-management technologies in maize production are evaluated in the study.

They are continuous alley cropping systems with leucaena (Leucaena leucocephala) hedgerows planted at 2-m and 4-m intervals, continuous no-till system, and two traditional bush fallow systems with 25% an 50% farming intensities.

Shifting cultivation is typical of traditional agricultural systems in tropical Africa.

The International Institute of Tropical Agricultural (IITA) has concentrated its research efforts over the past two decades on developing sustainable soil management technologies, which enhance food production and preserve the natural resource base.

Although some economic analyses are available on the viability of improved land-use systems in sub-Saharan Africa, none of them accounts for the erosion process with its resultant long-term impact on costs and returns.

These results confirm the hypothesis that there exists a positive correlation between intensity of land use and population density. The argument is that for given agroclimatic conditions, increases in population density will gradually move the agricultural system from forest fallow to annual cultivation. Thus intensive cultivation of permanent fields in the frontier, using labour-demanding technologies (such as the 4-m alley cropping) or external input demanding technologies (such as the no-till system), becomes the norm only when arable land is exhausted. It can, therefore, be concluded that where land value rises due to land shortages, farmers with lower discount rates are likely candidates for the adoption of the 4-m alley cropping system compared to the no-till. For those farmers exhibiting high discount rates under high population density conditions, research should focus on reducing the establishment cost of the 4-m alley cropping system to make it competitive with the no-till system.

To test if the technologies fit into the farmers' production plan, economic analysis based on a whole-farm modeling approach is necessary.

Whole-farm models reflect the basic production processes involved in agricultural (e.g., nitrogen-fixing capabilities of leguminous trees) as well as many of the resource characteristics and constraints with which farmers must work (e.g., labour, land, and credit, to name a few). This further research should now be a priority.

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Erosion and desertification control

Review, book, developing countries, soil conservation, conservation practices, watershed management, grassland management, research, organisation, education, extension, environment


5. Soil conservation and management in developing countries.[edit | edit source]

FAO Soils Bulletin No. 33, ISBN 92-5-100430-7, 1985, pp. 208 + appendices

The purpose of this book was to re-examine the question of soil conservation and management in the developing countries, bearing in mind socio-economic aspects, administrative structures, technology and financial resources.

The discussions concluded that there are problems in the organization of soil conservation and management and possible solutions were suggested.

Soil conservation in the past was commonly equated with the mere prevention of erosion or with the restoration of areas in which accelerated erosion has already taken place. The modern thinking however, assigns to soil conservation a more comprehensive and more positive role, in that sustained improvement complemented by the preservation of available resources should form the central concept.

Soil conservation is not merely a technical problem.

The basic concept of a multi-disciplinary approach to the solution of the problems has unfortunately been overlooked in most cases.

The following general recommendations were made amongst others:

- Soil erosion, and consequently the need for conservation, is not confined to land under arable use; it frequently affects grazing lands, and can be associated with mining, road construction, forestry and other kinds of land use.

  • Soil conservation refers not only to mechanical protection measures but includes all aspects of land use planning, development and management which contribute to the maintenance and improvement of soil resources.
  • Soil conservation is an interdisciplinary subject, which involves agronomy, soil science, range management, forestry, ecology, hydrology, engineering, geography, economics, sociology and other disciplines.
  • The damage caused by severe soil erosion is frequently irreversible.

It is consequently desirable to take conservation measures to prevent onset of erosion rather than acting after it has commenced.

- Detailed knowledge of the nature and distribution of land in an area are the basic pre-requisites of any conservation programme.

  • Soil is a basic resource, for the present and the future. As such, the value of its conservation extends beyond that which can be expressed in monetary terms.

Conservation education and extension are areas where particular attention must be directed in the developing countries. Many countries transfer without due consideration to socio-economic factors, conservation education methods from other environments with the pious hope of solving their own problems.

The organizational set-up is often uncoordinated with the general machinery of other Government Departments. This has in many cases resulted in ineffective, disorganized programmes which failed or even, in some cases, perpetuated the problem. There are examples in many countries of expensive soil conservation structures which are not properly maintained and which result in a worsening of the situation. In many of these countries, techniques need not always be complex. Such simple practices as contouring and terracing, constructed with the farmers' own tools, may in the aggregate, contribute as much as the more spectacular large scale development.

Specific guidelines are made for:

- research
- education
- extension and
- practical and technical aspects.

As a general principle, it is suggested that the contribution of FAO should be directed towards the coordination and dissemination of results and assistance to individual countries; and that individual countries and institutions should concentrate on work related to their local or regional circumstances.

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Erosion and desertification control

Review, book, land evaluation, rainfed agriculture, soil resources management, land utilization types, land-use, land-use requirements, crop requirements, land qualities, agroclimatic zones


6. Guidelines: land evaluation for rainfed agriculture.[edit | edit source]

FAO Soils Bulletin No. 52, FAO, Rome; ISBN 92-5-101455-8, 1984, 191 p. + appendices

The principal objective of land evaluation is to select the optimum land use for each defined land unit, taking into account both physical and socio-economic considerations and the conservation of environmental resources for future use.

The need for optimum use of land has never been greater than at present, when rapid population growth and urban expansion are making land available for agriculture a relatively scarce commodity. The increasing demand for intensification of existing cultivation and opening up of new areas of land can only be satisfied without damage to the environment if land is classified according to its suitability for different kinds of use.

These "Guidelines" are intended to assist field staff in carrying out land evaluation for rainfed agriculture according to the principles of the FAO Framework for land evaluation. The present publication is an expansion of the basic concepts of the framework giving procedures and methods necessary in evaluation for rainfed agriculture. It provides practical guidelines on the planning and execution of the various steps in land evaluation, from interpretation of basic data to the final recommendations which form a basis for land use planning and project implementation.

The "Guidelines" refer only to crop production. Both annual crops (arable farming) and perennial crops (tree and shrub crops) are included.

The procedures are applicable at all levels of scale, ranging from continental or national, through regional and district scales, down to detailed or intensive surveys for local projects, village-level schemes and farm planning.

These "Guidelines" occupy a position intermediate between the "Framework for Land Evaluation" and detailed local manuals on evaluation. The "Framework" gives the principles and basic concepts on which land suitability evaluation is based, and indicates overall strategies for their application. The "Guidelines" provide a detailed methodology for carrying out the strategies.

In attempting to be fairly comprehensive, the Guidelines present the maximum range of procedures or aspects to be covered. Some procedures are covered only briefly. Similarly, the checklists are intentionally long to ensure that no relevant aspect is overlooked.

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Erosion and desertification control

USA, study, wind erosion, mixed vegetation, control and prediction


7. Small-grain equivalent of mixed vegetation for wind erosion control and prediction.[edit | edit source]

Agron. J., 84, 1992, pp. 98-101

The purpose of this analysis was to examine this discrepancy and derive an improved expression to determine the small-grain equivalent of mixed vegetation.

Control and prediction of wind erosion requires knowledge of the effectiveness of surface vegetative cover. Scientists realized early the value of crop residue for controlling wind erosion and reported quantitative relationships.

Amounts of wheat (Triticum aestivum L.) straw needed to protect most erodible dune sands and less erodible soils against strong winds were determined. Standing stubble was much more effective than flattened stubble. Standing sorghum (Sorghum bicolor (L.) Moench) stubble controlled wind erosion more effectively with rows perpendicular to wind direction than with rows parallel to wind direction.

Siddoway et al. (1965) quantified the specific properties of vegetative covers influencing soil erodibility and developed regression equations relating soil loss by wind to selected amounts, kinds, and orientation of vegetative covers; wind velocity; and soil cloddiness. They found a complex relationship among the different kinds and orientations of residue in terms of relative effectiveness.

The relative value of kinds and orientations of residue in controlling erosion must be quantified by soil, wind velocity, and variable characteristics of the residues.

Therefore, control and prediction of wind erosion require knowledge of the effectiveness of surface vegetative cover. The effectiveness is usually referenced to as small-grain equivalent. The procedure used to convert mixed vegetation to small-grain equivalent was found faulty.

Improper weighting of regression coefficients caused the conversion procedure to predict that adding crop residue decreased small-grain equivalent. Therefore, the purpose of this analysis was to improve the conversion of mixed vegetation to a small-grain equivalent. The new expression derived for this purpose gave a logical conversion where the previous procedure failed. It did not predict a decreasing small-grain equivalent with increased soybean (Glycine max (L.) Merr.) residue in the 0 to 300 kg/ha range as did the former method. Applied to the same data that were used for testing the previous procedure, the new procedure reduced the error by almost 50%. The new procedure improves the conversion of mixed vegetation to small-grain equivalent.

1260 92 - 13/58

Erosion and desertification control

Asia, Philippines, survey, technology transfer, farmer-participatory research


8. A method for farmer-participatory research and technology transfer: upland soil conservation in the Philippines.[edit | edit source]

Expl. Agric., 25, 1989, pp. 423-433

This paper discusses farmer-to-farmer technology transfer and the participation of resource-poor farmers in the adaptation of agroforestry technologies, as well as a range of interlinked, mostly agronomic and biophysical, research issues.

The research was done on volcanic plateau and alluvial plain sites with moderately well drained acidic clay soils of pH 3.9-5.2.

Although rice, maize, cassava and perennials are grown throughout the area, there are three distinct zones which correspond roughly to increasing altitude and rainfall. Upland rice-fallow rotations and cassava are the main cropping patterns in the lowest altitude area (400-500 m). Maize-maize and maize-fallow rotations predominate in the middle area (500-650 m). Maize, vegetables (especially tomato) and perennials dominate the upper area (650-950 m).

The interdisciplinary research involved scientists from IRRI and the DA.

Efforts to incorporate a farmer perspective used methods from agricultural anthropology to understand farmers' practices, perceptions and technical knowledge, to link this to appropriate research into technology development and to incorporate both into farmer technology adaptation and dissemination.

Initially, 55 farmers were selected at random and informally interviewed using open-ended, interactive and structured guide questions which had been selected after a period of exploratory research had determined some of the key issues facing farmers.

Concluding, the author states, that in terms of farming systems methodologies, the experience shows that a simple alternative method for on-farm research and technology transfer might consist of first understanding farmer practice, perception and technical knowledge; using this and farmer experiments to help identify technical possibilities and research issues; back-up research on a combination of alternatives that integrates farmer and researcher concerns and contributions; and transfer of technology from adaptor-adopters to farmers who want solutions to problems addressed by the technologies.

This work supports the idea that participation is a two-way process and that a participation 'paradigm' should progress from the obsolete view that 'the experts know best' to the increasingly fashionable concept that 'the local people know best' and on to the realistic and helpful idea that 'both experts and local people have unique areas of expertise which collectively provide a better basis for development than either alone'.

1261 92 - 13/59

Erosion and desertification control

Africa, review, bean production, soil fertility, varieties, technology


9. African bean-based cropping systems conserve soil.[edit | edit source]

CIAT Annual Report 1989, pp. 49-52

Low soil fertility is as important as disease in limiting bean production in Africa. This is especially true in areas of high population growth. More people to feed means that land that once could be left fallow and allowed to recover its nutrients must be constantly used. Less good land to farm leads to more cultivation of steep slopes and marginal soils.

In response to the need to increase production and conserve the soil, CIAT is strongly promoting sowing climbing beans in the Great Lakes area. These beans generally yield higher than traditional bush beans; and when climbing beans grow upward rather than spreading across the ground, the plants are better protected from soil-borne pathogens and the damage caused by standing water.

But climbing beans need something to climb on. Having enough vegetative material suitable for making stakes is a major impediment to farmers growing this kind of bean. Appropriate kinds of trees are needed to plant to solve the stake shortage.

These trees or bushes would have several purposes: they would serve as stakes; they would conserve the soil by fixing nitrogen; they would produce organic matter which would be used as green manure or animal feed; and they would counter erosion by stabilizing the soil with their roots and by providing windbreaks.

Research conducted on Rwandan farms has shown that timely manure applications are important in increasing yield and reducing erosion.

Studies show that if manure is applied at a certain stage of growth of the bean plants - the third trifoliate stage - yields can be increased by 60%. This can help farmers maximize the benefit of their limited fertilizer resources.

Traditional soil conservation practices are studied so that accepted methods can be used as guidelines for proposing improvements. For example, in Zambia, farmers concentrate soil fertility through dirt mounds consisting of organic compost. On the other hand, Tanzanian farmers dig pits and compost grass to enrich the soil. In other areas, farmers grow their crops on contoured ridges which reduce erosion.

But population pressures on land are threatening these traditional systems and, in turn, increasing soil erosion. Finding solutions to these problems is vital so that the demands on the land do not ultimately destroy the very foundation of farming: the soil itself.

1262 92 - 13/60

Erosion and desertification control

Latin America, Ecuador, study, soil conservation strategies, mountain environment, climatic factor, basic terms, farmer practices, socio-economic factors, DESFIL, USAID

STAVER, C.P. et al.

10. Refining soil conservation strategies in the mountain environment: the climatic factor.[edit | edit source]

DESFIL Publication; prepared for USAID, USA; 1990, 36 pp. + appendices

The overall objective of this report is to establish simple procedures for the use of climate, soil, and slope data during the design phase of conservation projects with small farmers in the Latin American highlands. Use of these procedures can greatly facilitate the initial selection of soil conservation measures that might be employed.

The authors discuss briefly, but do not analyze, the role of socioeconomic and institutional factors, as they relate to the successful adoption of appropriate soil conservation measures. They set as their task in this report the development of a simple method for determining appropriate soil conservation technologies in areas of steep slopes. They are cognizant of constraints such as patterns of land tenure, social organization of labour, traditional crop preferences, existing traditional technologies, market patterns, and local perceptions of risk and costs versus benefits - to name a few of the more obvious socioeconomic variables - on the successful adoption of non-traditional technologies, no matter how appropriate from a strictly technical standpoint they may be.

The hill and mountain regions of Latin America represent the fragile land resource for innumerable families on small farms. A major threat to their survival is land degradation resulting from soil erosion. Soil conservation projects directed toward this problem have been implemented throughout the region with mixed results, and the design of such projects is the subject of this report.

Section 2.0 begins with a summary of contemporary soil erosion problems in Ecuador, followed by a brief introductory discussion of erosion and sedimentation process in Section 3.0. Section 4.0 provides a summary of the team's field and desk analyses conducted in Ecuador; the resultant decision tree, designed to assist the field manager in the preliminary selection of regionally appropriate erosion control techniques, is discussed in Section 5.0. Socioeconomic parameters of importance to a more effective use of the decision tree are discussed in Section 6.0, followed by a discussion of the study's major conclusions and recommendations in Section 7.0. Appendix 1 shows the average monthly water balance for 12 stations in the Ecuadorian highlands; Appendix 2 provides a method for approximating annual water balance by month; and Appendix 3 discusses a number of soil loss quantification techniques of potential use to ongoing and future projects. A model monitoring plan is also discussed. A brief description of contemporary soil conservation techniques is shown in Appendix 4.

To achieve site-specific project, implementation must take a learning approach. During the initial period, the project must learn what works.

This is a period of testing and validation to identify effective soil conservation interventions, effective institutional arrangements, and effective means to collaborate with farm families and communities. In the second phase learning should focus on efficiency, while in the later phases the project must learn to expand and achieve wider coverage. Many projects attempt wide coverage initially, and only by chance identify what works late in project life. Efficiency may never be achieved.

The study includes a decision tree which integrates rainfall, slope, and soil factors in the choice of conservation measures; a discussion of farmer practices and economic and social factors in soil conservation measures; and an appendix on techniques for monitoring soil loss as well as a discussion of monitoring programs.

Given the wide range of physical and social factors of influence to accelerated erosion processes, conservation projects should logically employ a site-specific approach. The development of additional procedures for the systematic consideration of socioeconomic, community, and institutional variables, in conjunction with the technical procedures described here, is highly recommended.

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Erosion and desertification control

Africa, Zimbabwe, project, land-use pattern, institutional framework, training, research approach, on-farm trials, GTZ


11. Conservation tillage for sustainable crop production systems.[edit | edit source]

Project Res. Report, No. 4, Departm. of Agricult. Technical and Ext. Services, Zimbabwe; 1992, pp. 22

"Conservation Tillage for Sustainable Crop Production Systems" is a collaborative programme between the Department of Agricultural Technical and Extension Services (AGRITEX) of Zimbabwe and the Deutsche Gesellschaft fnr Technische Zusammenarbeit (GTZ) GmbH of Germany.

The primary objectives of this technical co-operation project are:

- to assess the soil and water conservation merits and yield potentials of several conservation tillage techniques based on animal traction and/or manual labour,

  • to select appropriate cropping systems with smallholders.

Ultimate project purpose is to make adequately tested tillage and cropping technologies available to resource-poor farmers in the Communal

Areas of Zimbabwe. This will be done on the basis of synthesized results of complementary on-station and on-farm trials.

In addition to the technical programme, the project also comprises a staff development scheme for Zimbabwean counterparts by providing funds for post-graduate studies overseas and offering on-the-job training.

A major factor causing soil erosion in Zimbabwe is clean tillage involving the mouldboard plough which is often used too late (after the onset of the rainy season) and/or done too shallow (approx. 125 mm) because of a general lack of (suitable) draught animals. In order to alleviate this problem, communal agriculture requires conservation tillage systems which reduce runoff, soil loss and draught power and are both practical and acceptable to the farmer. Although techniques are available, they are yet to be tested and validated for the different agro-ecological regions and the prevailing socio-economic conditions.

A two-pronged approach of complementary on-station and on-farm trials has been adopted by the project, because there is widespread understanding that, in order to assist in the development and adoption of sustainable farming practices, comprehensive approaches are required that interlink the aspects of sustainability (technical and agro-ecological factors) and acceptability.

During the early stages of project formulation, three main treatments were selected for investigation, namely: mouldboard ploughing, ripping into bare ground and no-till tied ridging.

The results of three seasons (1988/89 to 1990/91 of on-station trials showed that no-till tied ridging was best from a soil conservation point of view. Except on one occasion, sheet erosion rates were in the order of only 0,1 to 0,3 t/ha/yr at both research sites. Higher soil loss (2,2 t/ha/yr) from ridge tilled plots was measured in 1989/90 at Domboshawa, when approximately 800 mm of rain fell in a period of just six weeks. At the same time, 9,6 t/ha/yr were lost from the fields ploughed with the mouldboard plough.

The results also revealed that the seasonal influence on yield levels was highly significant. In addition, topsoil depth and soil profile and/or physical characteristics were highly related to maize yield. This interaction was particularly evident with no-till tied ridging.

From the first three years' results it would appear that, in the dry region, tied ridging will meet the criterion of equal or improved yield levels compared to mouldboard ploughing only if existing management practices, in particular with respect to timely planting and first weeding, are improved.

The paper provides an insight into the multiple problems associated with on-farm research, which not only demand close cooperation between the farmers and researchers involved, but also require skills in communication by the researcher and a strong interest in working closely with farmers.

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Erosion and desertification control

Africa, Tanzania, highlands, technical aspects, soils, crops, macrocontour lines, plant protection, animal traction, agroforestry, livestock keeping, extension, nutrition, integrated approach, GTZ


12. Caring for the land of the usambaras - a guide to preserving the environment through agriculture, agroforestry and zero grazing.[edit | edit source]

Publ. of TIRDEP-Soil Erosion Control and Agroforestry Project (SECAP), Part.I, Tanzania; GTZ, Eschborn, 1986, pp. 261 + appendices

This book is about farming in the Usambara Mountains, but the suggested techniques are applicable to similar situations in other developing countries. Primary consideration has been given to providing guidance for specific situations encountered by village extension workers in Lushoto District.

The West Usambaras are a mountain range in the north-east of Tanzania.

They vary in altitude from 1,400 metres above sea level in the valleys up to about 2,200 metres on the upper mountain slopes. The surrounding lowland plains are only a few hundred metres above sea level. Much of the area was formerly covered with dense forests but over the past decades these have been largely cleared.

Intervention is based on establishing macrocontour lines which run across farmers' fields at prescribed intervals depending on the steepness of the slope. This line of permanent crops (usually fodder grasses and legumes like guatemala, desmodium, and leucaena), and trees provides a solid erosion control structure which slows the speed of run-off rainwater and traps soil particles. The line produces economically valuable outputs like fodder, fruits, firewood, and building materials.

Annual and biannual crops are planted between these macrocontours and these are called microcontours. The project strongly advises all farmers to plant permanent and annual crops across hillsides along contours and never to plant in rows running up and down slopes.

Farmers are also advised to increase soil fertility and improve soil structure by applying organic manures like compost, cow dung, and green manure and to practice mixed cropping since this provides diversification and reduces the risk of crop failure due to drought, pests, or disease.

The goal of the livestock program is to create an economically viable alternative to traditional livestock keeping which, through over stocking and grazing has caused serious erosion problems. The production and output of local animals is very low and they now graze on hillsides since the traditional valley grazing areas are now used for intensive vegetable production.

This alternative is the zero grazing system, whereby animals are confined to a stall and are fed with fodder grown on a macrocontour line. Improved crossbred dairy cattle generate considerable income from milk sales and provide manure which is used to improve soil fertility and improve crop yields.

Forestry included 2 programs; afforestating overgrazed eroded village pastures and planting multipurpose agroforestry species along macrocontour lines and in fields.

Monitoring and evaluation of the work carried out by the community nurseries tends to be insufficient.

This guide is well written.

Specific information on laying contour lines, managing nurseries, planting fruit trees, etc. is presented in easy to read form completed with supporting illustrations. There are also short sections on fish farming, biogas, rabbit rearing, and human nutrition.

The information and advice in this book was collected from farmers, extension workers, researchers, development workers, publications, and by personal observations. The book has been flexibly designed so additions can be made, as necessary.

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Erosion and desertification control

Review, book, Asia, India, soil and water conservation, farmer practices, vetiver grass


13. Vetiver grass (vetiveria zizanioides) - a method of vegetative soil and moisture conservation.[edit | edit source]

Publ. of World Bank, Agriculture Divison, New Dehli; 1988, 72 pp.

Soil conservation is a world problem.

Soil erosion has reached crisis proportions in India. Over half of India's crop land is losing productivity because top soil is being washed or blown away faster than natural forces can replace it. Reducing the topsoil layer causes part of the subsoil to be cultivated, meaning that plants will have reduced access to essential nutrients and water.

Changes in farming practices have accelerated this erosion in recent years, as farmers switched from traditional rotations to continuous row cropping in response to a growing need for grain.

Top level policy makers recognize the problem exists and have already spent Rs. 1,200 M on earthworks as preventative measures. But this has only covered a few million of India's 328 M hectares, 90% of which is afflicted with soil erosion.

The costs of constructed soil conservation measures would outrun the short-term benefits by three or four times, and these practices not only cost money, they also cut production. Farmers do not look kindly on these practices.

On the other hand, vegetative soil and moisture conservation measures are not only extremely cheap (less than 1/10-1/100 the cost of constructed banks and waterways) but the farmers can do the work themselves, and, if they have the planting material, at no cost. Once vegetative hedges are established (this usually takes two to three seasons) they are permanent. When they are followed as contour guidelines for cultivation and planting, the resulting "in-situ" moisture conservation increases yields by at least 50% over traditional methods.

Vegetative conservation measures hold the runoff water on the slopes longer than other methods, giving it a chance to soak in over a wide area and recharge the aquifers: Constructed measures are designed to dispose of runoff as fast as practicable, thus reducing any change of recharge. Dams rarely recharge aquifers; if they did, it would be considered that they were leaking.

The farmers regard the fodder value of vetiver grass as an additional merit. 3-4 cuttings can be obtained at an interval of 45 days, mainly during and shortly after the monsoon, yielding enough green fodder for two animals for 6 months in a year.

The farmers have developed their own ways of multiplying and propagating the grass. On sloped land, they form small section bunds across the slope and plant 2-3 slips per rill 20-30 cm apart on the upstream side.

In flat fields, the slips are simply planted in the plough furrow. In either case, they chop off the top of the plant and avoid planting inflorescence axles. The grass establishes well if planted after the first monsoon shower. Even without irrigation, the lines form hedges in about year. The slips for further planting are taken from 3-year-old bunds. When waste-weirs or drop structures are to be treated, even clumps of the grass are taken and placed at appropriate locations.

Vetiver has long been used by Indian farmers, but most scientists are still unaware of this. The indigenous knowledge of Indian farmers has not been appreciated. The knowledge they have gained in dealing with khus-based soil conservation systems needs to be documented and the other uses of khus, e.g. for fodder, should be studied.

This handbook has been prepared to support field workers and farmers in developing appropriate soil and moisture conservation measures using vegetative systems. Experience in India and in other countries has shown that conventional earth bunding systems on small farms have been expensive to develop and have in many cases proved ineffective.

Vegetative systems of soil and moisture conservation have proved cheaper and more effective when implemented correctly.

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Erosion and desertification control

Latin America, Colombia, Andes, hillside farming, water erosion, cassava, cropping systems, small scale agriculture, CIAT


14. Erosion in andean hillside farming.[edit | edit source]

Hohenheim Tropical Agricultural Series 1; Verlag J. Margraf, P.O.B. 105, 6992 Weikersheim, FRG; ISBN 3-8236-1211-5; 1992, 219 pp., price DM 35,00/USD 27.00

The investigations reported here were carried out to provide some basic information on characteristics of soil erosion processess in the Andean zone of Colombia. The effect of cultural practices in cassava cultivation systems on the process of soil erosion was investigated.

The research reported here aims to collect basic information on the characteristics of erosion processes in a defined area of the Andean zone of Colombia. Furthermore, conventional and improved cassava cropping systems adapted to local smallholder conditions were to be tested to obtain knowledge based on the influence of management practices on erosion processes. Erosion trials were established on slopes with a gradient of 7-20% at two locations in southern Colombia.

As expected, the greatest soil losses were found in the clean tilled fallow system. However, at the beginning of the growing period the greatest soil losses were measured where rill erosion was predominant.

This was especially evident in plots with cassava on ridges down the slope where greater soil losses were recorded during the first months after planting than in the plots with clean tilled fallow. These results show that soil conservation measures must be directed especially towards the reduction of surface runoff during the first months after planting.

In this context those cropping systems were the most efficient which reduced the velocity and the quantity of runoff by physical barriers.

This is especially evident for the contour ridges and to a limited extent also for the contour grass strips. Also, a high initial percentage of ground cover reduced effectively the surface runoff and prevented rill erosion.

Based on these site characteristics, a tolerable amount of a yearly soil loss of 1-5 t/ha-1 was calculated.

Under the test conditions the cropping systems with sole cropped cassava and cassava planted between contour strips of grass produced relatively high yields.

The results suggest that management practices such as planting on contour ridges or contour strips markedly reduce soil loss while producing optimum cassava yields.

This book is well worth the attention of those working with soil and water conservation in mountain areas. All chapters are well, documented and the conclusions drawn are verified by the text, graphs and tables.

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Erosion and desertification control

Review, USA, soil and water conservation, tillage systems


15. Conservation tillage systems.[edit | edit source]

Adv. Agron., 33, 1981, pp. 58

Conservation tillage systems are systems of managing crop residue on the soil surface with minimum or no tillage. Other names are stubble mulching, ecofallow, limited/reduced/minimum tillage, no-tillage and direct drill. Leaving crop residues serves water and wind erosion control, conservation of soil and water and reduction of energy use. The review is limited to the salient points that have been researched over the last twenty years and is limited to the United States. For our purposes general remarks in the sections on seed bed preparation and crop seedling, control of wind erosion, control of water erosion, weed control with tillage and the three sections on soil temperature and the same number on soil structure and other physical properties are of most importance. On wind erosion, after a general introduction the wind erosion equation is dealth with. Tillage has a direct bearing on the factors I, soil erodibility; K, soil surface roughness and V, equivalent quantity of vegetative cover. Surface residue influences V, tillage proper influences mainly I and K. partial (de)coverage of a field would influence L, equivalent width of field (maximum unsheltered distance across the field along the prevailing wind erosion direction). Kind, amount, texture, height and orientation of surface residue all influence wind erosion. Tillage operations that minimize soil pulverization and smoothing are effective for maintaining K and keeping clodiness for maintaining I. Examples are given from the USA. A comparable approach is followed in the chapter on water erosion, using the influence of residue and tillage effects on the Universal Soil Loss Equation. The section on soil temperature deals with the effects of surface residue: changing the radiation balance accompanied with an insulation effect, and with residue factors involved in these effects: residue age (decoloration; decomposition), color, geometry, distribution and amount. Again some examples. Finally its biological effects on crops are dealt with. After dealing with soil aggregation, porosity and density as affected by tillage, other soil physical factors dealt with as influenced by tillage operations are soil texture, crusting, hydraulic conductivity and water storage capacity. Tillage reduction in the USA can't be considered without the rapid technological advances in the use of herbicides. It is estimated to serve from 5 to 15 cm of additional water to rain-fed agriculture. Only more interdisciplinary knowledge will advance this field of soil science.

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Erosion and desertification control

Asia, Indonesia, highlands, study, water runoff, erosion control practices, small plots, steep slopes


16. Soil erosion, water runoff and their control on steep slopes in Sumatra.[edit | edit source]

Trop. Agric. (Trinidad), 68, No. 4, 1991, pp. 321-324

In this paper soil erosion research and water runoff rates under conventional cultivation (i.e., without soil conservation practices) and when several soil conservation measures were used on steep, intensively-cultivated slopes in Sumatra, Indonesia are examined.

Erosion-inducted effects on selected soil physical and chemical properties and on crop yields were also examined. Based on these results, recommendations were developed for the introduction of appropriate soil conservation measures.

This study was conducted in the highland valley of Kerinci, Sumatra, Indonesia. Irrigated rice cultivation is the dominant land use in the valley; annual and perennial cash crops are cultivated on the hills above the valley floor. Most farmers in Kerinci cultivate both a rice field and one or more hillside farms.

Soils in Kerinci are complex red-yellow podzolics.

Soil erosion and water runoff losses associated with conventional and conservation farming practices were measured on enclosed runoff plots, using a randomized complete block design with three replications.

Five practices (treatments) were selected for study:

- control by conventional cultivation (corn planted two seeds per hole at 75 cm intervals) with no soil conservation measures employed;

  • conventional cultivation at increased planting density (corn planted one seed per hole at 25 cm intervals) and NPK fertilizer application (groundnut, with 100 kg TSP ha-1 and 50 kg KCl ha-1; corn, with 100 kg urea ha-1, 100 kg TSP ha-1 and 50 kg KCl ha 1);
  • level bench terraces, with three terraces per 10 m plot, risers 75 cm tall and planted to Setaria sp. grass at 30 cm intervals;
  • grass contour bunds, with three bunds per plot, each 15 cm tall and planted to double rows of Setaria sp. at 30 cm spacing; and
  • grass and Gliricidia sepium (Jacq.) Kunth ex Griseb. (an N- fixing leguminous tree) contour bunds with mulch, two bunds per plot, each 15 cm tall and planted to one row of Setaria sp. and one row of G. sepium, each at 30 cm intervals. Mulch cover was maintained at approximately 50% ground cover by periodically adding G. sepium leaves following an initial application of 0.5kg m-2 (5000 kg ha-1).

A variety of soil conservation practices are used on small farms throughout the tropics. Some of the more common practices include: contour ploughing, conservation tillage, the use of cover crops and mulches, grass and leguminous shrub plantings along the contour, grassed runoff channels, contour bunds, ditches and bench terraces.

Agronomic soil conservation techniques are generally preferred to engineering methods (e.g., bench terraces) by low-income or subsistence farmers because of lower capital and labour requirements. The construction of bench terraces can result in reducing crop yields where shallow topsoils overlie undesirable subsoils.

In this study, the use of bench terraces, grass bunds and grass plus Gliricidia sepium bunds with mulch resulted in significant (P<0.05) reductions in soil loss and water runoff in comparison with conventional cultivation methods on steep hillside farms in Sumatra. No significant differences in soil erosion rates were observed between conservation treatments.

No significant differences in mean groundnut yields and total above ground biomass production were observed between the conservation or control treatments (on a per plant basis).

This research suggests that agronomic soil conservation practices known to be effective on gentle (less than 15%) slopes may also be suited to some steep tropical slopes. Simple agronomic conservation farming measures warrant careful consideration and empirical field-testing in soil conservation and watershed management projects throughout the tropics.

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