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Research Priorities To Support Sustainable Agriculture

Agriculture in tropical environments faces different constraints than in temperate regions, and this affects soil and water research needs. Six broad areas merit priority attention: overcoming institutional constraints on resource conservation, enhancing soil biological processes, managing soil properties, improving water resource management, matching crops to environments, and effectively incorporating social and cultural dimensions into research. In addition, better use of indigenous knowl-edge and improved communications can enhance the implementation of research results.

Two critical indicators of deterioration in agricultural systems are declines in the quality of soil or water. Poor management of either of these resources quickly leads to decreases in farm productivity. Thus there is an urgent and ongoing need for research to devise ways to manage soil and water resources more sustainably.

A large proportion of the world's developing countries is located in tropical environments.1 Tropical agricultural systems differ from temperate systems in significant ways, both physically and institutionally. Several of the unique characteristics of tropical environments—from mountain highlands to arid rangelands to humid forests—played particularly important roles in the

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Much of the developing world is located in Africa, Asia, and South and Central America. These are essentially tropical continents—that is, most of the land area is located either in tropical latitudes or is influenced by tropical atmospheric systems. Within these continental areas, there are several high mountain areas and plateau areas that are characterized by distinctly nontropical climates. The generalizations about tropical environments do not apply to these upland zones, which need a much more specialized regional approach to their particular soil and water systems than is possible in this overview document. It is essential to acknowledge that the developing world exhibits a tremendous diversity of environments and cultures.



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Toward Sustainability: Soil and Water Research Priorities for Developing Countries 3 Research Priorities To Support Sustainable Agriculture Agriculture in tropical environments faces different constraints than in temperate regions, and this affects soil and water research needs. Six broad areas merit priority attention: overcoming institutional constraints on resource conservation, enhancing soil biological processes, managing soil properties, improving water resource management, matching crops to environments, and effectively incorporating social and cultural dimensions into research. In addition, better use of indigenous knowl-edge and improved communications can enhance the implementation of research results. Two critical indicators of deterioration in agricultural systems are declines in the quality of soil or water. Poor management of either of these resources quickly leads to decreases in farm productivity. Thus there is an urgent and ongoing need for research to devise ways to manage soil and water resources more sustainably. A large proportion of the world's developing countries is located in tropical environments.1 Tropical agricultural systems differ from temperate systems in significant ways, both physically and institutionally. Several of the unique characteristics of tropical environments—from mountain highlands to arid rangelands to humid forests—played particularly important roles in the 1   Much of the developing world is located in Africa, Asia, and South and Central America. These are essentially tropical continents—that is, most of the land area is located either in tropical latitudes or is influenced by tropical atmospheric systems. Within these continental areas, there are several high mountain areas and plateau areas that are characterized by distinctly nontropical climates. The generalizations about tropical environments do not apply to these upland zones, which need a much more specialized regional approach to their particular soil and water systems than is possible in this overview document. It is essential to acknowledge that the developing world exhibits a tremendous diversity of environments and cultures.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries committee's determination of the major issues needing research. Some of the characteristics that make tropical environments especially challenging include the following: Lack of a cold season or frost, which in other climates brings a break in production, thus affecting pests, diseases, and moisture levels; Variable timing and duration of water supplies in both dry and wet regions, creating severe moisture stresses; Year-round growing seasons in some wet areas, with effects on crops and pests as well as accelerated leaching of nutrients; Greater biological diversity than temperate environments, and thus greater diversity of crops, soil organisms, and pests; Highly weathered soils, and in some places very young soils; Shortages of fossil fuel and other capital-intensive inputs; and Significantly different social and institutional contexts and traditions. In the tropics, especially where access to fossil fuel resources is limited, management strategies must be more biological in nature and must rely on the use of appropriate choices of germplasm, cropping systems, and techniques to fit specific ecological niches. Many methods employed in the tropics were developed over time through trial and error; they vary greatly among different geographic regions and cultures. Often, attempts to transfer research strategies elaborated in temperate zones into tropical environments have failed to recognize these fundamental differences. At the same time, the diverse social institutions, kinship patterns, resource access, and tenure relationships in developing countries do not necessarily operate in the same manner, or respond to the same logic, as parallel structures in the industrialized world. Indigenous, colonial, and modern patterns of resource access and regulation can, for example, operate simultaneously on a given water resource or piece of land, although often with conflict. Recognition of these basic differences between tropical and temperate agriculture must be a main factor in the selection of priority areas for research. Given the problems faced by tropical agriculture, the unique characteristics of the environments and cultures, and the strengths and weaknesses of the existing knowledge base, research in the following areas could offer great rewards in support of sustainable agriculture and natural resource management: Overcoming institutional constraints on resource conservation; Enhancing soil biological processes; Managing soil properties; Improving water resource management; Matching crops to environments; and Incorporating social and cultural dimensions into research.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries A wealth of time-tested indigenous knowledge exists and this human resource should be tapped to support these goals. Special potential lies in the blending of traditional methods with modern innovations. One of the most intractable problems yet to be faced is the difficulty of communicating new ideas to the farmer. Research and development organizations have struggled with this problem for many years, and it remains a high priority issue. The committee faced a difficult decision when deciding how to present these research priorities. On the one hand, it wished to stress the need for interdisciplinary research, particularly research that integrates technical and institutional dimensions. Such research often does not fit neatly into categories. On the other hand, the committee needed to use some organizing structure to make the ideas accessible and useful to the research community. Such structures often imply boundaries and separateness, however, and they diminish the importance of interrelationships. In the end, while the committee opted to present its priorities in six distinct categories, it wishes to stress the need to move beyond compartmentalized thinking and toward more integrated approaches (see chapter 4 for more discussion). The following discussion explores the six priority research areas and gives examples of the types of investigations most needed. Within each, some examples of research fields are listed. These are divided into two categories: critical research priorities and other priority topics. In defining research needs, the committee considered and set aside many potentially valuable areas of research. For instance, further research on ground water modeling and soil physics is not recommended, largely because our knowledge in those areas already is extensive. Research on the use of mycorrhizal fungi is not highlighted because it lacked immediate, practical value to the farmers in most need of sustainable agricultural strategies. Research on soil acidity and its effects on the growth of agriculturally important crops is not listed because this is reasonably well understood and many measures are already known to correct such problems. Likewise, nutrient requirements for most crops can be fairly well predicted, and the fundamentals of how to meet these needs have been extensively researched. The primary deficiency in our decision-making is the limited ability to specify appropriate management practices that will be socially and economically acceptable for site-specific conditions. Thus, while the emphasis of the research topics outlined here is less on individual components of soil and water systems and more on the broader, and variable, systems themselves, the need for location-and culture-specific adaptations of these general approaches is of course implied.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries OVERCOMING INSTITUTIONAL CONSTRAINTS ON RESOURCE CONSERVATION Resource conservation is at the heart of all efforts to develop and implement more sustainable approaches to agriculture. It is increasingly clear, however, that resource conservation must be understood to include more than the technical approaches. Sustainable agriculture cannot be obtained without attention to the economic, policy, and institutional elements of resource conservation. Although a large part of the focus on sustainability is directed at the farm level, it is obvious that soil and water management issues relate to the management of the whole environment. Soil and water management are affected by many factors external to the farm, such as the pricing policies of national or international bodies, tenure rights, or available labor. Institutional constraints on resource conservation are as critical to the sustainability of agroecosystems as on-the-ground soil and water management techniques. Critical research priorities should include: Studies of land and water resource tenure and access policies that affect long-term stewardship and sustainable agricultural practices; Analyses of social, political, and economic dynamics of pricing policies and how these affect the stewardship or degradation of land and water resources; and Thorough evaluations of in situ and ex situ germplasm conservation, and the relative merits and problems each offers for maintaining biodiversity to provide a wide range of genetic options for varying hydrologic regimes and soil fertilities. Other priority issues should include: Evaluation of local and regional institutional arrangements to improve the integrated conservation of soil and water; Evaluation of short-term incentives that might be used to implement long-range sustainability goals; and Assessment of the nature and impact of national policies that affect the use of industrial inputs such as fertilizers, pesticides, and mechanization. Both on-farm and off-farm resources affect resource management. On-farm factors such as labor availability, land tenure, and access to resources are influenced by larger scale economic and political forces that affect the choices that farm households and communities make about their resource use. On the farm, research should continue to address how sound stewardship can be used to meet the needs of both the farmer and society. However, off-farm questions, historically, have not received as much attention, especially as regards implementation of research findings.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries Resource conservation is a clear example of an issue that should unite agriculturalists, soil and water managers, and environmental scientists concerned with the long-term use and protection of the natural resources base. The sometimes adversarial relationship between these interests is counter-productive. Instead, all should be attempting to integrate their special knowledge in pursuit of answers to the complex local, regional, and institutional constraints on resource conservation. ENHANCING SOIL BIOLOGICAL PROCESSES Sustainable agriculture requires maintenance of the soil biota, particularly in areas of low-income, low-input agricultural systems where soil biological processes are critical for sustaining and enhancing soil fertility. Soil structure, nitrogen fixation, nutrient availability, and control of soil-borne pathogens and pests all can be manipulated by organic inputs and vegetation management. In most soils, high levels of soil organic matter are essential for good soil structure. Yet many important questions remain regarding the avail Improved methods of using soil biological processes to best advantage are particu-larly important in areas with low-income, low-input agricultural systems. Researchers at this field station in Senegal are investigating root nodulation on fast-growing trees; the AID-funded project involves Senegalese, French, and U.S. scientists. Credit: Michael McD. Dow, National Research Council.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries ability and management of organic matter. For instance, the release of plant nutrients through rapid decomposition is a key way to optimize crop yields, but more research is needed to understand the role of macrofauna in this process. Recent work on the manipulation of earthworms and termites appears promising. The benefits of organic matter in the maintenance of soil quality and crop productivity have long been well known, but only recently have researchers started to elucidate the role of organic matter additions in variable charge soils on soil acidity, the ability of soils to hold nutrients, and phytotoxicity. Another example of a promising research area is biological nitrogen fixation (BNF). Although the general process involved is well known, as evidenced in farmers' wide use of legumes, more needs to be known about its ecology—including plant-microbe-climate-soil interactions. A better understanding of these interactions would facilitate our capability to manage these processes. For instance, successful use of BNF in cropping systems is often erratic and unpredictable, and research could develop methods for BNF inoculation at different sites. New methodologies also need to be developed for quantifying BNF by trees, since current measurement techniques are difficult in the field and often inaccurate. Agroforestry systems are widely and traditionally used in many tropical areas. These practices are becoming increasingly important in agriculture for many marginal areas, especially the wetter tropics, and in areas where fuelwood is scarce. Nevertheless, little scientific data exists on the soil impacts of agroforestry elements such as rooting patterns, allelopathy, nutrient cycling, and the ability of some species to competitively take up or accumulate scarce nutrients. The complex manner in which tree products are integrated into household, local, and regional economies needs to be assessed as well. Issues related to the constraints imposed by limited human labor also require attention. Effective management of soil biological processes to cycle and fix essential crop nutrients can reduce expenditures on fossil fuels. The synchronization of nutrient release from organic inputs to meet nutrient uptake demand by crops is critical and little understood. Often, nutrients are released in the decomposition process when the plant does not need them, and subsequently may be lost. The use of cover crops, mulches, crop rotations, and minimum tillage are known to control many soil pathogens and nematodes and maintain soil tilth. More information is needed on the actual mechanisms involved. Although they vary by region, many sustainable agricultural systems in the tropics include livestock. Their role includes the consumption of crop residues and the production of organic matter and nutrients as well as the control of unwanted vegetation. Work on input-output or recycling models would help many small farm enterprises.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries ORGANIC RESIDUES AND SOIL ACIDITY PROBLEMS Soil acidity is a major problem in soil management, and the use of organic residues is a promising potential tool for farmers in the tropics. As commonly used, the term ''organic matter'' is not the same as "organic material." Organic matter, in the conventional sense, refers to the well-decomposed, origin-unrecognizable organic portion of the soil; organic materials include more intact organic residues such as plant residues, green manures, mulches, and composts. The potential role of organic material varies with its composition and the soil to which it is to be applied. Organic material additions can alleviate the low calcium, magnesium, and potassium conditions characteristic of acid soils because it contains relatively large amounts of these nutrients. Much remains to be learned about the potential role of organic residues in alleviating soil-acidity problems. Research could help fill some of the information gaps regarding the use of organic material to combat acidity. For instance, what organic materials and decomposition products are most effective in reducing aluminum content and solubility in soils? What are the effects of differing surface mineralogy on organic material and its decomposition products? What is the duration of the liming effect of organic materials? Is there an optimum quantity of organic material to add to the soil? In addition to the chemical and physical aspects of the practice, an important economic consideration is whether there is sufficient organic material available for application in the near proximity of the farmer's field, and, if not, what are the costs of labor and transportation to move large quantities of the material from adjoining land. One important variable to be considered when predicting the improvements possible through organic residue management is whether the organic material was grown in situ or obtained from an exterior location. If imported, the nutrient content of the organic material is contributed to the soil system. If it is grown in situ, the overall benefit is usually less because the nutrients are simply recycled. In some cases, however, recycling and bringing nutrients from deep zones in the soil profile can substantially improve the surface soil—the root zone for most annual food crops. The role of organic material in reducing aluminum toxicity, often the most detrimental aspect of the soil-acidity syndrome, includes the chemical complexing of the aluminum in solution, thereby reducing its activity. Organic material additions can, in some cases, also alleviate phosphorus deficiency in acid soils by supplying phosphorus directly, by reducing phosphorus sorption Capacity, and by complexing soluble aluminum and iron, thereby increasing soluble phosphate concentrations. In large amounts, organic materials can reduce acidity simply by increasing the soil pH. In smaller amounts, the type of organic material becomes important; for example cowpea is more effective in reducing acidity than leucaena.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries Critical research priorities should include: The ecology of biological nitrogen fixation (BNF), including plant-microbe-climate-soil interactions and improved methodologies for predicting BNF response and for quantifying BNF by trees; Analysis of agroforestry systems, including rooting patterns, allelopathy, nutrient accumulation, and nutrient cycling; The role of organic matter in variable charge soils on soil acidity, phytotoxicity, and similar factors; and Soil process-related management techniques to control soil pathogens and nematodes (e.g., crops rotations, cover crops, soil organic matter manipulations). Other priority issues should include: The role of macrofauna in soil fertility; The effects of minimum tillage on soil biota, including pests and animals; The role of livestock in small farm systems; and The enhancement and maintenance of biotic inputs for sustainability in low industrial input systems, including synchronization of nutrient release from organic inputs to meet nutrient uptake demand by crops and appropriate biotechnology efforts. MANAGING SOIL PROPERTIES Rarely do the inherent properties of the soil provide an ideal environment for agricultural use. Fortunately, many of the limitations are amenable to improvement through inputs, manipulation, and other management practices. Research has led to substantial progress in identifying the fundamental constraints and basic principles of soil management, although such work has been conducted largely in developed countries in temperate regions. However, for both the developed and developing world, a central weakness is our limited capability to provide optimal site-specific soil and water management practices that can be employed by individual land users within the context of their needs and the prevailing social, economic, and political climate. Thus, this ability to translate scientific knowledge about soil characteristics and plant growth into useful information for farmers is a major research need for the future. Better management of the chemical and physical characteristics of the soil is critical to sustainability. Critical research priorities should include: Efficiency in use of organic materials; Sources of nutrient amendments;

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries Mechanisms and amelioration of soil compaction and crusting; and Strategies for restoring degraded lands. Other priority issues should include: Soil loss and its effects under different management strategies; and Improvement and use of diagnostic technology for nutrient availability. Research on better management of soil properties will involve both the chemical and physical characteristics of the soil system, and this area offers special potential in the context of the limited use of capital-intensive input characteristics of many developing countries. For instance, work on sources of nutrient amendments is key because low residual levels of essential elements is a common cause of soil infertility in the tropics. This condition usually can be corrected through amendments. Much of the technology for these types of management practices has been developed in areas where purchased inputs are readily available. In developing countries, however, the capital for such investments and the managerial capability to deal with the type and level of technology is limited. Therefore, alternative practices should be provided that are compatible with local natural resources and social, cultural, and economic conditions. Special emphasis should focus on biotic amendments. Similarly, research on the efficient use of organic materials is critical. Organic materials can have multiple benefits in reducing or alleviating many soil chemical problems. Notable among these are providing nitrogen and other essential nutrients and correcting soil acidity. The technology for effective and efficient use of organic materials—for example, nutrient-accumulating species of plants and management of residue—is not available in a form suitable for most of the developing world. This is an area where the blending of scientific knowledge with indigenous knowledge offers great potential benefits. Mechanisms to ameliorate soil compaction and crusting are important because these frequently lead to decreased water infiltration, increased runoff, increased erosion, and reduced stand and growth of seedlings. General principles for dealing with these problems are reasonably well understood, but management practices that would be useful in the developing world require better knowledge of fundamental causes and alternative solutions. Given the ever-increasing pressures for production in the developing world, strategies for restoring degraded lands will also prove key over the long term. Past mismanagement has resulted in the abandonment of extensive areas. In the Amazon basin, for example, roughly half the area that has been cleared—some 6 to 7 million hectares—has been abandoned (Toledo and Serrão, 1982). The basic problems stem from a variety of causes, both chemical—such as loss of fertility and high soil acidity—or physical—such

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries A donkey-drawn sandfighter, shown here at the ICRISAT Sahelian research center near Niamey, Niger, is one technique for managing and improving soil properties. The sandfighter is used soon after a rain, when its tines can dig the damp sand into shallow depressions and small, tight clods. The broken surface traps windblown sand, reducing erosion and protecting young crops from sand blast and burial. Credit: Neil Caudle, North Carolina State University. as crusting, dispersion, or compaction. In many cases, application of limestone and phosphorus will ameliorate the chemical problems to the extent that the land can be used in an economically productive manner. But where the primary degradation problem is physical, remedial measures are more difficult and time consuming. The practices may require chemical treat

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries RAINWATER HARVESTING Rainwater harvesting is the practice of collecting precipitation for domestic or agricultural use. It has been employed in various forms for more than 4,000 years and in areas that range in annual rainfall from 20 mm to 1,800 mm. Collection schemes vary from clearing hillsides of rocks and gravel to increase runoff and direct it toward cultivated fields further down the slope to collecting water from rooftops in small impoundments. Rainwater harvesting is primarily for small-scale use for farms, villages, and livestock. Approaches to rainwater harvesting vary greatly. Some practices rely on alteration of the land surface and require construction, such as the building of water catchments and tied ridges. Another approach, one particularly good for porous or unstable soil, is to cover the soil with a waterproof cover. Plastic sheeting, butyl rubber, and metal foil are low-cost alternatives for rainfall catchments. Gravel can be placed on top of plastic to protect against wind and sun damage. These catchments, if properly built and maintained, can have an expected useful life of more than 20 years. Water harvesting has the potential to enhance food production in water-short semiarid and arid Third World countries. It is especially promising for developing countries because it provides water without requiring fuel or power. However, specific techniques will need to be developed to meet site-specific soil, climate, and socioeconomic conditions. Water harvesting schemes have the potential to be especially useful in areas with the following characteristics (NRC, 1974): Clay soils. On these sites much of the water runs off during rainstorms. Small ponds built in the local watershed can be used to harvest water during the rainy season and store it for use during the dry season for domestic uses and irrigation of food crops. Laterite toposequences. Many of these toposequences have impervious layers at the top that allow little or no vegetative growth. Thus rain falling on the impervious caps runs quickly down the slopes, causing erosion and exposing infertile subsoils. A series of check dams or levees can slow or stop the movement of water and store it temporarily for domestic or agricultural use. These check dams may also reduce erosion and make the soils down the toposequence more useful for crop production. Gravel mulches. One of the primary sources of water losses in semiarid environments is soil water evaporation. An established means to reduce such loss is by gravel mulches. In many areas, for example the Sahel, laterite gravel is abundant. Spreading this gravel over the surface can reduce water evaporation and thus increases the water available for human use.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries ments, but more frequently involve long-term fallow periods with trees or cover crops as the primary vegetation. As with other soil management practices, restoration strategies must be tailored to individual sites and circumstances. The ability to make these site-specific recommendations remains a major challenge for research. Soil degradation under different management strategies is important because the choice of cropping system can have a major influence on the loss or retention of soil. The challenge is to employ alternative systems that will enable the farmer to use the land in a manner that minimizes soil loss and damage. The option generally is not whether to use the land or not—circumstances often require it; it is the method of use that becomes the point at issue. On-site degradation is only one of the issues. Determining the effects of soil loss on off-site locations is increasingly important. The impact of erosion on downstream ecological and agricultural systems needs to be assessed. Acquiring a better understanding of the social and economic dimensions of soil degradation and providing incentives to the farmer for erosion control and prevention measures would go a long way toward enhancing land use. It is also essential to keep in mind the whole soil-water system and to conduct research that looks at the dynamic relationships between these critical elements. Finally, improvements are needed in diagnostic technologies to measure nutrient availability so deficiencies of essential soil nutrients can be corrected more easily. Such corrective practices are expensive, whether achieved by purchased inputs or by organic residues. The cost and efficiency of remedial measures can be improved if specific and quantitative data are available on the prevailing level of the nutrient in the soil. Substantial progress has been made in diagnostic analyses of soils to serve as a guide for nutrient inputs. However, the applicability and adaptation of these techniques to developing countries has been given relatively less attention. IMPROVING WATER RESOURCE MANAGEMENT For much of the tropical world, water is the key natural resource, and managing variable, dynamic water supplies thus is a critical challenge if agriculture is to be sustainable. As populations grow and urban and industrial water demands increase, competition for water has intensified. Research must address a spectrum of issues ranging from rain-fed agriculture to irrigation, from the effectiveness of small-scale indigenous techniques to the impacts of large-scale impoundments. It must look at water's role in dynamic agricultural systems and, in particular, its close interrelationship to soil resources. It must move beyond the technical questions toward questions of how to apply technology in the diverse cultures and ecosystems of the developing world.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries DEALING WITH THE UNCERTAINTIES OF EARLY RAINS One fundamental difference between most temperate climatic zones and the tropics is that in temperate areas crops generally are planted in the spring in a water-saturated soil environment, while in most parts of the tropics with a dry season, crops have to be planted in dry ground or in newly moist ground at the beginning of the rainy season. There is pressure to plant early because the food is needed and the growing season is limited, but there is also a real danger of planting too soon—the first rains may not be substantial and the crops may wither. Planting too late, in turn, cam present other problems. Wet soil is hard to work, and pests start to cause problems. Problems associated with vagaries of rainfall in the tropics may be reduced by selectively breeding crops to withstand early drought, by developing better predictions of the pattern of rainfall in a season and ways to communicate this information to farmers, and by developing transplant techniques for crops that have not traditionally been transplanted. Also, soil-imprinting techniques that act to concentrate sparse rainfall at the base of each seedling are helpful. All these areas need research. The use of rice nurseries before the onset of monsoon rains is certainly one of the oldest strategies to avoid water stress in the seedling stage. Rice is planted, irrigated, and fertilized in small nurseries at the end of the dry season. When the rains start, and fields are sufficiently, flooded, rice is transplanted. Other similar examples may be found in the savanna area of Africa where sorghum and corn are planted in small irrigated nurseries, and then transplanted to larger fields once the rains have commenced in earnest. The use of soil imprinting and tied ridges also can help to concentrate moisture at the base of seedlings. Four general areas merit attention: (1) techniques for water capture and impoundment, with attention to indigenous, small-scale techniques; (2) strategies to enhance water conservation so maximum return is gained from each drop of water; (3) methods to reduce irrigation-related soil degradation, such as salinization; and (4) larger-scale approaches for watershed and landscape management. Some of the greatest potential benefits of improved water management may well be found "at the margins" of the water management field, such as the improvement of little known or innovative approaches and technologies. The challenge is to help farmers optimize their use of available water while maintaining the quality.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries Critical research priorities should include: Developing techniques to help farmers plant and maintain crops during the uncertain, early stages of the rainy season. These might include studies of seedling resistance to the vagaries of water supply, transplanting methods, and strategies to provide more secure environments early in the cropping cycle. Describing and evaluating the array of existing water-harvesting techniques, particularly indigenous ones, and consider their possible effectiveness in new environments. Investigating the role of aquaculture in farming systems and especially in irrigation systems. Are there ways to combine irrigation and aquaculture in regions where this has not been a tradition? Investigating techniques for making the best combined use of surface and sub-surface water in irrigation and dealing effectively with drainage, including an analysis of indigenous technologies. Investigating the policy and political issues of pricing and subsidies of Innovative thinking can help surmount the constraints posed by insufficient rain early in the growing season. In Nigeria, local farmers have developed a system where sorghum is started in irrigated nurseries and then transplanted into the fields once the rainy season is under way. Credit: Hugh Popenoe, University of Florida, Gainesville.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries Many types of microcatchments are being developed to capture and channel limited or sporadic rainfall to crops. In the Negev Desert of Israel, this microcatchment concentrates water around an almond tree. Its design was modeled on evidence of similar structures discovered during archeological research. Credit: Mike Austin, University of Hawaii. water and products in water-scarce areas and the long-term impacts these have on agricultural strategies and soil management. Other priority issues should include: Conducting comparative institutional analyses of risks and benefits of water management strategies, including local as well as large-scale institutions. This would include attention to indigenous systems of water access and tenure. Analyzing the economic, social, and environmental effects of irrigation at various scales. There has been a plethora of studies of large irrigation projects and their problems, but much less attention on the smaller systems and on supplementation strategies. Can modern systems be adapted to augment various indigenous systems and vice-versa? Investigating the waterborne diseases and weed infestations associated with canals and drains for irrigation development and techniques to combat these problems. Analyzing adaptations to short-term drought within the cropping season.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries Fortunately, much of the knowledge about physically manipulating and managing water resources for both rain-fed and irrigated agriculture is more or less generically transferable, although the scales at issue and the socioeconomic impacts are quite diverse. However, large gaps in our knowledge base still remain, especially in the areas of agroforestry, mixed cropping systems, and sustainable low-input rain-fed agriculture. Current knowledge focuses on full reliance on irrigation, while many questions about supplemental irrigation remain unaddressed. In addition, our knowledge base is still severely lacking in areas related to the social and institutional aspects of managing public or village-level irrigation enterprises and dealing with the questions of conjunctive use. How policy and institutions affect the allocation and use of water resources, and thus sustainability, are complex but especially important questions. For instance, what incentives will encourage maintenance and repair of water management systems? What risks do farmers face—whether hydrologic, climatic, economic, or political—and how do farmers make decisions in light of these risks? What are the equity implications of particular interventions? Since both rain-fed and irrigated agricultural systems often produce significant environmental impacts, research is needed to evaluate and improve the criteria and methods for carrying out environmental impact studies for project design and existing projects. MATCHING CROPS TO ENVIRONMENTS Research to enhance the matches between crops and environments is an ongoing and still critical endeavor. This work should include studies focused on the concept of ecological niche and the ways in which agriculture might benefit from use of appropriate organisms, including opportunities offered by genetic manipulation. It also means more effort is needed to match crops and production strategies to social, cultural, and economic environments. Although much research remains to be done regarding alterations of the environment to suit crops, for sustainable agriculture the focus should be on selecting and adapting crops and management choices to various settings. Several processes are necessary to match crops to environment. First, the environment itself must be characterized in terms of soil parameters like salinity, alkalinity, aluminum toxicity, nutrient deficiencies, slope, and soil erodibility. Next, climatic features, including temperature, photoperiod, insolation, and availability and seasonality of water, must also be incorporated. Local vegetation types, including classification categories of local people, should be described. The broad varieties of crop plants themselves, including unusual genotypes of existing crops, merit description. As these are the outcome of manipulation of crosses and planting materials selected

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries MATCHING CROPS TO ENVIRONMENTS: THE WINGED BEAN The story of the winged bean provides an example of successfully matching crops to environments. This tropical legume was a little-known crop when the National Research Council (NRC) published a small report on the plant in 1975. At the time, there were only 12 known varieties, with most of those grown in Papua New Guinea and Southeast Asia. But the plant showed exceptional promise—its seeds had a nutritional value almost the same as soybean and, unlike the better known soybean, it thrived on poor, acidic soils in the humid tropics, tolerated high rainfall conditions, and was comparatively resistant to pests and diseases. By the time the NRC published a second edition of the report (NRC, 1981b), perhaps as many as 600 varieties had been collected; a worldwide information exchange network was in place; researchers in more than 50 countries received a newsletter, The Winged Bean Flyer; and research trials were under way at sites around the world. Ten million dollars had been invested in winged bean production in Thailand alone and 6,000 acres had been planted in the Ivory Coast. Few crops have risen so quickly out of obscurity. The winged bean's rapid success comes in part because it meets a real need: people of the hot, humid tropics need better plant sources of protein. Sometimes described as ''a supermarket on a stalk,'' winged bean meets this need and more. In addition to its soybean-like seeds, its leaves are rich in vitamin A and can be cooked and eaten like spinach; its shoots resemble asparagus; its flowers, when steamed or fried, make a mushroom-like garnish; and its tuberous roots are like nutty-flavored potatoes with twice the protein. But what really turned potential into success was a concerted research effort. The knowledge about the crop was assessed, gaps identified, and its potential investigated. A strategy for international research and testing was developed and pursued. All in all, the winged bean offers a concrete example of the benefits possible through the blending of indigenous knowledge and scientific method when it comes to looking for crops to suit particular ecological niches. over time to tolerate local constraints, they have particular merit in guiding sustainable agriculture research efforts. To comprehend underlying cultural, economic, and social context from the household level, two approaches are required. The first involves the scientific quantification of ecosystem parameters by standard analytic methods. The second involves the mobilization of local knowledge of landscapes, soils, weather, water cycles, and planting material, which can add

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries subtlety and depth that those outside the scientific community cannot readily see. One potential research area involves analyses of the processes of adaptation, and the emergence of new cultivars through the assiduous collection of land races, conventional plant breeding, and other forms of biological manipulation. In general, the matching of crops to tropical environments has not received adequate research attention because of a traditional emphasis on "conventional crops," annual crops, and monoculture production systems. Critical research priorities should include: Improved understanding of indigenous knowledge, especially local soil and crop taxonomies as well as the analysis of the array of environmental knowledge that could help orient current research; The potentials and problems of erosion-prevention crops and strategies; Crops developed and selected for their adaptations to chemical stresses such as aluminum toxicity, alkalinity, and soil and irrigation water salinity; More analysis of mixed management practices, including techniques such as alley cropping, agroforestry, and successional management, and their potential to meet multiple needs including, but going beyond, yield. Other priority issues should include: A typology of environmental parameters for different crops, including attention to climatic constraints, microclimates, and temporal changes. Local peoples tend to manage a diversity of agroecosystems and natural resources. Agriculture in many societies is not conceptually limited to what the developed world calls "crops"; instead, agriculture often includes the management of a variety of semi-domesticates, weeds, forests, wildlife, and other elements of the local environment. Indigenous management of landscapes is often difficult to see. The management of natural resources in this broad sense may have a diversity of goals beyond increased yields. Thus, low-yielding but highly reliable or low-risk varieties, ceremonial cultivars, or stress-tolerant varieties, personal favorites, starvation foods, and particular genetic lines may all be included in an agricultural strategy. These "other logics" may be overlooked or dismissed by those with only a yield-oriented outlook, but they are essential to any research agenda that focuses on land areas with serious water, soil, and income constraints or erratic and less predictable climate and economic milieus. Attention to such strategies, of course, should provide insights into long-term sustainability of regional production systems. Experimental evaluations of indigenous knowledge of land-vegetation management are scarce because these systems are too dynamic for most experimental agronomic research design. Still, the elements and principles embodied in such systems can provide hypotheses for later testing and can

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries serve as a springboard for forming agronomic strategies that enhance soil and water management in marginal or complex environments. For instance, such information could be particularly useful in identifying and disseminating plants that are effective for erosion control (for example, vetiver grass). These efforts can also provide new candidates for soil-nutrient management in various kinds of agroforestry and successional systems. If sustainability is to be incorporated into the development agenda, the relevant protective contributions of the elements of agricultural systems and their effectiveness must be evaluated and given weight in any economic and social evaluation. This information can provide insight into general principles with ecosystem or regional relevance. In matching crops to environments, large potential may exist for transferring valuable or useful plants from one ecosystem niche to other analogous sites. The winged bean is one of the better known cases, but many lesser known species could undergo similar development processes. The National Research Council, through its Board on Science and Technology for International Development, has published a series of books that seek to bring attention to underexploited crops with potential value for specific ecologi Amaranth is one of many lesser known crops with significant potential in sustain-able agricultural strategies. These researchers are on a field trip looking at different varieties of amaranth in Cusco, Peru, at the Center for Andean Crops Research. Credit: Michael P. Greene, National Research Council.

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries cal niches. For instance, reports on jojoba (NRC, 1985), saline agriculture (NRC, 1989c), and amaranth (NRC, 1983a) highlight crops for dry regions. The important role of livestock has been described in books on water buffalo (NRC, 1981a), little-known asian animals (NRC, 1983d), and one on microlivestock (NRC, 1991a). Valuable forestry options are examined in reports on calliandra (NRC, 1983b), casuarinas (NRC, 1983c), and leucaena (NRC, 1984). Many more crops and livestock, not widely known, show similar promise and could help to enhance the productivity of agriculture, particularly in marginal environments. INCORPORATING SOCIAL AND CULTURAL DIMENSIONS Most people involved in research and development for developing countries now agree that research—if it is to be of practical value—must incorporate social, cultural, and economic factors as well as technical and scientific ones. Just as a particular soil management strategy must match a particular soil, so must it match the people who will be responsible for implementing it. But actually accomplishing this goal is difficult. Agricultural scientists often lack the training, experience, and time to integrate such factors into their research (Colfer, 1997). Actively incorporating these dimensions into research and its applications requires a shift in the model common in developed country agriculture, where the researcher does the science and passes the product to the extension agent, who, in turn, conveys the information to the farmer. This unidirectional approach was successful in the United States in part because the scientists and extension agents involved typically had farm backgrounds—they instinctively knew the social, cultural, and economic constraints at issue because the environment (both biotic and social) was a familiar one. As the distance between farmer and researcher grows, however, the greater is the need for a different model of communication. The knowledge, experience, and capabilities of the local people must be incorporated into the research process so it is, in essence, a joint endeavor (Colfer, 1987). A collaborative approach is necessary, with mechanisms for feedback and refinement of the research plan. Although this need for a more interactive approach to research has been discussed widely and for some time, it is still a significant constraint on the effectiveness of research in support of agriculture, particularly efforts to develop sustainable agricultural strategies. Consequently, the committee wishes to emphasize the need for serious, continued attention to the social and cultural dimensions of research pursuits. In the end, this may be one of our most important findings. It is no longer appropriate to relegate these human dimensions of research to secondary, separate status. A soils project, for instance, should emphasize what people do to the soil at the site, and what other factors

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Toward Sustainability: Soil and Water Research Priorities for Developing Countries affect that action. The goal is to identify opportunities for constructive improvement in the existing system. The social and cultural dimensions of the research must be kept focused on issues of relevance to the other scientists involved, and on overall project goals. At most sites, important areas for research will include: Indigenous soil, water, and agricultural classification systems; Allocation of time and division of labor both by gender and seasonality; Land tenure and access to resources; Subsistence, nutrition, and the cash economy; and Values, indigenous views on the people-land balance, and attitudes toward agriculture, soil, water, children, and the future.