Food and Fertilizer Technology Center - publications

Sep. 01, 1999

Slopeland Use Capability

Sustainable agricultural systems must be based on a thorough understanding of the environmental impact of different kinds of land use. Only then can land users and policy makers select the patterns of agriculture which give a good economic return without endangering long-term productivity.


Land capability classification (LCC) is the tool by which this is achieved. In LCC, land units are grouped according to their fitness for specific kinds of land use, based on one or more inherent characteristics of the land (soil, vegetation etc). Recommended land use reflects the sustained capacity of the land to support this use. It takes into account both the environmental and socio-economic considerations, as well as the conservation of resources for future use.


When LCC first began in Asia around forty years ago, it was used mainly to classify agricultural land use. While it is still important for this, the emphasis is now shifting to the protection of environmental resources.


LCC has already had a positive impact on slopeland use in a number of countries. However, there are many recent developments, including computer modeling and database management, which make it possible to apply LCC more precisely and in more detail. In 1999, FFTC held a meeting to discuss the region's various LCC systems, and problems encountered in working with them. Most important, it was hoped that the meeting might provide guidelines and recommendations on how extension staff, farmers and others working in slopeland areas could apply LCC as a way of achieving sustainable and efficient land use.


Indicators of Sustainability


Monitoring to assess the impact of land use on the environment is a vital part of LCC. Sustainability can only be measured over time. Much discussion at the meeting centered on which are the best indicators for impact assessment. (An indicator is a descriptor which represents a set of conditions, and conveys information about changes in these conditions).


Some models proposed at the meeting were based on a complex set of indicators which included socio-economic status of farmers; yield trends; gradients; and fertility status and various physical and chemical properties of the soil (particularly OM content, the parent material, the nutrient balance, soil depth and soil loss rates). Nearly all models included erosion as an important indicator.


However, erosion is difficult to measure, and must be studied over the long term. Erosion sometimes stops because there is no soil left to erode! In other cases, erosion may involve the mass downward movement of sediments in which negative soil losses are balanced by soil gains from above. In such cases, sediment transport rather than simple erosion might be a better measure of possible losses and gains in soil fertility.


In the natural environment, the movement of energy and materials is cyclical. In slopelands today, the movement tends to become linear. Most nutrients and other resources leave the system and are transferred to the lowlands. While they will be returned to the system eventually, this is only in the context of geological time. To a large extent, a system is sustainable when materials and energy are recycled, so that there is a minimum net loss to the local ecosystem. However, this concept is difficult to quantify in the field.


Whatever the indicators which may be selected, assessment is a lengthy and expensive business. The impact of land management on most indicators is not immediate and not easily measured. Furthermore, the effects of agricultural activity are not only local. They are also felt downstream in what might be a very large catchment area.


Rather than trying to define indicators which give a very detailed picture of the economic and environmental situation, it might be better to use the minimum indicators that can give a useful result. Erosion rates and crop yield were two indicators suggested for this purpose. Crop yield in particular may be a useful minimum indicator, since it is easy to measure and shows the combined impact of many factors.


Data Collection


Data collection and a sound database are an essential part of LCC. Director Wu of FFTC emphasized the importance of collecting accurate and complete data at the beginning of any LCC program. While computer models and expert systems are valuable tools, their reliability depends on the accumulated data on which they are based. Data on soils, topography, climate etc. should be collected in a systematic manner throughout each country. In this way, they can be coordinated and used in a single database as a national resource.


While data has always been a valuable resource in land use planning, information technology has increased its value still further. Computers can now be used to combine information from different sources into a single database, or to produce thematic maps. While there is no substitute for field surveys, valuable data can also be obtained by remote sensing and automated data logging from satellites. Improved data processing software is now available which can handle large quantities of data, and use it to show trends in land use and their environmental impact.


Crop Selection


Most farmers do not cultivate sloping land from choice, but because no more land is available in the lowlands. As the result of population pressure, Asia's good arable lowland has been under the plow for many years. There is little or no more unused flat land left for agriculture. In fact, there is less flat agricultural land each year, as cities and industry spread out over the alluvial plains where most people live.


Slopeland use is a compromise between what is environmentally ideal, and what meets the need of local people. The land use system least likely to cause environmental damage in slopeland areas is forestry or some other system of perennial tree crops with good ground cover. However, slopeland farmers cannot select their crops according to what is likely to protect the environment. Many are subsistence farmers, which means that any food eaten by the farm family has to be grown each year on the family's own farm. Their farming system must be based on the production of staple foods.


Even where farmers are producing cash crops, they must be able to harvest a crop for which there is economic demand, and which has a high enough economic value to give them a reasonable annual income. In practice, this means that the options open to farmers are limited. If they are being asked to grow a new crop, they need technical support, planting materials and marketing assistance.


Sometimes improved cultivation practices may enable farmers to grow high-value crops without harming the environment. In Korea and many other countries, slopeland farmers are being encouraged to use cover crops, mulches and no-tillage, to protect the soil from erosion.


Agricultural scientists tend to classify slopelands as arable zones wherever possible. However, the same fertile soils which produce good crops also produce high-quality forests. If forests are constantly being removed from all but very marginal areas, the result will be an impoverishment of forest resources. Forests are important in the national economy, and also make a contribution to watersheds and water resources.


Acceptance of LCC by Farmers


The benefits of sustainable practices tend to be long-term and off-site, while the costs tend to be local and immediate. As a result, there is often a poor match between land use and erosion potential.


Betelnut is not a good crop for steep slopeland areas because it has a shallow root system and provides little ground cover. It is widely grown in Taiwan, where new betelnut plantations are a major cause of erosion in slopeland areas. However, government efforts to persuade farmers to grow less damaging crops have been largely unsuccessful. From the farmers' point of view, betelnut is a very good choice of crop, since it provides a high return for a low labor input.


If in spite of LCC projects no constructive changes are taking place in slopeland areas, we must ask why not and identify the constraints. An important problem is how to provide incentives which will encourage farmers to adopt conservation measures and sustainable cropping systems. Farmers' present choices are based on what they consider their best chances of a profit, given their current resources. If there are no incentives, it is unreasonable to expect farmers to change their farming in a way that involves economic loss, for the sake of unknown communities downstream.


It is easier to implement land use planning in areas that are not yet developed. In Vietnam, LCC is being used to help farmers who are being moved from high-density lowland areas to mountainous regions with low populations in central Vietnam. The government is providing farmers in resettlement programs with funding, technology and other support for the production of selected crops. LCC is being used to determine what crops should be recommended, using the GIS system. Since farmers are new to the area, it is easier for them to accept outside guidance on what crops to plant and how to grow them.


Once an area has been settled and farms are already in place, it is more difficult to persuade farmers to change their farming systems. Many slopeland programs in different Asian countries have failed in the face of refusal by farmers to adopt recommended practices and crops. Community involvement at an early stage is a key to obtaining community support for land use planning. It is also important to have enough trained people in place in the field. If all the trained manpower stays in the cities, the result will be all talk and no action.


"Conservation is not a conversation."


Modeling


Many land use models have been developed in the United States. These need to be revised before they can usefully be applied to Asian countries. In a land-rich country like the United States, models of sustainable land use tend to prohibit the cultivation of slopelands with more than a gentle gradient.


In Asia, the scarcity of land in relation to population size means that there is much greater pressure on available land resources. Much steeper slopes are considered an agricultural resource. With appropriate crops and conservation measures, cultivation of steep slopes need not damage the slopeland environment.


Conclusion


Sound data on soils, climate and land use, combined with long-term monitoring based on good indicators, are necessary to assess what is happening in slopeland areas, and measure the impact of conservation programs and land use planning.


Even after all this work has been done, it must be remembered that LCC is not an end in itself. It is a means to an end. The final aim is sustainable land management that conserves soil and water while giving a profitable return to the user. In planning for sustainable land use, competing needs must be taken into account, including the needs of different types of user. Different people have different aims: some have conservation of forest and watersheds as their priority, others want to produce crops or promote tourism


Whatever the ideal land use may be, the reality in most Asian countries is that the main users of slopeland areas are still small-scale farmers. Many of them have no legal title to their land, and nearly all of them have lower incomes than people living in the lowlands. The question of how far planning should meet their requirements, as opposed to national economic or environmental targets, is not an easy problem. In practice, LCC is not likely to work unless it gives some overall benefits to local farmers.


International Seminar on Slopeland Use Capability


HELD IN THE PHILIPPINES, SEPTEMBER 21-24


No. of Participating countries: 8 (Indonesia, Korea, Malaysia, Philippines, Taiwan ROC, Thailand, USA, Vietnam)


No. Papers: 12


No. Participants: 25 plus observers


Co-sponsors: Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD), Philippine Dept. of Science and Technology


Bureau of Soils and Water Management (BSWM), Philippine Dept. of Agriculture


Index of Images


Figure 1 Steep Slopeland Cleared for Slash and Burn Agriculture Erodes Rapidly under Heavy Rain


Figure 1 Steep Slopeland Cleared for Slash and Burn Agriculture Erodes Rapidly under Heavy Rain


Figure 2 Cultivated Slopeland with Low-Cost Vegetative Terraces


Figure 2 Cultivated Slopeland with Low-Cost Vegetative Terraces


Figure 3 Traditional Stone Terraces for Slopeland Fields in Taiwan


Figure 3 Traditional Stone Terraces for Slopeland Fields in Taiwan

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