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1 FOOD & FERTILIZER TECHNOLOGY CENTER LAND CAPABILITY CLASSIFICATION FOR HILLY WATERSHEDS USING EXPERT SYSTEMS Ted C. Sheng Colorado State University Department of Earth Resources Fort Collins, Colorado 80523, USA EXTENSION BULLETIN 485 July 2000

2 FOREWORD Land capability classification (LCC) is the means by which slopeland areas can be used for agriculture in a sustainable way. LCC has been in use in the Asian and Pacific region for more than forty years, and has already had a positive impact on slopeland use in a number of countries. This important Bulletin describes a' 'treatmentoriented' 'scheme oflcc, which links capability classes to land treatments and conservation needs. It is easy to understand and apply, and has already been applied successfully in a number of countries. Expert systems have been developed to facilitate its application in the field. It can be applied at the farm level, or on a larger scale at the watershed or regional level. The author has extensive experience in developing and applying LCC systems, especially for small-scale farmers in tropical slopeland areas. He presented the paper on which this bulletin was based at an international seminar on "Slopeland Use Capability", held in the Philippines on September 21-24, The co-sponsors were the Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD), and the Philippines Bureau of Soils and Water Management, Department of Agriculture.

3 LAND CAPABILITY CLASSIFICATION FOR HILLY WATERSHEDS USING EXPERT SYSTEMS Ted C. Sheng Colorado State University Department of Earth Resources Fort Collins, Colorado 80523, USA ABSTRACT Land capability classification is the basis for sustainable use of slopeland. Due to a lack of suitable criteria, such classification is seldom done on the watershed slopes of developing countries. This paper introduces a "Treatment-Oriented" land capability classification scheme which is particularly useful for hilly watersheds in the humid tropics. Its advantages, applications, and experiences are reviewed. Emphasis is put on field-level applications. Expert systems have been developed to facilitate field classification work. Explanations of procedures are given. INTRODUCTION Land capability classification is the foundation of proper and sustainable land use. The lack of such classification on watershed slopes not only makes the regulation of land use impossible, but also leaves farmers no guidelines to observe. In the hilly watersheds of the developing world, misuse of slopeland has caused serious land degradation, soil erosion and environmental problems. Unfortunately, there is a general lack of land capability classification serving as a sound basis for proper land use. Some countries using criteria from regions with a different environment resulted in land use problems, as in Taiwan in the 1950s and St. Lucia in the late 1980s. This paper first discusses ideal criteria for land capability classification in the context of developing countries. A practical classification scheme named "Treatment- Oriented Classification Scheme" is introduced and explained. Finally, the application of the scheme using expert systems is illustrated for field application. IDEAL CLASSIFICATION SCHEMES FOR DEVELOPING COUNTRIES Land Use and Management Conditions in Developing Countries It is generally recognized that many watersheds in developing countries, especially in Asia, are experiencing severe degradation and soil erosion. Because of population pressure and poor land distribution, small-scale farmers are cultivating steep slopes to make a living. Many national forest lands are also being abused. While the problems are mostly socio-economic in nature, a land use regulation or adjustment program based on a practical land capability classification scheme could greatly alleviate or improve the situation. People tend to overlook two facts. In a watershed, under-used lands often exist which can be used for resettling those who currently over-use the slopes. Even on a small farm, there are some parcels which can be cultivated intensively with conservation measures, Keywords: Jamaica, land treatment, land use, slopelands, Treatment-Oriented, watershed 1

4 thus freeing steeper slopes for other uses. To find the particular sites for land use adjustment or for intensive use, a land capability classification is needed. The lack of such a classification activity in many developing countries leaves both governments and farmers in a persistent deadlock, and their land mis-use problems cannot be solved. It is also recognized that local watershed administrations in developing countries are under-staffed in general, and lack soil scientists in particular. Land capability classification work is usually done by soil scientists from state institutions. The field workers and farmers looking at the beautiful maps can hardly understand the meaning of the maps, or even locate themselves, let alone use the results. Consequently, most of the maps and reports are left on the shelf to collect dust. Ideal Classification Schemes Ideal land capability classification schemes for hilly watersheds in developing countries should meet, but not be limited to, the following conditions: They can be used in the field by technicians with some trammg. They can be understood by land users and farmers. They are practical and flexible, and can meet the country's needs and alleviate land mis-use problems. They are helpful when people are making decisions and plans about land use and conservation. They are useful in promoting sustainable land use. THE "TREATMENT-ORIENTED" SCHEME Summary of Scheme and Brief Explanation The "Treatment-Oriented" scheme is based on criteria used in Taiwan in the early 1960s. It has been further improved in two ways: It uses a quantified approach for classification; and It links capability classes to land treatments and conservation needs, hence the name "Treatment-Oriented". Since the classification scheme was first used in the early 1970s (Sheng and Powell 1971; Sheng 1972), half a dozen developing countries have applied or modified it for their own environments. In addition, renowned soil scientists and soil conservationists such as N. Hudson, S.A. El-Swaify and R.P.C. Morgan have introduced the scheme in their books and papers (Hudson 1981; El-Swaify et al. 1982; Morgan 1980). Hudson commented that the scheme is "suitable for steep lands in the humid tropics... but applied only on a limited scale" (Hudson 1983). The detailed criteria and applications of the scheme can be seen in several documents and papers (Sheng 1972, 1986, 2000; FAO 1989, 1990). A summary form of the classification scheme is shown in Appendix 1. A brief explanation of the Scheme is as follows: Two main factors are employed for the classification: Slope and Soil Depth. Slope is classified according to soil conservation needs, and the tools for land treatment and tillage. These are based on actual field observation. Soil depth is classified according to the m1mmum soil depth required for appropriate land treatments. A third factor (Permanent Limiting Factors e.g. too wet, too stony, severely eroded or occasionally flooded, so that normal tillage or land treatment is prevented) is also considered in the scheme. Land treatments and soil conservation practices are considered as essential when using the land so classified. Land is classified into its most intensive tillage permissible. Less intensive use is allowable, but over-use should be discouraged or prohibited. The Advantages of the Scheme Major classification factors, slope and soil depth, are quantified and can be measured in the field or used for computer mapping. The classes such as C (Cultivable), P (Pasture), FT (Fruit or food trees), and F (Forest), etc. are easily understood. Linking classes to land treatment/soil conservation work facilitates land use planning and cost 2

5 estimates. Little formal trammg is needed to apply the scheme in the field. Mapping procedures are quite simple, either using manual methods or Geographic Information Systems (GIS). The scheme usually classifies a greater area of land as "cultivable". This helps solve some of the land use problems in slopelands. Finally, the scheme provides a simple and practical approach to distinguish proper use from mis-use when the results are compared with current, actual land use. Applications and Experiences Applications The scheme can be applied at three levels as follows: At the regional (or national) level, the scheme can be used with watershed reconnaissance surveys, resource inventory surveys or watershed classification, to determine management priorities and agricultural development potential. Using GIS technology to develop Digital Elevation Model (DEM) and slope classes, and overlaying soil information, a land capability map of the region can be produced for regional planning use. At the watershed level, the scheme should be applied with checks in the field of soil depth and limiting factors. The same type of soil at different topographic sites should be checked for soil depth. Slopes should also be checked on the ground against the value obtained from DEM or from the manual type of slope analysis (FAO 1990). As mentioned previously, the classification results can be superimposed on a current land use map to determine the land use adjustment requirements. Also, the results will provide a basis for estimating conservation needs and cost. At the farm level, each parcel of land needs to be measured by a hand level or a clinometer to obtain slope values, and by a soil auger to determine soil depths. After checking limiting factors, the land capability of a particular parcel of land can readily be determined. Land use and conservation needs can then be planned jointly with the farmer. Experience of the Scheme Jamaica The scheme was first applied in the early 1970s in a demonstration watershed, and then extended to a 1, 100 ha government property (Sheng and Powell 1971 ). The classification resulted in a 50% increase in "cultivable land", compared to a modified USDA classification scheme used in Later in the mid-1970s, the scheme was used to classify two watersheds in central Jamaica totaling 12,000 ha. USAID invested US$ 26 million for the watershed development work. In the 1980s, this scheme was used to plan six watersheds (36,000 ha in total) around the Jamaican capital, Kingston. An economic analysis of the scheme found that the classification "constitutes an important tool for land use planning" and its recommended land use "can be supported economically" (de Graaff and Sheng 1994). Recently, the "Trees for Tomorrow" Project supported by the Canadian Government has adopted a modified version of this scheme to make land use plans for their target watershed. Other Countries In Thailand, this scheme has been used to classify a 33,000 ha watershed near the city of Chiang Mai with a slight modification of slope limit for "cultivable land" (reduced 25 to 20 or 35%). In St. Lucia, modified schemes have been used on three groups of soils (stable, less stable, and fragile) for the whole island. El Salvador and Honduras have also used this scheme for their soil conservation demonstration areas and projects. Trinidad and Tobago, Nepal and Indonesia have either studied, modified, or used the essence of the scheme in their slopeland classification projects. Comments and Response Over the years there have been two major comments about the classification scheme. One is that the scheme does not consider soil types, particularly soil productivity. The answer is that soil 3

6 productivity or fertility is not considered a permanent limiting factor for land capability classification in this scheme, as in the USDA scheme. Using soil depth to determine whether the land is "cultivable" or not may be sufficient. In a recent paper, Rhoton and Lindbo found that soil depths "could be used to explain differences in soil properties, and accurately estimate the productivity and erodibility of a soil, two primary indicators of soil quality" (Rhoton and Lindbo 1997). As for soil types, the scheme does take into consideration "problem soils" which are too stony, wet, severely eroded, etc. During classification, "problem soils" should be first noted. Sandy soils are uncommon in hilly watersheds. The scheme is best used as a basis for changing improper land use in a watershed, in order to minimize erosion and land degradation. It is not intended for crop suitability rating. Another comment is that this scheme is not applicable to semi-arid or arid areas. This is true, the scheme is mainly designed for the hilly watersheds in the humid tropics where most developing countries are situated. It has limited use in semi-arid or arid regions without drastic revision. USING EXPERT SYSTEMS TO FACILITATE FIELD WORK While regional and watershed level capability maps can be produced by GIS technology (Sheng and Barrett 2000), the application of such maps to the field is often problematic. Due to map scales and the small size of farms, farm sites and classification results cannot be easily located or comprehended, particularly a small parcel of land on a farm. Usually, for planning of conservation farming, each parcel of the farm needs to be closely examined for its capability, intended use and conservation needs. Therefore, there is a need for a classification aid to be used in the field for such planning. The Systems A simple expert system called "LANDCONS" (Land Conservation) was jointly developed by a computer expert and the author. The system contains a series of queries about slope, soil depth, and limiting factors, in order to determine the land capability of the piece of land in question. Questions about intended cropping, available farm labor and farming tools are also asked to determine the land treatment needs. A detailed land treatment system named "CONTREAT" (Conservation Treatments) was also developed in conjunction with "LANDCONS" for planning purposes. "CONTREAT" contains nine types of major land treatments for slopeland, including bench terraces, hillside ditches and orchard terraces. Each type has specification details, i.e. volume of soil to be cut and filled per hectare, depth needed, net area available for cropping, etc. When the user enters a slope value of the land and/or the desirable width of a bench, all the relevant specifications will automatically be shown. The two systems, totaling 0.75 MB, are DOS based. With the use of a laptop computer, a mini notebook or a palm device, the system can be employed to assist field classification work. Improvements or modifications, however, can still be made to fit local requirements. For instance, crops can be changed and land treatments and conservation needs can be modified to meet local needs. Using the Systems: A Brief Explanation First, "LANDCONS" needs to be loaded into a computer. Then, when the screen is shown, select "Find Class". It prompts a question: "What is the slope of the land?" and shows the six classes described in the classification scheme. When the user enters the proper slope class, the next question is displayed: "Is there a soil limitation (stony, wet, flooding, erosion, etc.)?" Selecting "Yes" or "No" will result in different capability classes. If "No" is selected, a third question prompts: "What is the soil depth?" At the same time, a minimum required soil depth corresponding to this slope class is displayed in centimeters and inches. The actual soil depth obtained from field measurements, whether under or over the minimum depth, will determine the final capability class. After the land capability result is shown, further questions are asked about crops to be 4

7 planted, labor availability, tools to be used and other factors which affect recommended land treatments and conservation needs. "CONTREA T" is to be used in conjunction with "LANDCONS" to determine not only the type of treatment needed on the slope, but also detailed specifications such as the height and width of the terraces, the percent of flat benches for cropping and the labor demand (Sheng 2000). CONCLUSION For the sustainable use of slopelands and watershed resources, land capability classification is the first and most essential task to be taken. In the past, this type of classification work did not on the whole give useful results. This was either because impractical criteria and methodology were applied, or because it was too difficult to apply the scheme in the field. A simple and practical scheme which can be readily used by scientists and technicians at a regional, watershed, or farm level would help a great deal to promote proper and sustainable land use on slopelands, and benefit the developing world. REFERENCES De Graaff, J. and T.C. Sheng Land capability and the economic analysis of soil conservation and land use: A case study in Jamaica. In:Adopting Conservation on the Farm, Napier et al. (eds.). Soil and Water Conservation Society. Ankeny, Iowa, USA, pp El-Swaify, S.A., E.W. Dangler and C.L. Armstrong In: Soil Erosion by Water in the Tropics. University of Hawaii, Institute of Tropical Agriculture and Human Resources Research and Extension Series 204, 173. FAO Soil Conservation for Small Farmers in the Humid Tropics. FAO Soil Bulletin 60. Rome, pp , 70. FAO Watershed Survey and Planning. FAO Conservation Guide 13/6, Rome, pp Hudson, N Soil Conservation. Batsford Academic and Educational Ltd. London, pp Hudson, N Soil conservation strategies in the third world. Journal of Soil and Water Conservation 38, 6: pp Morgan, R.P.C Soil Erosion. Topics in Applied Geography. Longman. London & New York, pp Rhoton, F.E., and D.L. Lindbo A soil depth approach to soil quality assessment. Journal of Soil and Water Conservation. 52, 1: Sheng, T.C A treatment-oriented land capability classification scheme (For hilly marginal lands in the humid tropics). FAO Report on the Latin American Watershed Management Seminar. FAO, Rome, pp Sheng, T.C Watershed Conservation. Colorado State University, USA, pp Sheng, T.C Terrace systems design and application using computers. In: Soil erosion and dryland farming, Laflen et al. (eds.). Soil and water Conservation Society, Ankeng, Iowa, USA, pp Sheng, T.C. and W.I. Powell Land Capability Survey and Land Use Planning of Kenilworth Property. UNDP/FAO JAM 5 Project Report. Sheng, T.C. and R. E. Barrett Using GIS for land capability classification and conservation farming management. In: Soil erosion and dryland farming, Laflen et al. (eds.). Soil and water Conservation Society, Ankeng, Iowa, USA, pp

8 APPENDIX 1 NEW SCHEME OF LAND CAPABILITY CLASSIFICATION A Treatment-oriented Scheme for Hilly Marginal Lands Slope 1. Gently 2. Moderately 3. Strongly 4. Very 5. Steep 6. Very sloping sloping sloping strongly steep sloping Soil < > 30 depth (< 12%) (12-27%) (27-36%) (36-47%) (47-58%) (>58 &) Deep (D) > 36 in. C1 C2 C3 C4 FT F (> 90 cm) Moderately deep (MD) in. C1 C2 C3 ~ FT F (50-90 cm.) p Ff Shallow (S) 8-20 in. c C2 ~ (20-50 cm.) p p p F1 F Very shallow (VS) p p p.fl < 8 in. p F F (< 20 cm.) 1. Symbols for most intensive tillage or use: C1: Cultivable land 1, up to 7 slope, requiring no, or few intensive conservation measures e.g. contour cultivation, strip cropping, vegetative barriers, rock barriers and on larger farms, broad-based terraces. C2: Cultivable land 2, on slopes between 7 and 15, with moderately deep soils, needing more intensive conservation e.g. bench terraces, hexagons, convertible terraces for the convenience of four-wheel tractor farming. The conservation treatments can be done by medium-sized machines such as a bulldozer D 5 D 6. C3: Cultivable land 3, 15 to 20, needing bench terraces, hexagons and convertible terraces on deep soil, and hillside ditches, and individual basins on soil which is not so deep. Mechanization is limited to small tractors or walking tractors, because of the steepness of the slope. Terracing can be done by small machines. C4: Cultivable land 4, 20 to 25, all the necessary treatments are likely to be done by manual labor. Cultivation is practiced by walking tractor and hand labor. 1Author's Note: Since 1980, agroforestry (AF) has been added to this category where the soils are shallow but crops can still be grown, together with trees. 6

9 P: Pasture, improved and managed. No grazing should be practiced where the slope is approaching 25 or if the land is too wet. Rotational grazing is recommended for all slopes. FT: Food trees or fruit trees. On slopes of 25 to 30, orchard terracing is the main treatment, supplemented with contour planting, diversion ditches and mulching. Because of the steepness of the slopes, interspaces should normally be kept in permanent grass cover. F: Forest land, slopes over 30, or over 25 where the soil is too shallow for any of the soil conservation treatments. 2. Any land which is too wet, occasionally flooded or too stony, to an extent which prevents tillage and treatment, should be classified as follows: a) Below 25 : Pasture b) Above 25 : Forest. 3. Gully dissected lands which prevent normal tillage activities: Forest or pasture. 4. Mapping Symbols: Could be labeled as follows: Most intensive use Soil type - slope - depth Example: Means C D Cultivable land 2 Clay loam - 7 to inches or more Or, it could be simply labeled as C2. 7

10 ISSN TOPIC CODE EB F,H,U REF: FFTC EB 485 FOOD AND FERTILIZER TECHNOLOGY CENTER P.O. BOX TAIPEI CITY, REPUBLIC OF CHINA ON TAIWAN TEL: (886 2) FAX: (886 2) NOTE The major function of the Food and Fertilizer Technology Center is to collect and disseminate agricultural information throughout the Asian and Pacific region. In order to improve access to our publications, we have placed FFTC Bulletins published since 1980 on the Center's web site at Access to the full text of these publications is free of charge. Users are welcome to translate any of our publications into any language or dialect and/or to condense them for reproduction in newsletters and other means for free dissemination, provided acknowledgement is made to the source. A copy of the condensed, reprinted or translated Center's publication sent to use would be highly appreciated.