Food and Fertilizer Technology Center - publications

Jun. 01, 2002

Geographic Information Systems (Gis) for Soil Resources

The use of GIS for agricultural resources management is gaining interest among researchers in Asia. It is one of the tools that can be used by Asian countries in their bid to use their soil resources sustainably. It makes soil management less tedious and costly, by collecting a wider spectrum of data in a much shorter span of time.

This is a far departure from the labor- and time-intensive traditional on-site soil surveys and monitoring approaches. Some countries, including Japan, are already making advanced use of GIS. Other Asian countries are still in the process of evolving a GIS-driven baseline data, while building their human resources to strengthen their GIS capability in the future.

Both groups of countries need to continue exploring the merits of GIS, with the aim of counteracting the negative effects of development, such as soil erosion, soil salinity, soil pollution and flooding. Unless these can be reversed, they will cumulatively reduce the carrying capacity of land and soil resources over the years. GIS is a significant tool to help countries manage their land and soil resource sustainably, restoring their productivity for future generations.

The 15 papers presented covered such topics as precision farming approaches to small-farm agriculture, GIS-based soil erosion models, land classification and suitability evaluation, remote sensing and GIS for soil resource management, and an Internet service system of agro-soil environmental information.

Precision Farming

Precision farming was originally developed for large farming units, such as those found in the United States. More recently, it has been adapted to the needs of small-scale farms in Asia, which in some countries have an average size of only one hectare (2.6 acres).

Precision Farming consists of three technology levels: describing variability; using variable-rate technology (VRT) for adjusting agricultural inputs to site-specific requirements; and applying a decision-support system (DSS). The first level, describing variability (spatial, temporal, and predictive), is generally considered the key element. This variability includes both the range of variation in individual fields, and the variation found between fields in the area or region where the system is being applied.

Japan has recently developed automated ways of measuring the variability within fields, using a real time soil spectrophometer. Satellites are used to collect the data. This makes it possible to apply precision farming to small as well as large farms, and make it part of Asian rural development programs.

GIS is now being developed to help small-scale rice farmers in Taiwan improve their fertilizer applications. Although Taiwan has a strong island-wide soil testing service, some rice farmers in Taiwan do not know the nutrient status of their soils, particularly with regard to nitrogen, phosphorus and potassium (N, P and K).

Decision support systems are being developed which will be able to provide site-specific fertilizer recommendations. Initially, detailed information for farmers will be provided through the existing agricultural information services. Later, it is hoped to make the information directly available to farmers by Internet.

Gis-Based Mapping and Modeling of Soil Erosion

Conventional surveys of soil erosion in the field are costly in time and labor. All soil surveys are labor-intensive, but surveys of erosion usually have to cover several years, to get a reliable estimate of the rate of soil erosion and the main factors influencing it. GIS-assisted physical models are now available which can predict where erosion "hot-spots" are likely to occur.

In the Mapawa catchment area in the Philippines, where this approach was applied, the main erosion factor was found to be rainfall intensity. Road construction was also important. The model could thus be used to identify sites which were very vulnerable to erosion, and where conservation measures were urgently needed.

GIS could also be used to predict the effects of surface cover on the discharge of water and soil sediments from the catchment area. The rate of soil and water loss from bare soil was compared to vegetative cover with minimum conservation measures, the same cover with full conservation measures, and forest cover.

There was a close agreement between predicted and observed measurements, which implies that the model is a valid predictive tool. Interestingly, it was noted that canopy cover was not very effective in containing erosion. What was important was cover which lay in direct contact with the soil surface.

Using Satellites to Monitor Changes in Land Use

All Asian governments have legal restrictions concerning the use of public land, especially the cutting of forest, and the conversion of forest to arable land. In practice, it is difficult to monitor what are usually remote areas, and detect changes in land use at an early stage before environmental damage has become serious.

Satellite remote sensing is an effective way of monitoring resource management and changes occurring over large areas. The Gram-Schmidt Orthogonalization (GSO) technique is being used in Malaysia to detect and monitor changes in land use, using data transmitted by satellite.

This type of analysis is also very useful for showing the sustainability of different agricultural systems. Policy makers can only promote sustainable land use systems if they know which ones they are. GIS facilitates the classification of land into different land use classes, and can monitor the long-term impact of different kinds of land use.

In this way, policy makers can be helped to distinguish land where agriculture can be intensified or expanded, from land where rehabilitation and diversification are needed. The information from GIS is now becoming detailed enough to show which areas are suitable for specific crops.

Farmers and Gis

In discussions of sustainable land use, there is often a conflict between the wishes of policy makers and the needs of farmers. Policy makers wish to make their nation's use of resources sustainable, and take a broad view of the country's economic development. Farmers have an immediate need to support their families. Farmers response to GIS is more positive if they are consulted during the development of GIS-based programs. Participatory consultation is now becoming an important part of the Region's GIS programs.

Farmers can also be a key source of information. Often the local knowledge of farmers is more relevant and useful than the academic knowledge of scientists. GIS can also show gaps in infrastructure, such as a scarcity of roads or marketing centers, that may cause agricultural development programs to fail in an area which otherwise seems suitable.

Disseminating the Information

The great benefit of GIS and DSS is that they can provide site-specific information, including recommended practices. This is also a challenge, in that it is difficult to disseminate detailed information of this kind to specific farmers.

Korea and Taiwan are pioneering the use of information technology in environmental management for agriculture. Sources of data are land use surveys, aerial photographs, detailed soil survey maps etc. Maps are generated from these sources and encoded in central computers. The system is linked to related institutes and centers throughout Korea and Taiwan, and is then made available on the Internet.

Internet users, including farmers or extension staff, can easily find information at a provincial, county or district level. Information includes land use, drainage, soil type, soil depth and soil chemical properties. Recommendations for each type of land use are also being provided for farmers and other clients.


The general discussion focused on the direction for future development. Three topics were discussed: GIS-based technologies for use by farmers; farmers as potential GIS users; and training and education.

The Following Recommendations Were Proposed:

  • In adopting GIS, it is necessary to identify the specific clientele whom it will be serving. These may be small- or large-scale farmers, extension staff, or institutions who will be adopting GIS. Will these be the small- or large-scale farmer, the extension worker, or an institution?

  • If farmers are the main beneficiaries of GIS, their socio-economic background must be considered.

  • Soil management based on GIS should have the marketing aspect and risk management factored in.

  • The benefits of participatory GIS development should be explored further.

  • A network for GIS should be established among Asian countries.

  • In developing a GIS-based system, a decision needs to be taken about the best mode of information dissemination, based on the country's present situation. This might be a decision support system (DSS), stand alone or web pages.

  • Farmers should be asked for feedback on the validity of the GIS-derived data.

International FFTC Workshop on Geographic Information Systems (Gis) in Soil Resources Management

Held at PCARRD, Los Baños, Philippines, on November 27-30

No. of Countries Participating: 8 (Indonesia, Japan, Korea, Malaysia, Philippines, Taiwan ROC, Thailand, and Vietnam)

No. of Papers Presented: 15

No. of Participants: 25 plus observers

Co-Sponsors: Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD), Los Baños, Laguna, Philippines.

Bureau of Soils and Water Management Department of Agriculture, Philippines.

Index of Images

Figure 1 Gis Map Showing Zinc Status of Rice Fields in Central Taiwan (Pink=Deficiency, Brown=Excess).

Figure 1 Gis Map Showing Zinc Status of Rice Fields in Central Taiwan (Pink=Deficiency, Brown=Excess).

Figure 2 Gis Map Showing Changes in Soil Erosion between 1987 and 1992, Wusan Watershed, Taiwan (Green=No Increase).

Figure 2 Gis Map Showing Changes in Soil Erosion between 1987 and 1992, Wusan Watershed, Taiwan (Green=No Increase).

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