Sustainability analysis of existing land-use systems in northeast Thailand

Agricultural systems in Northeast Thailand have been developed on marginal sandy soils within an undulating landscape. Agricultural productivity has declined considerably under the currently adopted land use systems as indicated by declining crop yields and an increasing dependency on chemical fertilizers. This has resulted in skepticism with regards the sustainability of the current the land-use systems of the region. From 1999-2001 researchers at Khon Kaen University conducted research to evaluate the sustainability of currently adopted land-use systems using a nutrient balance model. The project was funded by the National Research Council of Thailand (NRCT) and the Thailand Research Fund (TRF). The specific objectives of the project were to investigate nutrient inputs and outputs from selected land-use systems in a micro-watershed area; investigate changes in land use and management as affected by socioeconomic and cultural factors; model the characteristics and dynamics of land degradation in a micro-watershed, and to identify factors affecting land degradation. It is envisaged that knowledge gained from this project will lead to the development of sustainable land use and management for Northeast Thailand. A micro-watershed at Ban Khummuang village, Khao Suan Kwang District, Khon Kaen Province, was selected as the study site. Nutrient balances were determined for the major land uses in the area, and for the entire micro-watershed under investigation. Specific studies relating to the different input and output parameters were also conducted. These include studies on (1) ground cover and placement of surface structures under current land uses in relation to soil erosion, (2) rainfall-runoff relationships, (3) sediment transport, (4) unconfined groundwater hydraulics, (5) subsurface flows of nutrients, (6) estimation of the water table in paddy systems, and (7) soil organic matter build up and dynamics under the selected land-use systems. A summary of the nutrient balance studies is presented in this paper. It should be noted that the nutrient balance analysis did not include nutrient loss from leaching; nutrient gain and loss from accumulated moisture and runoff or wind erosion; and nutrient gains from capillary water in the soil, and weathering of parent materials, N fixation, and livestock manure. The results represented in this paper can therefore only be considered as an incomplete and estimated nutrient balance for the agricultural systems evaluated.