Comparison of Nutrient Utilization Strategies of Traditional Shifting Agriculture Under Different Climatic and Soil Conditions in Zambia, Thailand, Indonesia, and Cameroon: Examples of Temporal Redistribution of Ecosystem Resources

Abstract

Based on the results of field studies in different regions of the tropics, land management strategies using shifting cultivation under different bioclimatic and soil conditions are comparatively discussed. Four regions are included in this study: eastern Zambia, northern Thailand, East Kalimantan of Indonesia, and eastern Cameroon. An increase in N mineralization and resulting increase in N flux, after the original vegetation was removed for cropping, were the highest for the eastern Cameroon forest, followed by northern Thailand, eastern Cameroon savanna, East Kalimantan of Indonesia, and eastern Zambia. This trend, however, was considered to coincide with mineral nutrient loss due to leaching. This loss would be more detrimental for the strong-weathered soils, such as Oxisols in Cameroon. The function of the fallow phase was the most clearly observed in shifting cultivation in northern Thailand; the soil fertility was reinstated in the later stage of the young fallow, around 8 years. A similar trend was also found for the soils in eastern Cameroon, in which the soil fertility was the highest in the young fallow forest. Such improvement in soil fertility during the fallow stage was not observed for the plots in East Kalimantan, Indonesia, and eastern Zambia, presumably due to the specific climatic conditions. Generally, the farmers’ practices and land uses during shifting cultivation in Southeast Asia were well adapted to the respective soil and climatic conditions. However, the present pattern of land use in eastern Cameroon has not been controlled solely by natural conditions; human factors, such as activities of neighboring agropastoralists, have a greater impact on these dynamics. In the case of eastern Zambia, limited and fluctuating precipitation may be the most important factor in agricultural production, and because primary production and soil organic matter decomposition rate are regulated by this, soil fertility status would not change considerably under the present land use practices. Therefore, the classical interpretation of slash-and-burn agriculture is not applicable to the agricultural practices in the latter two African cases.