Nutrient management in tropical agroecosystems

Abstract

West Africa faces a rapid growth in population and a subsequent demand for food production. Despite increasing demand, local farmers still follow traditional practices and try to overcome low productivity by continuously expanding cultivated areas. To assess the consequences of this expansion and to describe, based on anticipated population growth rates and land accessibility, the dynamics of agricultural land-use, we developed a spatially explicit agent-based ALADYN model of agricultural land use in the savannah around Kita, Mali. The model is based on remote sensing data on agricultural land use and data from field surveys. The ALADYN simulations clearly demonstrate that traditional agriculture is not sustainable. Even under the optimistic scenario of a declining rate of population growth, the current agricultural practices will result in the cultivation of all available agricultural lands by 2015. Under current practices, every farm will experience a period of 1–3 years every 15–20 years, during which field fertility will be too low to allow cultivation. Thus, to avoid severe food shortage, emigration or alternative sources of food are necessary. Comparison of the model and remote sensing data reveals that already in 2003 the cultivated part of the study area is lower than projected. That is, farmers anticipate overexploitation and, most probably, emigrate from the area. The model highlights the great need for new agricultural practices in West Africa.