Characteristics Of Major Agro Ecological Zones Environmental Sciences Essay

Characteristics Of Major Agro Ecological Zones Environmental Sciences Essay Africa is a very large continent with extremely wide range of soils (Bationo et al., 2006). The soils range from shallow with meager life-sustaining capacities to deeply weathered profiles that recycle and support large biomass. In many parts of Africa, inappropriate land use, poor management and lack of inputs have led to soil erosion, salinization and loss of vegetation resulting in a decline of agricultural productivity (Bationo et al., 2006). In Africa and particularly Southern Africa, the most limiting factor to agricultural productivity is soil fertility (Ramaru et al., 2000). Soil fertility is defined as a condition of the soil that enables it to provide nutrients in adequate amounts and in proper balance for the growth of specified plants when other growth factors, such as light, water, temperature, and physical, chemical and biological conditions of soil, are favorable (van der Watt and van Rooyen, 1995). Large areas of sub-Saharan African (SSA) soils, in particular, are af fected by various types of degradation, including fertility decline (FAO, 2001). Soil fertility decline is a deterioration of chemical, physical and biological soil properties. The main contributing processes, besides soil erosion, are: decline in organic matter and soil biological activity; degradation of soil structure and loss of other soil physical qualities; reduction in availability of major nutrients (N, P, K) and micro-nutrients; and increase in toxicity, due to acidification or pollution (FAO, 2001). Soils in most of SSA have inherently low fertility and do not receive adequate nutrient replenishment (FAO, 2001). The SSA has the lowest mineral fertilizer consumption, about 10 kg nutrients (N, P2O5, K2O)/ha per year, compared to the world average of 90 kg, 60 kg in the Near East and 130 kg/ha per year in Asia (Stoorvogel and Smaling, 1990). Agricultural growth in sub-Saharan African countries slightly increased over the past three decades, although not in line with the high population growth rate (FAO, 2001). Food production per capita in sub-Saharan Africa (SSA) has declined since the 1970s, in contrast with the increase in Asia and South America (Figure 1.1). Soil productivity in SSA is also constrained by aridity (low rainfall) and acidity (FAO, 2001) (Table 1.1). South Africa has to face high population growth, poverty, accelerated soil degradation and increasing pressure on land (FAO, 1999b) (Table 1.1). Depletion of soil fertility, along with the related problems of weeds, pests, and diseases, is a major biophysical cause of low per capita food production in Africa. This is the result of the breakdown of traditional practices and the low priority given by governments to the rural sector (Sanchez, 1997). The 1996 World Food Summit highlighted sub-Saharan Africa as the remaining region in the world with decreasing food production per capita (Figure 1.1). The worst levels of poverty and malnutrition in the world exist in this region (Sanchez et al., 1997). A team of scientists has identified declining soil fertility as the fundamental agronomic cause for declining food productivity in Africa. A â€Å"Soil Fertility Initiative for Africa† has been created by a group of international organizations including the World Bank, Food and Agriculture Organization (FAO), International Center for Research on Agroforestry (ICRAF), International Fertilizer Development Center (IFDC), International Fertilizer Association (IFA), and International Food Policy Research Institute (IFPRI).