There are more than 60 million smallholder farmers in Sub-Saharan Africa (SSA). Declining soil fertility is a fundamental impediment to agricultural growth and a major reason for slow growth in food production in SSA. In Africa, as a result of soil degradation, irrigated lands may be, on average, 7 percent below their potential productivity, rain-fed crop lands 14 percent below their potential and rangelands 45 percent below potential. Compared to parts of North America, Europe and of Asia, most SSA soils are naturally not very fertile. Low in a number of chemical constituents such as phosphorus, sulphur, magnesium and zinc, low amounts of soil organic matter (SOM) combined with poor land cover have resulted in poor soil structure, limited rooting depth and susceptibility to accelerated erosion. However, similar soils in other parts of the world have been made highly productive by using appropriate management techniques. There are two main approaches to improved soil fertility management. One is to attempt to meet plant requirements with purchased mineral fertilizers. The second relies on biological processes to optimize nutrient recycling, with little reliance on external chemical fertilizers, but maximizing the efficiency of their use. The more sustainable middle path borrows the best features from both and is referred to as Integrated Nutrition Management (INM). INM combines mineral fertilizers with organic resources, thus increasing fertilizer use efficiency, reducing the risks of acidification and providing a more balanced supply of nutrients.
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