Organic matter is essential for good soil quality. Soil with
sufficient amounts of nutrients, particularly nitrogen, is important for the
formation and maintenance of soil organic matter. If soil is fertile, there is more
plant growth which in turn increases inputs of roots and other plant debris
into the soil. As this plant debris decomposes, it adds to the soil organic
matter. This organic matter increases microbial activity because it provides a
food source for soil microorganisms. Fertilizers are a great source of nutrients
for soil. However, nutrient management is recommended to ensure that fertilizer
is used correctly.
Managing the quantity, timing and method of nutrient application in order to minimise nutrient losses and optimise crop yield is referred to as nutrient management. It promotes increasing soil quality without creating nutrient excesses. An important step in nutrient management is soil testing. This is the best way to determine the nutrient content of the soil and the amount of fertilizer needed. It enables farmers to know the accurate quantity of fertilizer required for a particular crop on a particular soil. Smallholder farmers in West Africa may not be able to conduct soil tests and therefore rely on governments, the private sector and development organisations in the region. The soil tests are conducted in different locations and recommendations are given for major crops. In Nigeria for instance, the government has made efforts to stop the use of NPK 15 15 15 for all crops in favour of creating new formulations of fertilizers based on soil tests.