The effects of fertilizer residues in soils and crop performance in northern Nigeria: a review.

This study seeks to review the effects of fertilizer residues in soils and on crop performance in the savanna agro-ecological zone of northern Nigeria. Studies conducted in some parts of northern Nigeria revealed that there are residual effects of fertilizers on soils and they significantly affect crop performance. The annual applications of nitrogen, phosphorus and potassium over the years significantly affected exchangeable cations and consequently crop yields. As the fertilizer rates are increased, the efficiency of fertilizer nutrient use decreases, leaving behind in the soil an increasing proportion of the added nutrients. This is more prominent in the savanna zone where rainfall is generally inadequate and the rate of weathering is high. Hence, when nutrient content of the soil is already sufficient, adding fertilizer to the soil is likely to be damaging to both the soil and the crop. Consequently, the use of organic and inorganic fertilizers in the savanna zone of northern Nigeria should be base on specific soil diagnoses to determine the need for adding nutrients.