Nutrient status of sandy soils in smallholder areas of Zimbabwe and the need to develop site-specific fertiliser recommendations for sustainable crop intensification

Abstract

Sustainable crop intensification in sub-Saharan Africa cannot be achieved if farmers cultivate inherently infertile soils that are deficient in key essential nutrients, such as nitrogen and phosphorus. Most smallholder farmers in sub-Saharan Africa are resource-constrained and apply suboptimal fertiliser amounts, which cannot support optimal plant growth and replenish depleted soil reserves, resulting in food insecurity and soil nutrient mining. Conversely, farmers who can afford adequate fertiliser amounts use outdated recommendations, which are blanket in nature, and which ignore spatial variability in soil nutrients across fields and farms, resulting in inefficient nutrient uptake and consequently depressed crop yields. There is a need to revise the blanket fertiliser recommendations in order to develop site-specific recommendations that are based on soil nutrient status and production system. This can be achieved through systematic soil sampling and analysis, and integration of soil analysis data with GIS in order to develop soil fertility maps that can be used to target fertiliser application. Data from identified soil fertility units can be extrapolated to similar soil units in areas were soil analytical data are not available.