Factors driving cereal response to fertilizer microdosing in sub-Saharan Africa: A meta-analysis

Fertilizer microdosing (FM) is being promoted in sub-Saharan Africa (SSA) to boost crop productivity on smallholder farms. However, yield response variability is a barrier to adoption. We conducted a meta-analysis to analyze the variability in cereal crop yield response to FM and to determine the main factors associated with this variability. Thirty publications pertaining to millet [Pennisetum glaucum (L.) R. Br.], sorghum (Sorghum bicolor L. Moench) or maize (Zea mays L.) were assessed. Factors analyzed were crop type, rainfall, soil texture, type and rate of fertilizer, and complementary practices. On average, FM improved millet, sorghum and maize crop yields by 68%. Yield response tended to increase with increasing rainfall and the largest yield gains were observed in medium-textured soils (81%), as compared to light (61%) and heavy-textured soils (30%). The combined application of N and P performed better than either element alone. Crop response tended to increase with increasing rates of N. In the case of P, this was true only on light textured-soils. On medium-textured soils, the response appeared independent of the rate of P. There was a synergetic effect of water conservation measures on the performance of FM, while combining FM with organic matter (OM) amendments decreased its performance. Results highlighted major trends in cereal crop response to FM that could be used to prioritize target areas. However, these may require additional, site-specific field experiments, especially for factors for which little data is currently available.