Assessing and understanding non-responsiveness of maize and soybean to fertilizer applications in African smallholder farms

•Occurrences of non-responsiveness ranged from 0%–68% across sites and seasons.•Fertilizer responses by each crop may contrast on a field during the same season.•Irregular rainfall patterns strongly limit soybean responses, while less for maize.•Maize non-responsiveness greater on soils with high silt and/or cation imbalances.•Soybean non-responsiveness greater on soils with high silt, low P and/or low TC:TN.