In the drylands of West Africa, low-cost methods such as seed priming and microdosing of fertilizer can boost sorghum and millet yields, but their effectiveness depends on local rainfall. Over four years in Mali, microdosing 0.4 g NPK per hill (4 kg/ha) worked best in central Mali, while 0.8 g NPK per hill (20 kg/ha) was best in southern Mali. Seed priming helped in central but not southern Mali. Adding a urea top dressing (1 g per hill, 25 kg/ha) improved yields only in southern Mali. Sorghum responded better to microdosing than pearl millet. A decision tree was created to guide farmers on crop and fertilizer choices based on rainfall.
Maize grain yield increased with NPK microdosing rates up to 93 kg/ha, producing 1029 kg/ha (61.3%) more grain than the control in Mali. A rate of 63 kg NPK/ha matched the yield and economic return of the recommended 100 kg NPK/ha applied in rows. The 78.1 kg NPK/ha rate gave the highest average gross margin and value-cost ratio across two price scenarios. All fertilizer treatments had a value-cost ratio above two, indicating low financial risk even with non-subsidized fertilizer. Manual sowing and microdosing required 11.4 man-days/ha, versus 1.0 man-days/ha for mechanized operations, suggesting farmers will adopt microdosing only if mechanized.