Crop management adaptations to improve and stabilize crop yields under low-yielding conditions in the Sudan Savanna of West Africa

Agriculture is a critical element of the West African Sudan Savanna's economy and the main livelihood strategy for many people, where food insecurity and poverty are widespread. Low soil fertility, high intra and inter-annual rainfall variability together with limited ability to invest in new technologies are among the major constraints to the predominantly smallholder, rainfed crop production in the region's mixed crop-livestock systems. We evaluated the effect of tillage practices (contour and reduced tillage), nitrogen fertilizer rates (no nitrogen -N0, recommended nitrogen -NREC and high nitrogen-N2REC) and residue management (improved and standard) on the yield of maize, cotton and sorghum for two landscape positions (upslope and footslope) for four growing seasons in three locations in the Sudan Savanna region of Burkina-Faso (Dano), Ghana (Vea) and Republic of Benin (Dassari). The studies aimed at assessing the potential of residue retention, tillage practices and nitrogen fertilization to (1) increase average yields and (2) stabilize yields under sub-humid conditions. Over the 4 year study period, across the 3 locations recommended N produced 17% higher crop yields than the N0 treatment. It was not worthwhile to double the recommended N as there was no yield benefit of applying more fertilizer. The results revealed no consistent interactions across sites except crop type and nitrogen fertilization. Stability analysis revealed that contour ridging was superior in stabilizing yield. Evaluation of the relative maize yield stability on different levels of nitrogen depicts variation and there is a tendency for an inverse relationship between mean yield of nitrogen levels and its relative yield stability since nitrogen application did not increase yield stability. The outcome of cost benefit analysis revealed that, return per cash invested favored non-degraded sites with cotton production and in years with favorable rainfall conditions. Thus, in the Sudan savanna of West Africa, it is economically risky to invest in mineral N fertilizers when cropping on degraded soils or when rainfall is expected to be erratic.