Response of Maize to Different Nitrogen Application Rates and Tillage Practices Under Two Slope Positions in the Face of Current Climate Variability in the Sudan Savanna of West Africa

An experiment managed by an on-farm researcher was conducted in Sudan Savanna of three West African countries, Ghana (Vea), Benin Republic (Dassari), and Burkina Faso (Dano), in 2012. The experiment evaluated the effects of tillage practices and nitrogen fertilizer regimes on the yield of short-season maize Dorke SR variety for two landscape positions (upslope and footslope). A stripe-split plot design with four replicates at each of the three sites was used. Tillage practices (contour and along-slope ridges) were applied in the main plots, whereas nitrogen treatments (no nitrogen, 0 kg N ha−1; moderate nitrogen, 60 kg N ha−1; and high nitrogen, 120 kg N ha−1) were applied in the subplots of each landscape position. Both potassium and phosphorus fertilizers were applied at optimum rates. Grain yield and growth parameters showed diverse responses to the treatments across sites. The effects of slope position and nitrogen fertilizer regime on grain yield were significant (p < 0.05) across sites; the grain yield at the footslope position was 25% higher than that at the upslope, and the high nitrogen treatment resulted in a 140% increase in grain yield compared to no nitrogen condition. An insignificant (p < 0.05) increase in grain yield was observed for sites with contour tillage compared to sites with along-slope ridges. Leaf area index was not significantly (p < 0.05) affected by the treatments during tasseling across sites, and the values were consistent with increasing nitrogen levels. These results suggest that to optimize maize yield under subhumid conditions, farmers should concentrate maize cultivation in low-lying areas and follow the recommended fertilizer application regimes given current climate variability.