Optimizing Inorganic Fertilizers Use for Sustainable Intensification of Rain-Fed Maize in Three Agro-Ecological Zones of Mali

Abstract

Maize yields on farmers' fields in Mali are usually less than 2 t/ha despite the availability of improved varieties that yield up to 8 t/ha under optimal management. The low yield is partly due to low soil fertility and lack of site-specific fertilizer recommendations. Studies were carried out in three different agro-ecological zones of Mali, namely the Manding Plateau, Koutiala Plateau and Upper Bani-Niger, to determine the response of maize to different combinations of nitrogen (N), phosphorus (P) and potassium (K) fertilizers. The objective was to determine agronomicaly and economically optimum rates of NPK for use by the smallholder producers in different agroecological zones of Mali. The experimental design was a randomized complete block with three replicates. The treatments were18 fertilizers rates each subdivided into two subplots for a hybrid maize variety (Tieba) and an open pollinated variety (Sotubaka). A diagnostic treatment including Zn, Mg, and B was compared with the different levels of NPK to evaluate the effect of trace elements on maize yield and yield components. In terms of grain yields, the best was the diagnostic treatment across the three agro-ecological zones. Increasing application rates to 200 kg N/ha + 80 kg P/ha did not significantly increase grain yields over application of 120 kg N/ha + 30 kg P/ha. Agronomic use efficiency of N and the value cost ratios (VCR) were negative for all treatments at Kolombada, where rainfall received during the growing season was very low (567-674 mm) relative to its historic average of 800-1000 mm. The VCR was highest with 90 kg/ha N + 10 kg/ha P at Bougouni and with 30 kg/ha P at Samanko although VCR was less than the cutoff point of 2 in all cases. At Kolombada, fertilizer use was unprofitable regardless of the amount of nutrients applied.