Maize-nutrient response functions for Eastern and Southern Africa

Information is scarce for maize (Zea mays L.) response to nutrient application for many production areas in tropical Africa. Research was conducted to determine macronutrient response functions and to diagnose Mg–S–Zn–B deficiencies. Site–year × N-rate interactions within countries often accounted for little variation in yield relative to the N-rate effect. Country mean grain yield responses to N-rate were curvilinear to plateau, but linear in Malawi. Although mean yields differed, the response to N was similar for Kenya, Tanzania, and Zambia with a mean yield increase of 0.94 Mg ha–1 due to 50 kg ha–1 N compared with 1.59 Mg ha–1 for Malawi and Rwanda. Response to N was related to yield with no fertilizer applied (r = 0.40). Only Rwanda had mean responses to P and K with respective yield increases of 0.99 and 0.22 Mg ha–1 due to 15 kg ha–1. Application of Mg–S–Zn–B caused a mean yield increase of 0.73 Mg ha–1 in Rwanda but had no effect in other countries. Application of affordable fer...