Maize Response to Fertilizer and Nitrogen Use Efficiency in Uganda

Abstract

Maize (Zea mays L.) is an important smallholder crop in Uganda. Yields are low because of low soil fertility and little fertilizer use. Yield response to nutrient application and economically optimal rates (EOxR, where x = N, P, or K) and N use effi ciency (NUE) were evaluated. Twenty-two trials were conducted in four agroecological zones. Yield was consistently increased with N application. Mean maize yield with no N applied (N0) was 1.79 Mg ha–1 and increased by 120% with N application. Mean EONRs were 45 to 24 kg ha–1 N with fertilizer use cost to grain price ratios (CPs) of 10 to 30. With N applied, the mean increase in yield due to P application was 0.28 Mg ha–1 and mean EOPRs were 9 to 1 kg ha–1 P with CPs of 10 to 50. Yield was not increased with K application. Profi tability was greater for N than P application. Mean aboveground biomass N with 0 and 150 kg ha–1 N applied was 46.3 and 94.3 kg ha–1, respectively. Mean N concentration and N harvest index at the EONR were 1.60 and 63.8%, respectively, and higher than for N0. Mean recovery effi ciency, partial factor productivity, and agronomic effi ciency declined with increasing N rate and were 66%, 86 kg kg–1, and 41 kg kg–1, respectively, at the EONR. Fertilizer N use can be very profi table, with high NUE, for smallholder maize production in Uganda, and the fi nancial capacity of smallholders to use fertilizer will increase with reduced CP