Integrating Soybean Residues With Nitrogen Fertilizer for Improved Maize Production in Eastern Uganda

Soybean has become one of the dominant crops in Ugandan farming systems; however the contribution of its residues to improve soil and crop productivity is less known. To investigate the role of soybean residues to enhance crop productivity, researcher-managed experiments were conducted for two seasons (2011B and 2012A) in Namayingo and Tororo districts, representing the L. Victoria crescent, and South-eastern L. Kyoga basin agro-ecological zones, respectively. Factorial treatments of three levels of soybean residues (0, 2 and 4 t ha-1) and four levels of N fertilizer (0, 30, 60 and 120 kg ha-1 N) in form of urea were applied in maize fields in a randomized complete block design so as to; determine the optimum nutrient combination for maize, and establish the added yield benefits, if any, of using soybean residues with N fertilizer in maize production. Site yields varied significantly (p < 0.001), with higher maize yields obtained in Namayingo compared to Tororo. Significantly (p < 0.05) higher maize grain yields were obtained with the highest nutrient input combinations of 2 t ha-1 residue and 60 kg ha-1 N (yield increment of 71.72% above the control) in Namayingo district and 4 t ha-1 residue combined with120 kg ha-1 N increased maize grain yield by 140.69% above the control in Tororo. The added maize grain yield benefits ranged from 2540 kg grain ha-1 to 3250 kg grain ha-1 in Namayingo and from 2000 kg grain ha-1 to 2310 kg grain ha-1 in Tororo. Combined use of soybean residue with N fertilizer has been found to have agronomic yield benefits to maize production.