Aggrandizing soybean yield, phosphorus use efficiency and economic returns under phosphatic fertilizer application and inoculation with Bradyrhizobium

Purpose This study assessed the synergistic effect of inoculation and phosphatic fertilizer application on nodulation, yields, economic returns, P uptake and use efficacy of soybean. Methodology The experiment was carried out during the two growing seasons of 2021 (long and short rains) in Uganda with experiment laid out under a split-plot arrangement with the main plots being two inoculation levels (with or without inoculation) and the subplots being the phosphatic fertilizer at four P levels: 0, 7.5, 15 and 45 kg P ha(-1). Results The total and effective root nodules increased with inoculation with a peak in fertilized plots with 15 kg P ha(-1) (11.8, 13.3). Under inoculation and P application, treatments that received 7.5, 15 and 45 kg P ha(-1) recorded 9, 30 and 25% higher yield than control. The highest net income and benefit-cost ratio were recorded in the inoculated and fertilized plots with 15 kg P ha(-1) (US$ 414.93, 1.87) and (US$ 390.23, 1.76). With inoculation, P use efficiency based on yield (PUEY) and economic returns (PUEE) decreased with increasing P levels in the orders of 165 > 73 > 54 > 21 kg grain kg P supplied(-1) and 51 > 24 > 20 > 8 US $ kg P supplied(-1) for the treatments that received 0, 7.5, 15 and 45 kg P ha(-1), respectively. Conclusion This study indicated that for optimal growth, productivity and economic benefits, soybean ought to be inoculated with Bradyrhizobium coupled with the application of phosphatic fertilizer at the rate of 15 kg P ha(-1).

Automated summary

This study assessed the synergistic effect of inoculation and phosphatic fertilizer application on soybean. The results showed that inoculation and optimal phosphatic fertilizer application can increase root nodules, improve yields, and enhance economic benefits. However, the use efficiency of phosphorus decreases with increasing phosphorus levels.