Response of soybean to Bradyrhizobium japonicum inoculation and phosphorus application under intercropping in the Central Rift Valley of Ethiopia

Abstract

Effective nodulation by legumes requires balanced availability of phosphorus (P); however, maximum responses to P can be obtained only when adequate mineral nitrogen or superior symbiotic systems are available. Hence, a field experiment was conducted at Metahara Sugar Estate under irrigation during 2014/15 to evaluate the effect of Bradyrhizobium inoculation and P rates on nodulation, yield and yield traits of soybean intercropped with sugarcane. The treatments consisted of three levels of inoculation (SB6B1, Legumefix and un-inoculated) and four rates of P (0, 23, 46 and 69 kg P2O5 ha−1). The experiment was laid out as a randomised complete block design in a factorial arrangement with three replications. The investigation revealed that inoculation of SB6B1 significantly improved nodules per plant, plant height, number of pods per plant, 100-seeds weight, dry biomass yield and grain yield. Legumefix inoculation resulted in the highest nodulation rating, nodule volume per plant, nodule dry weight per plant and crude protein content. Application of 69 kg P2O5 ha−1 significantly increased nodules per plant and nodule volume per plant. Similarly, application of 23 kg P2O5 ha−1 improved 100-seeds weight. However, inoculation with Bradyrhizobium substantially improved nodulation, yield and yield-related traits of soybean grown as an intercrop with sugarcane.