Integrating inorganic NP application and Bradyrhizobium inoculation to minimize production cost of peanut (Arachis hypogea L.) in eastern Ethiopia

Abstract Background Integrated application of inorganic NP and inoculation of Bradyrhizobium sp. exhibits various effect on nodulation and productivity of peanut in different locations. Therefore, this field experimental was set up in Fedis and Babile to investigate the effect of nitrogen, phosphorus and Bradyrhizobium inoculation on nodulation and yield of peanut. Methods Fourteen treatments were laid out in randomized complete block with three replications. Results ANOVA revealed that the main effect of Bradyrhizobium inoculation, N and P and their two and three ways interaction had significant effect on most of the investigated traits of peanut. Applying 20 kg N ha−1 significantly enhanced the nodule number (NN) and nodule dry weight (NDW) at Fedis but reduction of nodulation was found at Babile site. Phosphorus application at 60 and 30 kg P2O5 ha−1 significantly increased the NDW by 88.4 and 34% over the P control at Babile and Fedis site, respectively. A significant increase in grain yield at 60 and 30 kg P2O5 ha−1 was also observed at Babile and Fedis, respectively. Although Bradyrhizobium increased the nodulation at Fedis site, this effect was not observed on yield of peanut. A significant increase in NN and NDW by inoculation was found with only when N was not applied either of the locations. However, inorganic N application increased plant N accumulation at Babile site. Conclusions According to the results from the field experiments, the yield of peanut at Babile and Fedis can be enhanced by applying 60 and 30 kg P2O5 ha−1, respectively, with background rhizobia. Although P application increase the yield of peanut, the yield is still far below the potential yield of peanut reported elsewhere. Hence, further investigation of other yield limiting factors in the study sites is needed.