Evaluation of Elites Isolates of Bradyrhizobia Nodulating on Groundnut Varieties (Arachis hypogaea L.) at Assosa District of Western Ethiopia

A field experiment was conducted on Nitisols of Asossa Agricultural Research Centre during 2017/18 2018/19 cropping season to investigate the response of yield, partial budget analysis of ground nut varieties to bio-fertilizer and inorganic nitrogen. Two locally suitable varieties 4 groundnut rhizobial strains with control and 18 kg N ha-1, totally 12 treatments had combined in factorial RCBD. TSP fertilizer was applied uniformly to all plots at 46 kg P2O5 ha-1. The treatments consists of: two Varieties of groundnut (V1= Muniputer V2= Babile 2) and 4-strains with 18 kg N ha-1 and uninoculated (control) factorial treatment combination were tested. Analysis of variance for two factors randomized complete block design (Table 1) revealed highly significant difference (P < 0.001) due to the main effects of rhizobia and verities for the means of seed yield. On the other hand the interaction effects of rhizobia and varieties had non-significant (p>0.05) for the means of seed yield, nodule dry weight and straw dry weight. The highest (186.5) nodules per plants were recorded from the interaction effect of Dibate moderate and Maniputer variety, while less nodules per plant (76.25) were produced by Dibate moderate with Babile variety. The Dibate 2 rhizobia had the highest net-benefit of 67,655 Ethiopian birr. The lowest net benefit was obtained by the application of the Dibate moderate and none inoculant. The profitability of the study showed that application of Moderate 2 rhizobia which provided the relatively high net benefit (67,655 ETB), was recommended to apply bio fertilizers. The % MRR between any pair of undominated treatments denotes the return per unit of investment in fertilizer expressed as a percentage. Economic analysis revealed that maximum marginal rate of return was recorded with application of Dibate 2 (9257.2%). So we could be recommended Dibate 2 strain for ground nut production in Asossa district. The best recommendation for treatments is not necessarily based on the highest marginal rate of return, rather based on the minimum acceptable marginal rate of return and the treatment with the high net benefit, relatively low variable cost together with an acceptable MRR becomes the tentative recommendation.