Acidity and poor soil fertility are the major soil chemical constraints that limit crop productivity in western Ethiopia. This low productivity in leguminous crops is a result of declining soil fertility and reduced N2-fixation due to biological and environmental factors. Thus, a study was carried out to determine the influence of lime, Bradyrhizobium inoculation and phosphorus (P) fertilizer on soybean nodulation, phenological and growth parameters for two consecutive years during 2016 and 2017. Factorial combinations of three commercial Bradyrhizobium strains (non-inoculated, TAL379 and Legumefix), two lime levels (0 and 3.12 t ha-1) and four P levels (0, 23, 46 and 69 kg P2O5 ha-1) were laid out in Randomized Complete Block Design with three replications. The results showed that the application of lime significantly increased soil pH, plant height and number of primary branches per plant. Similarly, significantly higher plant height was obtained with inoculation of TAL379 whereas Legumefix inoculation provided the highest number of primary branches. The effect of P at 69 kg P2O5 ha-1also gave significantly highest plant height and number of primary branches. The interaction of Bradyrhizobium × lime × phosphorus, revealed that application of 69 kg P2O5 ha-1 withoutTAL379 inoculation under limed condition significantly resulted in the highest number of nodules per plant, number of effective nodules. On the other hand, the combination of lime (3.12 t ha-1) with TAL379 inoculation gave the highest nodule volume and nodule dry weight of soybean. Thus, application of phosphorus with other sources of nutrients are an alternative option to enhance biological nitrogen fixation and grain yield of soybean in smallholder farming system in a western part of Ethiopia.

Keywords: Biological nitrogen fixation, Legumefix, Nodulation, Soil acidity, TAL379