EFFICIENCY OFRHIZOBIUMINOCULATION AND P FERTILIZATION IN ENHANCING NODULATION, SEED YIELD, AND PHOSPHORUS USE EFFICIENCY BY FIELD GROWN SOYBEAN UNDER HILLY REGION OF RAWALAKOT AZAD JAMMU AND KASHMIR, PAKISTAN

Abstract

A field experiment was conducted in continuity of our previous study to assess the effect of Rhizobium inoculation (RI) and phosphorus fertilization (P) on growth, yield, nodulation, and P use efficiency of soybean. Different treatments were i) Rhizobium strains (0, S₃₇₇, S₃₇₉, and the mixture of S₃₇₇+S₃₇₉ i.e. S₀, S₁, S₂, S₃); ii) phosphorus fertilizer (0, 50, 100 kg ha⁻¹ i.e. P₀, P₁, P₂). Soybean variety NARC-1 was as used as a testing crop. Results indicated that root and shoot growth increased by RI treatments whether used alone or in combination with P. Rhizobium inoculation increased plant height up to 12% while P did not show significant effect. Increases in soot dry weight, root length and root dry weight due to RI and P was 57 and 22%, 42 and 7%, 55 and 25%, respectively, over the control treatment. Number of nodules increased from 73 in the control to a maximum of 151 in S₂ while the number increased from 90 in the control to 147 in P₂. Combine application of strains and P increased nodules number from 65 at S₀P₀ to a maximum of 183 at S₂P₂. Similar response was also observed for nodules mass. Soybean seed yields ranged between 1710 and 2335 kg ha⁻¹ against 1635 kg ha⁻¹ in the control indicating a maximum of 43% increase over control. Concentration of N and P in plants and their uptake was significantly increased by RI and P. RI also increased the N and protein content of soybean seed. Apparent recovery efficiency (ARE) of applied P was 10−12% and the agronomic, agrophysiological, recovery, utilization efficiencies, and harvest index of P decreased with increasing P rates. Nodule number significantly correlated with the DM yield (r² = 0.78) and seed yield (r² = 0.63) while P uptake significantly correlated with root length (r² = 0.48) and root mass i.e. dry weight (r² = 0.65). Also a significant correlation existed between N uptake and DM yield (r² = 0.98) and N uptake and seed yield (r² = 0.65), P uptake and DM yield (r² = 0.73), and P uptake and seed yield (r² = 0.83). The results of present study indicated a substantial growth and yield potential of soybean under the hilly region and increase in yield and N₂ fixing potential (nodulation) can be achieved by applying Rhizobium inoculation with P fertilization.