EFFICIENCY OF RHIZOBIUM INOCULATION 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.

Keywords:

• Bardyrhizobium japonicum
• nodulation
• P-use efficiency
• Rhizobium inoculation
• strains

ACKNOWLEDGMENTS

The authors are grateful to the University of Azad Jammu and Kashmir for financial support. We express our appreciation to our colleagues at National Agriculture Research Centre (NARC), Islamabad, Pakistan for their cooperation in chemical analysis of plant samples.