Effect of Rhizobium inoculation and NP fertilization on growth, yield and nodulation of soybean (Glycine max L.) in the sub-humid hilly region of Rawalakot Azad Jammu and Kashmir, Pakistan

This research experiment was conducted to examine the effect of Rhizobiuminoculation (RI) and P fertilization (P) on nodulation, growth and yield characteristics of soybean grown in the presence of starter N fertilizer (N). Treatments included: i) 02 levels of RI (RI0, RI1), ii) 02 levels of P (P0, P1 that is, P2O5 @ 90 kg ha-1) iii) 03 levels of N (N0, N1 and N2 that is, N at of 25 and 50 kg N ha-1) iv) 03 replication. Results of the experiment revealed that total number of nodules increased from 73 in the un-inoculated control to 125 and 95 following the application of RI and P representing 70 and 30% increase over control. N supply did not affect the number of nodules; however, combination of RI and P with 25 kg N ha-1 (RI1P1N1) produced the highest number of nodules (152). RI, P, N and their combinations increased shoot and root biomass. Seed yield in the control was 767 kg ha-1 that significantly increased to 1081, 907 and 940 kg ha-1 following the application of RI, P and N demonstrating a 41, 18 and 23% increase over control. The highest seed yield of 1208 kg ha-1 was recorded in the combine treatment of RI1P1N1 indicating 57% increase over control. Relative increase in dry matter yield due to RI, P and N was 63, 46 and 49%. Seed protein content in different treatments ranged between 33 - 40% while oil content ranged between 13 - 18%. Application of RI, P and their combinations increased protein content by 6 - 22% while increase in oil content was 12 - 35%. Concentrations of N and P in plants and their uptake was significantly increased and relative increase in N uptake due to RI, P and K was 77, 21 and 31% , respectively, while the corresponding increase in P uptake was 79, 92 and 56%. It was found that the efficiency of RI and P fertilization increased substantially with the application of 25 kg N ha-1 but the efficiency decreased when N supply increased from 25 kg N ha-1 to 50 kg N ha-1. The results demonstrate the potential benefits of using Rhizobium inoculation and P fertilization with reduced level of N as starter fertilizer in order to achieve plant-growth promotion, increased nodulation and seed yield of soybean.   Key words: Glycine max L., nodulation, N fertilization, P application, soybean,Rhizobium inoculation, soybean.