1Department of Soil & Environmental Sciences, Faculty of Agriculture, The University of Poonch, Rawalakot Azad Jammu and Kashmir, Pakistan.
2National Institute of Biology and Genetic Engineering (NIBGE), Faisalabad, Pakistan.
The use of efficient and effective nodulating Bradyrhizobia strains considered as an ecologically and environmentally sound management strategy for soybean production. A 2-yr (2009 and 2010) field experiment was conducted to evaluate the effects of seven indigenous Bradyrhizobium strains, one exotic TAL-102 and three N fertilizer rates, i.e., 25, 50 and 100 kg N ha-1 on the productivity and N2 fixation of rainfed soybean [Glycine max (L.) Merr.] grown in the Himalayan region of Rawalakot Azad Jammu and Kashmir (AJK), Pakistan. The experiment was conducted in a randomized complete block design with three replications. Bradyrhizobium inoculation accelerated plant growth by increasing shoot length (26-47%), root length (45-73%) and shoot dry weight (58-104%). Seed yield in the control was 861 kg ha-1 that significantly increased to 1450–2072 kg ha-1 with Bradyrhizobium strains. Seed yields under indigenous NR20 and NR22 strains was 24 and 28% higher than that recorded from the exotic TAL-102. Number of nodules, nodules dry weight and acetylene reduction assay with Bradyrhizobium strains were 55–123%, 94–178% and 38–103%, (respectively) higher than the non-inoculated control. The higher N rate (N100) depressed nodulation and N2 fixation. A significant variation in the symbiotic effectiveness and yield potential showed that inoculation response was site/strain specific. Two indigenous strains NR20 and NR22 were found highly efficient and displayed superiority over the exotic strain TAL-102. Multi-locational trials are required to check the suitability of these isolated isolates for other agro-climatic conditions before using as inoculants or bio-fertilizers.