Improving Soybean (Glycine max L.) Growth and Yield by Integrated Mineral and Bio-Fertilizers Management

In order to investigate growth indices, yield, and nitrogen and phosphorous content in soybean under bio- and chemical fertilizer application, a factorial experiment based on a randomized complete block design with three replications was carried out on the research farm of the Moghan College of Agriculture & Natural Resources during 2015. The first factor, Biosoy Bio-fertilizer containing different strains of Bradyrhizobium japonicum bacteria, included inoculation of seed and non-inoculation; and the second factor, chemical fertilizer, included non-application of fertilizers (0%), 50 kg.ha-1 urea 66 kg.ha-1 diammonium phosphate (33%), 100 kg.ha-1 urea 132 kg.ha-1 diammonium phosphate (66%), and 150 kg.ha-1 urea 200 kg.ha-1 diammonium phosphate (100%). The results showed that the lowest leaf area index (2.17), total dry matter accumulation (374.17 g.m-2), crop growth rate (8.6 g.m-2.d-1), grain yield (3738.3 kg.ha-1), and leaf chlorophyll index (20.83) values were observed from the combined treatment of non-inoculation and non-application of fertilizer. The highest values of leaf area index (5.46), total dry matter accumulation (784.5 g.m-2), crop growth rate (21 g.m-2.d-1), grain yield (7602.8 kg.ha-1), and leaf chlorophyll index (38.16) were recorded from the combined treatment of inoculation by Biosoy and 33% of chemical fertilizer. Inoculation treatments significantly showed higher nitrogen content and nitrogen to phosphorus ratio than non-inoculated ones. All-told, soybean inoculation with Biosoy bio-fertilizer containing Bradyrhizobium japonicum bacteria not only increases soybean growth, development and yield, but also, reduces chemical fertilizers usage, production costs, and environmental risks.