The effect of biofertilizers, Thiobacillus, Azotobacter, Azospirillum and organic sulfur on nodulation process and yield of soybean (Glycine Max L. Merr.)

Recently, because of high cost of fertilizer production and its environmental problems it is necessary to revise maximizing of crop production strategies. For this reason, an experiment was conducted to evaluate nodulation and grain yield of soybean (JK cultivar) in response to biofertilizer application at Sari Agricultural Sciences and Natural Resources University. Experiment was arranged in splitsplit plot based on randomized complete block design with three factors and three replications. Treatments were included four levels of organic sulfur (0, 25, 50 and 100 kg ha-1) as main plots, two levels of Thiobacillus (with and without application) as sub plots and two levels of co-inoculation of Azotobacter and Azosperillium (with and without application) as sub sub-plots. Results showed that application of sulfur fertilizer and Thiobacillus significantly improved number and dry weight of nodules in which the best combined treatment in terms of these parameters was application of 50 kg ha-1 sulfur plus Thiobacillus. Inoculation with Azotobacter and Azospirillum markedly increased root growth and nodulation compared to control. Generally, using of 50 kg ha- sulfur plus Thiobacillus significantly increased pod number per plants, grain yield, biological yield and plant height up to 19,, 41 and 26 percent, respectively.