Impact of pre-inoculation of soybean seeds with Bradyrhizobium spp. applied 60 days before sowing

Abstract

The pre-inoculation of soybean seeds optimizes sowing process, enhancing biological nitrogen fixation, seed quality, and overall crop yield. This study aimed to evaluate the efficacy of pre-inoculating soybean seeds with the commercial inoculant Biofix Premium (Bradyrhizobium diazoefficiens SEMIA 5080 and Bradyrhizobium japonicum SEMIA 5079, 5x10^9 CFU/mL), along with a cell protector and chemical treatment. Four soybean trials were performed in Paraná, São Paulo, Minas Gerais, and Goiás states during the 2021/2022 agricultural year, utilizing a randomized complete block design with four treatments and six replications. The treatments were: 1- Control (no inoculation); 2- Fertilization with 200 kg.ha-1 of nitrogen; 3- Commercial standard seed inoculation (50 mL/50 kg of seeds) on the sowing day; 4- Seed inoculation with Biofix Premium (125 mL/100 kg of seeds), Protetor Ultra (0.5 mL/kg), Potenzial TS (0.2 mL/kg), and CoMo Platinum (100 mL/ha), applied 60 days before planting. Results showed that Biofix Premium applied 60 days before sowing, formed nodules and nodule mass similar to the comercial inoculant applied at sowing day. This led to a similar nitrogen fixation, chlorophyll content, shoot dry mass accumulation, grain yield, and nitrogen content compared to the comercial inoculant applied at sowing day. Yield gains with Biofix Premium ranged from 5-8% compared to the control (without inoculation), with no significant differences from the commercial seed inoculation applied on the sowing day. The use of insecticides and fungicides together with Biofix Premium, Protector Ultra, and Potenzial TS is recommended in the pre-inoculation of soybean seeds up to 60 days before sowing, without compromising plant nodulation and crop yield