Survival of Bradyrhizobium and Germination and Vigor of Soybean Seeds Treated with Fungicide and Cell Protector.

Utilization of high quality seeds in the establishment of a soybean crop is essential for obtaining adequate plant population. In this crop, Bradyrhizobium japonicum is responsible for nitrogen nutrition and constitute an important factor for the economic production of this legume. Traditionally, seed inoculation is carried out after the treatment with fungicide immediately before planting; when planting delay occurs, re-inoculation is recommended. However, the use of a cell protector polymer can be a form to protect the bacteria during the inoculation and may extend the period of survival of bacterial cells on the seeds. Therefore, the objective of this work was to evaluate the survival of B. japonicum and germination and vigor of soybean seeds treated with fungicide, cell protector and inoculant, at different periods prior to planting. Seeds of soybean TMG 131 RR cultivar were treated or not with Derosal Plus^® fungicide (carbendazin + thiram), EnVigor^TM cell protector, RizoPlus peat inoculant, and stored at environmental conditions in paper bags for a period of zero, one, two and three weeks before planting. To evaluate the number of colony-forming units (CFU) per gram of inoculant on seeds a completely randomized experimental design with three replications and 16 treatments in a 2x2x4 factorial (fungicide x polymer x periods) was used. For the evaluation of germination and vigor (first counting of germination test) the experimental design was a randomized blocks with four replications and 32 treatments in a 2x2x2x4 factorial (fungicide x polymer x inoculation x periods). Germination and vigor improved with the application of any product, either alone or combined. The use of polymer, with or without fungicide, increased the average number of CFU in all studied period, maintaining the viability of the bacteria until the sowing date.