CHANGES IN SOYBEAN PRODUCTIVITY UNDER DIFFERENT DURATIONS OF PRETREATED SEED INOCULATED WITH BRADYRHIZOBIUM ELKANIIWILSON STORY VENANCIO, PEDRO HENRIQUE DE MEDEIROS BUSO AND MARTIN DIAZ-ZORITA
This work aimed to establish the contribution on soybean productivity of seed inoculated with Bradyrhizobium elkanii applied at different days of pretreatment before planting, under field conditions in regions of Brazil. Fifty soybean field trials were conducted in the Brazilian States of ParanÃ¡, GoiÃ¡s and Mato Grosso. In each site, seven seed treatments were established in combination with twelve chemical products [i) seeds without inoculation; ii) fertilization with 200 kg ha-1 N without rhizobia inoculation; iii) seeds inoculated with rhizobia at planting; iv) to vii) seeds inoculated with rhizobia and biological protectants applied at planting and at approximately 38, 52and 66 days before planting. Plant nodulation, vegetative growth and grain yield components were evaluated and the data analyzed based on ANOVA and regression procedures. Independent of the time of pretreatment of inoculant as a seed treatment, the combined use of the inoculant, with a specially formulated protectant, favored greater nodulation and grain productivity than the control without inoculant. These results validate that, under regular Brazilian soybean production conditions, pretreatment of seed with inoculant from 26 to 78 days before planting, using a formulation containing Bradyrhizobium elkanii strains, combined with chemicals and a specially formulated microbial protectant, is as effective as the inoculation applied at planting.