Interação entre agroquímicos e inoculante com Bradyrhizobium japonicum na qualidade fisiológica de semente de soja e fixação biológica de nitrogênio.

Abstract

On the world stage, the soybean is one of the largest crops of economic and social importance and, in Brazil, its productive complex is the leader of agribusiness.Demands by technological innovations, aiming at successive gains in profitability, imply in constants investigations.Among these, stands out the treatment of seeds with phytosanitary products and fertilizers associated to inoculants and cellular protectors.This process has generated uncertainty concerning the effects of agrochemicals on physiological seed quality and effectiveness of rhizobia on biological fixation of nitrogen.The objective of this study was to evaluate the treatment effect of soybean seeds, involving phytosanitary products, of nature insecticide and fungicide, in mixtures or not, with strains of Bradyrhizobium japonicum, with and without protective cell phone, on germination and vigor of seeds, in the survival of rhizobia inoculated to seed over storage periods and on infectivity and efficiency of rhizobia on biological fixation of atmospheric nitrogen.To meet these goals, three experiments were implemented: effect of seed treatment on physiological quality of seeds; effect of seed treatment on survival of colony-forming units rhizobia inoculated on the seeds; and effect of seed treatment on infectivity and efficiency of rhizobia on biological fixation of nitrogen.The three experiments were structured with 12 treatments, involving seed treatment, and an absolute witness, in experimental design completely randomized with four replications, except for the third which had five replications.The experiments were conducted in the laboratory and in the greenhouse, in the period December 2013 to July 2014.In the lab, on sandy substrate, proceeded to: seed germination test in zero time, 15and 150 days after seed treatment; seed vigor test at 150 days after the seed treatment; and concentration of colony forming units adhered to seeds in time zero and 15 and 150 days after seed treatment.In the greenhouse, the treated seeds were sown, in time zero, in Leonard vessels, evaluating, in the stage of full flowering of plants: dry matter mass of plants; dry matter mass of roots; dry matter mass of nodules; number of nodules; total nitrogen in aerial part of plants.The results obtained show that the use isolated and combined of the phytosanitary products tested, as well as their associations with the inoculant and the cellular protector used, generate specific interactions that prevent generalized conclusions.