Does Canavalia ensiformis inoculation with Bradyrhizobium sp. enhance phytoremediation of sulfentrazone-contaminated soil?

Abstract Symbiosis among herbicide-metabolising microorganisms and phytoremediation plants may be an efficient alternative to remediate sulfentrazone-contaminated soils. This work evaluated the bioremediation of sulfentrazone-contaminated soils by symbiosis between bacteria (Bradyrhizobium sp.) and jack bean (Canavalia ensiformis L.). The experiment was carried out in a greenhouse between March and May of 2018, in the Universidade Federal do Espirito Santo (UFES). Four doses of sulfentrazone (0, 400, 800, and 1200 g ha−1 a. i.) were tested with and without inoculation with Bradyrhizobium sp. BR 2003 (SEMIA 6156) After 80 days of cultivation, plants were cut and soil was collected for determination of the herbicide residual levels and millet bioassay. The sulfentrazone concentration was significantly reduced by plant inoculation with Bradyrhizobium sp.: on average, concentrations were 18.97%, 23.82%, and 22.10% lower than in the absence of inoculation at doses of 400, 800, and 1200 g ha−1, respectively. Symbiosis promoted a reduction of up to 65% in residual soil herbicides. Under the 1200 g ha−1 dose, inoculation promoted greater plant height than in the uninoculated plant. Regardless of the dose of sulfentrazone, the dry root mass was higher in the inoculated plants. The microbiological indicators showed satisfactory results mainly for the dose of 400 g ha−1. The results of this study highlight the potential of positive interactions between symbiotic microorganisms and leguminous species, aiming toward the phytoremediation of sulfentrazone herbicide.