The residues of Canavalia ensiformis and Crotalaria juncea after phytoremediation in soil contaminated with sulfentrazone do not result in soil recontamination

Abstract

Phytoremediation is an alternative for the decontamination of areas that have received intense applications of herbicides. This study aimed to verify the reuse possibility of Canavalia ensiformis and Crotalaria juncea as green manure and the influence of the vegetation cover after phytoremediation of soil contaminated with sulfentrazone on the growth and development of Pennisetum glaucum. Two experiments were carried out in a greenhouse. One of the experiments was conducted with C. juncea and the other with C. ensiformis, two phytoremediation species of the sulfentrazone herbicide. The experiments were set up in 4 x 3 factorial, with the first factor being four population densities of the phytoremediate species (C. juncea - 0, 60, 120 and 240 plants m-2; C. ensiformis - 0, 10, 20 and 40 plants m-2), and the second composed by three sulfentrazone doses (0, 200 and 400 g ha-1). Seventy-five days after emergence (DAE), the plants were collected by separating the aerial parts and roots to determine the sulfentrazone accumulation in the plants by using high performance liquid chromatography. Plant extract was prepared from the vegetable material and applied in pots containing washed sand, followed by the sowing of the indicative plant (Pennisetum glaucum). It was evaluated as to its phytotoxicity plant height, aerial part and roots dry matter. P. glaucum cultivated in the substrate that received leaf extract from C. ensiformis and C. juncea cultivated in soils with presence of sulfentrazone did not display any intoxication symptom to this herbicide. The extracts from Canavalia ensiformis and Crotalaria juncea were not phytotoxic to the millet, indicating that these species can be used as green fertilization after phytoremediation of the sulfentrazone in the soil.