Espécies cultivadas no inverno com potencial fitorremediador de solos contaminados com herbicidas

Abstract

Phytoremediation is a technique for depollution of contaminated areas that has been gaining prominence in recent years, being an economical, simple and efficient way to remove mainly herbicides from the soil. Therefore, the objective of this work was to evaluate the potential of cover crops sown in winter to phytoremediate soil treated with the herbicides diuron, sulfentrazone and diuron + sulfentrazone. The experiment was carried out in the field, in a randomized block design, arranged in a factorial scheme, with four replications. The herbicides diuron (490 g ha-1 ), sulfentrazone (245 g ha-1 ) and diuron + sulfentrazone (490 + 245 g ha-1) were applied in pre-emergence of phytoremediating species (black oat - Avena stigosa, vetch - Vicia sativa, rye - Secale cereale, turnip - Raphanus sativus, buckwheat - Fagopyrum esculentum, ryegrass - Lolium multiflorum, lupine - Lupinus albus, mixtures of black oats + vetch + rye + turnip + ryegrass) and uncultivated soil. At 7, 14, 21, 28 and 35 days after emergence (DAE) phytotoxicity assessments of the species were carried out. At 75 DAE the species were sectioned close to the ground, placed in kraft paper bags, dried in ovens to determine the dry mass of the aerial part (g). In the second stage, the species that are bioindicators of soil depollution were sown, the sunflower and sorghum crops. In sunflower and sorghum, at 55 days after sowing (DAS) gas exchanges were analyzed and at harvest the weight of a thousand grains and grain yield were determined. Diuron caused less phytotoxicity to all species tested as potential soil phytoremediators. Vetch and lupine showed less phytotoxicity to diuron, sulfentrazone and diuron + sulfentrazone and can be used as soil phytoremediators. Dry mass production of rye shoots was not affected by the application of the tested herbicides. The gaseous exchanges of sorghum and sunflower show alternating behavior against the use of herbicides and winter coverings with phytoremediation potential. The weight of a thousand seeds of sunflower was higher when using lupine and buckwheat as soil depolluting plants for the control without herbicide and the use of diuron, respectively. The highest sunflower grain yield occurred in bare soil for the control without herbicide application, lupine for sulfentrazone use and black oats when diuron + sulfentrazone was applied. In general, sulfentrazone was the treatment that showed the greatest negative effects, affecting the thousand-grain weight of sorghum compared to other herbicides. The highest sorghum grain yields were obtained in the control without herbicide, for diuron, sulfentrazone and diuron + sulfentrazone when using buckwheat, ryegrass, mixture of species and black oats as depolluting covers, respectively.