Fitorremediação e emissão de CO2 de solos de mata nativa e de lavoura contaminados com os herbicidas imazapir+imazapique e imazetapir

Abstract

The excessive use of pesticides in agriculture in Brazil is causing many negative impacts on the environment. The exclusive use of herbicides from the chemical group of imidazolinones in the Clearfield® system, used in large scale, mainly in Rio Grande do Sul, to combat red rice weed in flooded rice fields can cause problems in sensitive crops due to their residual effect in the soil. These substances can cause impacts that are difficult to predict due to the complexity of the relationship between contaminant/soil, and are easily leached into groundwater and surface waters. Bioremediation is a technique that uses microbial community and plants (phytoremediation) in the degradation, extraction, stabilization, metabolization and/or compartmentalization of the pollutant in the soil or water. In view of the above, the present work aimed: 1) to evaluate the CO2 emission of native forest soil and tillage soil, with and without cover residues, contaminated with the herbicides imazethapyr and imazapyr+imazapic in three different doses; 2) to evaluate the remedial potential of the species Lotus corniculatus and Lolium multiflorum using Raphanus sativus as bioindicator, through the dry matter production of the shoot tissue of the three species - including in the bioindicator the germination rate analysis -, in native forest soil and tillage soil, contaminated with imazapyr+imazapic in three doses. The results showed that soil was the main factor influencing the microbial activity in the study of CO2 emissions, with and without cover residue, and in the study of phytoremediation, being the native forest soil the one who provided the greatest emission of gases, dry matter production of the shoot and germination rate. Different doses did not influence the rate of CO2 emission, dry matter production and germination. The imazapyr+imazapic was responsible for the greater significant emission of CO2 in the soil of native forest, presenting statistical difference when compared to imazethapyr in the experiment without cover residue. There was no statistical difference between the remediator species.