Lixiviação de herbicidas do grupo químico das imidazolinonas em solos de cultivo de arroz irrigado

Abstract

Herbicides are used intensively in agriculture as an important tool in obtaining high yield and quality products. In irrigated rice, herbicides belonging to the imidazolinone chemical group, are an effective alternative for controling major weeds, among them, the red rice. However, the dynamics of these herbicides in the environment should be clarified to avoid contamination of surface and groundwater and to reduce carryover effects on non-tolerant crops. Therefore, three studies were conducted at the Universidade Federal de Pelotas in the years 2010/11 and 2011/12. In article I the objective was to evaluate the effect of different rice soils in the leaching of imazethapyr, imazapyr and imazapic. In article II, the objective was to evaluate the effect of increasing soil pH by liming on leaching of imazethapyr and imazapyr. Lastly in article III, the objective was to evaluate the persistence and leaching of the herbicide imazethapyr, and formulated mixtures of imazethapyr + imazapic and imazapyr + imazapic in irrigated rice field. With the results of this dissertation, it was conclude that the soil with low clay and organic matter have greater leaching of herbicides, with injury symptoms in non-toletant rice cultivar being detected to a depth of 30 cm. Leaching is lower in soils with higher clay and organic matter. Elevation of soil pH by liming increases leaching of the herbicide imazapyr and imazethapyr in irrigated rice soil. Moreover, it can be concluded that herbicides imazethapyr and formulated mixtures of imazethapyr + imazapic and imazapyr + imazapic have high leaching potential, reaching depths of up to 25 cm in irrigated rice soil one year after their application. The imidazolinone herbicides used in the Clearfield™ rice system have high persistence in soil and their phytotoxic effects can be observed up to two years after application.