Dissipação de imidazolinonas em solo de cultivo de arroz irrigado

Abstract

Herbicides used in the Clearfield® rice production systen are characterized by their high mobility and persistence in the environment. Association of environmental factors and physicochemical properties of molecules are the main factors for these herbicides behavior. Moreover, the irrigation management adopted directly affects by rice farmer’s influence these herbicides’ dynamics. Knowledge about the dynamics of these molecules in soil does not occur in a timely manner, but by analyzing the behavior of all the above conditions. Four studies were conducted at the Federal University of Pelotas in the years of 2010/11 and 2011/12, aiming to understand the effects of environmental degradation and transport of imidazolinones. The first study aimed to evaluate the effects of different managements of water irrigation in the leaching of herbicides belonging to the imidazolinone chemical group (Paper 1). The second study aimed to evaluate the runoff of herbicides used in irrigated rice with different rainfall and periods after application (Paper 2). The third study aimed to verify the effects of temperature and soil moisture on the degradation of imidazolinone herbicides (Paper 3). The fourth objective was to evaluate the rate of CO2 emission from soil with and without a history of application of formulated mixtures imazethapyr+ imazapic and imazapyr+imazapic treated with different imidazolinone herbicides (Paper 4). With these results, we concluded that the formulated mixture Imazapyr + imazapic showed the largest leaching, for the herbicides alone; imazapic was the most leached, followed by imazethapyr and imazapyr; continuous and intermittent irrigation managements did not differ and led to greater leaching potential of herbicides compared to the soil at field capacity 11 (Paper 1). Clomazone and penoxsulam herbicides show the highest average mass values carried by runoff, high volumes of rainfall after application of herbicides promote greater runoff (Article 2). High temperatures associated with anaerobic soil promote further degradation of imidazolinone in lowland (Article 3). Imazametabenz herbicide has faster accelerated degradation in soils with history of application of Imazethapyr + imazapic; soils with history of Imazapyr + imazapic inhibit microbial populations able to degrade imidazolinone (Article 4).