Avaliação do efeito residual de herbicida clomazone aplicado em solos com textura argilosa e arenosa, em diferentes doses, ao longo do tempo.
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Abstract
The incidence of weeds stands out as one of the main challenges in Brazilian crops. For control, the most commonly used method is the application of herbicides, which, in turn, requires conscious and effective application. These precautions are related to the final fate of these compounds, i.e., their residual effect. This study aimed to evaluate the residual effect of the herbicide clomazone, recommended for pre-emergence application in irrigated rice and sugarcane crops, considering the interactions between the applied dose, soil texture, and depth. The field experiments were conducted in an experimental area with a Yellow-Red Latosol soil type. For both field experiments (1 and 2), the same methodologies were used. Experiments 1 and 2, carried out with sandy and clayey soils, respectively, followed a randomized block design in a 4 x 2 factorial scheme. Factor 1 included 4 doses, ranging from 0 to 150% of the recommended rate on the product’s commercial label, and factor 2 involved two depths, with 4 repetitions, totaling 32 plots. The residual effect of the herbicide was determined through bioassays. In addition, a chromatographic analysis at 93 days after application (DAA) was conducted to quantify herbicide residues. Data analysis showed that clomazone causes injury to bioindicator plants up to 33 DAA at doses of 360 and 720 g ha-1, and up to 63 DAA at a dose of 1080 g ha-1 in the 0-10 cm soil layer for both sandy and clayey soils. The remaining clomazone at 93 DAA in the sandy soil, at doses of 360, 720, and 1080 g ha-1 at a depth of 0-20 cm, was 117.3 g ha-1; 260.8 g ha-1; and 376.2 g ha-1, respectively. For the clayey soil, the recovered amounts at these same doses and depths were 120.3 g ha-1; 252.9 g ha-1; and 281.9 g ha-1. Thus, it is concluded that clomazone persists in the soil after application, with the residual amount varying according to the dosage used and the soil depth.