Dinâmica de atrazina e clorpirifós em lisímetro cultivado com milho (Zea mays L.).

Abstract

The use of pesticides is essential in agriculture in the current contexto. Several molecules are used to control adverse factors that can damage agricultural production. Atrazine is na importante herbicide from the group of triazines widely used in weed control. Chlorpyrifos is na inseticide belonging to the group of organophosphates used to minimize the impact of insect pests both of wich are used in corn growing. After the application of pesticides in the environment, these substances can udergo several interactions that will dependo n combinations between edaphoclimatic factores and physical and chemical properties inherent to each compound being subject to process of transformation, retention and transport. The result of these combinations in certain situation can compromisse the quality of the environmental compartments, including surface and underground water. Thus, the presente work aims to evaluate the transport of pesticides molecules, by determining the surface runoff and percolation of the molecules of the herbicide atrazine and insectside chlorpyrifos in a Oxisol growing with corn, using suction and percolation lysimeters. In addition, the study aims to evaluate the influence of simulated precipitation in diferente phenological stages of summer and winter maize during two agricultural Years and the possibility of percolation and runoff of pesticides and contamination of surface and groundwater. For that, a percolation lysimeter was used with an undisturbed soil sample (1m³) and suction lysimeters were used to conduct the field study, with the objective of evaluating the transport of atrazine, by determining the runoff and percolation in Oxisol cultivated with corn. Atrazine transport was evaluated under the influence of simulated precipitation (150 mm h-¹), 24 h and 48 h after application of the pesticide, in different phenological stages of crop and off-season corn during two agricultural years (2019/2020), being the determinations performed by Gas Chromatography with ECD detection (GC-ECD). According to the results obtained, there was a greater sorption capacity of atrazine in oxisol at lower temperatures (15 ºC). In runoff 24 h after application of atrazine, the highest concentrations and highest frequency of detections were obtained. Its presence was detected in 26% of the total samples, with the highest concentrations being higher than permitted by law. Regarding chlorpyrifos, the results suggest that temperatures above 25 ºC favor the insecticide sorption process, while at lower temperatures the adsorptive capacity is reduced. The sorption of the insecticide in this type of soil occurs mainly due to the interaction with the mineral fraction, with little influence of the organic matter content. The highest concentrations and the highest number of detections occurred in runoff samples 24h after the application of the insecticide in crop corn. Its presence was detected in 60% of the total samples, and the highest concentrations were higher than allowed by the legislation. The results warn of the risk of contamination of surface waters by atrazine and chlorpyrifos, mainly in events of intense precipitation in a short period of time after the application of the pesticides. Keywords: