Calagem na lixiviação de picloram em latossolo vermelho amarelo distrófico

Abstract

Picloram is a herbicide widely used in Mato Grosso in pastures. It presents long persistence in the soil, which can impact the environment, due to its high leaching potential. Studying the leaching process of herbicides while maintaining soil integrity is of great importance, as it assists in understanding soil dynamics. In addition, the liming effect, which is widely used in tropical soils, may be one of the determining factors in the behavior of this herbicide in the soil. Thus, the objective of this work was to determine the leaching of the herbicide picloram in a dystrophic Yellow Red Latosol, with or without soil pH correction. The experiment was organized in a completely randomized design (DIC), in the plot of subdivided plot, with factorial in the plot. The plot factors corresponded to 2 soil conditions (without and with liming) and 5 doses of picloram (0, 384, 768, 1152, 1536 g e.a. ha-1 ), and the subplot factor were 5 soil depths (0- 8, 8-16, 16-24, 24-32 and 32-40 cm) with four replicates. For this, PVC pipes 15 cm in diameter and 40 cm in length were introduced in the soil and limestone applications were applied in part of the treatments. Three months after soil correction, picloram was applied to the surface of each tube at 5 doses (384, 768, 1152, 1536 g per ha-1 , in addition to the control), allowing a natural precipitation accumulated at 128 mm. Subsequently, the tubes were removed from the soil and taken to greenhouse, where seeds of cucumber (Cucumis sativus) were sown at the following depths: 0 a 8, 8 a 16, 16 a 24, 24 a 32 and 32 a 40 cm. The cucumber was the bioindicator species of the presence of picloram in each depth. Cucumber development evaluations (phytotoxicity, aerial weight, leaf area) were performed 21 days after sowing. There was a high rate of leaching of the herbicide picloram in the Latosol Yellow Latosol (LVAd), where it was possible to be verified through the evaluations of the development of the bioindicator plant. It was concluded that the leached intensity of the picloram was reduced along the soil profile, independently of the application of limestone. The application of surface limestone increases the leaching of picloram at doses 384 and 768 g ha-1 .