“CARRYOVER” DE HERBICIDAS PARA DESTRUIÇÃO DE SOQUEIRAS DE ALGODÃO NA SUCESSÃO ALGODÃO-SOJA

Abstract

After the cotton harvest, the crop residues must be destroyed to mitigate the risks of pest and disease proliferation. Among the usual methods, the chemical is widely spread. However, the use of herbicides can cause the “carryover” effect in soil and impair the development and productivity of the subsequent crop. The objective of this work was to evaluate the carryover effect of treatments with herbicides used in the destruction of cotton ratoons in soybean. The work was developed in two parts. Part 1: a 5x4 factorial experiment was installed, with 5 herbicide treatments in 4 sowing periods after herbicide application (0, 3, 6 and 9 days) with four replications. Soybean cultivar 80IX83RSF I2X was sown in 5 L pots placed in a greenhouse. The treatments had the herbicide 2,4-D (1 L.ha-1) associated with glufosinate ammonium (2 L.ha-1); carfentrazone-ethyl (0.05 L.ha-1); flumiclorac-pentyl (0.6 L.ha-1) and saflufenacil (0.07 g.ha-1). In this, visual phytotoxicity, chlorophyll index, plant height, shoot, root and nodules dry mass and the number of nodules were evaluated. Non-parametric (Kruskal-Wallis at 5% probability) and parametric (Dunnett 5%) statistics were used for data analysis. Part 2: yield data for soybean cultivars TMG-4182 and TMG-4377 in 56 plots were analyzed in terms of herbicide applications for destruction of cotton ratoons in succession. The 5% Tukey test was used. It is concluded that the possibilities of negatively impacting the number of nodules is greater when soybean sowing occurs close to the herbicides 2,4-D + ethyl carfentrazone and 2,4-D + glufosinate ammonium salt applications. TMG-4182 and TMG-4377 soybean yields were not influenced by herbicide applications before sowing for the purpose of destroying cotton ratoons.