MANEJO DE PLANTAS DANINHAS COM HERBICIDAS PRÉ-EMERGENTES NA CULTURA DA SOJA

Abstract

Brazil stands out as the largest soybean producer in the world. The coexistence of the soybean crop with weeds reduces production. Currently, avoiding competition is a challenge for soybean farmers. Faced with the difficulties of controlling some weeds in post-emergence, this research aimed to evaluate the control of weeds with pre-emergent herbicides applied in soybean crops, and also to evaluate the residual effect of herbicides for corn crops, sorghum and Urochloa ruziziensis cultivated in succession. The experiment was conducted under field conditions, in the 2020/2021 crop, in an area of commercial farming, in the Municipality of Rio Verde, Goiás. The treatments were added to the sourgrass management, applied with a pressurized backpack sprayer. Management was carried out in pre-sowing, with application of the herbicide glyphosate in combination with the herbicide Cletodim. Sowing was carried out in no-tillage, with minimal soil disturbance, conducted in a randomized complete block (CBD) design with four replications and eleven treatments. The parameters evaluated at 7, 14, 21 and 35 DAA in soybean cultivation were: plant phytotoxicity, weed emergence, by counting the number of weeds with the sampler square with 0.5 m side. In full bloom, the stand and dry biomass of soybean plants were evaluated. At harvest, the productivity was evaluated in four linear meters of the two central lines for the soybean crop. After the soybean harvest, four rows of corn, sorghum and U. ruziziensis were sown in twenty square meters of the plots. The stand and phytotoxicity were evaluated at 7, 14, 21, 28 and 35 days after emergence of corn and sorghum crops and productivity in four linear meters of the two central lines. In U. ruziziensis, phytotoxicity and soil cover percentage were evaluated 7, 14 and 21 days after emergence and dry mass at 110 days after emergence in eight square meters in the center of the plot. In soybean, the use of herbicides did not cause phytotoxicity. The evaluations showed that all herbicide managements were efficient in reducing weed coverage. The weeded control showed the highest dry mass and soybean plants and the treatments with Sulfentrazone and Diclosulan + Clomazone showed the highest yields. In sorghum cultivation, there was no difference in stand, with the managements with Sulfentrazone and Diclosulan + Clomazone having the highest yields. In corn, treatments did not show differences in stand and managements with Sulfentrazone, Sulfentrazone+Clomazone, Sulfentrazone+Imazetapir, Sulfentrazone+Diclosulan, Diclosulan+Clomazone, Diclosulan and Stone showed higher yields, with a significant difference compared to the other managements, and for the cultivation of U. ruziziensis, there were no differences in the percentage of cover and dry mass at 110 days after emergence.