Manejo de plantas daninhas em lavouras de soja do sul do Brasil e impacto na produtividade

Abstract

The productivity and quality of soybean grains can be compromised by several factors, including competition with weeds. Despite the technological advances obtained with the evolution of herbicides, weeds have also shown evolution of resistance to the mechanisms of action of these molecules. Soybean crops can experience 52% productivity loss due to competition with weeds. In this sense, the objective of this work was to evaluate the relationship between weed management practices adopted by soybean producers in Southern Brazil and grain productivity. 805 interviews were carried out in 208 municipalities in the state of Rio Grande do Sul, where farmers provided information on weed management and the resulting productivity for soybean crops. Horseweed (Conyza spp.) was the most economically important weed for producers. Furthermore, management practices that do not involve chemical control, such as crop rotation and fall/winter cover crops, had higher productivity results (4,266 kg ha-1 and 4,152 kg ha-1, respectively). Mixing herbicides in a tank was the main resistance management practice declared by producers (40.5% of responses). Growers who applied tank mixes with ALS inhibitors + auxin mimics and ALS inhibitors alone demonstrated better results (3,939 kg ha-1 and 3,723 kg ha-1, respectively). Among the producers interviewed, 89% said they used a direct planting system, which showed greater productivity compared to the conventional cultivation system. This study highlights the importance of producers' knowledge regarding weeds, as well as demonstrating that the appropriate use of integrated management techniques reduces productivity losses related to weed resistance.