Performance of pre-emergence herbicides in weed competition and soybean agronomic components

Abstract

Soybean is the most important oilseed over the world. Different factors interfere in its development, among them, the interference of weeds. Thus, the objective was to analyze the performance of pre-emergence herbicides on the weed competition and agronomic components of soybean. For this, an experiment was carried out in commercial farming. The experimental design was in randomized blocks with three treatments and nine repetitions. The following treatments were tested: S-metolachlor (1,152 g a.i. ha-1); diclosulam (35 g a.i. ha-1; 42 g a.i. ha-1) + imazethapyr (164.8 g a.i. ha-1). Two phytosociological surveys were carried out at 21 and 32 days after sowing (DAS) for controlling the weed competition. At 14, 21, 32, and 37 DAS, stem height and diameter were analyzed, while at 115 DAS, the production components were estimated. The application of S-metolachlor (1,152 g a.i. ha-1) was efficient for pre-emergence weed control of weed competition in commercial soybean crops. Through this treatment, the conventional cultivar Ansc 89109 produced between 130,5 and 255,8 kg per hectare, this result is superior those obtained in plots treated with diclosulam (35 g a.i ha-1) + imazethapyr (164.8 g a.i. ha-1) and diclosulam (42 g a.i. ha-1) + imazethapyr (164.8 g a.i. ha-1). Thus, the application of higher-doses of diclosulam (42 g a.i. ha-1) in a mixture with imazethapyr (164.8 g a.i. ha-1) is not recommended since it presents eminent agronomic, environmental, and economic risks.