Manejo de plantas daninhas com herbicidas pré-emergentes associados ao glufosinate de amônio em soja com tecnologia Enlist®

Abstract

The use of pre-emergent herbicides in soybeans has increased in recent years, mainly to control weeds that are tolerant or resistant to glyphosate. Therefore, the objective of this study was to evaluate the phytotoxicity and weed control when applying herbicides in the pre-emergence of soybeans and associated with these glufosinate ammonium in the postemergence. The experiments were conducted in the field, in two agricultural harvests (2022/23 and 2023/24) in a randomized block design, with four replications. The treatments used were: two controls, one weeded and the other infested, the pre-emergent herbicides; pyrazosulfuronethyl+ flumioxazin (120 + 80 g ha-1), diuron+sulfentrazone (490 + 245 g ha-1), imazethapyr+flumioxazin (127 + 60 g ha-1), sulfentrazone+imazethapyr (360 + 96 g ha-1), Smetolachlor+ fomesafen (1036 + 240 g ha-1) applied alone and/or associated with glufosinate ammonium (600 g ha-1) in post-emergence. The phytotoxicity of the herbicides and the control of milkweed, radish and Alexandergrass were evaluated from 7 to 42 DAT (days after application of the treatments). At 21 DAT, the physiological variables of soybean were measured. At harvest, the grain yield components (number of pods and grains per plant, thousand-grain weight and grain productivity) were determined. All herbicides used, alone or in combination, were selective for the Brasmax Venus soybean cultivar, with the symptoms of phytotoxicity disappearing as the crop developed. Glufosinate ammonium, when applied postemergence in combination with the pre-emergence herbicides pyrazosulfuronethyl+ flumioxazin, diuron+sulfentrazone, imazethapyr+flumioxazin, sulfentrazone+imazethapyr and S-metolachlor+fomesafen, improved the control of milkweed, radish and Alexandergrass. There was an increase in turnip control by glufosinate ammonium when applying pyrazosulfuron-ethyl+flumioxazin, diuron+sulfentrazone, imazethapyr+flumioxazin, sulfentrazone+imazethapyr and S-metolachlor+fomesafen in the pre-emergence of soybean. The application of diuron+sulfentrazone and Smetolachlor+ fomesafen+glufosinate ammonium caused negative effects on the physiological characteristics of soybean. The use of pyrazosulfuron-ethyl+flumioxazin, imazethapyr+flumioxazin, sulfentrazone+imazethapyr, pyrazosulfuronethyl+ flumioxazin+glufosinate ammonium, diuron+sulfentrazone+glufosinate ammonium, sulfentrazone+imazethapyr+glufosinate ammonium and Smetolachlor+ fomesafen+glufosinate ammonium were the treatments that demonstrated the best results of the soybean grain yield components, with grain productivity being higher than the weeded control. The lack of weed control caused soybean grain losses of over 88%.