Weed management with pre-emergent herbicides in soybean crops

Abstract

The use of pre-emergent herbicides in soybean crops is fundamental, among other reasons, to maintain a clean crop in the initial stages, alter mechanisms, and consequently manage weed resistance. However, there is a considerable demand for information about the efficiency and selectivity of systems with residual herbicides applied in different modalities. This study evaluated the efficiency and selectivity of pre-emergent herbicides doses applied singly or mixed in a tank on soybean crops. The experiment was installed in randomized block design with 21 treatments and four repetitions. The treatments were composed of weeded and unweeded witnesses and pre-emergent application of isolated S-metolachlor or the herbicides diclosulam, flumioxazin, and sulfentrazone isolated or together with S-metolachlor in different doses with the addition of post-emergent S-metolachlor (soybean stage V2). Associations of residuals herbicides applied in pre-emergence or sequential mode increased the control levels of mono and dicotyledonous weeds. The treatments, including single or associated diclosulam and the systems with S-metolachlor sequentially, caused the most significant toxicity (up to 17%) for soybeans. High doses of S-metolachlor (2592.0 g ha-1), diclosulam (33.6 g ha-1), and the associations of S-metolachlor + diclosulam, S-metolachlor + flumioxazin, and S-metolachlor + diclosulam with sequential S-metolachlor should be avoided to obtain higher levels of soybean yield. The use of pre-emergent herbicides demonstrated to be an efficient and viable option to control weeds in soybean crops.