Weed Control J 2021; 20: e202100772

ISSUE Cover

Efficacy and selectivity of residual herbicides associated with cover crops in soybean.

DOI: 10.7824/wcj.2021;20:00772

Abstract

Introduction

Obtaining good results in the no-tillage system is directly related to the adequate management of cover crops, combined with an efficient chemical control of weeds, involving residual herbicides.

Objective

To evaluate the effectiveness and selectivity of two mixtures of residual herbicide molecules (imazethapyr + flumioxazin and imazethapyr + saflufenacil) in different cover crops in soybean cultivated in the plant-apply system.

Methods

A completely randomized design was used, in a 3×3 factorial scheme, consisting of nine treatments and four replications. The treatments used were based on the application of imazethapyr + flumioxazin and imazethapyr + saflufenacil and the absence of herbicide, applied on three plant covers: millet, brachiaria and fallow previously desiccated with glyphosate at 1.44 kg ha-1 of acid equivalent + clethodim at 192 g ha⁻ ¹ of active ingredient. The following were evaluated: weed population density, phytotoxicity with the distance between canopies of the plant mass between the rows, biometric and productive characteristics at the end of the soybean crop cycle.

Results

The results showed that the use of cover crops reduced weed infestation, although it did not eliminate the use of residual herbicides.Conclusions: Braquiaria had the greatest effect on weed suppression. The competition caused by the weed community resulted in a reduction of soybean grain yield by around 25%. The treatments of imazethapyr associated with saflufenacil or flumioxazin were selective for soybean cultivar Syn 1163 RR, for the conditions in which this study was carried out.