Pre-emergence herbicides mixture in soybeans: Amaranthus hybridus control and crop selectivity on cover crops soil.

The objective was to evaluate the efficacy of pre-emergence herbicides mixture applied to the soil with and without dead cover crops ( Sorghum bicolor ) for the control of Amaranthus hybridus L. (smooth pigweed) and its selectivity in soybeans. This study was structured in split plot (2 × 6 + 2), where factor A plots (with and without dead cover) and factor B six herbicides mixture: flumioxazin + S-metolachlor (50.4 + 1,008 g a.i. ha -1 ), flumioxazin + imazethapyr (60 + 127.2 g a.i. ha -1 ), pyroxasulfone + sulfentrazone (137.6 + 160 g a.i. ha -1 ), diuron + sulfentrazone (400 + 200 g a.i. ha -1 ), metribuzin + S-metolachlor (326.4 + 1,344 g a.i. ha -1 ) and sulfentrazone + imazethapyr (200 + 100 g a.i. ha -1 ) and two untreated control plots. As for the results, the herbicides flumioxazin + S-metolachlor, flumioxazin + imazethapyr and pyroxasulfone + sulfentrazone showed excellent control (97-99%) and were not influenced by the plot with and without dead cover. They also showed higher yield soybeans (<2,244 kg ha -1 ). All herbicides were selective to the soybeans. Overall, pre-emergence herbicides and cover crops were efficient methods for the control of A. hybridus , which farmers should use to avoid losses in yield soybeans due to weed competition.