Influence of cover crop termination strategies on weed suppression, concentration of residual herbicides in the soil, and soybean yield

Abstract Cover crops and soil-residual herbicides are considered essential tools within integrated weed management practices. However, interception of soil-applied herbicides by cover crop residue can reduce weed control and crop yield. Field trials were conducted in 2022 and 2023 in Indiana to investigate the effect of cereal rye ( Secale cereale L.) termination strategies on the concentration of sulfentrazone, S -metolachlor, and cloransulam-methyl in soil, weed control, and soybean [ Glycine max (L.) Merr.] yield. Soybeans were planted at cereal rye anthesis. Termination strategies included roller-crimped cereal rye, standing cereal rye, and a fallow control. The average cereal rye biomass in 2022 and 2023 was 4.06 and 14.2 Mg ha −1 , respectively. Soybean stands were unaffected in 2022 but were reduced by 24% and 69% in the presence of roller-crimped and standing cereal rye, respectively, in 2023. On average, 75% and 84% of the soil-residual herbicides applied were intercepted by the roller-crimped cereal rye residue in 2022 and 2023, respectively. The use of cereal rye did not improve overall weed control relative to fallow at 18 after soybean planting in 2022 and 2023. In 2022, roller-crimped cereal rye reduced soybean yields by up to 13% in comparison with the fallow. In 2023, regardless of management strategy, the use of cereal rye as a cover crop reduced soybean yields by an average 44% in comparison to the fallow. Results from this research suggest that the adoption of the planting green system can significantly reduce soybean yield primarily due to stand losses if proper planting equipment is not used. Furthermore, the high levels of cereal rye biomass achieved in both years of the study did not provide additional season-long weed suppression relative to the non-cover crop control.