Responses of waterhemp and horseweed to cereal rye cover crop termination timing in soybean

Abstract

Field experiments were conducted in soybeans (Glycine max L.) to determine the effects of a cereal rye (Secale cereale L.) cover crop (CC), two CC termination timings (TTs), and four herbicide programs (HP) on the emergence, biomass, and seed production of waterhemp (Amaranthus tuberculatus [Moq.] J.D. Sauer) and horseweed (Erigeron canadensis L.). The early cereal rye CC termination occurred seven days (d) before soybean planting, and the late termination occurred 12 days after soybean planting. The presence of a cereal rye CC, regardless of the TT, reduced waterhemp emergence by 39% and 44% compared to no CC at 5 and 10 weeks after planting (WAP), respectively. The late termination of the CC reduced waterhemp population density and biomass by 49% and 44%, respectively, compared to no CC 10 WAP. The presence of a cereal rye CC reduced horseweed population density and biomass at 5 WAP by 90% and 80%, respectively, compared with no CC. Horseweed seed production was 89% lower with a CC compared to no cover crop and was reduced to 0 seeds plant⁻¹ at the late TT. Delayed cereal rye CC termination reduced soybean plant width but not yield. This research highlights the utility of multi-tactic strategies for controlling waterhemp and horseweed in soybeans.