Field experiments were conducted from 2021-2023 to evaluate how mechanical rolling methods and termination timing of cereal rye affects horseweed (Conyza canadensis L.) suppression and soybean yield. At the time of postemergence (POST) herbicide application, cereal rye terminated prior to soybean planting provided less ground cover, which led to more horseweed than the delayed terminations. Horseweed suppression was not influenced by flattening cereal rye with a roller, roller-crimper, or cultipacker. At soybean harvest, cereal rye reduced horseweed biomass 44 to 91%. Applying an effective POST herbicide after these treatments further improved horseweed control. Delaying cereal rye termination until unifoliate soybean, regardless of termination method, hindered soybean growth and development, leading to an 18 to 93% reduction in yield. Cereal rye termination time more than method affected horseweed suppression and soybean yield. Separate field experiments were also conducted to determine cover crop sensitivity to carryover from spring-applied winter wheat herbicides (8 site-years) and cover crop establishment from postharvest herbicide applications (5 site-years). From 8 site-years, all nine cover crop species were safe to plant following spring applications of eight commonly used winter wheat herbicides. All cover crops were also safe to plant following postharvest glyphosate and glufosinate applications. Annual ryegrass, cereal rye, and oat were safe to plant following postharvest saflufenacil and 2,4-D. However, saflufenacil should not be applied before crimson clover, red clover, mustard, oilseed radish, or dwarf Essex rapeseed. Do not apply 2,4-D prior to seeding Austrian winter pea, crimson clover, or red clover.
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