Field experiments were conducted in 2013, 2014, and 2015 in Columbia and Moberly, Missouri to determine the effects of cereal rye, Italian ryegrass, winter wheat, winter oat, crimson clover, Austrian winterpea, hairy vetch, oilseed radish, and cereal rye plus hairy vetch on winter and summer annual weed emergence in soybean. For comparison purposes, each experiment in each year included a Fall PRE, Spring PRE without residual, and Spring PRE residual herbicide programs. Cereal rye and cereal rye plus hairy vetch reduced winter annual weed emergence by 72 and 68%, respectively, but were not comparable to the Fall PRE which reduced winter annual weed emergence by 99%. The following spring, early-season waterhemp emergence was similar among treatments of cereal rye, cereal rye plus hairy vetch, and the Spring PRE residual herbicide program. In contrast, all cover crop species other than Italian ryegrass reduced late season waterhemp emergence between 21 and 40%, but were not comparable to the Spring PRE residual herbicide program, which reduced late season waterhemp emergence by 97%. All other summer annual weeds excluding waterhemp showed a similar response among cover crop and herbicide treatments. Overall, results from this experiment indicate that certain cover crops are able to suppress winter and summer annual weed emergence, but not to the extent of soil-applied residual herbicides.
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