Effects of Cereal and Legume Cover Crop Residues on Weeds, Yield, and Net Return in Soybean (Glycine max)1

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Abstract
A 2-yr field study was conducted during 1998 and 1999 at Stoneville, MS, on a Dundee silt loam to determine weed control, yield, and net return associated with winter cover crops in soybean. Cover crop systems included Italian ryegrass, oat, rye, wheat, hairy vetch, crimson clover, subterranean clover, no-cover crop conventional tillage (CT), and no-cover crop no-tillage (NT), all with standard preemergence (PRE), postemergence (POST), PRE + POST, and no-herbicide weed management. Oat (11.1 Mg/ha) had highest dry biomass compared to all other cover crops (6.0 to 7.6 Mg/ha) at soybean planting. Biomass decreased 9 wk after planting (WAP) compared to the respective biomass at soybean planting in all cover crops. Italian ryegrass and rye biomass decay was slow and about two-thirds of plant residue persisted at 9 WAP. Cover crops had no effect on densities of barnyardgrass, prickly sida, and yellow nutsedge, but altered the density of browntop millet. Total weed biomass was higher in rye, wheat, and subterran...