Field studies were conducted to compare preplant-postemergence-applied paraquat, glyphosate, SC-0224, and HOE-39866 on subterranean clover, crimson clover, and hairy vetch cover crops. Subterranean clover control with paraquat at 1.1 kg ai/ha was about 80 and 100% when applied in early April and early May, respectively, regardless of spray volume (190 vs. 370 L/ha). Glyphosate and SC-0224 at 1.7 and 2.8 kg ai/ha applied in April controlled about 53% of subterranean clover. Subterranean clover control with HOE-39866 at 0.8 kg ai/ha applied in April was excellent. Paraquat at 0.6 kg ai/ha and HOE-39866 at 0.8 kg/ha regardless of application time controlled both crimson clover and hairy vetch. Grain sorghum and soybean yields following the legume cover crops generally were similar for the herbicide treatments.

Eight herbicide treatments per crop were evaluated for hairy vetch and crimson clover cover-crop control in no-till corn and cotton at two locations in North Carolina. Paraquat alone or combined with dicamba, 2,4-D, or cyanazine, and cyanazine alone, controlled clover the best in both crops. All herbicide treatments, except glyphosate alone, controlled at least 89% of hairy vetch in corn. However, only 2,4-D and cyanazine alone or combined with glyphosate controlled greater than 89% of hairy vetch in cotton. Except for poor control of hairy vetch and crimson clover by glyphosate alone, reduced legume control did not consistently decrease corn or cotton yield. Weed control was reduced in crimson clover treated with glyphosate alone, but control was similar among the remaining herbicide treatments. Effectiveness of legume control did not influence the N concentration of corn or cotton. Corn stand, height, and yield were greater in hairy vetch than in crimson clover. Seed cotton yield did not differ between vetch and clover.