Field studies were conducted in 2014 and 2015 at Pontotoc, MS to evaluate combinations of metam-potassium and S-metolachlor for yellow nutsedge control and sweetpotato crop response. Treatments consisted of a factorial of five metam-potassium rates (0, 149, 261, 372, and 484 kg ha(-1)) by three S-metolachlor rates (0, 0.80, and 1.34 kg ha(-1)). Additionally, a hand-weeded check was included for comparison. Crop injury was limited to <= 4 at 4 weeks after transplanting (WAP) and was transient. At 2 WAP yellow nutsedge control was 58, 74, and 76 in plots treated with S-metolachlor at 0, 0.80, and 1.34 kg ha(-1), respectively. Nutsedge control in all treatments decreased from 2 to 15 WAP. At 15 WAP, S-metolachlor at 0, 0.80, and 1.34 kg ha(-1) provided 35, 68, and 70 yellow nutsedge control, respectively. Metam-potassium rate did not influence yellow nutsedge control after transplanting. Sweetpotato yields in the hand-weeded check were 4,640; 22,180; 7,180; 34,000; and 1,360 kg ha(-1) for jumbo, no. 1, canner, marketable, and cull grades, respectively. S-metolachlor applied at either 0.80 or 1.34 kg ha(-1) provided jumbo, no. 1, and marketable sweetpotato yields equivalent to the hand-weeded check. Canner and cull yields were not influenced by S-metolachlor rate. Metam-potassium rates used in the present study resulted in yields equal to or greater than the hand-weeded check.
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