Nutgrass (Cyperus rotundus L.) control in cotton (Gossypium hirsutum L.)

Abstract

The effects on cotton lint yield and nutgrass tuber density of 12 treatment combinations were examined. Treatments included preplant norflurazon and benfuresate, in-crop cultivation, glyphosate and MSMA, and post-harvest glyphosate. The effects on tuber density of a further 14 treatment combinations of cultivation, MSMA, glyphosate, and norflurazon were examined in fallow. Under a traditional nutgrass control program of in-cotton cultivation and MSMA, nutgrass tuber density (no./m2) increased from 216 (0-0.15 m soil core) in 1990 to 1112 in 1992, with an average cotton yield of 1239 kg lint/ha. This result compared well with the untreated control, where the tuber density increased to 1641 tubers/m2 in 1992, with an average lint yield of 959 kg /ha. The best treatment was a combination of norflurazon, benfuresate, glyphosate, and cultivation, resulting in a tuber density of 220 tubers/m2 in 1992 and an average lint yield of 1217 kg/ha. Repeated applications of glyphosate in fallow effectively controlled nutgrass, with incremental improvements in control from additional glyphosate applications. Monthly glyphosate ap lications reduced the tuber density from 334 tubers/m in 1990 to 47 in 1992 at one site, and from 334 tubers/m2 in 1990 to 50 in 1992 on a second site. Overall, the results showed that traditional nutgrass control techniques were unsatisfactory, but repeated glyphosate applications gave effective nutgrass control both in cotton and in fallow.