The effects of metham on nutsedge control and cotton vigor were examined. Metham was applied as a preplant fumigant at 25, 45, and 65 gallons per treated acre. Each rate of metham was applied using three different application techniques; a single spray blade (SSB), fertilizer shanks (Fert.), and a triple spray blade (TSB).

All metham treatments provided excellent nutsedge control for 21days (89-100% control). There were minor differences in nutsedge control among the three types of shanks used. Only the 65 gallon per treated acre rate provided acceptable nutsedge control (77%) for 44 days. Increasing rates reduced seedling disease and increased seedling vigor. Although metham reduced weed competition, it also reduced the percentage of roots infected with mycorrhiza fungi. As a result, seedling phosphate levels were significantly lower in all metham treatments than the untreated control. However, this effect was only temporary in that by the first bloom evaluation, phosphate levels in metham treatments were equivalent to that of the untreated control. Tissue analyses were also evaluated for nitrogen, potassium, and zinc; however, differences were minor. A mid-season soil sample was taken to determine nutsedge tuber counts and distribution in the soil profile. All metham treatments seemed to have higher tuber counts than the untreated control, with the exception of the triple spray blade in the top eight inches of soil.