A field experiment was conducted at Rio Claro, SP, Brazil, during 1991/92 to evaluate the efficacy of nicosulfur on for post emergence control of johnsongrass (Sorghum halepense) in field com grown under conventional conditions. Nicosulfuron was applied on early postemergence, on johnsongrass with 2 to 5 leaves, at rates of 40, 50, 60 e 80g/ha, and late post emergence (4 to 6 leaves) at rates of 50 , 60 an d 80 g/ ha . Two additional treatments of atrazine + simazine (1500 + 1500g/ha), with and without mineral oil, were applied at the same time of nicosulfuron. Treatments of nicosulfuron showed an exellent control of Johnsongrass, irrespectively of rate and timing appli catio n, reaching 100% control at 50 days after application. Atrazine + simazine treatments were no effective on johns ongrass control mainly at late postemergence application with addition of mineral oil. Corn yield increased 44 and 34%, respectively, on early and late postemergence applications of nicosulfuron. No com injury was observed for any herbicide treatments.
Sorghum halepense; sulfonylurea; postemergence control; application timing; triazines