Studies on bioefficacy, phytotoxicity of atrazine and its residues in maize under North Western Himalayas conditions

Among different herbicidal treatments, atrazine 1.0 kg/ha (Pre) fb. 0.75 kg/ha (Post) being at par with atrazine 1.5 (Pre) fb. post emergence application of either paraquat 0.6 kg/ha or 2,4-D 0.75 kg/ha recorded significantly lower total count and dry matter of predominant weeds appearing right from the beginning of the crop season which was comparable to hand weed twice during both the years, which have contributed in getting significantly higher grain yield of maize. However, pre-emergence application of atrazine 1.5 or 3.0 kg/ha behaved similarly to these treatments for recording higher grain yield. However, with respect to Agetratum conyzoides which appeared beyond critical period of competition at tasseling stage of the crop, all the weed control treatments except handweeding twice during both the years and pendimethalin 1.0 kg/ha (Pre.) and atrazine 0.75 kg/ha (Pre.) during second year were effective in reducing the count and dry matter of this weed. No visual symptoms of injury or phytotoxicity have been observed due to any of the treatments after 15 and 30 days of spraying. Atrazine residues in all atrazine applied treatments were found below detectable levels in soil, maize grain and maize stover. From the study, it may be concluded that pre emergence application of atrazine in maize for weed management could be considered safe.