Atrazine in Surface and Subsurface Runoff as Affected by Cultural Practices

Abstract

Abstract Atrazine (2-chloro-4-ethylamino-6-isopn>pylainino-6-triazine) concentration in surface runoff and tile drainage was monitored from small plots managed with conservation tillage and banded herbicide application in com. Atrazine concentrations were larger in surface runoff than in tile drainage. Surface runoff and tile drainage events soon after herbicide application had the greatest atrazine concentrations. When the entire area was treated with atrazine, the maximum concentration recorded in surface runoff was 700 µg/L from conservation tillage compared to 400 µg/L from conventional tillage. Banded application of the herbicide over the seeded row reduced maximum atrazine concentrations in surface runoff to less than 140 µg/L. Atrazine concentration of tile drainage was reduced from a maximum of 350 µg/L in broadcast preemergence treatments to less than 105 µg/L when atrazine was applied preemergence in a band over the seeded row. Deethylatrazine (2-chloro-4-amino-6-isopropylamino-$-triazine) concentration was 0.6 and 0.7 times that for atrazine in surface runoff and tile drainage, respectively, coincident with its transience as an intermediate metabolite of atrazine. Atrazine and deethylatrazine are unlikely to have a direct affect on aquatic life; however, changes in phytoplankton diversity and amounts could indirectly have an adverse affect. Preemergence application of atrazine in a band over the seeded row will reduce the impact of this herbicide on the water quality of surface waters.