Asymmetrical Distribution and Dissipation of Band‐Applied Atrazine in Soil

Abstract

AbstractMovement of herbicides, particularly atrazine [2‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], is of great interest, as farming systems are designed to protect water quality. The effects of time and precipitation on the distribution of atrazine banded over corn (Zea mays L.) rows were measured for 2 yr in a ridge‐tillage corn‐soybean [Glycine max (L.) Merr.] rotation. The soil was a Zimmerman fine sand (mixed, frigid Lamellic Udipsamment). During the growing season, soil atrazine was determined at 0.1‐m horizontal intervals perpendicular to the row to a depth of 0.3 m. Within the first 22 days after treatment (DAT), atrazine concentrations decreased 65% in the application zone and had not leached below 0.075 m. A 60‐mm rain between 22 and 29 DAT first moved atrazine into the 0.075‐ to 0.15‐m depth increment. By 60 DAT and 240 mm of accumulated rain, atrazine concentrations had decreased by an estimated 90% in the zone of application. Atrazine movement appeared to be greater on the windward side of the row. An estimated 98% of applied atrazine was dissipated by the end of the first growing season and by the end of the second year, detections of residual atrazine were very limited and confined to the zone directly below the treated area. Significant horizontal movement of atrazine was never observed. Atrazine was not detected in soil samples below 0.6 m to a depth of 2.4 m.