Runoff Losses of Surface‐Applied Herbicides as Affected by Wheel Tracks and Incorporation

Abstract

Abstract The effects of incorporation and wheel‐track compaction on runoff losses of herbicides were determined by measuring losses of propachlor (2‐chloro‐ N ‐isopropylacetanilide), atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine], and alachlor [2‐chloro‐2′,6′‐diethyl‐ N ‐(methoxymethyl) acetanilide] in water and sediment from small plots during 122 mm of simulated rainfall. Losses of propachlor, atrazine, and alachlor that were surface‐applied to plots without wheel tracks were 3.0, 4.7, and 8.0%, respectively. Corresponding losses from plots where the herbicides were incorporated by disking were only 0.8, 1.6, and 1.7%. Hydrologic differences (more and sooner runoff) caused by wheel tracks on plots where herbicides were surface‐applied increased the corresponding losses to 12.7, 18.3, and 22.1%. Although herbicide concentrations were greater in sediment than in water for all treatments, from 82 to 89% of the losses were in solution.