FACTORS AFFECTING PREFERENTIAL FLOW OF WATER AND ATRAZINE THROUGH EARTHWORM BURROWS UNDER CONTINUOUS NO-TILL CORN

Watershed studies have documented that summer storms produce less runo ff from fields farmed with continuous no-tillage corn (Zea mays L.) th an from the same soils when corn is produced with conventional tillage practices. The lack of tillage favors a continuous surface cover of c rop residue and the persistence of earthworm burrows, which have been shown to be preferential flow paths for water and chemicals, especiall y during intense summer storms. We investigated factors affecting pref erential water and chemical transport in burrows formed by the earthwo rm Lumbricus terrestris (L.) in the field using individual burrow samp lers and in the laboratory using blocks of undisturbed soil subjected to simulated rainfall. Rainfall amount and intensity and antecedent so il moisture content affected the amount of water transmitted in earthw orm burrows, with high intensity storms on relatively dry no-till soil s producing the greatest amounts of preferential flow. Atrazine 2-chlo ro-4-ethylamino-6-isopropylamino-s-triazine) transport was affected by the factors influencing the amount of preferential flow and by the ti me of storms relative to the time of herbicide application. Atrazine m ovement in earthworm burrows was greatest when high-intensity rainfall occurred shortly after application. Atrazine transport was reduced by a delay in rainfall and by low-intensity events prior to high intensi ty, percolate-producing events.