INFLUENCE OF RAINFALL INTENSITY AND CROP RESIDUE ON LEACHING OF ATRAZINE THROUGH INTACT NO-TILL SOIL CORES

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Abstract
Pesticide leaching may be affected by rainfall parameters and the amount and type of vegetation on the soil surface. This study was conducted to determine the effect of rainfall intensity and crop residue on the movement of [ring-14C]atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and bromide (Br) through no-till (NT) cores. Undisturbed soil cores (10 cm diameter by 8 cm depth) were taken from the surface horizon of a NT corn (Zea mays L.) field. The cores were surface treated with 1.3 kg ai ha−1 atrazine and 150 kg ha−1 of Br and subjected to simulated rainfall at 3, 6, 9, or 12 mm h−1. The amount of crop residue on the surface of another set of soil cores was adjusted to 0, 2000, 4000, and 8000 kg ha−1, then treated with atrazine and subjected to 9 mm h−1 of simulated rain. Overall, the transport of atrazine and Br were significantly (P < 0.01) affected by rainfall intensity. An average of 92% (Br) and 52% (atrazine) of the total amount applied was leached through the soil cores by 2 pore volumes (520 ml) of simulated rain applied at 12 mm h−1 compared with 61% for Br and 33% for atrazine at the 3-mm h−1 rate. Covering soil cores with 2000 or 8000 kg ha−1 of crop residue reduced atrazine leaching by 26 to 37%, respectively, compared with soil cores without crop residue. Soil cores covered with recently harvested vegetation reduced atrazine leaching by 39% compared with cores covered with aged crop residue. © Williams & Wilkins 1993. All Rights Reserved.

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