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Herbicide Leaching under Tilled and No‐Tillage Fields

1995; Wiley; Volume: 59; Issue: 3 Linguagem: Inglês

10.2136/sssaj1995.03615995005900030038x

1435-0661

T. J. Gish, Adel Shirmohammadi, Raviraj Vyravipillai, Brian J. Wienhold,

Soil and Water Nutrient Dynamics

Abstract The effect of no‐tillage practices on water quality exiting the root zone of deep, well‐drained fields is largely unknown. This project was initiated to determine herbicide leaching characteristics as influenced by tillage practice and herbicide formulation. The research site consisted of four adjacent (0.25‐ha) fields, two fields each dedicated to either tilled or no‐tillage management. One field in each tillage regime received a controlled‐release formulation of atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] and alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)‐acetamide, starch encapsulated], while the others received standard herbicide formulations of atrazine and alachlor. Both herbicide formulations were annually applied at the same rate: 1.7 kg ha −1 for atrazine and 2.8 kg ha −1 for alachlor. Atrazine, deethylatrazine [DEAT; 6‐chloro‐N‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], alachlor, and Br − concentrations were monitored with 12 suction lysimeters (six each at 1.5‐ and 1.8‐m depths) in each field. Alachlor was detected in <3% of all samples collected, regardless of tillage practice or berbicide formulation, while atrazine was detected in >41% of the samples. Under no‐tillage, atrazine was detected in <28% of the samples with <13% exceeding the U.S. Environmental Protection Agency Health Advisory level of 3 µg L −1 atrazine. Under tilled conditions, 53% of the samples contained atrazine, with 35% exceeding 3 µg L −1 atrazine. Averaged atrazine metabolite concentration of DEAT under no‐tillage was 0.52 µg L −1 vs. 0.39 µg L −1 for tilled fields. Similar Br − transport between tillage practices and reduced atrazine levels under no‐tillage fields suggest that no‐tillage management, on deep well‐drained soils, can have a positive impact on groundwater quality.