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Effect of Conventional vs. No‐Tillage on Pesticide Leaching to Shallow Groundwater
Author(s) -
Isensee A. R.,
Nash R. G.,
Helling C. S.
Publication year - 1990
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1990.00472425001900030014x
Subject(s) - alachlor , carbofuran , atrazine , groundwater , pesticide , leaching (pedology) , environmental chemistry , acetanilide , chemistry , acetamide , hydrology (agriculture) , environmental science , zoology , agronomy , soil science , soil water , geology , biology , geotechnical engineering , organic chemistry
A field site was established at Beltsville, MD, in 1986 to assess the effect of conventional and no‐till cultural practices on the movement of pesticides into shallow groundwater. Groundwater samples taken from unconfined (<1.5 m deep) and confined (<3 m deep) monitoring wells in 1986–1988 were analyzed for atrazine [6‐chloro‐ N ‐ethyl‐ N ′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], deethylatrazine [6‐chloro‐ N ‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], alachlor [2‐chloro‐ N ‐(2,6‐diethylphenyl)‐ N ‐(methoxymethyl)acetamide], cyanazine [2‐[[4‐chloro‐6‐(ethylamino)‐1,3,5‐triazine‐2‐y1]amino)‐2‐methylpropanenitrile], and carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl methylcarbamate). Atrazine was found in groundwater all year, while cyanazine, alachlor, and carbofuran were present only for a short period (<3 mo) after pesticide application. Fairly constant background levels of <0.5 µ g L −1 atrazine were found under fields treated before 1986, while levels under continuously treated fields were <2.0 µ g L −1 for 22 of 25 samplings. Pesticide residues in unconfined groundwater were usually higher (ca. 2 to 4×) than in confined groundwater. Rainfall timing relative to pesticide application was critically important to pesticide leaching. A prolonged rain immediately after the 1988 application resulted in peak atrazine and cyanazine levels of ca. 200 µ g L −1 in unconfined and ca. 30 to 40 µ g L −1 in confined groundwater, which resulted in short‐term levels ca. 2 to 50× greater under no‐till than conventional till plots. Results of this study suggest that preferential transport occurred.