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Effects of Long‐Term 2,4‐D and MCPA Field Applications on the Soil Breakdown of 2,4‐D, MCPA, Mecoprop, and 2,4,5‐T
Author(s) -
Smith A. E.,
Aubin A. J.
Publication year - 1991
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/jeq1991.00472425002000020016x
Subject(s) - mcpa , mecoprop , soil water , chemistry , agronomy , environmental chemistry , weed control , environmental science , soil science , biology
Under laboratory conditions, the rates of breakdown of ( 14 C)2,4‐D (2,4‐dichlorophenoxyacetic acid), ( 14 C)MCPA (4‐chloro‐2‐methylphenoxyacetic acid), ( 14 4C)mecoprop (2‐[4‐chloro‐2‐methylphenoxy]propionic acid), and 2,4,5‐T (2,4‐5‐trichlorophenoxyacetic acid) in soils from Canadian prairie field plots, 6 wk after receiving the 43rd annual application of 2,4‐D formulations or the 37th annual treatment with MCPA, were compared with those in soils from untreated plots. Loss of 2,4‐D and MCPA was faster in soils that had received continuous applications with the appropriate herbicide than in soil from the control plots. There was some indication that ( 14 4C)2,4‐D was dissipated more rapidly from soils treated annually with MCPA than from the control soils, though breakdown was slower than in soil from the 2,4‐D‐treated plots. In contrast, ( 14 C)MCPA breakdown in the 2,4‐D‐treated plots was similar to that in untreated soils. Breakdown of ( 14 C)mecoprop and 2,4,5‐T in the 2,4‐D and MCPA‐treated soils was very similar to that in the control soils. Thus, there was no support for the phenomenon of cross‐enhancement. Forty‐eight weeks after the last herbicide applications, the field soils still maintained their ability to degrade 2,4‐D or MCPA more rapidly than soil from untreated control plots.