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Title: MINERALIZATION OF ATRAZINE, METOLACHLOR, AND THEIR RESPECTIVE METABOLITES IN VEGETATED FILTER STRIP AND CULTIVATED SOIL

Author
item Krutz, Larry
item GENTRY, T - UNIV OF ARIZONA
item SENSEMAN, S - TEXAS A&M UNIV
item PEPPER, I - UNIV OF ARIZONA
item TIERNEY, D - SYNGENTA CROP PROTECTION

Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2005
Publication Date: 4/12/2006
Citation: Krutz, L.J., Gentry, T.J., Senseman, S.A., Pepper, I.L., Tierney, D.P. 2006.Mineralization of atrazine, metolachlor, and their respective metabolites in vegetated filter strip and cultivated soil. Pest Management Science 62:505-514.

Interpretive Summary: Vegetated filter strips (VFS) are narrow strips of permanent vegetation planted adjacent to cropland with the intent to reduce herbicide transport from agricultural application zones. In VFS soil, the presence of perennial vegetation, deposition of organic substrates, and the accumulation of an organic residue layer may enhance microbial numbers and activity, thereby increasing the potential for mineralization of herbicides and herbicide metabolites retained during runoff events. The objective of this laboratory experiment was to compare the mineralization of atrazine and metolachlor to their respective metabolites in VFS and cultivated soil. With the exception of total bacteria, propagule density of the microbial groups, endogenous soil enzymes, and microbial diversity were higher in the VFS soil. This correlated with increased mineralization of metolachlor and its metabolites in the VFS soil and indicates potential for the VFS to curtail the subsequent transport of these compounds to surface and ground water. In contrast, the mineralization of atrazine and the majority of its metabolites were substantially reduced in the VFS soil relative to cultivated soil. Consequently, the potential for subsequent transport of atrazine and many of its metabolites to water bodies may be greater in VFS soil compared to cultivated soil if reduced mineralization is not offset by increased sorption in the VFS.

Technical Abstract: In vegetated filter strips (VFS), the presence of perennial vegetation, rhizodeposition of labile organic substrates, and the accumulation of an organic residue thatch layer may enhance microbial numbers and activity, thereby increasing the potential for mineralization of herbicides and herbicide metabolites retained during runoff events. The objective of this laboratory experiment was to compare the mineralization of atrazine and metolachlor to their respective metabolites in VFS and cultivated soil. With the exception of total bacteria, propagule density of the microbial groups, endogenous soil enzymes, and microbial diversity were higher in the VFS soil. This correlated with increased mineralization of metolachlor and its metabolites in the VFS soil and indicates potential for the VFS to curtail the subsequent transport of these compounds. In contrast, the mineralization of atrazine and the majority of its metabolites were substantially reduced in the VFS soil relative to cultivated soil. Consequently, the potential for subsequent transport of atrazine and many of its metabolites may be greater in VFS soil compared to cultivated soil if reduced mineralization is not offset by increased sorption in the VFS.