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United States Department of Agriculture

Agricultural Research Service

Research Project: MAINTAINING SOIL RESOURCES FOR EFFECTIVE CONSERVATION AND HERBICIDE MANAGEMENT IN MID-SOUTH CROP PRODUCTION Title: Simazine degradation rates in central valley soils with varying simazine use histories

Authors
item Abit, M -
item Rainbolt, C -
item Krutz, Larry
item Shaner, Dale
item Hanson, B -

Submitted to: Clean (Soil Air Water)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 11, 2012
Publication Date: N/A

Interpretive Summary: Repeated and extensive use of simazine over several years in Central Valley soils have prompted grower concerns about reduced residual weed control arising from enhanced degradation. Experiments were conducted to determine if enhanced simazine degradation occurs in Central Valley vineyards, and if residual weed control is affected. Simazine persistence was four-fold lower in soil with a long simazine use history relative to soil with no recent simazine application history. Residual weed control, however, was not always different between sites during the growing season possibly due to environmental effects, long-term cropping factors, or previous selection for enhanced degrading microbial populations. Results indicate that enhanced simazine degradation occurs in Central Valley vineyard soils but the phenomenon may not always be accompanied with reduced residual weed control.

Technical Abstract: Simazine is an important management tool for weed control in vineyards because of its relatively low price, reliable control of several problem weeds, and long residual activity. Repeated and extensive use of simazine over several years in Central Valley soils have prompted grower concerns about reduced residual weed control arising from enhanced degradation. Experiments were conducted to determine if enhanced simazine degradation occurs in Central Valley vineyards, and if residual weed control is affected. Two vineyard locations were used in all studies, one with extensive simazine use history (adapted) and one with no recent simazine use history (non-adapted). Simazine dissipation arising from microbial processes was four-fold greater in soil with a long simazine use history relative to soil with no recent simazine application. Residual weed control, however, was not always different between sites during the growing season possibly due to environmental effects, long-term cropping factors, or previous selection for the enhanced degrading microbial populations. Results indicate that enhanced simazine degradation occurs in Central Valley vineyard soils but the phenomenon may not always be accompanied with reduced residual weed control.

Last Modified: 10/21/2014
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