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Title: FOLIAR WASHOFF POTENTIAL AND SIMULATED SURFACE RUNOFF LOSSES OF TRIFLOXYSULFURON IN COTTON

Author
item MATOCHA, M - TEXAS COOPERATIVE EXT.
item Krutz, Larry
item Reddy, Krishna
item SENSEMAN, SCOTT - TEXAS A&M UNIV
item Locke, Martin
item Steinriede, Robert
item PALMER, ERIC - SYNGENTA - LELAND, MS

Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2006
Publication Date: 7/18/2006
Citation: Matocha, M.A., Krutz, L.J., Reddy, K.N., Senseman, S.A., Locke, M.A., Steinriede Jr, R.W. and Palmer, E.W. 2006. Foliar washoff potential and simulated surface runoff losses of trifloxysulfuron in cotton. Journal of Agriculture and Food Chemistry 54:5498-5502.

Interpretive Summary: Trifloxysulfuron is a new herbicide labeled for use in cotton. The environmental fate of this herbicide in Mississippi Delta cotton production systems has not been evaluated. The objectives of this study were to determine binding of trifloxysulfuron to soil, quantify the loss of herbicide from cotton leaves from rain and runoff loss from soil and the amount of trifloxysulfuron that may be dislodged from cotton during a rainfall event, from cotton and non-vegetated soil. Trifloxysulfuron binding to a soil was moderate suggesting that soluble herbicide on the soil surface can be lost in surface runoff water. A large percentage of trifloxysulfuron was washed-off cotton plants if significant rainfall occurs 72 hours after application. Run-off losses of trifloxysulfuron were moderate averaging 2.7% for cotton plots and 1.7% for non-vegetated plots. These data indicate that potential run-off losses of trifloxysulfuron in the Mississippi Delta are small. Moreover, losses may be curtailed if the herbicide is applied when rainfall is not imminent and cotton canopy closure is minimal.

Technical Abstract: The surface runoff potential of trifloxysulfuron in Mississippi Delta cotton production systems has not been evaluated. The objectives of this study were to 1) determine sorption/desorption coefficients for trifloxysulfuron; 2) quantify foliar washoff of trifloxysulfuron applied to cotton at the 5-leaf stage; 3) and determine average edge-of-field concentrations and total mass losses of trifloxysulfuron when applied to cotton at the 5-leaf stage and to bare soil. Sorption and desorption of trifloxysulfuron to Dundee silt loam was described by the Freundlich equation. The Freundlich sorption and desorption coefficients were 1.2 and 1.2, respectively. Sorption data indicated that trifloxysulfuron is moderately sorbed to soil and will likely be transported primarily in the dissolved phase of surface runoff. Foliar washoff studies indicated that the amount of 14C-trifloxysulfuron available for washoff decreased logarithmically with time. Ninety-one % of the applied trifloxysulfuron was available for washoff after 72 h. Average edge-of-field concentrations of trifloxysulfuron were 0.8 µg L-1 and 1.3 µg L-1 for bare plots and cotton plots, respectively. Cumulative trifloxysulfuron losses in runoff from cotton plots were 0.21 g ha-1 while losses from bare plots were 0.13 g ha-1. These values correspond to fractional losses of 2.7% for cotton plots and 1.7% for bare plots. Greater runoff loss of trifloxysulfuron from cotton plots relative to bare plots is likely due to foliar washoff. Losses of trifloxysulfuron in runoff may be reduced if applied when canopy closure is minimal.