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Title: Effect of meteorology and soil condition on metolachlor and atrazine volatilization over a 10 year period

item Gish, Timothy
item Prueger, John
item Hatfield, Jerry
item McKee, Lynn
item Kustas, William - Bill
item Daughtry, Craig
item Russ, Andrew - Andy

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/23/2009
Publication Date: 8/16/2009
Citation: Gish, T.J., Prueger, J.H., Hatfield, J.L., McKee, L.G., Kustas, W.P., Daughtry, C.S., Russ, A.L. 2009. Effect of meteorology and soil condition on metolachlor and atrazine volatilization over a 10 year period [abstract]. American Chemical Society. 2009 CDROM.

Interpretive Summary:

Technical Abstract: A 10-year study was conducted to focus on the impact of soil and climatic factors governing herbicide volatilization from an agricultural field. For the first 5 years, metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] and atrazine [6-chloro-N-ethyl-N’-(1-methylethl)-1,3,5-triazine-2,4-diamine] concentration profiles were continuously monitored for the first 5 days after application. For the second 5-year period, herbicide concentration profiles were monitored at two locations in the same field where only the surface soil water contents differed in response to the presence and activity of subsurface flow pathways. A flux gradient technique was used to compute volatilization fluxes from herbicide concentration profiles and turbulent fluxes of heat and water vapor as determined from eddy covariance measurements. Differences in meteorological and surface soil water contents resulted in variability of volatilization losses among years. When soil surface conditions approached saturation 62.2% of the applied metolachlor was lost to volatilization compared to 11.8 % of the atrazine. Detailed soil moisture observations in the second 5-year period showed that surface soil water contents and surface meteorological conditions are critical factors governing herbicide volatilization losses. For example, during 2004 and 2005 surface soil water contents at the “dry” location were nearly half those at the “wet” location. Meanwhile, cumulative metolachlor vapor fluxes during 2004 and 2005 at the dry location were also about half that of the wetter location. However, when drought conditions render the subsurface flow pathways inactive the surface soil water contents and herbicide vapor losses at the two locations were nearly identical. Analysis of infrared soil surface temperatures (IRT) also suggests a correlation between surface soil temperatures and metolachlor volatilization when soils are wet but not when the soils were dry.