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| Web URL(s): | http://archive.lib.msu.edu/tic/rpr/1997/54842,%20U%20Maryland, Carroll.PDF
Last checked: 10/29/2013
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| Publication Type:
| Report |
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| Material Type: | Manuscript |
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| Monographic Author(s): | Carroll, Mark J.; Hill, Robert L.; Herner, Albert |
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| Author Affiliation: | Carroll and Hill: Principal Investigator, Department of Agronomy, University of Maryland; and Herner: Cooperator, Environmental Chemistry Laboratory, USDA: Beltsville |
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| Monograph Title: | Modeling Pesticide Transport in Turfgrass Thatch and Foliage: [1997 Annual Research Report], 1997. |
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| Publishing Information: | [College Park, Maryland]: Department of Agronomy, University of Maryland |
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| # of Pages: | 14 |
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| Collation: | [14] pp. |
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| Abstract/Contents: | "Pesticides applied to mature turf move into the soil only after being washed off the foliage and moving through the turfgrass thatch. Any attempt to predict the movement of pesticides applied to turf requires that the retention characteristics of the pesticide to foliage and thatch be known. In 1996 and 1997 a series of sorption and transport studies were conducted to characterize the movement of 2,4-D acid in soils containing a surface layer of turfgrass thatch. The sorption studies were conducted using a device called a mechanical vacuum extractor. This device precisely controls the rate at which a solution moves through a column of porous media. The adsorption and desorption properties of a 3.5 year old, 2.3 cm thick SOUTHSHORE creeping bentgrass thatch, and a 6 year old, 3.4 cm thick MEYER zoysiagrass thatch were compared with the soil residing below each thatch layer. The adsorption of 2,4-D to soil was found to be nearly instantaneous. In contrast, 2,4-D adsorption to thatch was dependent on the residence time of the solution containing this pesticide. The adsorption kinetics of the two turfgrass species thatch were similar. The quantity of 2,4-D adsorption to thatch increased 72% as the solution residence time increased from 15 minutes to 24 hours; however, even at a residence time as brief as 15 minutes, 2,4-D adsorption to thatch was three times greater than to soil. Desorption losses were evaluated by subjecting columns of thatch or soil to three successive leaching events. The leaching events took place after allowing 2,4-D to adsorb to the thatch or soil for 24 hours. The quantity of 2,4-D detected in the leachate was used to determine the proportion of 2,4-D that was desorbed from the sample. The proportion of 2,4-D that was desorbed during the three leaching events was slightly less for thatch than for soil. The difference in proportional losses of 2,4-D, however, was small when compared to the total proportion of 2,4-D that was lost from each media. In a previously conducted desorption study, we found that desorption losses of dicamba were greater from soil than from thatch. Our earlier results suggest that some water soluble pesticides may be more tightly bound to thatch than soil. Undisturbed cores of soil and soil plus a surface layer of thatch were used to determine the effect of thatch on the 2,4-D transport in soil. Cores having a surface layer of SOUTHSHORE creeping bentgrass thatch were more effective in reducing 2,4-D transport than cores having a surface layer of MEYER zoysiagrass thatch. Bromide and 2,4-D breakthrough curves obtained from the transport study were used to evaluate the performance of linear equilibrium (LEM), two-site non-equilibrium (2SNE) and one-site kinetic non-equilibrium models to predict the transport of 2,4-D. The latter two models use non-equilibrium forms of the convection-dispersion equation to predict solute movement. The bromide data did not present strong evidence of significant physical non-equilibrium or two domain flow in any core. In addition, all three models described in 2,4-D transport fairly well with slightly improved fits resulting from the 2SNE model. Research in 1998 will focus on completing sorption and transport studies involving pesticides having low to moderate water solubilities (carbaryl and chlorothalonil). The data collected will be used to further evaluate the predictive capabilities of the three aforementioned models. Goals: To quantify the washoff of pesticeds from bentgrass foliage as a function of time after application and pesticide formulation.; To determine the effect of solution residence time on the sorption of pesticides to turfgrass thatch.; To compare the use of linear equilibrium, to-site non-equilibrium and one-site kinetic non-equilibrium forms of the convection-dispersion equation to predict pesticide transport through turf containing a surface layer of thatch." |
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| Language: | English |
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| References: | 4 |
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| See Also: | See also related summary article "Modeling pesticide transport in turfgrass thatch and foliage" 1997 Turfgrass and Environmental Research Summary [USGA], 1997, p. 70-71, R=54842. R=54842 |
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| Note: | Also appears as pp. 767-780 in the USGA Turfgrass Research Committee Reporting Binders for 1997.
"1997 Annual Report presented to the United States Golf Association Green Section Research"
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