The Development of a Standard Turf Scenario: Notes of an External Review of the USEPA Turf Scenario

摘要

The use of agricultural field scale runoff models to predict pesticide runoff losses from turf poses some unique modeling challenges. There are a number of aspects of turf grass culture which differ significantly from row crop agriculture in how they affect runoff processes. In particular, the generally high tiller and leaf density of the verdure reduces exposure of the soil surface to the direct impact of rain droplets and hence, mitigates the potential for agrochemical transport in runoff. The development of increased surface soil organic matter levels, in varying stages of decomposition and incorporation into the soil matrix as 'thatch', should also be taken into account. Highly managed turf grass areas susceptible to runoff are generally smaller than the typical field size for agricultural row crops; the potential for soil erosion is therefore, again, much reduced under turf The United States Environmental Protection Agency (USEPA) evaluated data from a small-plot turf runoff study published by researchers at the University of Georgia (UGA) to enable development of a standard turf scenario, now in regulatory use. The USEPA scenario was then evaluated by the authors using the same publications, i.e., the small-plot data generated on the transport of the herbicides mecoprop, dicamba, dithiopyr and 2,4-D in runoff, with the addition of more detailed, unpublished data from the University of Georgia study files. In addition, the UGA-measured transport of chlorpyrifos, a strongly adsorbed compound, was included in the present evaluation. Model performance using the key features of the standard turf scenario was generally good for the weakly adsorbed compounds. Performance for the more strongly adsorbed compounds was poor, and over-predicted adsorbed chemical losses in eroded soil. Adjustments to soil erosion parameters and consideration of scale effects resulted in improved predictions.