ABSTRACT

Process based models are frequently used to assess the impact of turfgrass management practices on the quality of water emanating from proposed or existing golf course sites. This study was conducted to determine the effect of thatch on the transport of two pesticides and to evaluate the use of a volume averaging approach to account for the presence of thatch in model simulations. Pesticide breakthrough curves were obtained from columns of soil and thatch+soil by subjecting the columns to a constant flux of 1 cm hr−1 one day after applying triclopyr and carbaryl. Columns containing zoysiagrass thatch had lower triclopyr and carbaryl leaching losses than did columns containing soil only. Pesticide and bromide transport parameters indicated that non-equilibrium processes were affecting the transport of both pesticides. Overall, use of a two site non-equilibrium model correctly predicted the peak concentration and tailing behavior of triclopyr and carbaryl when a volumetric averaging approach was used to account for the presence of thatch. Relatively good agreement between actual and model predicted pesticide leaching losses indicates that volume averaging thatch and soil retardation factors can be used to satisfactorily predict the transport of pesticides applied to soils that contain a surface layer of thatch.