Co-Authors:
Shalit, G., Dept. of Agric. and Biol. Eng., Cornell University, Ithaca, NY 14853, United States
Steenhuis, T., Dept. of Agric. and Biol. Eng., Cornell University, Ithaca, NY 14853, United States
Abstract:
Concern about the environmental effects of agricultural chemicals through preferential flow has risen in recent years. A simple model is presented describing the processes involved in preferential transport of both soil-adsorbed and non-adsorbed solutes. The model assumes that water and solutes are mixed into an upper soil layer. The water and solutes then flow through macropores to the groundwater. Analysis of the solute breakthrough curves in subsurface drainage effluent makes it possible to calculate the depth of the mixing layer or the adsorption desorption partition coefficient. Data from a drainage experiment with chloride, 2,4-D and atrazine were used to test the model. The study was performed on a no-till and a conventionally tilled plot. The model and experimental results indicate that only a fraction of the field area participates in transport to the macropores. Differences between breakthrough curves from the conventionally tilled and no-till plots are explained well by the mixing of solutes and water in the upper layer. This simple, physically based model can help us to understand and estimate the environmental threats of herbicides shortly after application.