Simulation of the impact of agricultural management practices on chemical transport in macroporous soils

A simulation model capable of describing preferential movement of water and pesticides in macroporous soils has been developed. The model assumes a bi-continuum, with flow and transport in and between each of two coexisting pore domains (matrix and macropore). In each pore domain, water pow is assumed to obey Richards' equation and chemical movement is assumed to obey the convection-dispersion equation. Interdomain transfer of water and chemicals occurs under pressure and concentration gradients. The model incorporates features such as root water extraction, rate limited sorption and desorption, and first-order decay. The macropore volume fractions are allowed to vary with space to accommodate variabilities in soil propel-ties. The model can represent two-dimensions, to simulate the impact of agricultural management practices, such as tillage, irrigation, cropping practice, and organic addition, on pow and transport.