The leaching of pesticides and fertilizers applied to turfgrass will be affected by microbial and plant activity unique to this system. The objectives of this research were (i) to measure the degradation of dicamba in thatch and soil using a small-scale, laboratory, batch experiment; (ii) to investigate the effect of turfgrass on water flow and the leaching of nitrate, chloride and dicamba applied to field lysimeters packed with a sandy loam soil profile and topped with turfgrass, and (iii) to test the ability of the model LEACHM (within EXPRES) to simulate these processes. Degradation of dicamba was 5.9 to 8.4 times faster in thatch than in soil, with a half-life as low as 5.5 days. Drainage and leaching occurred primarily in autumn, being strongly controlled by evapotranspiration. LEACHM predictions mirrored the fluctuations in water contents, solute concentrations and drainage well, though the predicted values often differed from field measurements.