The objectives of this study were: to investigate the transfer to runoff of surface-applied bromide and potassium (representing a nonadsorbed and an adsorbed-exchangeable chemical, respectively) from two different soils, at various initial soil moisture contents and with a surface mulch; and to test the applicability of a nonuniform mixing model developed in earlier work. The studies were conducted under controlled conditions in the laboratory, with soil boxes and simulated rainfall, and supplemented by measurements in grassed field plots of one of the soils. Study materials, methods and results are discussed.