Changes in equilibrium infiltration rates (ie) of bare tilled and untilled soils were investigated by simulating five 150-min rain storms every 24 hours at a constant rate of 70 mm h−1on tilled and untilled micro-catchments. Decreases iniein the tilled soils were more strongly associated with initial tillage-induced surface roughness than with total porosity and water transmission characteristics of the sublayers. Regression analysis indicated that the changes iniecould be predicted by an exponential function which relatedieto accumulated rainfall.