Soil porosity increase on arable fields is mainly the result of cultivation while sealing and crusting are natural processes. The first is a rapid change the latter is slower, however, little is known about the time scale of soil sealing and crusting. Crusting rainfall simulation experiments were carried out to investigate the role of single rainfall events on soil sealing and crusting, on an intensively cultivated arable field. To follow porosity changes trough out the year, undisturbed samples were analyzed. High seasonal differences were identified in bulk density and porosity during the vegetation period that appeared to be the results of tillage. The results of rainfall simulation underline the rapid influence of a single storm in sealing and crusting of a Cambisol by decreasing the final infiltration rate and increasing runoff and sediment load. Porosity reduction manifested first of all in surface crust formation, however, kaolinite was the dominating cay mineral in the investigated Cambisol. Bulk density of the tilled soil layer enhanced by 15% in case of structural and 40% in erosion crust. The higher value could be the result of the continuous deposition according to Stoke’s law creating a clay film cover on the surface. The sealing and crusting effect of a single storm could be of the same order as the influence of tillage on soil porosity runoff and soil loss. The porosity created by tillage can collapse during one precipitation event.