The purpose of this study was to evaluate the influence of successively repeated precipitation patterns applied to bare and to covered soil, to quantify their effect on the formation of a soil crust and, consequently, on the soil water infiltration rate (Ti). Three rainfall events were simulated in 24 h intervals, with constant, decreasing exponential, early and late double exponential precipitation patterns, at a rainwater amount corresponding to 55 mm. The decrease factor of the infiltration rate (Ti) was adjusted as a function of the accumulated kinetic energy of the rainwater, called factor f, given by the ratio between the stable infiltration rate (Tie) affected by rain, and Tie with no effect of rain. Two situations of soil cover were evaluated: bare soil and soil covered with crop residues. A rainfall simulator was used in the infiltration experiments, on 1.0 x 0.7 m plots. The results were evaluated by graphical analysis, analysis of variance and means testing. It was found that the different precipitation profiles did not affect Ti of bare or covered soil. The Ti values were only influenced by successive rainfall, and the water infiltration rate was lowest after the 2nd and 3rd application. The decrease in Ti of bare soil was due to a crust on the soil surface, which was first formed after the 1st application. The stable infiltration rate (Tie) on bare soil decreased by 75 % when compared to Tie of covered soil. The infiltration depth was not influenced by any of the tested rainfall patterns. The factor f was described by an exponential equation.
soil cover; soil crusting; kinetic energy of rainfall
