Infiltration studies were performed on arenic chernozems of quarternality fluvial terrace of Labe (Elbe). We studied the applicability of infiltration equations of Philip (2-pararnetric ), and 3-pararnetric, of Brutsaert and Swartzendruber, using 70 inflitration tests performed on a regular grid on a plot covered for 4 years by grass. The best applicability was found for the 3-pararneter equations, but there is no unique recommendation. The probability density function (PDF) of estimates of soil hydraulic characteristics is deformed by errors of estimates due to the approximate character of equations used. The log-normal distribution is a well-acceptable approximation for sorptivity S, saturated hydraulic conductivity Ks and rates of inflitration. Only for some estimates of hydraulic functions a weak spatial variability was found for the distance of 7.5 m. Long time variability of infiltration and its parameters after ploughing and subsequent grass planting was studied on the other plot. There was a significant drop of Ks just after one season of grass growth and harvests. Low soil structural stability was indicated by the infiltration tests.