In agriculture and environmental studies, the hydraulic conductivity equation, that is, the hydraulic conductivity (K) as a function of soil-water content (theta), plays an important role in the resolution of practical problems related to irrigation, drainage, and leaching of nutrients and pollutants. In order to quantify and characterize this hydric soil property it is essential to obtain representative values that can be safely used in a number of applications. With the objective of characterizing the statistical behavior and of quantifying the variability of the hydraulic conductivity equation parameters, an instantaneous profile field experiment was carried out at 50 points spaced 1 m apart in a transect in a Typic Hapludox. Equations were of the type K = Ktheta=0 exp(<FONT FACE=Symbol>bq</FONT>) and results showed that the variability patterns of the parameters beta and lnKtheta = 0 as well as of theta during the water redistribution increased with soil depth, and that there were no relationships among them. It was also observed that the presence of extreme values changes the statistical measurements of the K equation parameters, affecting the number of samples necessary to estimate the mean values of these parameters. It is important to identify these values prior to the use of any method of soil hydraulic conductivity sampling.
soil variability; statistical methods; water content
