Spatial variability of atrazine sorption parameters and other soil properties in a podzoluvisol

The spatial variability of the Kf and n parameters of the Freundlich sorption isotherm for atrazine and their correlation with soil textural variables, cation exchange capacity and organic carbon content were studied in a stagnic podzoluvisol. Ninety-three sample points were organized on an irregular three-dimensional grid to a depth of 3.2 m. A trend in the vertical direction explains, for most variables, about 85% of the observed variance. This trend also significantly influences the observed correlation structure between the variables. The horizontal and vertical trends were removed from the data set with the median polish algorithm. The residuals resulting from this technique obey the intrinsic hypothesis. Organic carbon content, cation exchange capacity and n revealed spatial structure. The estimated correlation length scales in the vertical direction were between 0.63–0.81 m for n and the organic carbon content, and between 0.25–0.40 m for the cation exchange capacity. The variograms of sand, loam, clay and Kf exhibited pure nugget. The correlation structures between the variables differ for different spatial increments. Variables appeared correlated at small spatial increments whereas they are not correlated if the spatial location of the sample points is neglected.