A central Iowa glacial till soil under no‐tillage condition was studied for its spatial behavior of saturated hydraulic conductivity ( K ) at the surface soil layers. Hydraulic conductivity measurements both in situ and in the laboratory were made at two depths of 15 and 30 cm at regular intervals of 4.6 m on two perpendicular transects crossing each other at the center of the field. Simplified split‐window median polishing in conjunction with a robust semivariogram estimator were used to examine the spatial structure of the glacial till material. Results of this study indicated a nested structure of K at 30 cm depth. Soil clustering at the experimental site at intervals of 20 m, in addition to the soil microheterogeneity, contributed to variation in K , with an overall range of spatial dependence of K up to 60 m. Medians of split windows of 23 m width were found to be the “solo representatives” or “summary points” of the soil clusters contributing to spatial structure. In situ and laboratory measurements for K showed consistency in their trends even though some parametric variations were observed. K values observed near the soil surface at a depth of 15 cm were dominated by white noise and directional trends.
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Mohanty et al. (1991) studied this question.