A Robust-Resistant Approach to Interpret Spatial Behavior of Saturated Hydraulic Conductivity of a Glacial Till Soil Under No-Tillage System

Abstract

<p>A central Iowa glacial till soil under no-tillage condition was studied for its spatial behavior of saturated hydraulic conductivity (<em>K</em>) 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 <em>K</em> 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 <em>K</em>, with an overall range of spatial dependence of <em>K</em> 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 <em>K</em> showed consistency in their trends even though some parametric variations were observed. <em>K</em> values observed near the soil surface at a depth of 15 cm were dominated by white noise and directional trends.</p>