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

摘要

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.