STATISTICAL AND AUTOREGRESSIVE ANALYSIS OF SOIL PHYSICAL-PROPERTIES OF PORTSMOUTH SANDY LOAM

Reliable estimates of soil physical and hydraulic properties are needed for designing drainage systems for soils with limited natural drainage. The objective of the study was to determine the autocorrelation structure of soil physical properties in a poorly drained soil. Saturated hydraulic conductivity, soil-water characteristic, soil-water diffusivity, texture, and bulk density were measured on undisturbed soil cores sampled from the A, Btg, and Bg soil horizons at 150 points on two transects in a field of Portsmouth sandy loam (Typic Umbraquults). Unsaturated hydraulic conductivity for each of the 450 cores was computed using a quasi-analytical expression utilizing measured soil-water diffusivity data and the derivative of the inverse of the van Genuchten equation for the measured water characteristic. Hydraulic conductivity values at a given soil-water pressure had a high coefficient of variation, ranging from 130 to 3300%, and were lognormally distributed.