Estimating Saturated Hydraulic Conductivity from Soil Morphology

Guidelines were developed for estimating the saturated hydraulic conductivity ( K sat ) class of soil horizons from observations of soil morphology by checking estimates against K sat values measured in the field by an air entry permeameter. For 78 soil horizons ranging in texture from sand to clay, the estimated K sat class (of eight classes) was the same as the measured class for 45% and within one class of the measured class for 87% of the horizons. Some horizons fell into each of the classes defined, from H1 (>50 cm/h) to L3 (<0.017 cm/h). The major factors contributing to high K sat values were abundant biopores, textures coarser than loamy fine sand, and strong, fine to medium blocky structure. The lowest values were associated with clayey horizons that had been compressed or puddled by cultivation. Useful estimates of K sat can be made during soil survey by careful observations of morphology and frequent checks of estimates against measured values.