SOIL MORPHOLOGY AND SOIL PHYSICAL PROPERTIES. II. MECHANICAL IMPEDANCE AND MOISTURE RETENTION AND MOVEMENT

Abstract

The relations among soil structure, soil mechanical impedance, and moisture retention and movement were investigated on undisturbed soil cores from soil horizons exhibiting six distinct kinds of soil structure (prismatic, columnar, blocky, granular, platy, massive) over a broad range of soil texture. Mechanical impedance was characterized by measurements of bulk density and soil strength. Moisture retention and movement were characterized by measurements of [Formula: see text]-atm moisture content and saturated hydraulic conductivity. The columnar structures from Solonetzic soils were singled out as having a higher mechanical impedance and lower hydraulic conductivity than the other structures, most of which were sampled from Chernozemic soils. Total porosity (P) and bulk density (Db) were highly correlated; however, the regression coefficient for P vs. Db for columnar structures was significantly higher than that found for the other five structural types. Regression equations predicted that the hydraulic conductivity of platy structures could be zero for samples having as much as 15% air-filled pore space at [Formula: see text]-atm suction as compared with 6–8% for the other structures.