Soil Anisotropy and its Relation to Aggregate Stability

Abstract

A study was made to correlate soil anisotropy to aggregate stability. For soils having similar pedality, texture and mineralogy, aggregate stabilities increase with increasing anisotropy. Soil anisotropy in turn is an index of the degree of organization of the primary inorganic constituents. It was demonstrated that relative measurement of soil anisotropy can be made by the use of a photometer. The anisotropy of a given soil can be evaluated quantitatively if the anisotroplc materials are evenly distributed throughout the matrix. Soils which have illuviation cutans or pressure cutans on ped faces but possess isotropic ped interiors cannot be measured in the absence of a suitable sampling technique that will represent an average cross section of the soil. A possible mechanism of aggregate formation with plates (kaolinite) and cementing agent (hydrated iron oxide) was elucidated not on the basis of the amount or concentration of each component but on their pedological organization. This mechanism has been shown to hold true for a group of Hawaiian Latosols.