INTERPARTICLE FORCES - A BASIS FOR THE INTERPRETATION OF SOIL PHYSICAL BEHAVIOR

Micromorphologists have made substantial efforts toward defining soil structure and have generated numerous terms to describe soil characteristics as observed by the microscope. Soil structure has been defined by Baver as “the arrangement of soil particles,” which determines the arrangement and size of soil pores. In addressing the operation of interparticle forces, it is necessary to know the interparticle distances. This has been achieved by the measurement of pore size distributions using low temperature nitrogen desorption isotherms and other means. Swelling is one way in which the reaction between clay and water is manifested. The forces that give rise to a greater separation of two interacting clay particles (swelling) are restrained by the suction in the soil water, by London–van der Waals forces, and by ion–ion correlation forces. The chapter discusses the soil water relations. Considerable attention has been given to the extensive crystalline swelling, of Na clays because such swelling can be readily followed by low-angle X-ray diffraction and also because of the possible implications that such research has in relation to sodic soils. The Brunauer–Emmett–Teller (B.E.T.) equation and the Kelvin relationship is applied to low temperature nitrogen adsorption-desorption isotherms to obtain, respectively, surface area and pore size distribution of clays and soils. © 1994, Academic Press Inc.