A PROCEDURE FOR EVALUATING THE COMBINATIONS OF SOIL-FORMING FACTORS THAT FAVOR THE DEVELOPMENT OF VERTIC PROPERTIES IN SOILS

A procedure for the integral qualitative and quantitative evaluation o f soil-forming factors and their combinations that favor the developme nt of vertic properties in soils is outlined. The following factors ar e considered: (1) climate, i.e., the ratio of annual precipitation to evapotranspiration and the value of moisture deficit for the whole yea r and for the dry season; (2) geomorphic conditions, i.e., the positio n of a site in relief that dictates the character of surface runoff (t he proportion between the input and loss of surface water); and (3) li thology, i.e., the proportion of clay and physical clay in the fine ea rth fraction and the content and qualitative composition of smectitic minerals. The integral estimate of a combination of these factors is c alculated from the assessments of separate factors and their combinati ons with the help of special diagrams and tables.