The grouping of soils with similar charge properties as a basis for agrotechnology transfer

Abstract

A set of 94 variable charge soils (Oxisols and Ultisols) from humid tropical Queensland has been formed into three groups on the basis of their surface charge characteristics. Mean curves of basic cation exchange capacity (CECB) against pH, total cation exchange capacity (CECT) against pH, and anion exchange capacity (AEC) against pH for each group at various soil depths were derived, to describe the essential features of each group, designated as Type 1, Type 2 and Type 3 soils. Type 1 soils have high CEC and low AEC, Type 2 soils have low CEC and low AEC, and Type 3 soils have low CEC and high AEC. A number of statistical devices were employed to illustrate the clear separation of the three groups. Additional Oxisol and Ultisol soils from southern China, Peru and the south-eastern United States were successfully allocated to our three groups, but this was not possible for some Andisols from Papua New Guinea. Aspects of possible different management requirements of each group are discussed.