DISAGGREGATION AND CLAY DISPERSION OF OXISOLS - NA RESIN, A RECOMMENDED METHODOLOGY

Comparison of five different dispersion techniques on six different low-activity clay-soil pedons showed that Na-resin treatment was the most efficient particle-size distribution method for the very stable Oxisols rich in gibbsite. In these Oxisols, and particularly in their strongly aggregated A horizons, clay dispersion with combined controlled ultrasonic or vigorous mechanical and chemical treatments was lower and was partly pH-dependent. The role of gibbsite, crystalline Fe oxides and oxyhydroxides, organic materials and poorly-ordered Al and Fe hydrous oxides on the aggregate stability of low-activity clay soil and clay dispersion is discussed.