THE MOVEMENT OF SALTS THROUGH SOIL AS AFFECTED BY SUBSOIL STRUCTURE (OKLAHOMA)

Scope and Method of Study. One meter of undisturbed and packed columns from four Payne County, Oklahoma, soils (three Cumulic Haplustolls and one Pachic Argiustoll, all sandy clay loam soils) were collected to study the effect of subsoil structure on salt movement through soils. Undisturbed soil cores (10 cm x 1 m) were obtained with a coring machine. A solution containing 100 ppm Rb was added to each column at a rate of 10 ml every 8 hours for 6 weeks and then 1000 ppm for a 4-week period. Solution samples were collected at periodic intervals along the columns. Collected samples were analyzed for Rb('+) content. At the end of the solution sampling period, the columns were dismantled. Soil Samples were taken at periodic intervals along the columns. Ped surface and ped matrix samples were taken from the angular, subangular blocky, and prismatic soils. The samples were then analyzed for Rb('+) on the Atomic Adsorption Spectrophotometer.; Findings and Conclusions. Analyses of the soil extraction data indicated Rb('+) was transported 25% faster in well-structured soils compared to weakly structured and massive soils, all other factors being constant. Rb('+) movement through prismatic soils is to a greater depth than the other structural types. Analyses of ped surface-matrix samples by depth supports the conclusion that flow is primarily down the defined macropores and vertical axes of the well-structured soils. Where soil selection permits the use of comparable soils differing in structure for waste disposal, weakly or massively structured soils can provide better protection from groundwater pollution. Whenever column studies are used in lieu of field experiments, use of undisturbed soil columns are recommended.