Adsorption of nitrate, chloride and sulfate by some highly weathered soils from south-wast Queensland

Soil was collected from a number of sites and depths to 300 cm within four great soil groups (krasnozem, red earth, xanthozem, podzolic). Nitrate, chloride and sulfate adsorption were determined at the soil pH. Various soil properties likely to influence the magnitude of adsorption were determined, and their relative importance to adsorption was assessed using stepwise multiple regression. The subsoils of all four soil groups adsorbed nitrate ranging up to 0.47 mmoles/100 g from 0.005 M potassium nitrate solution. The mean adsorption for soil groups decreased in the order krasnozem, xanthozem, red earth and podzolic. Chloride and sulfate adsorption was largely equivalent to that of nitrate. The variations in adsorption between and within great soil groups could be attributed to changes in organic matter, smectite minerals, hydroxy aluminium, surface area and pH.