Potassium and chloride movement in a forest soil under simulated rainfall

Abstract

An initial appraisal of the mechanisms involved in reactive solute transport through a weathered soil profile was made by following the movement of potassium and chloride during prolonged leaching on a sprinkle-irrigated native forest plot. The soil was an acid, strongly base-unsaturated red duplex soil with a high surface and subsurface hydraulic conductivity. Water movement was followed by tensiometers located at regular depth intervals to 1.5 m, and soil water samplers with ceramic cups were used to collect soluble potassium and chloride. Some 650 mm of water moved beyond 1.5 m depth in the profile, but chloride did not move beyond 1 m. Nearly all of the potassium was retained in the soil above 0.6 m depth. Although both ions underwent ion exchange, adsorption of potassium was reasonably uniform through the profile, whereas chloride adsorption increased with depth. Immediate ground- and stream-water contamination did not occur under these conditions.