Soil morphological and chemical profiles adjacent to a bore drain in south-western Queensland, Australia

Abstract

A recently abandoned artesian bore drain in south-western Queensland was sampled to investigate soil morphology and chemistry under, and adjacent to, the drain. Such drains are supplied with alkaline, sodium-rich artesian groundwater and they provide a long-term example of the impacts of these waters on soils. A Red Kandosol and a Grey Vertosol were sampled, in the drain and at 2, 4 and 25 m perpendicular to the drain. Morphological attributes indicative of long-term saturation, such as mottling, were evident around the drains, but were absent at the control sites (25 m away). At the Kandosol location, pH and exchangeable sodium were elevated within 4 m of the drain, and salinity data suggested a horizontally displaced wetting front at ~4 m from the drain. In the Grey Vertosol, which was naturally saline and sodic below 0.5 m, substantial leaching of salts had occurred around the drain, but a horizontal wetting front was also evident and exchangeable sodium was increased within 4 m of the drain. A thin, weak pan was detected in the subsoil of the Red Kandosol under the drain bank, but pans were otherwise absent under the drains. The results indicate that deep drainage is a feature not only of the Red Kandosol, but also the Grey Vertosol, despite it being sodic and despite the application of sodic, alkaline water. The findings reiterate the importance of investigating soil and water chemistry interactions when designing channels, storages and irrigation systems, in particular those using sodic–saline waters.