Chloride leaching in a newly irrigated sodic duplex soil from the Burdekin River Irrigation Area

Abstract

An investigation was undertaken to describe chloride and water movement in a newly irrigated sodic duplex Gaynor soil from the Burdekin River Irrigation Area, north Queensland. After landforming, this sodic duplex soil is considered suitable for irrigation of rice but marginal for irrigation of row crops due to the need for further amelioration. In this unreplicated study, chloride leaching was observed under both furrow and ponded irrigation. In furrow irrigated plots, gypsum influenced root zone hydrology such that greater chloride leaching and, hence, infiltration occurred. Chloride leaching, however, decreased with distance along the furrow suggesting 'intake opportunity time' decreased down the furrow. This has management implications in terms of obtaining uniform water application with minimal runoff and deep drainage losses. Under ponding, chloride leaching was not clearly related to landforming or use of gypsum but did appear consistent with ponding plus some form of subsurface drainage, in this case via gravel layers. Use of gypsum increased water use raising the question of increased deep drainage and accessions to local and regional groundwater systems.