Validating laboratory assessment of threshold electrolyte concentration for fields irrigated with marginal quality saline-sodic water

Abstract

The use of marginal quality saline-sodic (MQSS) water for agricultural production is important in water limited environments and with a growing demand for food and fibre. Soil structural response to irrigation water quality is known to be a function of sodium contained in the irrigation water and the electrolyte concentration of that water. The threshold electrolyte concentration (CTH) is classically used to determine the suitability of water to be applied to a soil, and is usually conducted as a laboratory analysis utilising saturated hydraulic conductivity. This work aimed to validate the laboratory based semi-empirical disaggregation model approach to CTH against field soils where MQSS water had been applied for an extended period of time. Unirrigated locations proximal to long-term irrigation sites were paired to provide control conditions and the CTH was determined. Reduction in hydraulic conductivity from the control was determined as both observed and predicted data. Results supported validation of the approach, indicating the disaggregation model as useful for proactive planning of irrigation systems with regard to water quality and a good measure for identification of MQSS water as a strategic resource. Applicability of the results to irrigation guidelines was discussed with particular focus on removal of generalised guidelines and identification of what constitutes tolerable hydraulic conductivity reduction.