Declining water quality and quantity is a threat to the production of food and fibre worldwide. While irrigation using marginal quality saline-sodic (MQSS) water is emerging as a more common practice, it is still an under-utilised resource because of its potential detrimental impact on soil structure and crop production. The aim of the research was to enhance the current understanding of, and capability to, strategically utilise saline-sodic water as an irrigation resource through further investigation of the theory of threshold electrolyte concentration (C TH).