Optimization Study on the Freshwater Production Ratio from the Freezing and Thawing Process of Saline Water with Varied Qualities

Freezing saline water irrigation is an effective technique for leaching soil salts. However, the coupling effects between initial salinity, sodium adsorption ratio (SAR), and freezing temperature of saline water have not been systematically studied. Therefore, a three-factor and five-level quadratic general rotation combination design was adopted, employing indoor simulated freeze–thaw experiments to investigate the influence of these three factors on the freshwater production ratio. The results indicated the following: (1) Within the range of the set experimental factor levels, the freshwater production ratio after the freezing of saline water ranged from 23.34% to 81.11%. (2) The significant negative effect of the main factor on the freshwater production ratio was descending order: initial salinity > freezing temperature. Although the impact of saline water SAR on the freshwater production ratio is insignificant, the interaction between saline water SAR and the freezing temperature has a highly significant negative effect on the freshwater production ratio. (3) At least 83% of the salt content was leached out in the first 16 h when the ice was thawed at 6 °C. These findings are beneficial for selecting appropriate irrigation times based on irrigation water quality in the actual field application of saline water freezing irrigation, with the aim of more efficiently reducing soil salt content.