Effects of magnetized saline water and gypsum amelioration on soil water-salt movement

Saline water has been widely used to alleviate the freshwater shortage during agricultural production in arid and semi-arid regions. However, continuous saline water irrigation can easily lead to soil salinization, even soil degradation, and reductions in crop yields. It is critical to select the appropriate water treatment and soil amendment for sufficient water, but less accumulation of salinity in the soil. In this study, the magnetized saline water and gypsum ameliorate were served as the ecologically pure, safe, and simple treatment on soil water-salt movement. One-dimensional vertical infiltration experiments were conducted to investigate the infiltration with/without magnetized saline water into the saline soil with different gypsum applications. Five gypsum application (0, 0.1, 0.2, 0.4, and 0.6 kg/m2) were used. The results showed that the cumulative infiltration and the depth of wetting front decreased, with the increase of gypsum application with/without magnetized saline water. There was a significant decrease in the final cumulative infiltration and the depth of wetting front of magnetized saline water for different gypsum applications. The cumulative infiltration of magnetized saline water decreased by 14.9%, 10.9%, 9.5%, 8.0% and 8.9%, respectively, under five gypsum application of 0, 0.1, 0.2, 0.4 and 0.6 kg/m2, compared with non-magnetized saline water. The cumulative infiltration of 0.1, 0.2, 0.4, and 0.6 kg/m2 application amount for non-magnetized saline water treatments decreased by 9.8%, 13.3%, 17.1% and 21.5%, respectively, compared with the control (0 kg/m2), whereas, those decreased by 5.6%, 7.8%, 10.4% and 16.0%, respectively, in magnetized saline water treatments. The sorptivity of magnetized saline water decreased by 24.4%, 22.7%, 19.1%, 19.1%, and 19.2%, respectively, under the five gypsum applications, compared with non-magnetized saline water. The soil water content decreased, as the depth increased for the saline water. The soil water content of magnetized saline water increased by 12%, 11%, 14%, 14%, and 11%, respectively, compared with the non-magnetized saline water. There was the highest soil water storage for 0.4 kg/m2 gypsum application under magnetized saline water irrigation, which was 14.9% higher than that of non-magnetized saline water. The depth of the desalination zone increased firstly and then decreased, with the increase of gypsum application amount. The soil salinity content of magnetized saline water decreased by 48.8%, 28.7%, 37.5%, 29.1%, and 60.0% at 20cm soil depth, respectively, compared with non-magnetized saline water, indicating that the magnetized saline water decreased the infiltration rate of soil water and the transport speed of wetting front. The gypsum can be used to reduce the soil sorptivity of the Philip equation, but to significantly increase the soil desalination rate and efficiency. There was the highest desalination efficiency for the 0.4 kg/m2 gypsum application, where the desalination rate increased by 59%. Thus, the magnetized treatment and gypsum application can serve as an effective way to improve soil water retention and enhance desalination salt leaching. This finding can provide theoretical support to efficiently utilize the irrigation water in the saline-alkali soil.