Effects of saline ice-melt water irrigation on soil water, salt movementand corn growth in agricultural fields

Freshwater is widely regarded as the most important and fundamental natural resource that is integral to all ecological and societal activities, including food and energy production, industrial development and human health. At the global or even country level, there exists significant spatio-temporal variability in renewable water resources, resulting in severe freshwater shortages in some regions of the world. Underground salt-water deposits could not meet domestic water supply requirements due the generally high salt content even for agricultural irrigation, let alone for domestic consumption. So desalination, which is the separation of water form salt solution for freshwater supply, could be a viable option needing facilitation. Four laboratory irrigation modes were designed in Dezhou Experiment Station of Chinese Academy of Agricultural Sciences. The irrigation modes included control treatment (freshwater irrigation, CK), saline water irrigation (SW), saline ice-melt water irrigation (MI) and saline ice-water irrigation plus wheat straw mulch (MI+SW). The mechanisms of water and salt movement in the soil during saline ice-water melt were studied in a soil column experiment. Corn was planted in the soil column after seven days and the effects of saline ice-melt water irrigation on soil water content, salt movement and corn growth determined. The results showed soil water content in the 0~40 cm layer under saline water irrigation treatment was lower and that in the deeper soil layer higher compared to that under freshwater irrigation treatment. Compared with freshwater irrigation treatment, saline ice-melt water irrigation treatment also showed a similar trend; where there was lower water content in surface soil and higher water content in deep soil layers. However, wheat straw mulching increased soil profile water content. Soil salinity under freshwater irrigation treatment was very low in the 0~60 cm soil later, less than 0.2 dS·m^-1. In the 60~80 cm soil layer, however, salinity increased significantly (0.4 dS·m^-1), although still much lower than that under saline water irrigation treatment. While saline ice-water irrigation treatment decreased salinity in the 0~40 cm soil layer, it increased salinity in deep soil layers. Salt accumulation was higher under saline water irrigation treatment with aggregation properties in surface soil. The 0~40 cm soil layer accounted for 62.2% of accumulated salt in the 0~80 cm soil layer. However, accumulated salt in the 0~40 cm was 18.6% of accumulated salt in the 0~80 cm soil layer under saline ice-water irrigation treatment. Saline ice-water irrigation plus straw mulching accelerated desalinization of soil surface, especially in the 0~10 cm soil later. Salinity under saline ice-water irrigation plus straw mulching was only 0.15 dS·m^-1 with a salt content of 67.8 g·m^-2, which showed no significant difference with freshwater irrigation treatment. This suggested gradual reduction in total salt content of melt-water. Saline ice-water irrigation improved surface soil desalination and maintained low root-zone soil salinity, which alleviated or even eliminated salinity-driven hazards in agricultural crop and soil environment. Agricultural soil conditions even improved further when saline ice-water irrigation was combined with straw mulching, under which corn graw well as under freshwater irrigation. In a conclusion, underground salt water was usable during ice-melt in the Huang-Huai-Hai Plain.