Salt leaching process in coastal saline soil by infiltration of melting saline ice under field conditions

Abstract

Freezing saline water irrigation (FSWI) in winter has been shown to be an effective way to reclaim heavy saline soils. In this four-year experiment, the salt leaching process during saline ice melting and infiltration after FSWI was investigated. Saline water was frozen in saline ice on top of soil after irrigation. Over 70 or 80 days of ice melting and infiltration, ice and soil samples were taken at 10-day intervals to quantify the soil salt leaching process. The results showed that salt leaching mainly occurred in the initial 30 days after irrigation (DAI); approximately 72% of the total salt reduction was the result of salt migrating out of the 0 to 20 cm soil layer. Furthermore, in this period, the amount of salt that leached out of the 0 to 20 cm soil layer with meltwater was greater than the total salt from the irrigation water. Approximately 15% of the total salt reduction in the 0 to 20 cm layer occurred from 60 to 80 DAI; in this period, the infiltrating meltwater accounted for more than 30% of the total irrigation water, and the electrical conductivity of the meltwater was below 4.5 dS m⁻¹. After the meltwater had infiltrated the soil completely, the electrical conductivity of saturation paste (EC_e) in the 0 to 20 cm layer for FSWI was below 4.3 dS m⁻¹, significantly lower than the EC_e of 16.7 dS m⁻¹ of the nontreated soil. These results indicated the soil salt leaching was mainly determined by the melting process of saline ice under the FSWI treatment.