Long‐term freezing saline water irrigation and cotton cultivation improved soil properties and maintained low salinity in the root zone of coastal saline soil

Abstract Freezing saline water irrigation in winter has been shown to be an effective method for improving heavy saline–alkali soil via the use of local high‐salinity water. However, the long‐term effects of freezing saline water irrigation on the soil physicochemical properties in the root zone are still unclear. In this study, the dynamics of soil water, electrical conductivity (EC e ) and the sodium adsorption ratio (SAR e ), and changes in relevant soil physicochemical characteristics were investigated on the basis of 11 consecutive years of freezing saline water irrigation and cotton cultivation (FSICC). Although FSICC significantly increased water consumption (ca. 465.92 mm) compared with that of the CK (ca. 133.38 mm), a significantly lower soil EC e in the root zone was still obtained under FSICC than under CK. An annual decrease in soil EC e and an increase in seed cotton yield were observed during the initial 4 years of the FSICC. Thereafter, the soil EC e and SAR e in the 0–20 cm layer were stably maintained below 6.1 dS m −1 and 12.9 (mmol L −1 ) 0.5 , respectively, and a stable seed cotton yield of 3.92 t ha −1 was obtained. Compared with those of the CK treatment, the long‐term FSICC increased the saturated hydraulic conductivity, water retention, soil organic matter and water‐stable aggregates in the 0–20 cm layer, which further increased the available water content and total pore volume (>0.2 μm). These results indicated that the long‐term FSICC significantly improved the soil physicochemical properties and maintained lower levels of soil salinity and SAR e in the root zone, although it significantly increased water consumption.