Evaluate the necessity of autumn irrigation on salinized soil by considering change in soil physicochemical properties

Abstract Agricultural irrigation is an effective way to control soil salinization in cold/arid regions. Specifically, autumn irrigation before soil freezes can inhibit the salt accumulation that occurs on the soil surface from freezing and thawing. However, changes in planting structure have resulted in farmers no longer conducting autumn irrigation, which may exacerbate the degree of soil salinization should this continue. Because autumn irrigation is very important for farmland management strategies, this study set up three management measures, autumn irrigation, no autumn irrigation and straw mulching, to evaluate the need to conduct autumn irrigation on salinized soil based on soil physicochemical properties. The results showed that autumn irrigation increased the soil water storage after thawing by 3.36×10− 2 m, soil salt storage increases were low, and the topsoil salinization grade did not change. However, with no autumn irrigation and straw mulching, the salt storage at 0–20 cm increased by 178.08% and 133.44%, respectively, and the topsoil became intensely salinized. Compared with that before freezing, the decrease in total soil porosity with autumn irrigation was smaller, but autumn irrigation exacerbated the fragmentation of large soil aggregates. The ≥ 0.3–100 µm pore size was reduced by 12.23% and 7.43% with no autumn irrigation and straw mulching, respectively, and the structure and function showed a degradation trend. Conversely, autumn irrigation improved soil water retention. The structural equation model further showed that autumn irrigation positively impacted the physicochemical properties of saline soil. This study provides new insights into mitigating salinization and developing farmland management measures.