Leaching salinity and mulching straws during freeze-thaw period enhance post-thawing cotton yield and quality by optimizing soil aggregates stability

The salinization of arable land in Xinjiang poses a significant barrier to local agricultural development, with seasonal freeze-thaw cycles intensifying the problem of soil salinization. Implementing agronomic measures to enhance soil properties during these cycles is crucial for mitigating salinization and promoting sustainable agriculture. This study presents the results of the simultaneous application of winter irrigation and straw mulching measures in saline areas of Xinjiang. A field experiment was conducted from the end of the 2022 cotton (Xinluzao 52) growing season to the end of the 2023 season, employing three winter irrigation quotas (1800, 2400, 3000 m³ ha⁻¹) and three straw mulch thicknesses (0, 10 cm (800 kg ha⁻¹), 20 cm (1600 kg ha⁻¹)) across, along with a control check (CK) without irrigation or mulching. We evaluated the 0–40 cm soil layer for changes in aggregate distribution and stability, soil salinity, and soil organic carbon (SOC) content before and after the freeze-thaw cycle. Additionally, we analyzed differences in cotton yield quality under each plot in 2023. The results showed that combination of winter irrigation and straw mulching significantly increased the content of large-aggregates (> 2 mm) and enhanced aggregate stability, as measured by mean weight diameter (MWD) and geometric mean diameter (GWD). This combination also reduced soil salinity and increased soil organic carbon (SOC) content within the 0–40 cm soil layer during the freeze-thaw period, leading to improved cotton yield and quality in the subsequent year. Post freeze-thawing, large aggregate content, MWD, GMD, and SOC storage increased by 1.59 %-11.64 %, 1.61 %-21.61 %, 12.80 %-33.90 %, and 12.80 %-33.90 %, respectively, while salt storage decreased by 37.71 %-52.17 %. Compared to CK plots, seed cotton yield in winter irrigated and straw mulched plots increased by 844.70–2298.07 kg ha⁻¹. Pearson correlation and principal component analysis (PCA) revealed that winter irrigation combined with straw mulching enhances cotton yield and quality by increasing SOC content, reducing salinity in the tillage layer, and improving aggregate stability. Based on our findings, we recommend the application of winter irrigation and straw mulching before the freezing of saline soils in Xinjiang.