Evaluating the influence of different straw mulch-autumn irrigation patterns on soil water, heat, and salt in seasonally frozen regions with distributed SHAW model

Abstract

Water scarcity and soil salinization are significant challenges to agricultural production in the Hetao Irrigation District (HID). Autumn irrigation is a crucial strategy for water conservation and salt leaching, and straw mulch is an effective method for alleviating soil salinization. This study used the distributed SHAW model to analyze the spatiotemporal distribution of soil water-heat-salt during the freeze-thaw period (FTP) and spring sowing period (SSP) under various straw mulch-autumn irrigation (SMAI) patterns in the HID from 2000 to 2017. Suitable SMAI modes were recommended and quantitatively evaluated. Results showed that straw mulch thickness influenced soil water, heat, and salt dynamics and the effect of autumn watering was not obvious. Compared with no mulch, under different straw mulch patterns, the 0–40 cm soil water content (SWC) increased by 12.9∼13.1 % on average, the soil temperature (ST) rose by 31.6∼33.6 %, and the soil salt content (SSC) decreased by 38∼49.5 %. Aiming at "low soil salt", "suitable soil moisture and temperature", "water saving", and "straw mulch cost saving", an autumn irrigation quota of 90 mm and straw mulch of 0.9 kg/m² were recommended for Dengkou County (DK) and Hangqinhouqi (HH); Linhe District (LH) and Wuyuan County (WY) were advised to adopt an autumn irrigation quota of 90 mm and straw mulch of 0.6 kg/m²; Wulateqianqi (WQQ) was recommended to adopt an autumn irrigation quota of 90 mm with no mulch. Compared with traditional autumn irrigation, under the recommended SMAI mode, the average annual increase in SWC was 0.1∼6.6 %, ST varied from −6.6–6.2 %, and SSC changed from −34.6–20.8 %. Implementing the recommended mode could save approximately 494 million m³ of Yellow River water annually, despite an average annual cost of about 13.77 million RMB (1.97 million US $) for straw mulch. The results offer useful references for optimizing SMAI modes and conserving water resources in the HID.