Distinct pathways of straw management practices regulate soil water, salinity, fertility and barley productivity in coastal saline soil

Abstract

Introduction Soil salinity severely constrains crop productivity in coastal agricultural regions by impairing soil water availability, nutrient acquisition, and root-zone conditions. Straw-based soil management practices have been widely proposed for saline soil improvement, but their comparative effectiveness and underlying mechanisms remain unclear. Methods A two-year container experiment with barley (Hordeum vulgare L.) was conducted during the 2023 and 2024 growing seasons to compare the effects of surface straw mulching (SM), straw incorporation (SI), and straw-derived biochar incorporation (BC) with an unamended control (CT) on soil physicochemical properties, crop growth, and yield formation in coastal saline soil. Results The results showed that the three straw management practices improved soil–crop performance through distinct pathways. SM exhibited the strongest capacity for regulating soil water and salt dynamics, increasing soil moisture content by 84.9% compared with CT at the heading stage in 2024 and maintaining positive salt migration index values throughout the growing season. Consequently, SM produced the highest grain yield in both years, reaching 6581.95 and 7532.59 kg·ha-1 in 2023 and 2024, respectively, representing increases of 6.25% and 19.42% compared with CT. BC showed the greatest potential for improving soil fertility, increasing soil organic matter by more than 33% and enhancing available potassium by 11–26% relative to other treatments in 2023, while maintaining the highest fertility index values (1.55–1.65). SI promoted nutrient accumulation but showed greater interannual variability in soil water and nutrient responses. Structural equation modeling revealed that soil moisture was the most consistent driver of barley yield formation, with its effects primarily mediated through yield components. Discussion Overall, surface straw mulching was the most effective strategy for simultaneously improving soil water conservation, salt regulation, and barley productivity, whereas biochar incorporation provided greater benefits for soil fertility improvement. These findings highlight the importance of matching straw management strategies with specific soil constraints to enhance crop production in coastal saline agroecosystems.