Improving saline–alkali soil physicochemical properties and microbial diversity for sunflower yield optimization: Integrating precision irrigation, organic substitution, and straw return

Soil salinization and declining microbial diversity present significant challenges to sustainable agriculture. This study investigated the effects of combined agronomic practices on soil quality, microbial diversity, ecological functions, and sunflower ( Helianthus annuus L.) productivity in arid regions from 2022 to 2023. The treatments included conventional drip irrigation, irrigation on crop demand (IOD), chemical fertilizer only, organic substitution (OS), straw return (SR), and straw not return. Mantel analysis and partial least squares path model (PLS−PM) were used to access the interrelationships among microbial diversity, soil properties, and sunflower productivity. The results showed that OS and SR significantly improved soil structure by reducing pH, bulk density, and electrical conductivity (EC). While IOD had no significant impact on soil properties ( P > 0.05), it increased sunflower yield by 18.81 %. The combined IOD+SR+OS treatment produced the highest yield (4.35 t hm −2 ), reflecting a 12.11 %−44.52 % increase compared to other treatments. This treatment also enhanced microbial diversity (Shannon index) and richness (Chao 1 index). The dominant bacterial and fungal phyla included Proteobacteria, Actinobacteriota, Acidobacteriota, Ascomycota, and Basidiomycota. Co−occurrence network analysis revealed greater microbial network stability under IOD+SR+OS treatment, with bacterial and fungal nodes reaching 199 and 139, respectively, and the number of edges increasing to 6678 and 3139. Functional analysis further indicated that this treatment enriched amino acid metabolism, carbohydrate metabolism, and membrane transport. PLS−PM identified soil EC as the primary yield−limiting factor, whereas OS and SR were key yield−enhancing drivers. These findings contribute to sustainable sunflower production in saline–alkali soils of arid regions. • Integrated agronomic practices improved soil microbial diversity and ecological functions in arid regions. • Integrated agronomic practices showed superior effectiveness in enhancing saline-alkali soil quality. • Integrated agronomic practices significantly increased sunflower yield by up to 44.52 %. • Organic substitution strongly correlated with enhanced microbial richness and diversity.