AimsStraw return is a key conservation practice for enhancing soil fertility and sustainability in dryland agriculture. However, its long-term effects on soil microbial function and crop productivity in semi-arid regions remain insufficiently understood. This study aimed to elucidate how different straw-return practices influence soil quality, microbial functional potential, and maize yield in a semi-arid agroecosystem. MethodsA four-year field experiment (2021-2024) compared deep ploughing with straw return (DPR), subsoiling with straw incorporation (SSR), and no-tillage mulching (NTR) against shallow rotary tillage (CK). Soil physicochemical properties, enzyme activities, microbial carbon-source utilization, and maize yield were analyzed to calculate the Soil Quality Index (SQI) and Ecosystem Multifunctionality (EMF). ResultsStraw-return practices markedly improved soil fertility, microbial activity, and maize yield compared with CK. DPR, SSR, and NTR increased SQI by 1.5-2.1 times and EMF by 1.1-1.6 times. DPR reduced bulk density by 8.7%, raised soil organic matter and total nitrogen by 26.4% and 18.2%, and enhanced beta-glucosidase, RUBP, and H2O2 activities, resulting in a 14.18% higher yield than CK (P < 0.01). PLS-PM revealed that yield formation was primarily governed by the "structure-nutrient-microbial metabolism" pathway (R2 = 0.85; GOF = 0.84), integrating soil physical improvement with microbial functional enhancement. ConclusionsDifferent straw-return practices enhance soil quality through contrasting functional mechanisms. DPR mainly enhanced soil structure and nutrient availability, while SSR and NTR improved microbial functions via biological feedback. Overall, DPR proved to be the most effective strategy for improving soil fertility and sustaining maize productivity in semi-arid farmland. Highlights center dot A four-year field study (2021-2024) evaluated the coupled effects of deep ploughing, sub-soiling, and no-till straw return on soil quality and maize productivity in semi-arid farmland. center dot Straw return significantly enhanced soil structure, nutrient status, enzyme activities, and microbial car-bon-source utilization compared with shallow rotary tillage (CK). center dot Deep ploughing with straw return (DPR) reduced bulk density, increased SOM and TN, and improved hydrolytic and oxidative enzyme activities, achieving the highest maize yield. center dot Soil quality index (SQI) and ecosystem multifunc-tionality (EMF) were strongly correlated with micro-bial metabolism and yield (R-2 = 0.85), indicating a "structure-nutrient-microbial metabolism" pathway. center dot Soil Quality Index (SQI) and Ecosystem Multifunc-tionality (EMF) were strongly correlated with micro-bial metabolism and yield (R-2 = 0.85), revealing a "structure-nutrient-microbial metabolism" pathway. center dot The study refines the"structure-dominant-biologi-cal feedback" model of soil quality evolution and pro-vides a mechanistic basis for optimizing straw-return strategies in semi-arid regions.