Vermicompost combined with nano-SiO2 improves overall soil quality and tomato productivity in a degraded soil

Global soil degradation has emerged as a critical constraint to sustainable agriculture. While organic and inorganic amendments are widely employed for degraded soil remediation, each is plagued by inherent limitations, and their combined synergistic mechanisms remain unclear. To address these gaps, a three-year field experiment was conducted using two tomato varieties to investigate the effects of vermicompost, nano-SiO 2 , and their combination on degraded soil quality and tomato productivity. A multi-dimensional soil quality index (SQI) integrating physical, chemical, microbial, and nematode traits was constructed for comprehensive evaluation. Results showed that compared with the control, vermicompost and nano-SiO 2 alone increased SQI by 175.1% and 21.4%, respectively, while their combination achieved a 248.8% SQI increase and 10.9% higher yield, outperforming the individual applications. The SQI was significantly positively correlated with tomato biomass and yield, verifying the strategy’s practical value. The structural equation model elucidates a cascade mechanism involving physicochemical reconstruction, microbial activation, and nematode food web optimization, confirming that the combined effect arises from coordinated interactions among soil components rather than simple additive effects. Collectively, these findings provide a useful, sustainable approach for degraded soil management and theoretical support for the efficient application of organic–inorganic combined amendments in agriculture.