Optimizing organic fertilization towards sustainable vegetable production evaluated by long-term field measurement and multi-level fuzzy comprehensive model

Precision and efficient management of organic substitution fertilization is crucial in balancing soil health, environmental risks, and economic benefits for intensive crop cultivation. However, effectively determining the optimal organic substitution ratio in vegetable production remains uncertain and still relatively unexplored. We conducted a five-year vegetable field experiment and established four nitrogen-equivalent fertilization treatments: mineral fertilizer alone, and organic fertilizer substituting a quarter, half, and entirety of the mineral nitrogen. Employing a specialized multi-level fuzzy comprehensive evaluation model, our study assessed impacts of different organic substitution ratios on soil qualities, microbial diversity, vegetable yield and quality, environmental risks, and economic benefits in sustainable vegetable production of eastern China. Our results showed that the 50% organic substitution was optimal, significantly improving soil qualities and microbial characteristics, particularly in the topsoil layer. Compared to the control, this approach significantly reduced methane by 6.6–48.3%, nitrous oxide by 49.5–79.1%, and nitric oxide by 36.5–50.0%, while enhancing vegetable yield by 16.0–28.3% and its five-year average stability as well as quality as evidenced by increased protein, soluble sugar, and vitamin C contents. Economic analysis revealed that while it maximized environmental benefits, complete organic substitution did not consistently yield positive economic returns. In contrast, a 50% substitution ratio was identified as the most economically viable, representing a sustainable compromise that balances environmental health with economic feasibility. Further modeling analysis indicated an optimal comprehensive range between 42.9% and 64.5% for achieving the best balance of multiple objectives in vegetable fields. The study underscores the intricate organic substitution effects on intensive vegetable production, highlighting the necessity for tailored organic substitution strategies that integrate environmental sustainability with agricultural productivity and economic practicality.