Subsoil incorporation of vegetable waste reduced odor emissions and promoted nutrient recovery

Vegetable industry generates massive perishable waste during refrigerated transportation and storage, emitting malodorous NH₃ and H₂S gases that pose severe environmental risks. Current treatment technologies (e.g., composting, energy recovery) struggle to balance efficiency, cost, and pollution control. This study developed a novel approach-subsoil incorporation of vegetable waste (SIVW)-to achieve simultaneous odor mitigation, soil nutrient recovery in reclaimed farmlands, and resource circulation. The field experiment included three VW incorporation rates: 80 t ha^-1 (dry weight, W1), 160 t ha^-1 (W2), 240 t ha^-1 (W3), and two burial depths: 30 cm (D1) and 50 cm (D2), alongside a layered burial treatment (M-W3) with dual-layer placement of 240 t ha^-1 VW separated by 25 cm soil intervals. Controls included open-air stockpiling of VW (ND-W3) and no VW incorporation (nVW). SIVW reduced cumulative NH₃ and H₂S emissions by 87.3-93.7 % and 83.6-89.7 %, respectively, compared to open-air stockpiling. Concurrently, SIVW enhanced soil nutrient availability: NH₄⁺-N and NO₃^--N concentrations increased by 49.2-176.9 times and 53.8-80.6 times, respectively, while K⁺, Ca²⁺, Mg²⁺, and other ions rose in the topsoil and subsoil. Notably, soil salinization risks were manageable under moderate application rates (<222 t ha^-1), and heavy metals (HMs) accumulation remained below regulatory threshold (Nemerow Index≤0.7). Field trial revealed that SIVW significantly improved maize growth without affecting emergence rates, with plant height and biomass increasing by 1.4-2.0 times and 3.4-7.3 times, respectively. This productivity boost arose from synergistic effects of enhanced nutrient supply and reduced the pH of high-alkaline soils. This approach aligns with circular economy principles by transforming waste into a resource, offering a scalable paradigm for sustainable agriculture.