C/N-Driven Synergies: Earthworms optimize CO₂/N₂O mitigation and soil quality in floral waste recycling

The expansion of floriculture has increased the need for sustainable floral waste management to support agricultural carbon neutrality. This study assessed the impact of carnation, lily, and rose straw amendments (with varying C/N ratios, lignin, and cellulose) on GHG emissions and soil quality with earthworm (Eisenia fetida). Controlled microcosm experiments were conducted to examine the effects of straw types and earthworms on CO₂ and N₂O fluxes, as well as soil properties, enzyme activities, and microbial functions. The results revealed that Earthworms enhanced straw mineralization, increasing cumulative CO₂ emissions by 1.09-1.50-fold compared to controls (P < 0.05). N₂O emissions varied by C/N ratio: earthworms reduced N₂O emissions by 42.7 % (carnation) and 20.3 % (lily), but increased it by 56.4 % (rose). Optimal GHG mitigation was achieved in low-C/N systems (carnation + earthworms) which reduced N₂O emissions by 42.7 % with a moderate CO₂ increase (9.1 %), highlighting the risks of high lignin content and microbial N limitation. Soil quality, measured through the Soil Quality Index (SQI), was significantly improved by earthworm-straw interactions in all treatments (TDS-SQI: 0.61-0.68) compared to straw-alone controls (TDS-SQI: 0.53-0.60) (P < 0.05). The TDS-SQI revealed that Earthworm-straw combinations, especially those with low C/N ratios, optimized both soil quality and GHG mitigation. This study highlights earthworms' potential to modulate carbon-nitrogen cycling, offering a feasible strategy for sustainable floral waste recycling that supports carbon neutrality goals. Prioritizing this approach in floral waste recycling programs is recommended for sustainable agriculture.