Vermicompost Modulates Copper Tolerance and Accumulation in Chives (Allium schoenoprasum L.)

Abstract Copper (Cu) contamination compromises soil quality and crop development and may pose risks to food safety at elevated concentrations. In this study, the effects of increasing Cu doses in soil (0–800 mg dm⁻ 3 ) on the growth, root biomass, root morphology, and Cu accumulation in Allium schoenoprasum L. and the influence of vermicompost, were evaluated. After 30 days of soil incubation, available Cu concentration in the soil increased proportionally with the applied dose, reaching 163.8 mg dm⁻ 3 at a dose of 800 mg dm⁻ 3 . Vermicompost contained 43.2 mg Cu kg⁻ 1 , contributing to an increase of approximately 1.295 mg Cu dm⁻ 3 in the soil upon application. Compared with that in the control treatment, a high Cu dose (800 mg dm⁻ 3 ) reduced the root dry biomass by 93.9% and decreased the root length and surface area, indicating phytotoxicity. Compared with a dose of 200 mg dm⁻ 3 but no amendment, vermicompost increased the root dry biomass by 143.1%. Across treatments, Cu accumulation decreased in the order of roots > bulbs > leaves. The maximum concentration reached 236.20 mg kg⁻ 1 in the roots (200 mg dm⁻ 3 + vermicompost), exceeded 70 mg kg⁻ 1 in the bulbs (800 mg dm⁻ 3 ), and reached 9.90 mg kg⁻ 1 in the leaves (800 mg dm⁻ 3 ). At a dose of 200 mg dm⁻ 3 , vermicompost increased the total plant Cu content by 62.8%, whereas no increase was observed at a dose of 800 mg dm⁻ 3 . These results demonstrate that the addition of vermicompost modulated Cu tolerance and tissue accumulation in Allium schoenoprasum L., with beneficial effects at a dose of 200 mg dm⁻ 3 but no mitigation of phytotoxicity at a dose of 800 mg dm⁻ 3 . Graphical Abstract