Copper sulfate causes greater toxicity and growth inhibition in grapevine seedlings compared to copper chloride in different vineyard soils

Context Understanding copper (Cu) toxicity and distribution is crucial for mitigating its accumulation in vineyards and ensuring safe grape production. Aim This study investigated the dynamics and stability of Cu forms and the effects on grapevine growth through a 112-day incubation pot experiment under greenhouse conditions. Method Exogenous Cu was applied at three concentrations – control (0), low (1.5×: CuCl-1, CuSO-1) and high (3×: CuCl-2, CuSO-2) – of the Chinese national standard screening values (GB15618-2018) in two vineyard soils in China. After 112 days of ageing, uniform grapevine seedlings were transplanted into experimental pots. Key results The stability of exogenous Cu was mainly affected by soil type and Cu salt. In red soil, Cu was predominantly found in the acid-soluble fraction, reaching a peak of 86.67% under CuSO-2. Black soil showed a balanced distribution, with 47.71% in acid-soluble and 51.675% reducible fractions. The CuSO-2 lowered soil pH by 20.95% (5.47–4.32) in red soil and 7.49% (7.33–6.78) in black soil. Structural equation modelling revealed that Cu distribution was affected by total Cu, organic matter and pH. Low Cu concentrations promoted seedling growth in black soil; while high concentrations inhibited growth in red soil, peaking at 77.45% inhibition under CuSO-2. Conclusion This study reveals that exogenous Cu stability in vineyard soils is strongly influenced by soil type and type of Cu salt applied, affecting grapevine seedling growth, and highlights the need for targeted remediation strategies. Implications This study establishes a robust scientific foundation for managing Cu contamination in vineyard soils and guides future research.