Zinc shields against copper phytotoxicity in a contaminated soil.

While zinc protects plants from copper in hydroponics, its behavior in soil remains unclear. We investigated the potential of zinc sulfate to protect ryegrass from copper toxicity in contaminated soil. Twelve soil treatments combined varying levels of copper oxide (CuO) and zinc sulfate (ZnSO 4). Increasing CuO significantly stunted ryegrass, but adding ZnSO 4 mitigated the effects at each CuO level. ZnSO 4 had no effect in unpolluted conditions. These results, supported by the Terrestrial Biotic Ligand Model, indicate that zinc competes with copper for binding sites, reducing copper uptake by ryegrass and mitigating its toxicity. Application of zinc sulfate to copper-contaminated soils appears promising for ryegrass growth, although field studies are critical to confirm real-world efficacy. • Ryegrass shoot length increased in CuO-treated soils following ZnSO4 addition. • Under unpolluted conditions, ZnSO 4 addition had no statistically significant effect. • The Terrestrial Biotic Ligand Model provides a theoretical framework. • Zn2+ likely competed with Cu2+ for binding sites in ryegrass. • Future field studies will be essential to assess real-world effectiveness. [ABSTRACT FROM AUTHOR]