The role of leaf litter as a protective barrier for copper-containing pesticides in orchard soils

This study assessed the capacity of leaf litters to adsorb copper ions applied as a copper-based pesticide. Leaf litters of two fruit tree species with different lignin/N ratios were examined to determine their protective role against the incorporation of Cu into soil. A leaf litter Cu-adsorption capacity assay and a degradation assay were performed using table grape (lignin/N = 2.35) and kiwi (lignin/N = 10.85) leaf litters. Table grape leaf litter had a significantly (p = 0.001) higher Cu-adsorption capacity (15,800 mg kg(-1)) than kiwi leaf litter (14,283 mg kg(-1)). Following leaf litter degradation, significant differences (p = 0.011) were observed in the release of Cu from Cu-enriched leaf litter into soil, showing that kiwi litter has a greater protective effect against the incorporation of Cu into soil, regardless of the amount of Cu applied. This protective role is reflected in a significantly higher (p = 0.015) Cu concentration in table grape soil (41.71 +/- 2.14 mg kg(-1)) than in kiwi soil (35.87 +/- 0.69 mg kg(-1)). Therefore, leaf litter with higher lignin/N ratio has greater protective role against copper incorporation into soil.

Automated summary

This study found that leaf litters with a higher lignin/N ratio have a stronger protective role against the incorporation of copper ions into soil.