Soil Metal Immobilisation and Ryegrass Uptake of Lead, COPPER and ZINC as Affected by Application of Organic Materials as Soil Amendments

Field soil which was contaminated due to long term deposition of waste from an old Pb/Zn mine in Tyndrum, Scotland was used in a greenhouse pot experiment. The field soil was amended with green waste compost, peat, coir and wood bark applied at the rates of 1%, 10% and 20% of soil and then planted with ryegrass.

Addition of the organic amendments led to increased biomass yield of ryegrass in all soils after 8 weeks of growth, while EDTA extractable Pb, Cu and Zn was significantly reduced in amended soils. Leaf and root metal concentration was also significantly reduced by the application of amendments, especially at applied rates of 10 and 20%.

Coir, green waste compost and wood bark stood out as amendments which were consistent in immobilising the metals in soil as well as reducing plant uptake of Pb, Cu and Zn; while peat rates above 10% enhanced solubility of Cu and Zn.