Amendments promote the development of Lolium Perenne in soils affected by historical copper smelting operations

The Puchuncaví valley, central Chile, has been exposed to aerial emissions from a copper smelter. Nowadays, soils in the surroundings are sparsely-vegetated, acidic, and metal contaminated, and their remediation is needed to reduce environmental risks. We assessed effectiveness of lime, fly ash, compost, and iron grit as amendments to immobilize Cu in soils and promote plant growth. Amended soils were cultivated with Lolium perenne for 60 days under controlled conditions. Total dissolved Cu and Cu²⁺ activity in the soil solution, ryegrass biomass, and Cu accumulation in plant tissues were measured. Addition of lime and fly ash decreased Cu concentrations and Cu²⁺ activity in the soil solution, increased plant biomass, and reduced shoot Cu concentration below 22 mg kg^-1 (the phytotoxicity threshold for the species). The most effective amendment with respect to the shoot biomass yield was a combination of lime and compost. Water content of the substrate and the K accumulation were positively correlated with the compost application rate. Compost combined with iron grit decreased dissolved Cu concentrations during the period of highest solubility, i.e. during the first 60 days after the compost application. However, iron grit incorporation into soils amended with lime and compost decreased the shoot biomass of ryegrass.