Changes in cadmium and zinc phytoavailability in agricultural soil after amendment with papermill sludge and biosolids

Abstract

The co‐disposal of papermill sludge with biosolids is seen as an alternative soil amendment to papermill sludge and inorganic fertilizer. The objectives of this study were to assess the suitability of co‐disposal of papermill sludge and biosolids by measuring changes in the soil physicochemical properties and the phytoavailability of cadmium (Cd) and zinc (Zn). Biosolids were applied with papermill sludge as an alternative source of N to inorganic fertilizers at rates calculated on the basis of C:N ratios of the amendments and common papermill sludge disposal practices. Perennial ryegrass (Lolium perenne L.) was grown on amended soils for 6 months under glasshouse conditions. The papermill sludge amendment alone increased soil pH and the rate of carbon degradation compared to the control (no amendment) and biosolid co‐disposal amendment. There was no difference in dry matter yield per pot of ryegrass between the treatments. Cadmium concentrations in plant tissue increased through the trial with the application of biosolids and papermill sludge. These findings were correlated well with the sorption properties of the soils for Cd as derived from isotherms. However, Zn uptake was unaffected by the application of the papermill sludge and biosolids.