Sewage sludge as an amendment for calcareous bauxite mine spoils reclamation

Dried aerobically digested sewage sludge applied at seven rates (0, 10, 20, 40, 60, 80, and 120 Mg ha(-1)) in a field experiment on calcareous bauxite mine spoils significantly increased the available water capacity, concentrations of organic matter, total N, extractable P (Olsen), exchangeable Mg2+, and diethylenetriaminepentaacetic acid (DTPA)-extractable Cu, Mn, Zn, and Pb of mine spoils. Total N and extractable P concentrations decreased with time after sludge application. The DTPA-extractable Cu concentration was high 4 yr after application at sludge rates of 80 and 120 Mg ha(-1). Extractable Cu and Zn concentrations correlated significantly and positively with Cu and Zn concentrations in burnet (Sanguisorba minor snbsp. minor) and fiddleneck (Phacelia tanacetifolia Benth) tissue. Sludge application depressed plant Mn uptake. Plant biomass, plant density, and foliar cover significantly increased with treatment rates in the first and fourth growing seasons but decreased with time. Fiddleneck and burnet were the species favored by the high rates of sludge application.