Effect of aging biosolids with soils of contrasting pH on subsequent concentrations of Cu and Zn in pore water and on their plant uptake.

Purpose: The study examines if a short period of reaction after addition of biosolids to soils can reduce the solubility and potential phytotoxicity of biosolid-borne Zn and Cu.

Methods: The effects of period of aging (zero, 60, and 120 days) of biosolids (applied at 0, 10, 20, and 30 g kg⁻¹) with an acid, neutral, or alkaline soil on pH and concentrations of Zn, Cu, and dissolved organic C in solution over a 60-day growth period of spinach were investigated using Rhizon pore water samplers.

Results: In the acid and neutral soils, increasing aging period markedly reduced the concentrations of Zn and Cu in solution and there were concomitant increases in solution pH.