N2O, CO2, and CH4 Fluxes from Deep Row Applied Biosolids for Production of Hybrid Poplar in Virginia Coastal Plain Mineland Reclamation Sites.

Research is being conducted on a mineral sands mine reclamation site near the Coastal Plain-Piedmont fall line in Dinwiddie County, Virginia to compare the effects of deep row application of lime stabilized and anaerobically digested biosolids, and conventional N fertilizer application on the N₂O emission from soil. We also investigated N₂O, CO₂, and CH₄ emissions from freshly applied and two-year old entrenched lime stabilized and anaerobically digested biosolids. Lime stabilized and anaerobically digested biosolids were applied in trenches on a one-time basis at 656 Mg ha^-1 and 426 Mg ha^-1, respectively, and synthetic nitrogen fertilizer was applied annually at 0 and 504 kg N ha^-1 in the hybrid poplar study. Nitrous oxide flux measurements were performed in the field on the monthly basis by means of gas chambers between October 2006 and October 2008. Nitrous oxide, CO₂, and CH₄ emissions were measured in an incubation experiment on the core samples from the original biosolids and on cores collected from three depths (0-25 cm, 25–50 cm, and 50–75 cm) at the edge and in the center of the biosolids trench two years after entrenchment. Biosolids produced significant amounts of N₂O, with anaerobically digested type contributing most to the emission. Nitrous oxide emission fluxes peaked during the spring and summer periods, attaining the highest rates of 265 mg m^-2 day^-1 for the anaerobically digested biosolids. Both biosolids gas profile analysis and surface gas measurements indicate that entrenched biosolids are an important source of highly potent greenhouse gases, having a potential impact on the global climate change.