Monday, November 5, 2007

Transformation of Phosphorus and Nitrogen in Deep Row Biosolids Incorporation Technology in Coastal Plain Mining Sites in Virginia.

Kirill Kostyanovsky, Katrina Lasley, Beshr Sukkariyah, Gregory Evanylo, and Chao Shang. Virginia Tech, 416 Smyth Hall, Blacksburg, VA 24060

Annual rates of land-applied biosolids for restoration of disturbed mine lands in Virginia are limited to 112 Mg/ha. Deep row incorporation of biosolids is a unique alternative land application method that will prevent odor problems and may permit the application of considerably higher than currently permitted biosolids rates. The goal of our research is to assess potential environmental consequences of employing the deep row incorporation of biosolids to restore productivity of mined land for the production of hybrid poplar as a potential bioenergy crop. Our objectives are to quantify the transformations of nitrogen and phosphorus applied to the soil as entrenched biosolids. The study is being conducted on a mineral sands mine reclamation site near the Coastal Plain-Piedmont fall line in Dinwiddie County, Virginia. The experimental design consists of 8 treatments replicated four times. Two types of biosolids were applied in subsurface trenches at two rates: lime-stabilized at 328 and 656 tons/ha and anaerobically-digested at 213 and 426 tons/ha. Four additional treatments include four rates of nitrogen fertilizer. The site has been instrumented with shallow wells and suction and zero-tension lysimeters for collection and analysis of groundwater and leachate from which are determined subsurface loss of nitrogen, phosphorus and their binding constituents (e.g., Al, Fe, Mn, Ca and organic carbon). Denitrification chambers have been used to collect soil air samples for analysis of gaseous N loss from the entrenched biosolids. Redox potential, pH, dissolved oxygen and electric conductivity are determined in groundwater, leachate and incorporated biosolids to account for physical-chemical conditions influencing nitrogen and phosphorus mineralization rates. Hybrid poplar will be evaluated as biological sinks for nutrients. The data will be employed to evaluate the environmental viability of the deep row biosolids incorporation technology.