Using Coal Fly Ash in Agriculture: Combination of Fly Ash and Poultry Litter as Soil Amendments for Bioenergy Feedstock Production

Increasing fiscal, human, and environmental costs of coal fly ash (FA) management are leading to advocacy for greater beneficial uses of the by-products as soil amendments in agriculture. Greenhouse experiments were conducted in Armour silt loam (ASL) soil that was amended with FA (10%, wt/wt) with and without poultry litter (PL 5 75 mg N/kg). Biomass productivity of eastern gamagrass (GG), a warm-season perennial grass, was measured to serve as complementary biofuel feedstock to switchgrass (SG). FA was obtained from a site at the 2008 ash spill in Kingston, TN. GG and SG were grown individually in 15-cm-wide 3 41-cm-high tree pots, each containing 6 kg of oven-dry soil equivalent (ods) and treated with the following combinations: 0FA/0PL, 10FA/0PL, 0FA/PL, and 10FA/PL. Each treatment was replicated eight times. The tree pots were randomly arranged on greenhouse benches and watered as needed. Biomass production was assessed in soil adjusted to initial pH 5 4.5 or 6.5. After 12 weeks at initial pH 5 4.5, GG produced significantly higher biomass (p , 0.05) in acidic ASL soil that was amended with a combination of 10FA/PL (21.8 g/tree pot) than in unamended ASL soil (13.3 g/tree pot). At initial pH 5 6.5, total biomass productivity of GG ranged from 13.2 to 15.7 g/tree pot, and the differences were not significant. Biomass productivity of SG trended similarly, with the highest biomass productivity (18.2 g/tree pot) observed in ASL soil amended with the 10FA/PL combination, which was significantly higher than the control (14.3 g/tree pot). The treatment combinations did not have a significant effect on biomass productivity of SG at pH 5 6.5. X-ray imaging and analysis of selected washed roots grown at pH 5 4.5 confirmed significant enhancements of root system architecture traits, including root length and area, in the 10FA/PL treatments compared with other treatments. We conclude that FA and PL can be beneficially used to produce biofuel feedstock in acid-impacted soil.