Semester

Summer

Date of Graduation

2010

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Horticulture

Committee Chair

Jeffrey Skousen.

Abstract

Climate change mitigation and the high cost of transportation fuels have created an interest in utilizing biofuels to supplement the nation's energy portfolio. Switchgrass (Panicum virgatum) has been suggested as a possible biofuel feedstock because of its ability to produce large amounts of biomass over a wide range of growing conditions and its ability to sequester atmospheric carbon (C) into stable soil organic carbon. Appalachia has the potential to become a center of biofuel production with its large expanses of reclaimed mine land. Switchgrass production on surface mine land offers the opportunity to increase the land resources devoted to energy crops without decreasing land resources devoted to food and livestock feed production. To examine the feasibility of establishing switchgrass as an initial reclamation species, three varieties of switchgrass were planted into 0.4 ha plots at three different surface mines in WV. Each variety was replicated three times for a total of nine plots at each site. Planting was conducted in May of 2008. The varieties Carthage, Cave-in-Rock and Shawnee were chosen for their favorable growing characteristics and adaptation to WV climate. Cover and frequency data from the first growing season showed switchgrass successfully established at all three sites with both broadcast planting and hydroseeding. Cover and biomass data from the second growing season showed that switchgrass performed much better on finer textured soils with higher amounts of soil organic matter, such as was seen with soils reclaimed with municipal biosolids. Biomass averaged 207 kg ha-1 at the Hobet 21 site, 784 kg ha-1 at the Coal-Mac site, and 4,501 kg ha-1 at the Hampshire Hill site. The Cave-in-Rock variety yielded the highest biomass at both Coal-Mac and Hobet 21. Relatively poor performance of switchgrass at Coal-Mac and Hobet 21 indicated that switchgrass, while tolerant of poor soils once established, is unsuited for initial reclamation of nutrient poor and rocky minesoils where good cover and biomass production are expected within one or two years of planting.;Another reclaimed mine site in southwestern PA was selected to study C sequestration under different-aged switchgrass stands on mined and unmined soils. Fourteen stands of switchgrass were measured across a chronosequence of establishment on mined and unmined soils ranging from 1991 to 2008. Soil organic C was 1.7% for the 0-15 cm depth and 0.8% for the 15-30 cm depth and was identical for both mined and unmined soils. Switchgrass biomass was higher on unmined plots than mined plots with yields of 8745 kg ha-1 and 6024 kg ha-1, respectively. Biomass was not correlated with stand age. Soil organic C was not correlated with the age of the established switchgrass stands suggesting that either the soils were in equilibrium with respect to C or that switchgrass was sequestering C at a rate indistinguishable from the previous cool season grass cover. Other factors were correlated to soil organic C. On mined areas, pH was highly correlated with both soil organic C and biomass. This suggests that acidity was a limiting factor and that managing soil fertility through liming treatments was effective at both increasing soil organic C and switchgrass biomass.;The chemi-thermal method of Ussiri and Lal (2008) was used to distinguish between C from soil organic, carbonaceous rock, and inorganic carbonate sources. A methodological evaluation of this method was performed to test the hypothesis that C was being removed from shale and coal mixtures often found in mine soils. The removal of geogenic C with this method would cause an overestimation of soil organic C. The chemi-thermal method was performed on pure coal and three mixtures of coal and shale. The pure coal lost 20% of its original C. The coal and shale mixtures lost between 6 and 25% of their original C. The chemi-thermal method was also compared to two simple thermal oxidation steps (340°C for 3 hr and 360°C for 4 hr) by measuring added geogenic C in manufactured carbonaceous rock:soil standards. Two different groups of standards were used consisting of added pure coal and added coal and shale at known concentrations. For both groups, simple thermal oxidation at 340°C at 3 hr was able to more accurately measure added geogenic C than the chemi-thermal method.

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