Switchgrass Yield on Reclaimed Surface Mines for Bioenergy Production

Abstract

Th e high cost of transportation fuels and the environmental risks associated with acquiring and using nonrenewable energy sources have created a demand for developing renewable bioenergy crops. Switchgrass (Panicum virgatum L.), a warm-season perennial grass, is a promising feedstock due to its high biomass production under a wide range of growing conditions and its satisfactory forage quality and chemical composition. West Virginia contains vast expanses of reclaimed surface mine lands that could be used to produce switchgrass as a bioenergy feedstock. Th is study determined dry matter yields of three switchgrass varieties (Cave-In-Rock, Shawnee, and Carthage) during the second to fourth years of production. Two research sites were established on reclaimed surface mines in southern West Virginia: Hobet and Hampshire. Th e Hobet site was prepared using crushed, unweathered sandstone as the soil material, and yields were signifi cantly lower at 803 kg ha −1 averaged across varieties and years than annual yields at Hampshire. Th e highest yield at Hobet, with Shawnee in the third year, was 1964 kg ha −1 . Th e Hamphire site, which was reclaimed in the late 1990s using topsoil and treated municipal sludge, averaged 5760 kg ha −1 of switchgrass across varieties and years. Th e highest yield, obtained with Cavein-Rock during the third year, was 9222 kg ha −1 . Switchgrass yields on agricultural lands in this region averaged 12,000 kg ha −1 . Although average switchgrass yields at Hampshire were about 50% lower than agricultural lands, they were greater than a target yield of 5000 kg ha −1 , a threshold for economically feasible production. Yields during the fourth year from a two-harvest per year system were not signifi cantly diff erent from a single, end-of-year harvest at both sites. Reclaimed lands show promise for growing bioenergy crops such as switchgrass on areas where topsoil materials are replaced and amended like that at the Hampshire site.

Switchgrass Biofuel Production on Reclaimed Surface Mines: I. Soil Quality and Dry Matter Yield

“…This result is consistent with reports of slow switchgrass establishment and low amounts of biomass during the first few years after planting [5,11,16,27]. Higher yields were apparent by 2013, after the third growing season, and should continue to increase based on the yields at Hampshire after 6 years.…”

“…Biomass collected in our plots was composed of current year's growth, with less than 5 % being from previous year's growth. Yield data from 2010 and 2011 (previously published in [11]) were included with 2012 and 2013 yield data to analyze over a 4-year period. Yields in experiment 1 (Hampshire and Hobet) were analyzed using a mixed-model, repeated-measures analysis of variance (ANOVA) of the Statistical Analysis System [23] with years as repeated measures and effects of site, cultivar, year, and interactions.…”

“…When extracted with Combining the data for Hampshire and Hobet showed a nearly identical figure since Hobet yields were essentially the same for all cultivars during all years. Yield data in 2010 and 2011 were previously published in Marra et al [11] Mehlich 1, these overburden-derived mine soils often contain high levels of P, but Skousen and Emerson [20] found that the P is tightly bound to Ca minerals and unavailable to plants.…”

“…At Hampshire, two samples per plot were obtained: Three subsamples were composited from each pair of three biomass sampling points. Interactions were significant for cultivar × site (p < 0.01) and site × year (p < 0.01) a Data from Hampshire and Hobet in 2010 to 2011 were previously published in Marra et al [11] b Different letters for each main effect denote difference at p ≤ 0.05 according to ANOVA or Tukey's HSD For Hobet, three samples were composited per fertilizer treatment subplot, giving two soil samples per plot. For Black Castle and Coal Mac, soil samples were collected at biomass sampling points and composited for each treatment providing four soil samples per block, so five samples were obtained for each treatment.…”

“…However, significant differences were found for many properties between sites. Soils data from 2010 and 2011 (previously reported in [11]) were included with values from 2012 and 2013 to calculate 4-year means.…”