Semester

Spring

Date of Graduation

2024

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Forest Resource Management

Committee Chair

Charlene Kelly

Committee Member

Louis McDonald

Committee Member

Zac Freedman

Committee Member

Jamie Schuler

Abstract

Bioenergy crops offer a promising strategy for renewable energy production, accompanied by carbon (C) storage benefits when managed sustainably. Utilizing marginal lands for energy feedstock production presents an opportunity for bioenergy generation and concurrent climate mitigation without competing with food crops. However, achieving optimal yields requires strategies to restore soil fertility, which require increased understanding of the interactive effects of prior land use, energy crop species, and fertility amendments available. This study, conducted as part of the Mid-Atlantic Sustainable Biomass (MASBio) Consortium, investigated the effects of biochar incorporation—a C-rich charcoal derived from biomass, intended for soil enhancement—on bioenergy cropping systems in the Appalachian region. Field experiments were conducted on reclaimed mine and marginal agricultural sites across West Virginia, USA, where plots were planted with either willow (Salix spp.) or switchgrass (Panicum virgatum) and treated with amendments of biochar, nitrogen (N) fertilizer, or left untreated. Results revealed minimal effects of biochar on soil greenhouse gas (GHG) production or N dynamics compared to inorganic nitrogen (N) fertilizer. Instead, land use history emerged as the primary determinant of potential GHG production, with mine sites exhibiting 18% higher CO 2 emissions per gram of fine soil compared to agricultural sites (p < 0.0001). No significant trend on per gram of soil potential production of N 2 O or CH 4 was observed. Adjusting for site characteristics and global warming potential (GWP) revealed 5% greater CO 2 equivalent N 2 O production from untreated switchgrass plots relative to biochar switchgrass plots on mine sites (p = 0.030), but not agriculture sites, emphasizing the influence of site characteristics on potential GHG production. Land use also exerted the greatest influence on soil aggregate distribution where mine sites exhibited higher bulk SOM and greater soil mass within larger aggregate size fractions (>2000 μm and 1000-2000 μm) (Ag: 14.22 mg kg -1 Mine: 31.6 mg kg -1 , p = 0.001; Ag: 221.21 mg kg -1 , Mine: 268.42 mg kg -1 , p = 0.003) compared to agricultural sites, which exhibited lower bulk SOM content and clustered aggregates in smaller fractions (53-250 μm, 250-500 μm) (Ag: 200.9 mg kg -1 , Mine: 175.8 mg kg -1 , p < 0.0006; Ag: 186.39 mg kg -1 Mine: 175.8 mg kg -1 , p = 0.03). Correspondingly, aggregate-associated organic matter (OM) was greater in mine sites within larger fractions (>2000 μm, 1000-2000 μm) (Mine: 0.805 g 100 g -1 soil, 3.519 g 100 g -1 soil; Ag: 0.261 g 100 g -1 soil, 2.778 g 100 g -1 soil) indicating potential long-term benefits from accumulation and intra-aggregate storage. Biochar-amended switchgrass plots in mines had higher OM contents in larger fractions (250-500 μm and 500-1000 μm) compared to control and fertilized plots (Biochar: 2.98 g 100 g -1 soil, Control: 1.77 g 100 g -1 soil, Fertilized: 1.57 g 100 g -1 soil; p = 0.023, p = 0.045, p = 0.031). Additionally, biochar significantly increased bulk SOM content in agricultural lands, where biochar plots contained 2.38% higher OM contents than untreated control plots (p = 0.021), indicating potential for long-term soil health benefits. Overall, results suggest that land use history and energy crop species outweighed the effects of biochar at this application rate, emphasizing the need for further research into understanding the effects and interactions between site characteristics and associated energy crops.

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