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      • HARVEST
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      Biomass production and nutrient cycling in short-rotation coppice willow (Salix spp.) bioenergy plantations in Saskatchewan, Canada

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      HANGS-DISSERTATION.pdf (12.58Mb)
      Date
      2014-01-09
      Author
      Hangs, Ryan
      Type
      Thesis
      Degree Level
      Doctoral
      Metadata
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      Abstract
      Biomass energy is currently the largest renewable contributor to global energy supply and there is increasing demand for bioenergy feedstock. Consequently, the production of purpose-grown woody bioenergy crops, such as short rotation coppice (SRC) willow, is expected to proliferate. Although the economic and environmental benefits associated with SRC willow production are well documented, systematic assessments of nutrient cycling within these plantations are rare. The objective of this study was to examine biomass production and biogeochemical cycling of nitrogen (N), phosphorus (P), potassium (K), sulphur (S), calcium (Ca), and magnesium (Mg) during an initial four-year rotation of six willow varieties grown at four plantations along a 500 km north-south pedoclimatic gradient within Saskatchewan, Canada. Nutrient budgets were also calculated after quantifying various nutrient inputs (e.g., atmospheric deposition, soil mineral weathering, and organic matter mineralization), outputs (e.g., above- and below-ground biomass, leaching, and denitrification), and transfers (e.g., canopy exchange, leaf litter decomposition, and fine root turnover) affecting the plant available soil nutrient pool. Total stem, leaf litter, and below-ground (primarily fine roots) biomass production after four years averaged 19.0, 7.1, and 12.5 Mg ha-1, respectively, with corresponding soil nutrient budget deficits of 17, 39, 112, 271, and 74 kg ha-1 of N, P, K, Ca, and Mg, respectively, but a soil S surplus of 60 kg ha-1. Despite willow’s relatively low nutrient-demanding nature, negligible leaching and denitrification losses, and substantial nutrient cycling from leaf litter, the nutrient export in harvested biomass over multiple rotations will require soil nutrient amendments, particularly N and P, to maintain plantation productivity. Given the apparent eventual need for supplemental fertility to support adequate willow growth over the 22-yr plantation life span, the fate of broadcast 15N-labelled fertilizer was also examined. Though the willow accumulated less than ⅓ of the applied fertilizer N after one year, the majority of the residual fertilizer N (51%) remained available for willow uptake in subsequent years. Further research is needed to track the fate of applied fertilizers over multiple rotations to better understand fertilizer dynamics for optimizing SRC willow agronomy; thus helping to promote its viability as a biomass energy feedstock option.
      Degree
      Doctor of Philosophy (Ph.D.)
      Department
      Soil Science
      Program
      Soil Science
      Supervisor
      Schoenau, Jeff
      Committee
      Knight, Diane; Van Rees, Ken; Steppuhn, Harold; Bélanger, Nicolas
      Copyright Date
      December 2013
      URI
      http://hdl.handle.net/10388/ETD-2013-12-1322
      Subject
      Chernozem
      decomposition limit value
      decomposition rate constant
      canopy exchange
      dry deposition
      fine root turnover
      leaching
      leaf litter decomposition
      mineral weathering
      nutrient budgets
      15N-labelled fertilizer
      principal component analysis
      Vertisol
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