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

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Date
2014-01-09Author
Hangs, Ryan
Type
ThesisDegree Level
DoctoralMetadata
Show full item recordAbstract
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 ScienceProgram
Soil ScienceSupervisor
Schoenau, JeffCommittee
Knight, Diane; Van Rees, Ken; Steppuhn, Harold; Bélanger, NicolasCopyright Date
December 2013Subject
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