Influence of Nitrogen Application and Crop Residue on Drivers of Microbial Nitrous Oxide Emissions in Canola (Brassica napus L.) Production
Date
2020-07-17
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0003-4323-5232
Type
Thesis
Degree Level
Masters
Abstract
Agricultural soils are the major anthropogenic source of nitrous oxide (N2O), which because its global warming potential is almost 300 times greater than that of carbon dioxide (CO2), has been linked to climate change. Canola (Brassica napus L.) is an important crop in western Canada, and in Saskatchewan, canola production accounts for 34.8% of the seeded area. However, canola production depends heavily on nitrogen (N) fertilizer application, and in a semi-arid environment such as Saskatchewan can be increased through irrigation. Microbial communities play a critical role in soil N-cycling—including N2O production via nitrifier and denitrifier activity—and are affected by agricultural management practices. To better understand the drivers of N2O emissions that result from canola production, two studies were designed to (i) determine if different N fertilizer application rates and timing of application affects microbial drivers of N2O emissions in irrigated canola, and (ii) investigate why canola residues induce greater than expected N2O emissions, using 15N- and 13C-labelled residues of wheat, pea, flax and canola to trace sources of N2O and CO2 emissions. My findings showed that existing soil conditions prior to management events affected the magnitude and possibly the source pathway of soil N2O emission. Enzymatic response to N application was mainly affected by differences in soil moisture content. Analysis of 15N2O and 13CO2 data revealed that N2O production stimulated by canola residue addition was coming from the soil N pool and the stimulatory effect of canola residues on N2O emissions is due to differences in microbial assimilation of residue C, causing a shift in microbial community structure.
Description
Keywords
N-conversion enzymes, Nitrification and Denitrification, 15N and 13C labelled residue, labile organic C, N-cycling genes, Microbial community composition, 13C-PLFA
Citation
Degree
Master of Science (M.Sc.)
Department
Soil Science
Program
Soil Science