Thesis
Measuring continuous nitrous oxide emissions with an automated flux chamber system in an agricultural field from a cover crop and winter wheat system
Washington State University
Master of Science (MS), Washington State University
08/2020
DOI:
https://doi.org/10.7273/000004172
Handle:
https://hdl.handle.net/2376/125229
Abstract
Globally, agroecosystems contribute approximately 60% of total anthropogenic N2O emissions, a potent greenhouse gas (GHG), mainly due to excessive application of nitrogen (N) fertilizer to croplands. High spatiotemporal resolution flux measurements are necessary for improving our understanding of the episodic and microscale behavior of soil N2O emissions and the complex biogeochemical processes that trigger them. This study used two Li-Cor 8100A Automated Soil CO2 Flux Systems coupled with laser spectroscopic Los Gatos Research (LGR) N2O analyzers to measure continuous soil GHG fluxes from an automated closed static chamber system. A small-scale study plot in an agricultural field was divided into 16 microplots and a chamber was installed on each one, ensuring high-spatial coverage. The system monitored CO2 and N2O fluxes from a cover crop (CC) study from 15 May - 23 August 2019, where four treatments with four replications were established on the microplots as a randomized block design. The treatments were: lynx winter pea (WP), verdant winter barley (WB), a WP+WB 50-50 mix, and fertilized WB (WBfert; 112 kg N ha-1 fertilization rate). Combined mean cumulative emissions from the CC study were 78 ± 21 g N2O-N ha-1 d-1. Daily emissions were generally low, however, a few N2O pulses were observed following drying/rewetting cycles, which were likely nitrification driven. Mean cumulative emissions from the WBfert microplots were higher than mean cumulative emissions from all unfertilized microplots by 34%. Following CC termination, a fertilized winter wheat (WW; 168 kg N ha-1 fertilization rate) treatment was implemented on each microplot and monitored from 16 October 2019 - 29 February 2020. Mean combined cumulative N2O emissions were 1217 ± 99 g N2O-N ha-1 d-1, which were predominantly attributed to high denitrification rates driven by high moisture soil conditions following rainfall and snowmelt. During both studies, soil moisture and N availability were the main drivers of N2O emissions. Overall, the automated flux chamber system provided high-quality long-term flux data that effectively captured the high spatial and temporal variability of N2O fluxes from various cropping treatments, which is important for determining regional N2O budgets and mitigating emissions through improved N use efficiency in agroecosystems.
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Details
- Title
- Measuring continuous nitrous oxide emissions with an automated flux chamber system in an agricultural field from a cover crop and winter wheat system
- Creators
- Alicia Iwanicki
- Contributors
- Shelley Noelle Pressley (Advisor) - Washington State University, Voiland College of Engineering and Architecture
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900890769101842
- Language
- English
- Resource Type
- Thesis