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Soil Nitrogen Cycling and Nitrous Oxide Emissions: Interactive Effects of N Fertilization Options, Soil Management, Cropping Systems and Climatic Factors in Central Alberta
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- Author / Creator
- Shakila Kalhari Thilakarathna Ekanayaka Mudiyanselage
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Increases in nitrous oxide (N2O) emissions derived from inorganic nitrogen fertilization has become a major environmental concern due to the significant contribution of N2O to global warming, and the deterioration of the stratospheric ozone layer. Effective N fertilization management strategies can reduce the N losses to the environment and enhance the N use efficiency by crops which is required to meet the global demand for food production.
The effect of N fertilization options (conventional vs. enhanced efficiency N fertilizers (EENFs)) and application timing (fall N vs. spring N) on N2O emissions and plant productivity were studied in a 2.5 year field experiment, a laboratory incubation, a modelling experiment and a greenhouse experiment. The field study revealed that the beneficial role of EENFs on N2O emissions and crop yield were limited under N rich, fertile soils. Irrespective of the timing of N fertilization (fall vs spring), weather and soil conditions drove N2O fluxes. In our incubation study, we used 15N-N2O isotopic composition to identify the soil N2O sources following N additions and under five moisture contents. Results from 15N-N2O site preference indicated that denitrification was the major process contributing to N2O flux. The N2O fluxes from soil N were primed by both urea additions and high moisture. To improve quantifications of N2O fluxes, a simulation experiment was conducted using ecosys model. Both modelled and measured data showed that environmentally smart nitrogen (ESN) reduced N2O emissions relative to conventional urea and anhydrous ammonia fertilizers. Finally, a controlled greenhouse study was conducted to evaluate the differential effects of contrasting cropping management histories including continuous annual cropping, a complex crop rotation and a perennial forage as well as urea addition with and without nitrification inhibitors. This study revealed that long-term cropping systems that lead to greater soil C and N can enhance N2O production via denitrification. Nitrification inhibitors used in our study were effective in reducing the effect of priming on N2O emission and soils received long term fertilization enhanced the primed N2O emissions over cumulative total N2O emissions. Overall, the findings of these studies collectively enabled an improved understanding of soil N dynamics and associated N2O production which can aid in developing N management strategies for sustainable agriculture. -
- Subjects / Keywords
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- Graduation date
- Fall 2020
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.