Nitrous Oxide Emissions From Drip Irrigated Tomatoes Subjected to Elevated Carbon Dioxide Levels.

Increase in atmospheric greenhouse gas (GHG) concentrations, including those stemming from nitrous oxide (N₂O) and carbon dioxide (CO₂), has been partly attributed to agricultural and industrial activities.  N₂O is emitted from soil to the atmosphere as part of the nitrogen (N) cycle, and the addition of N through fertilizers in intensive cropping systems increases N₂O emissions.  CO₂ enters the atmosphere as the result of fossil fuel, solid waste, wood burning and other industrial production processes.  However, CO₂ can also be sequestered by plants as part of the biological carbon cycle.  Thus, sustainable agricultural practices are necessary to minimize GHG emissions while maintaining optimal crop production.  Particularly, it is important to quantify N₂O emissions in fields fertilized with N sources and subjected to elevated atmospheric CO₂ levels.  The objective of this study was to assess N₂O emissions in tomatoes grown under both ambient and elevated CO₂ levels and fertilized with Urea Ammonium Nitrate and Calcium Ammonium Nitrate.  The tomatoes were irrigated with a sub-surface drip irrigation system.  In elevated CO₂ plots, CO₂ was applied through surface drip lines.  A system’s approach that considers N fertilization, crop N use, N loss as N₂O, and soil physical and chemical properties was employed.  Data of ancillary variables, such as soil moisture and temperature, known to affect N₂O emissions were also collected.  Static flux chambers and a Photoacoustic Field Gas-Monitor were used for N₂O emission measurements before and after fertilization events.  Daily levels of atmospheric CO₂ within the plant canopy were monitored using a CO₂ Analyzer.  Comparison of N₂O emissions observed as a result of N fertilization events during the 2010 tomato growing season will be presented.