Spring Nitrous Oxide Emissions

Ranae Dietzel

Working towards a global estimate of N2O emissions

Why is N2O important?


Don’t know how much N2O we produce

Don’t know how to control N2O

What is N2O to an agronomist?

By-product of microbially mediated nitrogen transformations


Worked on N2O during Masters

Before that worked at USDA-ARS North Central Soil Conservation Research Lab in Morris, MN

Worked on 4 N2O experiments May-December

Greenhouse Gas Emission from Contrasting Management Scenarios in the Northern Corn Belt

Johnson et al., 2010, SSSAJ 74:396-406

Freeze-Thaw N2O Peaks

Great White Whale of Greenhouse Gases

Emissions of nitrous oxide from soils - Nature 1982, Duxbury et al.

Seasonal variability in emission of nitrous oxide from soil, Geophysical Research Letters, 1980, Bremner et al.

Bremner et al., 1980, Geophysical Research Letters 7:641-644

What causes peaks in the spring?

Wet conditions leading to anaerobic respiration (denitrification)

What causes peaks in the spring?

What causes peaks in the spring?

Nitrate reduction efficiency plays a huge role in spring peaks

What causes inefficiency?


Dietzel et al., 2011, Soil Biology & Biochemistry 43:1989-1991

More evidence from Canada

Wagner-Riddle et al., 2007, Global Change Biology 13:1722-1736

Colder winters -> more N2O

Modeled spring emissions from freezing degree days

Scaled model up to find current estimates miss ~ 28% of annual emissions

But acknowledged parameters beyond freezing degrees days are needed

Let’s do this


Greenhouse gas Reduction through Agricultural Carbon Enhancement network

GRACEnet collection and sites

GRACEnet Pubs up to 2012

GRACEnet data is/was available in easily accessible public database

All available sites

Sites that experience freezing

Soil Hydrological Properties

Clay (%)
Sand (%)
Silt (%)
Fine Silt (%)
Coarse Silt (%)
\(\theta\)s (L L1)
\(\theta\)r (L L1)

Substrate Properties

Organic Carbon
Organic Matter
Total Nitrogen
C:N Ratio

Soil Chemical Properties

Cation Exchange Capacity
Exchangeable Mg
Exchangeable K
Exchangeable K Saturation
Excahgeable Ca
Base Saturation

Antecedant Weather Conditions

How cold - sum of daily minimum temperatures below 0
How warm - sum of daily maximum temperatures
How sunny - sum of daily total radiation
How wet - sum of daily precipitation
How snowy - sum of daily snowfall

How do these contribute to magnitude of spring N2O emissions?

Partial Least Squares (PLS) Regression

Bjørn-Helge Mevik, Ron Wehrens and Kristian Hovde Liland (2016). pls: Partial Least Squares and Principal Component Regression.

Partial Least Squares (PLS) Regression

Kuhn and Johnson, 2013, Applied Predictive Modeling DOI:10.1007/978-1-4614-6849-3

What does this mean?

What does this mean?

Early spring emissions are still important, neglected, and probably underestimated

Need better modeling of this phenomenon

Nitrous oxide reduction efficiency drivers still in question

Variables listed should lead to more denitrification, but what controls nosZ?

Thank You!