Forage conservation is a neglected nitrous oxide source.

Area of Science:

• Agricultural Science
• Environmental Science
• Atmospheric Chemistry

Background:

• Agricultural activities are a primary source of nitrous oxide (N2O), a significant greenhouse gas and ozone-depleting substance.
• The contribution of forage conservation, specifically silage production, to N2O emissions has been largely understudied.

Purpose of the Study:

• To investigate nitrous oxide (N2O) production during simulated silage fermentation of major US forage crops.
• To identify effective mitigation strategies for N2O emissions from silage production.

Main Methods:

• Simulated silage production using maize, alfalfa, and sorghum.
• Measurement of N2O production under various conditions, including the application of chlorate, acetylene, and intermittent oxygen exposure.
• Molecular analyses to identify microbial pathways responsible for N2O production.

Main Results:

• Substantial N2O emissions were observed from simulated silage, potentially positioning forage conservation as the third largest agricultural N2O source.
• Chlorate addition significantly reduced N2O production.
• Acetylene and intermittent oxygen exposure had no significant impact on N2O emissions.
• Molecular analyses confirmed denitrifiers, not nitrifiers, as the primary drivers of N2O production.

Conclusions:

• Forage conservation, particularly silage production, represents a significant and previously underestimated source of agricultural nitrous oxide (N2O).
• The use of chlorate as an additive shows promise as an effective mitigation strategy to reduce N2O emissions from silage.
• Understanding the microbial mechanisms, specifically the role of denitrifiers, is crucial for developing targeted strategies to mitigate N2O emissions from agricultural practices.