CO₂ and N₂ O emissions and microbial community structure from fields that include salt-affected soils.

Area of Science:

• Agricultural Soil Science
• Environmental Science
• Biogeochemistry

Background:

• Salinity and sodicity are significant global agricultural challenges.
• Limited data exists on greenhouse gas (GHG) emissions from salt-affected agricultural soils.

Purpose of the Study:

• To quantify carbon dioxide (CO₂ -C) and nitrous oxide (N₂ O-N) emissions from agricultural soils with varying degrees of salinity and sodicity.
• To investigate the impact of nitrogen (N) fertilization on GHG emissions in these different soil zones.
• To explore the relationship between soil properties, microbial communities, and GHG fluxes.

Main Methods:

• Field experiment across three zones (productive, transition, saline/sodic) in the U.S. Northern Great Plains over two years (2018-2019).
• Measurement of CO₂ -C and N₂ O-N emissions using chambers with and without N fertilization (224 kg N ha^-1).
• Analysis of soil inorganic nitrogen, microbial biomass (phospholipid fatty acid analysis), and denitrification gene (nirS) abundance (real-time PCR).

Main Results:

• The saline/sodic zone exhibited the lowest CO₂ -C emissions and the highest N₂ O-N emissions compared to the productive zone.
• Urea application significantly increased N₂ O-N emissions in the saline/sodic zone (84% in 2018, 57% in 2019) relative to the productive zone.
• The saline/sodic soil had substantially lower microbial biomass but a 42-fold higher abundance of the nirS gene, indicating high denitrification potential.

Conclusions:

• Salt-affected soils, particularly saline/sodic ones, are significant sources of N₂ O-N emissions.
• Targeted management strategies, such as avoiding N application in saline/sodic zones, can mitigate GHG emissions.
• Understanding soil properties and microbial functions is crucial for predicting and managing GHG fluxes from agricultural lands.