Mitigating greenhouse gas emissions in subsurface-drained field using RZWQM2

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Greenhouse gas (GHG) emissions from agricultural soils are influenced by environmental factors and farming methods.
• Nitrogen (N) fertilization and water table management are critical components affecting soil GHG emissions.

Purpose of the Study:

• To investigate the impact of N fertilization rates, timing, and water table management on N₂O and CO₂ emissions.
• To propose mitigation and adaptation strategies for agricultural GHG emissions using simulated results.
• To validate the Root Zone Water Quality Model 2 (RZWQM2) for predicting GHG emissions.

Main Methods:

• Calibrated and validated the RZWQM2 model using field data from 2012-2015 on a corn field in Southern Quebec.
• Simulated long-term (1971-2000) N₂O and CO₂ emissions under free drainage (FD) and controlled drainage with sub-irrigation (CD-SI).
• Evaluated the effects of varying N fertilization rates, application timing, and crop rotation (corn-soybean vs. continuous corn).

Main Results:

• Optimal N fertilization rates of 125-175 kg N/ha improved nitrogen use efficiency (NUE) by 7-14% and reduced N₂O emissions by 8-22% compared to 200 kg N/ha for corn-soybean rotation.
• Splitting N application decreased total N₂O emissions by 11.0% while maintaining crop yields.
• Controlled drainage with sub-irrigation (CD-SI) reduced CO₂ emissions by 6% but increased N₂O emissions by 21% compared to free drainage (FD).
• Corn-soybean rotation reduced CO₂ and N₂O emissions by 18.8% and 20.7%, respectively, compared to continuous corn production.

Conclusions:

• The RZWQM2 model is effective for predicting agricultural GHG emissions.
• Agronomic management practices, including optimized N fertilization, split N application, controlled drainage, and crop rotation, can effectively mitigate GHG emissions from agricultural soils.