Legacy N₂O Emissions Overlooked and Crop-Specific Mitigation Solutions

Area of Science:

• Agricultural Science
• Environmental Science
• Climate Science

Background:

• Nitrous oxide (N₂O) emissions from agricultural soils are a major concern.
• Current IPCC methodologies underestimate N₂O emissions by not fully accounting for legacy effects of nitrogen fertilization.
• This leads to significant variance in N₂O emission estimates.

Purpose of the Study:

• To map crop-specific legacy N₂O emission factors (EF_L) for wheat, maize, and rice.
• To quantify the contribution of legacy N₂O emissions to overall agricultural emissions.
• To provide insights into mitigation strategies for climate-resilient agriculture.

Main Methods:

• Synthesized global long-term field data (≥3 years).
• Calculated crop-specific legacy N₂O emission factors (EF_L).
• Compared findings with IPCC tier 1 estimates.

Main Results:

• The global mean EF_L was 0.09% for wheat, 0.17% for maize, and 0.04% for rice.
• Legacy N₂O emissions from wheat, maize, and rice were 0.02, 0.04, and 0.01 Tg N₂O-N season^-1, respectively.
• Total direct and legacy N₂O emissions from these crops were ~30% higher than IPCC tier 1 estimates, with background emissions contributing 24.8%.

Conclusions:

• Findings update the IPCC EF methodology to include legacy N₂O emissions.
• Improved nitrogen management can reduce global N₂O emissions from staple crops by 0.47 Mt.
• Mitigation strategies can enhance crop production and support global food security.