By Scout Nelson
Nitrogen is essential for healthy corn growth and strong yields, but preventing nitrogen loss remains a major challenge for farmers. Nitrogen can enter waterways or escape into the air as nitrous oxide (N₂O), a powerful greenhouse gas, or ammonia (NH₃), which contributes to air pollution and can affect human health. Researchers must first measure and understand these emissions to develop effective management practices that reduce nitrogen loss and limit environmental impacts.
Timothy Griffis, a professor of Soil, Water, and Climate at the University of Minnesota, and his research team have been studing where and when nitrogen emissions occur across the US Corn Belt. Their work uses field measurements, tall towers, and airplanes fitted with sensors to track nitrogen and understand how weather affects its movement through farming systems.
Griffis began working on this research after arriving at the university in 2002. He focuses on nitrous oxide (N2O), a greenhouse gas that is about 300 times more powerful than carbon dioxide at trapping heat over a 100-year period. Nitrous oxide also contributes to the loss of protective ozone in the upper atmosphere.
The team studies how much nitrogen crops absorb and how much escapes into the air. This information helps researchers understand where nitrogen losses occur and how farming practices can reduce them. The main goal is to help crops use more of the applied nitrogen while reducing harmful emissions.
Understanding Different Forms of Nitrogen Loss
Nitrogen can leave agricultural fields in several ways. Heavy rain can carry fertilizers away from fields and into streams, rivers, and other waterways. Nitrogen can also enter the atmosphere as nitrous oxide or ammonia (NH3).
Nitrous oxide contributes to global warming, while ammonia can contribute to air pollution and affect human health. Understanding these different forms of nitrogen loss is important because each one can create environmental problems.
Researchers need reliable measurements to identify the areas where emissions are highest. These areas are known as hotspots. They also study hot moments, which are periods when nitrogen emissions rise sharply.
By finding these hotspots and hot moments, scientists can better understand when and where improved nitrogen management may have the greatest effect.
Climate Conditions Can Increase Emissions
Weather and climate have a major influence on nitrogen loss. Griffis and his team find that warmer and wetter spring conditions can increase nitrous oxide emissions. These conditions may also reduce nitrogen use efficiency, meaning crops receive less benefit from the nitrogen applied to fields.
“We’ve identified that warmer and wetter springs can enhance N2O emissions. We’re concerned that a warmer and wetter climate will reduce nitrogen use efficiency,” Griffis says. “We are very interested in identifying hot moments so that we can develop better mitigation strategies. For example, our long-term measurements have identified that spring thaw results in very large N2O emissions, which can account for over 30% of the annual budget.”
These findings show why the timing of nitrogen emissions matters. Spring thaw alone can account for more than 30% of annual nitrous oxide emissions in the team's long-term measurements.
Climate change may make this challenge more serious. Warmer and wetter conditions can increase nitrogen emissions, while nitrous oxide adds to global warming. This creates a possible cycle in which warming leads to conditions that cause even more emissions.
Nitrogen Losses Beyond Farm Fields
Research from Griffis and his team also shows that a substantial amount of nitrous oxide comes from indirect processes outside agricultural fields.
For example, nitrogen fertilizer can move from fields into nearby watersheds through water drainage. When excess nitrogen reaches these areas, it can create conditions that increase nitrous oxide emissions.
This means nitrogen pollution does not always remain where fertilizer is applied. Emissions can occur in connected waterways and other areas beyond the farm itself.
Understanding these indirect emissions helps researchers measure the full environmental impact of fertilizer use. It also shows why nitrogen management needs to consider both farmland and the surrounding environment.
Testing Better Farming Practices
The research team uses long-term measurements as a baseline for studying ways to reduce nitrogen emissions. These measurements help scientists compare different management practices and determine which approaches work best under changing climate conditions.
One practice under study is living mulch, which involves growing plants alongside or between the main crops to help cover the soil. The researchers compare this approach with conventional cropping systems to see whether it changes nitrogen emissions.
“We’re comparing alternative management practices, like living mulch, to conventional cropping systems to see if they impact emissions,” Griffis explains. “We really want to know what the impact is before we recommend specific strategies on the basis of emissions. We want to make sure we provide the best science possible.”
The team aims to base recommendations on measured results rather than assumptions. This helps ensure that proposed practices provide real environmental benefits.
Supporting Better Nitrogen Management
Nitrogen is essential for corn production, but losses can create problems for water quality, air quality, and the climate. Research at the University of Minnesota helps explain how weather, soil conditions, and farming practices affect these losses.
Photo Credit: gettyimages-klosfoto
Categories: Minnesota, Crops, Corn