A large-scale analysis of global nitrous oxide emissions was published in the scientific journal "Earth System Science Data" in June.
Pep Canadell, director of the Global Carbon Project and one of the study’s authors, said nitrous oxide is the third most important greenhouse gas, after carbon dioxide and methane.
“The amount of greenhouse gasses has increased dramatically over the last 200 years," Canadell said, "and therefore the warming and the extreme events that we see nowadays.”
Many human activities have caused these gases to build up in the atmosphere, Canadell said.
Savannah Adkins, a Ph.D. candidate at Utah State University in the Department of Biology, studies mechanisms of nitrogen and carbon cycling. She said nitrous oxide can be produced by combustion engines, but the primary sources of emissions in Cache Valley are related to agriculture.
Nitrous oxide is produced by microbes in soil when there is excess nitrogen that is not used by plants.
“Nitrogen is an element that all living organisms need to function," Adkins said. "Before what we would call the Green Revolution when modern fertilizer was produced, there were only a few ways that organisms could get access to usable nitrogen."
The invention of nitrogen fertilizers helped to increase crop yields, but it also led to the saturation of soil with excess nitrogen.
Canadell said 70% of human-driven nitrous oxide emissions come from agriculture.
“So you have not only more fertilizers to eat more veggies, you need more fertilizers to have more crops to feed more animals because we want more meat and then those animals — more manure,” Canadell said.
The accumulation of cow manure is another source of these emissions. Adkins said manure is very nitrogen-rich.
“And so, when it's accumulated in small areas, microbes are in that manure, they eat the nitrogen, and because there's excess nitrogen, they transform it into nitrous oxide," Adkins said.
Canadell said the link between nitrous oxide and agriculture is one reason that this greenhouse gas is understudied.
“When we come together in these international negotiations to address climate change, a lot of countries, they do not want to touch on this, because this is, you know, food security — you would not want to do anything that makes your system more vulnerable,” Canadell said.
Some countries have even subsidized the use of nitrogen in the name of increasing food production, Canadell said.
“And we've seen this leading to major hotspots around the world where clearly the amount of nitrogen that has been put into the fields … it's way, way too excessive," Canadell said. "So these are things that can actually be fixed with, you know, proper policies.”
Canadell said there are also steps that can be taken at the level of the individual farm. For best practices, farmers should try to implement the “three Rs.”
“And with that, I mean … the right amount of fertilizer in the soil, at the right time (that is when plants really need it), and at the right depth,” Canadell said.
There are resources available for Utah farmers who want to learn more about their soil and what fertilizers to apply.
“The USU Extension program, you can have your soil testing done there, and they can help you calculate your nitrogen needs, which can help prevent over-application of nitrogen fertilizer,” Adkins said.
As for reducing nitrous oxide emissions from livestock, Adkins said having a manure management plan is important, especially for animals kept in confined areas. Dairy cattle operations produce a high concentration of manure in a small area because the cows must be kept close for daily milking.
“When we compare them to cattle on the range, those cattle are roaming," Adkins said, "and because they're moving, their manure is more spread out, so it’s not as big of a problem.”
On an uncultivated landscape where fertilizers are not applied, nitrogen from manure can actually support native plants.
“Cattle, while they often get a bad rap, especially in the Intermountain West, they don't necessarily have to be bad," Adkins said. "Cattle can be managed in ways that are beneficial to ecosystems.”
As of now, there is no feasible way to remove nitrous oxide from the atmosphere, Canadell said.
“So therefore, the only solution is to reduce those emissions – they don't have to go to zero, but they have to be reduced," Canadell said. "At this point, they continue to increase."
To learn more about soil nutrient management and testing by USU Extension, visit https://extension.usu.edu/yardandgarden/soils.
