From a crop nutrition perspective, nitrogen losses as N2O or nitrous oxide pale in comparison to what’s lost in N2 form, but N2O has a much greater impact on the total greenhouse gas emissions from fertilizer.
As part of this Wheat School episode filmed at Manitoba Crop Diagnostic School, Manitoba Agriculture’s John Heard shares a moving-parts demonstration of the nitrogen cycle, with a series of plumbing valves and pipes (on an artistic backdrop!) showing how nitrogen losses occur.
“We’ve decided that people were bored to death of seeing the nitrogen cycle the way it’s normally put together, so we have an actual moving parts nitrogen cycle that we set up, because really, we need to lay the groundwork for dealing with nitrous oxide,” Heard explains.
“In the past, what we were concerned about was the nitrogen losses due to N2 gas. This is agronomic. But the thing we’ve got to talk about are things that are not agronomic, but environmental. That’s the N2O.”
In dollar terms, N2O losses might be worth pennies compared to the five dollar bills Heard uses to represent N2 losses, but when it comes to climate policy, nitrous oxide is very potent greenhouse gas.
“So the little bit of N2O gas that we lose through this leaky pipe, that’s what magnifies — 100 pounds of N per acre (when broadcast applied) is like 460 pounds CO2 equivalent,” he explains. “So that all of a sudden puts a little bit of impetus on understanding how this works. And how these knobs, by using different practices, can slow down and do a better job of controlling nitrous oxide losses.”
There are tools and practices that are shown to substantially reduce nitrous oxide emissions, says Heard, ranging from variable rate and split applications to enhanced efficiency fertilizers to changes in cropping systems, such as growing more pulse crops — but they also tend to come with increased costs.
Watch John Heard demonstrate the nitrogen cycle, and discuss different approaches that reduce N2O emissions: