Agriculture is the major emitter of nitrous oxide, researchers say
The 4Rs of nutrient stewardship can decrease emissions of the greenhouse gas nitrous oxide (N2O) anywhere from 20 to 40 per cent, according to research out of the University of Manitoba.
“The vast majority of the nitrous oxide that is emitted is from agriculture,” said Mario Tenuta, professor of soil ecology at the University of Manitoba.
A significant drop in ag-related N2O emissions could reduce Canada’s overall greenhouse gas emissions by two or three per cent — a not-insignificant number, Tenuta told the Co-operator.
“It all adds up, particularly because we’re going to need as much as possible in terms of reduction,” he said.
Tenuta and other researchers from the University of Manitoba presented this and other research in a self-guided tour near Carman in late July. The tour relied on signs and ‘QR codes,’ which led to videos and handouts explaining research at the plot.
The tour was a joint initiative between the province, university, and the Natural Sciences and Engineering Research Council’s Industrial Research Chair program. The site is one of three spread across Manitoba, Ontario and Quebec.
“The aims of the projects now are to increase nitrogen use efficiency of grain corn,” Tenuta said in a video overview of the site. “That’s to meet national objectives of reducing greenhouse gases and other nitrogen losses to the environment.”
Nitrous oxide gas is released from soil during the cycling of nitrogen. It traps heat and destroys ozone in the upper atmosphere.
N2O accounts for about five per cent of Canada’s greenhouse gas emissions, according to a 2018 report from Environment and Climate Change Canada — by comparison, carbon dioxide is 80 per cent, and methane is 13 per cent.
However, because the emissions are concentrated in a particular activity, it can be identified and perhaps targeted.
The project tested combinations of the 4Rs (rate, source, timing and placement) in three groups of pre-plant broadcast incorporation of urea-based sources; in-season top-dressed UAN with urease/nitrification inhibitors; and in-season UAN placement through surface dribble or side dress at various depths.
Preliminary results show enhanced efficiency fertilizers reduce N2O emissions compared to conventional urea when broadcast before planting.
Some are able to reduce emissions 30 to 50 per cent, which tracks with research out of Eastern Canada and the United States.
“I think that’s pretty exciting,” Tenuta said.
Granted, enhanced efficiency fertilizers are generally costlier than conventional ones. Tenuta said they’re working to find payoffs for the extra expense — whether in increased yield, reduced application rate, or increased convenience and peace of mind.
Research also showed that placement of the fertilizer has important effects. Subsurface banding, for instance, effectively reduces emissions.
“We want to reiterate that that’s a good practice to our farmers,” said Tenuta.
They’ve also found that if farmers wait to apply fertilizer into late October or November just before freeze-up, they lose less fertilizer and less becomes N2O gas.
Right now, enhanced efficiency fertilizers are using old chemistries and old approaches, Tenuta said. Fertilizer companies are investing a lot of money to come up with new chemistries and new products. In a couple of decades, nitrogen losses will likely be reduced by new technology.
This might include “super-smart fertilizers” that can sense their environment and nutrients on hand and be triggered by plants to release, Tenuta said. This might be through plant breeding, molecular or nanotechnology.
“I’m envisioning quite a drastic change, let’s say — here I’m talking 20 years from now — a farmer could put fertilizer down and it does nothing. It does nothing unless there’s a plant that triggers the fertilizer,” he said.