INDIAN HEAD, Sask. – Depending on soil zone and source, the amount of unused nitrogen ranges from 30-70 percent of what goes into the soil.
For farmers footing the fertilizer bill, nitrogen not used by the crop is a big economic loss. For scientists charged with tracking greenhouse gases, it’s a perplexing question that demands answers.
For the agricultural sector, it’s a critical issue because it will have a major impact on farming in the future.
Soil scientists across the Prairies have begun measuring the release of nitrous oxide at the soil surface. Their gas gathering equipment is being set up in fields in Edmonton and Three Hills, Alta., Swift Current, Scott, Melfort and Indian Head, Sask., and Brandon and Carman, Man.
Read Also
VIDEO: Green Lightning and Nytro Ag win sustainability innovation award
Nytro Ag Corp and Green Lightning recieved an innovation award at Ag in Motion 2025 for the Green Lightning Nitrogen Machine, which converts atmospheric nitrogen into a plant-usable form.
Curtis Cavers, soil specialist with Manitoba Agriculture, said the nitrogen loss question posed by the Kyoto Accord is the same basic question asked by farmers.
“The nitrogen numbers often don’t add up,” said Cavers.
“Let’s say I put on 100 pounds of N at the beginning of the growing season. The soil test tells me there’s 20 lb. left over at the end of the season. Then I calculate that my crop took maybe 50 lb. of nitrogen. Where did the other nitrogen go? Did it simply disappear? Did we miss seeing it? Is our math wrong? It’s perplexing.”
Cavers said there are four loss factors that are difficult to measure and document. Soil scientists and farmers alike know that nitrogen is lost to denitrification, leaching, mineralization and immobilization. He added that nitrous oxide is the most potent of the three greenhouse gases being addressed by Kyoto.
Although the recent surge in nitrogen loss research was triggered by Kyoto concerns, Cavers said the technology being developed can evolve into an on-farm tool that producers can use in soil management programs.
“Eventually, I’d like to get it set up so farmers can have access to a quick and relatively easy method for measuring nitrogen loss in the field. The kit is not difficult to use. I’d like to get enough people trained so these kits could actually be used someday to manage N in the field,” said Cavers.
“Denitrification is not a common occurrence, but when it happens, it happens in a big way. Once we have a better handle on these massive nitrogen loss events, we’ll be better set to make management decisions that will avoid the big nitrous oxide blow-offs.”
He said the information provided by the kits will become more important as farmers try different crops, rotations and fertilizer schemes.
The first nitrogen loss test was developed by the United States Department of Agriculture as a basic measurement of soil quality.
“It was a quick and dirty method of using basic equipment to measure water infiltration, soil respiration, earthworm numbers, aggregate stability and carbon dioxide levels. The carbon dioxide was perhaps the most important because it is an indirect indicator of how much microbial activity you have in the soil.
“Probably 90 percent of the stuff in that first stage kit was available in a hardware store.”
Cavers said that the second stage of the kit is still no technological marvel. It uses PVC rings pounded into the soil to seal the test area. An airtight cover goes over this ring.
A syringe is used to capture air samples coming off the soil surface at the time of sealing and then again at 10, 20 and 30 minutes. The vials of air are sent to a lab where the different gases in each sample can be determined and measured.
By measuring the flux, or the rate at which these various gases are given off, researchers get some idea of what is happening in the soil.
Some of the research is specific, and while it may not provide the overall answer, it will provide key pieces to the puzzle.
Hilary Hunter is a greenhouse gas technician working for the Indian Head Agricultural Research Foundation, documenting the long-term effects of zero-till on nitrous oxide emissions.
This summer she has been measuring the net nitrous oxide contribution of Metcalfe barley in a no-till management system.
Hunter said that in some regions of the world, no-till fields have been shown to have higher annual losses of soil-emitted nitrous oxide. Because conditions are different in Western Canada, it’s important to determine what losses can be expected in prairie conditions.
It takes years for no-till fields to mature and undergo the many physical, chemical and biological changes that occur. Hunter’s studies in 2005 compare mature fields that have been in no-till more than 20 years with short-term no-till fields. This is the first year in a three-year study.
“We sometimes rag on the soil test because they don’t tell us everything we want to know,” said Cavers.
“But a soil test is nothing more than a snapshot of what is in the soil on that particular day. Just part of the whole picture. It doesn’t tell us what’s happening in the soil or what will happen the next day. If we really want to track nutrients in the soil, we’re gong to have to do a lot more of this focused kind of testing.
“These GHG kits are only one more tool, but it’s the kind of tool that will lead us to soil test recommendations that are more relevant.”
Hunter agreed the data is vital to understanding nitrogen loss, but she isn’t as certain that the measuring equipment can be an on-farm tool for prairie producers.
“I’ve read some of the research from Quebec,” said Hunter. “It may be more practical there, but that’s because they don’t have the wind like we do here in Saskatchewan.
“There’s a Quebec company called Campbell Scientific. They sell an instrument that monitors nitrous oxide emissions 24 hours a day. If you didn’t have the wind to contend with, it might be more feasible.”
