The loss of ammonium nitrate should not be viewed as a major problem for winter wheat growers, says Cindy Grant, a researcher with Agriculture Canada in Brandon.
She said there are two good alternatives: liquid UAN 28-0-0 and granular 46-0-0 with a urease inhibitor.
Grant, who conducted 12 years of field research on urease inhibitors starting in the mid-1990s, said ammonium nitrate was once the product of choice for surface nitrogen application because there was less volatilization.
“Urea ammonium nitrate was considered to be good from an efficiency standpoint, but a lot of times, unless you got really very bad field conditions after applying your urea ammonium nitrate, there wasn’t that big of a difference,” she said. “It just didn’t matter that much.”
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As well, ammonium nitrate was expensive, prompting producers to look at less costly products.
“Farmers have two good options with either surface dribble-banded liquid UAN in the spring or urea granular (treated) with Agrotain.”
She reminded producers that Agrotain can be used as a coating on granular or mixed with liquid, but she added that liquid soaks into the soil quickly.
“So I don’t think there’s that big of an advantage using it with liquid.”
Grant said Agrotain works on the enzyme that enhances the conversion of urea to ammonium and ammonia. It is engineered to be specific to that one enzyme.
“It ties the enzyme up for a while. Over time, the inhibitor breaks down, the enzyme gets busy and away it goes to continue its work.”
The length of time Agrotain ties up the enzyme depends on the rate of application. The standard low rate gives five days inhibition, the medium rate gives seven days and the high rate gives 14 days inhibition.
“In our research, we often saw enzyme inhibition lasting longer than 14 days, but we know for sure we could always be comfortable with 14 days,” she said. “In surface application, you primarily want to reduce volatilization losses, where it’s going off as ammonia. The advantage of Agrotain is it keeps it in the urea form. Urea is water soluble, but it’s not volatile, so that gives you more time for rain to come along and move it down into the soil. The Agrotain protects it from being lost.”
However, Grant cautioned that Agrotain is not a foolproof answer to the problem of nitrogen loss.
“If you don’t get rain sooner or later, the urea eventually has to convert to ammonium and ammonia, and then it can volatilize off and it’s lost.”
28 day protection
Under some circumstances, Agrotain can provide growers with Stabilized Nitrogen for nearly a month, according to Philom Bios senior research agronomist Gary Hnatowich.
“At the highest rate, you can get up to 28 days of protection, if weather conditions are conducive,” Hnatowich said.
Stabilized Nitrogen is the Philom Bios trademark name for the three products it markets for reducing nitrogen losses.
Philom Bios said the 28 day volatilization protection is not a new feature. Agrotain at the high rate has always halted the conversion process for 14 days. At the 14 day point, it begins to diminish in strength, but continues to provide smaller degrees of protection against gassing off.
If the soil remains warm and moist, but there is no rain, the inhibitor is still working to slow down the conversion process at 28 days after application.
Agrotain, the original product, is a urea stabilizer that can be applied directly to granular urea at the fertilizer dealer or mixed into the UAN tank on the farm.
Nitrogain is the urea or UAN Agrotain product that is applied by Saskferco at its central plant. Like the locally applied product, it can also be ordered through local fertilizer dealers.
Agrotain Plus is a dual inhibitor designed to reduce losses from denitrification and leaching, in addition to the basic Agrotain protection. It starts with the original urea inhibitor, but a secondary nitrification inhibitor is added that works at a later stage of the conversion process. The second inhibitor slows the nitrification process where the fertilizer converts to nitrate.
“It’s ideally suited for surface dribble-banded applications in high rainfall areas or for irrigation. Or, a guy would use it if he’s putting a fair amount of nitrogen down in the fall and he’s worried about conversion over to nitrate or worried about leaching in the spring thaw.”
Agrotain Plus is only for liquid fertilizers and should not be used for seed-placed applications or with granular urea. Prices are based on the rate of product per pound of actual nitrogen. The low rate for five-day protection costs about 4.5 cents per pound of actual nitrogen. The top rate for 14 to 28 days of protection costs about 10 cents per pound of actual nitrogen.
