Polymer coating has jumped from seed to fertilizer.
Agrium’s new environmentally sensitive nitrogen granular urea is now registered for Canadian non-food products such as forages and timothy, which do not go directly into the human food chain.
In the United States, where environmental legislation affecting agriculture is much stricter, some states now pay farmers an incentive as high as $8 per acre for using environmentally friendly time-release nitrogen fertilizer products such as polymer-coated granules and urease inhibitors.
The polymer coating chemistry is roughly similar to that used in coating canola seed.
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Agrium senior agronomist Ray Dowbenko expects the Canadian Food Inspection Agency to soon approve the company’s polymer-coated urea granules for use on wheat. He said approval should be in place to allow its use with winter wheat this fall.
The concept of time management – to feed nitrogen to a crop only when it is needed – is old hat to Dowbenko. He performed his first research on polymer-coated urea at the University of Manitoba in 1988 and conducted early Canadian work on urease inhibitors in 1992. As nitrogen costs continue to soar, both types of nitrogen time management are moving into the western Canadian spotlight.
Dowbenko said protection against leaching is a significant characteristic of the polymer coating.
“If you get a deluge of rain within the first two weeks after your nitrogen goes down, conventional non-protected nitrogen fertilizer is flushed out of the root zone. It’s gone,” he said.
“Polymer-coated granular material does not get flushed away. It will not release its nitrogen if it’s too wet. It’s like a time-release cold capsule for people. It’s metered out over a predetermined period of time to meet the requirements.”
Leaching can only occur after conversion to ammonium; it can’t occur while nitrogen remains in urea form. With a polymer-coated granule, water slowly moves into the capsule and dissolves the urea to form a water-soluble urea solution.
This nitrogen gradually moves into the soil, where it eventually converts to ammonium. In another three to five days, it becomes nitrate.
Dowbenko said a crop can use the ammonium and nitrate forms of nitrogen, but only the nitrate form is susceptible to losses from leaching and denitrification. ESN retards the conversion process by slowing the flow of water into the granule.
He said polymer coating’s chemistry is key to making this work. Water penetrates the ESN coating at a controlled rate, like putting a sponge in a plastic bag and holding it under water.
The sponge wants to absorb water, but the bag keeps the water out. If the inflow of water is controlled with tiny pin holes in the bag, the rate at which the sponge becomes water saturated is also controlled.
“With ESN, higher soil temperatures trigger the polymer coating to let more water into the urea granule. If the soil stays cool, the conversion slows right down. When the weather warms up so the crop wants nitrogen, the polymer coating lets more water into the granule.”
When Dowbenko attends producer meetings on soil fertility, he often hears people talk about urea volatilization losses of 30 to 60 percent, with horror stories going up to 80 percent.
“I’ve seen, in real world situations, nitrogen losses of 30 percent in one week and 50 percent losses if there’s a month without rain,” he said.
“But when that’s the case, it’s a disaster anyway, so N loss isn’t the biggest problem. In typical real world situations, we would normally see urea volatilization losses ranging from a half percent to three-quarters of a percent each day. So if you’re putting on 80 pounds of surface applied urea without incorporation by tillage or by rain, you could lose four or five lb. per week.”
Dowbenko said the opposite circumstances, in areas with wet heavy soil, can still create losses as high as 70 percent with fall nitrogen application.
“It’s common in the Red River Valley to see guys out on Thanksgiving weekend putting down nitrogen, and the soil temperature is still 20 C. It could be a long wait before that soil freezes up, plus there can be significant rainfall coming. In the worst case scenarios, up to 70 percent of that nitrogen is lost.
“Now, if that fall-applied N went down as ESN, the producer has a three or four week safety period before any of it starts converting to the nitrate form. You could virtually cut your N losses to zero.”
Dowbenko said all of Agrium’s ESN trials on winter wheat have been in Alberta, where it now has nine site years of data.
Researchers put 100 percent of the nitrogen down with the winter wheat seed without any measurable seedling damage.
“The numbers show us that 25 percent of the nitrogen is released before freeze-up. That means that when spring comes and the crop breaks dormancy, the nitrogen is right there for the plants, immediately.”
He said researchers have discovered that applying the ESN one month later is too late.
“Timing is critical with ESN. We know it works. You just have to know how to use it to your benefit.”
To demonstrate how high losses can be under the worst possible conditions, Agrium researchers conducted a “forced” volatilization lab study showing that at 14 days after application, loss from uncoated urea already approaches 50 percent, while ESN coated urea has just begun to release nitrogen.
“We don’t present this study as a real world situation,” Dowbenko said.
“This was a controlled lab situation, with the temperature at a constant 23 C and electric fans running to simulate the prairie wind. We did everything we could think of to replicate a really bad field situation, where urea is not incorporated with tillage or rainfall. This is what might happen in an absolute worst case scenario.”
Dowbenko said polymer-coated urea works well on zero till and reduced till farming operations.
“If you put down nitrogen fertilizer, and you have a high level of crop residue or your soil has high organic matter content, then whatever nitrogen that isn’t taken up by the crop becomes immobilized. It’s tied up in association with the straw.”
He said that if a zero till producer puts that nitrogen down in the form of polymer-coated urea, he gets a timed release so the crop is able to take up the nitrogen as it becomes available. There is no excess nitrogen floating around waiting to become immobilized by residue and organic matter.
“This technology has the potential to solve a lot of the problems associated with fertilizer placement in direct seeding and zero till,” Dowbenko said.
With a controlled-release nitrogen product, researchers can study the nitrogen uptake curves for various crops and the charts will explain when each type of plant requires a specific amount of nitrogen.
Chemical engineers can then custom blend a coating and a fertilizer product tailored to the needs of that crop.
With further research and development, he added, ESN may allow all nitrogen fertilizer to go down with the seed without risk to the seed or young plants.
By closer control of nitrogen release, it may be possible to use the ESN to boost protein levels.
One of the immediate opportunities for ESN is the niche left when ammonium nitrate disappeared from the market.
ESN coated urea provides the same or better performance compared to ammonium nitrate.
Although producers in Saskatchewan and Manitoba have not mourned the loss of ammonium nitrate, it’s a different story in Alberta, where farmers bought 67 percent of what was sold in Western Canada.
“I’ve had many letters and phone calls from concerned producers, particularly here in Alberta,” Dowbenko said. “The loss of ammonium nitrate has caused a lot of heartache and stress.”
Once ESN has full CFIA approval, it will be a viable alternative to ammonium nitrate.
The price premium a producer pays for ESN is approximately the same as for ammonium nitrate: 14 to 17 cents more per pound of actual nitrogen.
“At today’s price (May 2) ESN costs 15 cents per lb. more than straight urea,” said Dowbenko.
“That’s roughly the same price premium that AN carried last time it was available.”
However, Dowbenko said the price quote is deceiving. In many fertilizer blends, the ESN is mixed in as only one-third or one-half of the total volume, which means much of the fertilizer goes in unprotected, while a third or a half goes in the ground with ESN protection.
Producers using ESN on timothy and forages are using a blend of one-third ESN, one-third straight urea granular and one-third ammonium sulfate.
Another popular option is one-half ESN with one-half either urea or ammonium sulfate.
“If you blend ESN at the one-third rate, it works out to six cents per lb. of the total fertilizer volume. That’s about the same price as Agrotain at the low rate,” he said.
“If you blend ESN at the one-half rate, it works out to nine or 10 cents per lb. over the whole volume. And that’s similar to Agrotain at the high rate. For timothy and forages, most people are using the one-third or the one-half rate. But as we learn more, this is going to vary a lot in different soil zones and different areas. We are right now beginning a series of tests across the Prairies, in conjunction with the federal and provincial governments.”
