How To Choose The Best N Form

Getting the full bang for every buck spent on nitrogen (N) fertilizer can be difficult. Under some conditions, losses from volatilization (off gassing) can exceed 50 per cent, according to a Quebec study. With the current cost of fertilizer, no operation can afford that. However, two N treatments, ESN and Agrotain, can significantly decrease those losses. But knowing which one to apply and under what conditions they work is important before deciding to make the extra investment.

“Many people get them confused and think they are actually very similar or the same,” says Ross Mckenzie, a research scientist with Alberta Agriculture and Rural Development. He has been conducting research on both products. “They each have unique situations when I would recommend you use them and then there are other situations when I would probably just recommend you use normal urea,” he says.

In order to decide which, if any, of the features they offer can provide a benefit to your operation, you need to first understand what they are and how they work.


ESN is an acronym for environmentally smart nitrogen. “It’s the only controlled-release nitrogen source that is widely available to farmers,” says Jason Kuhlemeier, product manager, ag products, for Agrium Advanced Technologies. Agrium produces ESN.

ESN is normal urea with a semi-permeable polymer coating around the granule. The coating makes it a slow-release fertilizer. When placed in the soil, moisture gradually penetrates the coating and puts the urea into solution. The coating then gradually allows the solution out. The rate at which it releases the N depends on soil temperature. “The release of that solution will match up well with the time of the year the plant most needs it,” says Kuhlemeier.

By releasing nitrogen slowly, leaching, volatilization and denitrification are minimized, ensuring more of the nitrogen remains in the soil to feed the crop. Under most situations, a blend of regular urea and ESN will best suit a farmer’s needs. The regular urea is immediately available to plants, and the ESN granules provide additional N later in the season.

“The majority of times we would recommend a blend,” says Kuhlemeier.

“Typically, under warm, moist conditions, it takes between 20 and 30 days for half of that (ESN) fertilizer to move into the soil,” says Mckenzie. “The thinking is if you put it on at the time of seeding, the release of that nitrogen will more closely match the needs of plants.” Normal urea could be lost under conditions, such as heavy rain, that can cause leaching or denitrification. “That’s when ESN tends to shine,” he says. “When you have wet conditions ESN can make quite a difference.”

Mckenzie notes test plots treated with ESN for the 2010 growing season were visibly better than untreated plots due to the unusually wet year, but under drier growing conditions, results are likely to be less spectacular. “Usually we will see some slight advantage but not in the range of 20 or 30 per cent, it might only be in that five or 10 per cent range. Farmers have to decide if it’s really worth it and look at what would be typical conditions in normal years. Farmers in the wetter regions might prefer to use ESN. Farmers in the drier regions of the Prairies often probably wouldn’t see a huge benefit.”


“With ESN, when you put it in the seed row it releases quite slowly, so we don’t have the injury to germinating crops we do with urea. With urea, for example, you really can’t put on more than 25 to 30 pounds of actual N. By going to ESN, you can go to three or four times that safe range. Really, we can be in that 90 pound range with wheat or barley.”

Farmers operating a single-shoot seed drill would be able to place much or all of the necessary N down when seeding with their existing equipment by using ESN. That could make a second field pass with a spreader unnecessary or eliminate the need to invest in updated seeding equipment. Although, the extra cost associated with ESN would add to the annual fertilizer bill.

“That would be a time I would suggest farmers want to look at utilizing ESN,” Mckenzie adds. “But if a farmer has a double-shoot or side-row banding system, there would be no advantage unless they are concerned about nitrogen loss.”

But growers considering ESN for broadcast spreading on forage stands, should think again, according to Mckenzie. “The problem with ESN when you just broadcast it on the surface is it releases too slowly to be effective. I know other researchers have found that as well. So, I don’t recommend ESN on forages. On the other hand, I would recommend Agrotain (in that situation).”


Neil Yelland, Canadian sales director for Agrotain, agrees his product is ideally suited for broadcast applications. “Top dress, that’s our marketplace,” he says.

Agrotain works by inhibiting an enzyme in the soil called urease and prevents it from breaking down urea. Urease converts urea to ammonia gas, which can release into the atmosphere resulting in lost N. That can take a real toll on N that is surface-broadcast or placed at a shallow depth in the soil.

“If you coat the urea with Agrotain it’s a urease inhibitor, so it inhibits the enzyme from attacking the urea and you usually have 10 to 14 days of protection,”says Mckenzie. “As long as you get some rain in those 10 to 14 days you’ll get pretty good protection.”

“If you’re going to broadcast urea on the surface and you don’t get any kind of moisture event, then the losses due to volatilization — the conversion of urea to ammonia gas — are going to be very high, says Yelland. “What Agrotain does is minimize those losses and allow time for rainfall. For top dressing, it’s an absolute no-brainer. Without Agrotain, the losses from volatilization can be anywhere from zero to 50 per cent.

And by using the product to reduce those losses, Yelland believes producers who previously hadn’t considered top dressing N on crops other than forages can now do so. Agrotain can also be used with top-dressed liquid N.

Agrotain can also be applied to fertilizer placed in a seed row to increase the safe application rate in a single-shoot application, but it can only increase that rate by about 50 per cent, which leaves ESN the best bet for those who need to significantly bump up seed-placed fertilizer amounts.


For top dressing, Agrotain will cost about five to nine cents per pound of actual N, according to the company’s price sheet. For seedling safety, the cost is only about 80 per cent of that because the rate of Agrotain per tonne can be reduced when used that way.

When it comes to handling and applying treated N, there isn’t much difference than when using untreated fertilizer. Agrotain is a powder applied to fertilizer in a similar way to how inoculant is applied to seed. It can be blended by a retailer or done right on the farm, if a farmer has the equipment required to add inoculants.

When it comes to shelf life, Agrotain can last six to eight months inside a bin. “Agrotain goes to work when it comes into contact with soil and water,” says Yelland. It needs to be kept dry. ESN has a very long shelf life. As long as the coating isn’t damaged, it can remain in storage indefinitely.

Farmers need to exercise extra care when handling ESN, though. If the coating is damaged, the slow-release capability is lost and it will react just like untreated N. That means being extra careful when transferring loads and making sure an air seeder’s fan speed isn’t set too high. Agrotain, on the other hand can’t be damaged that way. “As long as it makes it into the seed row, it’s going to do what it’s supposed to,” says Yelland.

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About the author


Scott Garvey

Scott Garvey is a freelance writer and video producer. He is also the former machinery editor at Grainews.



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