Urea on snow? Just say no

The calendar says, ‘yes, do it,’ but the data says, ‘whoa’; researchers adamant that applying urea on frozen fields is a bad idea

A few prairie farmers are taking advantage of fields almost barren of snow this winter to apply urea, a practice akin to spreading hundred dollar bills to frozen soil.

That’s the opinion of Rigas Karamanos, senior agronomist for Koch Agronomic Services in Calgary.

“This is not agronomically sound. Somebody’s telling them it’s OK, but it’s not OK,” he said.

“When nitrogen fertilizer sits in snow or frozen ground, your losses can be as high as 50 percent. It’s terrible.”

Karamanos said the people who are advising this practice are not being honest with their clients.

“Who, you ask? It’s people who simply want to sell fertilizer, that’s all,” he said.

“That’s who’s telling producers it’s OK. There’s so much research that’s been done on this practice proving that it’s absolutely wasteful. It is not a good practice at all.

“It’s interesting you ask about this now because I’m right now dealing with a complaint from last year. The farmer applied his fertilizer on frozen hard ground and didn’t get the results he wanted. Now he’s complaining the fertilizer was bad. Well, why would he expect to get results in those conditions?”

The perceived benefits of spreading urea on snow are obvious. Producers who engage in this practice see it as just another step forward, expanding their fall fertilizer program deeper into the calendar. Once the frozen ground is too hard for banding, they simply switch from in-ground application tools and keep on trucking with surface application spreaders.

While farmers know they’ll take a big hit on return on investment, the operation does give them two distinct time advantages in the spring:

  • All fertility is already in place, so they can get the seeding rig on the field sooner.
  • They don’t have to waste time stopping for fertilizer fills. With only seed and micro-nutrients in the air cart, an operator can run his full shift without stopping.

The perceived time advantage may be obvious to growers, while the genuine dollar cost is well-known to agronomists but probably not to all producers.

North Dakota State University soil scientist David Franzen conducted field trials comparing snow-applied urea to soil-applied urea in the fall of 1995. The fields were seeded with wheat in the spring of 1996. Franzen said the bushel and protein numbers speak for themselves.

Franzen said urea stays on the surface when applied to frozen soil. If it cannot penetrate all the way through the snow, it becomes part of the snow and blows wherever the wind takes it. In spring snow melt, it dissolves and moves with the water to potholes, lower spots in the field or off the field completely into the waterways.

If you’re on flat land where the spring melt remains in your wet spots, the runoff may not be a big agronomic problem or a public perception issue. However, these are the kinds of scenarios cited by members of the public who want to clamp down on farming practices.

Karamanos gave a presentation to the Farm Forum in Calgary in 2016 in which he outlined the conditions to avoid if you are pressed into broadcasting on snow. His ongoing concern with this issue dates back to research he did with Westco in 1989:

  • Avoid fields that are very wet or the surface is saturated.
  • Avoid fields that froze while the soil was wet.
  • Avoid fields with compacted, drifted or crusted snow.
  • Avoid fields with more than four inches of fresh snow.
  • Avoid extreme cold that prevents urea from rapidly penetrating snow.

“Westco trials conducted under the above unfavourable conditions consistently resulted in worse performance than if the urea had been broadcast in snow-free conditions,” he said.

Karamanos said avoiding those conditions pretty well eliminates all possibilities of broadcasting urea on snow and expecting good results.

He said one of the best studies demonstrating this fact was conducted at Swift Current, Sask., where researchers covered some sites with plastic until it snowed and then removed the plastic. Nextthey applied fertilizer on sites with snow on the ground and on sites with no snow where the plastic had been.

The study measured how much fertilizer can be recovered in the spring. In essence, they measured nitrogen loss over the winter.

“In the field, ammonium nitrate and urea were applied to snow-covered and bare plots of grass sod and cereal stubble,” the researchers said when they published in the Canadian Journal of Soil Science in 1989.

According to the paper, nitrogen recovery from ammonium was 55 to 59 percent, meaning nitrogen loss ranged from 41 to 45 percent.

For urea, nitrogen recovery was only 39 to 51 percent, meaning nitrogen loss ranged from 49 to 61 percent.

Mineral nitrogen declined from fall to spring in all treatments because of denitrification and immobilization.

“Producers must consider the benefits of …. lower fertilizer costs in the fall against the risk of large potential N losses over winter,” the study said.

According to a fact sheet published by Alberta Agriculture: “The fertilizer granule needs to go through the snow, contact the soil and dissolve. It’s also important to recognize there are economic losses and environmental considerations.

“Productivity with fertilizer applied early in the winter dropped by as much as 15 percent over the same application occurring in early spring.”

Another fact sheet published by Manitoba Agriculture said: “In the case of urea, hydrolysis converts the urea to ammonia, and if the urea is not incorporated, the ammonia is lost to the air.”

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