New study finds risks in broadcasting urea

The research in eastern Sask. also found that advanced efficiency products do not reduce losses in all situations

Spreading urea on the soil surface is coming back into favour as farmers look for quicker ways to cover acres in the spring seeding window.

The resurgence has researchers re-examining the strategy.

“Our board said, ‘there are a lot of guys throwing fertilizer down on top of snow; I wonder how much nitrogen they’re losing when they’re doing that sort of thing,’ so we put together another study that looks at broadcast urea and SuperU (fertilizer),” said Mike Hall of the East Central Research Foundation (ECRF) and Parkland College.

During Hall’s presentation at the Agri-Arm research update during Crop Week in Saskatoon, he described a study he ran with ECRF near Yorkton, Sask.

Hall examined three broadcast applications timings of 174 pounds per acre of urea and also of Koch Fertilizer’s SuperU on wheat plots: early fall application on Oct. 2, late fall application on Oct. 27 and applications on top of snow on Nov. 5.

“We compared those broadcast applications to banding urea in the fall, and I know that’s really not a common practice but we don’t really handle ammonia, so that was my closest facility, but our real main check was comparing side banding urea at seeding,” Hall said.

He said the check — side banding urea at seeding — had by far the best yield and protein results.

“That’s the best timing and the best placement, is the most efficient use of nitrogen,” Hall said.

Spring side banding urea at seeding yielded 78.9 bushels per acre and a protein level of 12.5, while the early fall broadcast of urea had a yield of 57.6 bu. per acre and a protein level of 10.9 percent.

The early fall broadcast application is “one of the poorer yielding and poorer protein treatments that we had out there,” Hall said.

“Basically it’s been out there too long and we probably converted a lot to nitrate and we lost a lot to denitrification. When we used SuperU, that improved the situation substantially. We got quite a bit more yield out of it and quite a bit more protein.”

The use of SuperU proved to be beneficial in the early fall broadcast timing because it has a yield of 66.7 bu. per acre and protein level of 11.6 percent.

SuperU protected nitrogen from being lost in the study to denitrification and possibly some volatilization as well, Hall said.

Broadcasting on 10 centimetres of snow also had poor results with a yield of 59.4 bu. per acre and a protein level of 11.3 percent.

This treatment showed signs of nitrogen deficiency through poor canopy colour long before harvest.

“You could tell during summer that the broadcast on snow wasn’t doing so great,” Hall said.

The use of SuperU didn’t reduce losses compared to straight urea when broadcasted on snow because this treatment had a yield of 61.4 bu. per acre and a protein level of 11.3 percent, similar to broadcasting straight urea on snow.

“When we used SuperU in this case, it didn’t do us much favour at that time,” he said.

“Basically we’ve got frozen ground, we’ve got melting snow on top of frozen ground; it just wasn’t a good situation for hanging onto your nitrogen.”

The late fall application treatment had a 64.7 bu. per acre yield and 11.9 percent protein content, and the late fall application of SuperU had a 68.8 bu. per acre yield with a 12 percent protein content.

An economic analysis of the treatments were calculated, which used protein spreads taken from a local elevator on Feb. 9, 2018. Urea was priced at $509 per tonne, and SuperU was priced at $725 per tonne.

By far the most economical treatment was applying nitrogen in a side band during seeding because it had the best protein, yield and the highest returns of $414 per acre.

Side-banded urea in the fall was the second best use of nitrogen with $331 per acre in economic returns, while a late fall broadcast of SuperU provided $323 in returns.

Broadcasting urea in early fall provided returns of $252 per acre, and an early fall broadcast of SuperU provided $292 per acre.

“If you look at the early fall broadcast of urea, SuperU definitely paid for itself in this scenario. We’re making more money despite the highest cost of the fertilizer. The same is true when we were applying it in late fall,” Hall said.

“When we were applying it on snow, SuperU wasn’t doing us any favours at this time. This really isn’t the most ideal time to be putting nitrogen down.”

The treatment in which urea was broadcast on 10 cm of snow provided $264 per acre of returns, while broadcasting SuperU on snow also provided $264 per acre in returns.

Hall said the study shows growers should continue to follow the 4Rs of nutrient management.

“Don’t put more than you need down, try to put it down as close to when the crop needs it as possible, put it under the ground and there is a better chance that it will stay with you,” Hall said.

“If you can’t do those things because of time management and you’re going to be out there broadcasting, particularly if you’re going to be broadcasting out there in early fall, try and use a product that is going to reduce your losses.”

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