By Mike Surbrugg
msurbrugg@joplinglobe.com
MOUNT VERNON, Mo. — “Nitrogen is a tricky, slippery thing to work with.”
That was the assessment from Peter Scharf, a University of Missouri plant scientist, during a recent meeting held in Mount Vernon where he talked about different sources of nitrogen fertilizer.
He focused of using urea or ammonium nitrate sources.
There is potential for nitrogen loss from any source, he said.
A lot of fertilizer in Missouri is broadcast on the surface of pastures and hay fields. “Grass is king in Southwest Missouri,” he said.
A lot of broadcast urea can be lost through volatilization, he said. The loss is greatly reduced when the urea can be knifed into the soil or by tilling it into the soil within four days of application.
In grass-covered fields, an answer to the loss has been to pay a higher price to get more results by broadcasting ammonium nitrate that is less volatile, he said.
Missouri, Oklahoma and Texas are the states where farmers use the most ammonium nitrate because these states have a lot of grass and cattle, he said.
A major concern is that ammonium nitrate is also used to make bombs. National security requires constant armed guards when any of this product is stored near any navigable waterway.
Agrium is among corporations no longer making ammonium nitrate. It had been the largest manufacturer of ammonium nitrate in North America, he said. Some plants are shutting down in face of high natural gas prices and in the face of restrictions.
It is not practical to blend urea and ammonium nitrate in a fertilizer spreader, he said.
The gap left by less ammonium nitrate production means the United States is importing more urea. More urea plants are being constructed worldwide because the world wants fertilizer, Scharf said.
More farmers are using less or no tillage to reduce erosion and lower production costs. An average 25 percent of nitrogen is lost into the air as a gas when urea is spread on the ground.
Loss ranges from none to 50 percent, based on the method of application and if it rains at least a half-inch a day after urea is spread. Water carries urea into the ground.
Losses mount when it is spread on a hot and dry day and wind is blowing, he said.
Scharf cited information from preliminary tests that show a $5 premium to use ammonium nitrate rather than urea to get an extra 320 pounds of fescue per acre. More studies are to be done.
Most comparisons have been made with grain crops. If corn sells at $3 a bushel, the yield increase from either product shows a $10.50 higher return from ammonium nitrate than with urea, Scharf said.. There is an average $5-$6 premium to use ammonium nitrate to grow wheat.
“Ammonium nitrate is better, if you can get it,” he said.
Farmers need to know the quality of any fertilizer they purchase and to check it before spreading to assure it does not clump and will flow with an even distribution.
A lot of fertilizer used on American fields is imported and the more handling of any product can cause lower quality, he said.
His recommendations for getting better returns from urea is to knife or inject it into the soil or use urea with different coatings to reduce volatilization.
Switching to ammonium sulfate is not a solution. Its supplies are limited because it is a by-product of the nylon industry, Scharf said.
Mike Surbrugg is the farm editor for The Joplin Globe.
