In the midst of a hot, humid southern Georgia summer, Lee Trice applied urea with a nitrogen-efficiency enhancer to his Coastal bermudagrass. Then he waited 12 days before rain arrived to soak in the fertilizer. Much to the grower’s relief, the urea performed just fine.
“Agrotain worked,” says Trice of the N-efficiency enhancer he used. “The field produced as well as other fields with ammonium nitrate applications. And urea with Agrotain might have been a little cheaper.”
The grower now splits his fertilizer needs between ammonium nitrate and urea. “Fertilizer prices have really jumped. The summer can be so hot and dry; I worry a lot about the weather, and if it is going to rain.”
He adds Agrotain to urea when dry weather is forecast or if he’s concerned about potentially high volatilization loss.
Judicious use of a proven N-efficiency enhancer is a great strategy when using urea with hay crops, says Dennis Hancock, University of Georgia Extension forage specialist. As security safeguards make ammonium nitrate more difficult to find, urea is becoming an increasingly important N source.
But, warns Hancock, “with urea, volatilization can be a major risk.” As much as 20% of N – and up to 50% in extremely hot and humid situations – can escape into the environment. Enhancers slow the chemical conversion of urea to ammonia, which allows time for the N to be absorbed into the soil as ammonium.
Georgia studies show that, in bermudagrass, Agrotain reduces ammonia volatilization an average of 60% and increases yields about 10%. “The bottom line? With Agrotain, urea will go 20% further in terms of recovery of nitrogen,” Hancock says.
Chris Teutsch, Virginia Tech Extension forage specialist, isn’t keen on urea as an N source for hay crops, advising Virginia growers to stick with ammonium nitrate or ammonium sulfate. Yet urea, at times, is the best option, and Agrotain is a benefit, he concedes.
“In some years, it has worked out very well for growers to use it,” he notes. “The whole quandary is trying to predict the weather. Agrotain isn’t needed in every situation.”
Teutsch suggests applying urea and an enhancer in late summer-early fall, when temperatures are high with high volatilization loss potential.
The N-efficiency enhancer isn’t needed, Hancock says, in spring when N is applied to annual ryegrass.
“We tend to get good rainfall, the risk of volatilization is low, and you’re not likely to get a significant benefit from Agrotain. In August, it is hot, very humid and maybe there’s some wind. Those three factors increase volatilization, so you might want Agrotain for your bermudagrass.” If a cold front comes through with rain, Agrotain may not be needed, he adds.
More data on N-enhancing products is needed, Teutsch says. In Virginia trials, Agrotain’s visible benefit isn’t as measurable as he’d like to see. Other products that claim to enhance N availability haven’t shown a benefit, and one product may decrease N availability in fall.
“Growers need to be careful,” he cautions, of product claims.
Cost should also figure in a grower’s strategy. Agrotain adds 7-9¢ to the per-unit N cost, Hancock says, and will likely pay when urea is expensive, but not when it costs less.
“We are trying to determine the breakeven point,” he says. “But because of the 10% increase in yield, I feel confident that Agrotain will pay for itself as long as nitrogen prices stay where they are or go higher and conditions are such that volatilization is a major risk.”
Studies are under way to determine if growers can apply less N if they add Agrotain, Hancock says. He hopes additional N-efficiency enhancers that work with field crops may be reformulated to be effective with hay and on pastures.