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New ideas block N loss

It's a sobering fact that one half or more of the high-priced nitrogen that farmers will apply prior to growing this year's corn crop will be wasted. In the U.S. alone, this loss will amount to more than $1 billion. The nitrogen-use efficiency of wheat is even lower; it averages around 35% worldwide.

The major causes of nitrogen loss are leaching, denitrification, and volatilization. There are ways to manage these culprits through application methods and timing, but these often don't fit the logistics of many farming operations. However, technology is continuing to develop new products aimed at improving the economic and environmental impact of nitrogen.

Agrium's ESN (Environmentally Smart Nitrogen) is a controlled-release product that utilizes a polymer membrane that coats high-quality urea fertilizer. The membrane allows water to enter to dissolve the urea, but nitrogen must then diffuse through the membrane and into the soil. This diffusion is controlled by soil temperature and moisture, so it can be matched to the rate of crop growth.

"At soil temperatures around 65 degrees Fahrenheit, the nitrogen releases over a 60- to 80-day period," explains Agrium agronomist Alan Blaylock.

"With corn, this means you can apply it just ahead of planting, and the bulk of the nitrogen will be available 40 to 50 days later, when the crop enters its rapid-growth stage. As a result of that delay, most of the nitrogen is not available in the early spring when heavy rains often cause leaching and denitrification. You get the efficiency of sidedressing without the time and trouble of making that extra application," Blaylock says.

Winter wheat growers can apply ESN when soil is frozen, eliminating the need for split springtime applications to maximize efficiency. "Put it on in early February, and the nitrogen will become available in the spring when it is often too wet to be on the field making split applications," says Kelly Nelson, agronomist at the University of Missouri Greenley Research Center.

Compared to urea, ESN typically costs about 10¢ more per pound of nitrogen. "Our data shows the average advantage from ESN use on corn is 8 to 10 bushels per acre," says Blaylock. "In specific situations where the probability of nitrogen loss is high (such as wet, poorly drained soils), the benefit is twice that much. However, in dry conditions there is no benefit to ESN."

At the University of Illinois' Dixon Springs Research Center, agronomist Steve Ebelhar evaluated nitrogen products, separating findings for wet locations (more than 12 inches of rain within 15 weeks) and dry locations that got less. He found no difference in dry areas. But at wet locations, sidedressed UAN produced the highest average yield of 143 bushels per acre. ESN was next at a 138-bushel average, followed by urea with Agrotain (130 bushels) and UAN with AgrotainPlus (127 bushels per acre).

"In contrast, the average yield from traditional broadcast urea was 123 bushels per acre, and dribble-applied UAN was 125 bushels. It appears significant improvement in nitrogen-use efficiency can be made with these products, especially in wet years," says Ebelhar.

Nelson says his research indicates that in no-till situations with nitrogen application rates of 150 pounds per acre, it may be possible to reduce the application rate of ESN by 30% compared to urea, without reducing yields. "This may be a cost-effective method for farmers to offset the added cost of the ESN product," he says.

Nelson says the return to ESN could be spectacular when applied only to areas of the field likely to encounter nitrogen loss. "We found a yield benefit of nearly 25 bushels per acre compared to urea in low-lying areas of fields but no benefit in other areas. This suggests a strategy of variably applying ESN and urea. An example is spot applying the coated product only where there's a high risk for leaching and denitrification."

A recent review of ESN research in six Midwestern states highlighted other experiences with the product. ESN use in the fall was generally equal to NH3 with N-Serve. ESN can be blended with a rapid-release nitrogen source if nutrients are needed quickly, and ESN causes few germination problems when applied with the seed.

"Because of the environmental benefits of ESN, government cost- sharing programs (EQUIP and the Conservation Security Program) may help offset the added cost," says Nelson. "In Missouri, this incentive may be $7 to $10 per acre."

Newest among the flush of enhanced-efficiency fertilizers is NutriSphere-N. This product, from Speciality Fertilizer Products of Belton, Missouri, is available either as a coating on urea or in liquid form with UAN at an added cost of five to 10 cents per pound of N.

NutriSphere-N works to prevent the loss of nitrogen by influencing the microbial activity that causes those losses in the soil. It reportedly prevents the action of urease that results in volatilization and slows the nitrification reactions that lead to nitrate leaching.

"The material impacts reactions caused by soil enzymes by compromising the activity of the metals nickel, copper, and iron. In effect, this creates a shield, preventing the action of urease in volatilization and slowing nitrification reactions," says Larry Murphy, president of Murphy Agro, Manhattan, Kansas.

Murphy coordinates research with NutriSphere-N, some of which is being done by Kansas State University agronomist Barney Gordon. "We've studied the product for five years, which was before it was introduced," says Gordon. "In that time, NutriSphere-N has performed as well as ESN and Agrotain sources of nitrogen and much better than urea and UAN alone."

In 2004, Gordon saw irrigated corn yield increases, compared to urea alone, of 22, 18, and 24 bushels per acre at N rates of 80, 160, and 240 pounds, respectively. Similar increases were seen in 2005.

However, University of Illinois agronomist Lyle Paul has found tests at the Northern Illinois Research Center to be less positive. "Results have been mixed, but they’re intriguing enough that we will continue the research," he says.

ATS is not a new source of nitrogen, but efforts to apply it in conjunction with anhydrous ammonia in no-till are focusing new attention on its ability as a stabilizer.

"A standard product of the fluid fertilizer industry, ATS (12-0-0-26S) is a source of both nitrogen and sulfur," says North Dakota State University soil scientist Jay Goos. "When it's applied in a concentrated band, ATS also has an ability to slow soil urease and nitrification, so if the farmer needs sulfur anyway, it's a logical choice."

ATS is not as strong of an inhibitor as Agrotain in UAN or N-Serve in NH3, but it's not as expensive. "It's roughly one third the cost," says Guy Swanson, who encourages farmers using his Exactrix delivery systems to co-band ATS with NH3.

Seneca, Kansas, farmer Ryan Hammes has seen that combination pay. "We mix ATS with 10-34-0 and inject it right ahead of our NH3. This combination is one of the main reasons we've been able to reduce nitrogen application rates on our corn by one third," he says.

It's a sobering fact that one half or more of the high-priced nitrogen that farmers will apply prior to growing this year's corn crop will be wasted. In the U.S. alone, this loss will amount to more than $1 billion. The nitrogen-use efficiency of wheat is even lower; it averages around 35% worldwide.

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