Faced with expensive fertilizer prices, fickle weather and the threat of activist regulators, no-tillers are using nitrogen stabilizers and other nutrient enhancements more than ever to avoid the losses between application and crop uptake.
Higher fertilizer costs make over-application an expensive way to compensate for nitrogen loss.
“Nowadays, the amount you spend on fertilizer is a number to be reckoned with,” says Edwardsport, Ind., no-tiller Jason Misiniec.
Educating farmers on spending fertilizer dollars wisely is the focus of University of Missouri agronomist Peter Scharf. He emphasizes that nitrogen stabilizers are just part of a nutrient-management system that includes a host of agronomic practices.
“Everything comes down to making sure there’s adequate nitrogen there when the corn needs it and not lost to the water or the air,” he says.
Do Your Homework
Scharf cautions that results vary with stabilizers and some may not warrant the extra investment.
He advises no-tillers to be skeptical of unscientific trials and suggests they utilize university-based research to facilitate decision making. Even better, farmers should consider conducting their own onfarm testing that includes at least three side-by-side comparisons to help assess product performance.
“First, understand what the product does, if it’s cost-effective and if it addresses your situation. Nothing is bullet proof,” he says. “Don’t adopt the mentality that you’ve bought a stabilizer and now you’re protected.
“Weather and timing are still important. Any product can, to some extent, be overpowered by weather conditions — especially in late spring, right ahead of when your corn crop really needs the nitrogen. It’s critical to pay attention to what’s actually happening in the field so that if you experience nitrogen loss you still have time to address it.”
Among the available products, Scharf considers the use of Agrotain to be a best-management practice when urea is surface-applied.
Urea left on the soil surface begins losing nitrogen within the first few days and continues to do so until at least a half-inch of rain has fallen. Unprotected-nitrogen losses can be as much as 50%, depending on weather conditions but regardless of timing.
“This is pure chemistry — it’s not a biological process,” Scharf says. “The nitrogen in urea is not protected by cooler temperatures and you can lose about one-quarter of your nitrogen, regardless of timing. We did a wheat topdressing study comparing January, February and March applications and, in each case, the lowest yields were the treatments in which urea was applied with no inhibitors.”
Using N-Serve, made by Dow AgroSciences, with fall-applied anhydrous is also recommended, though Scharf still considers fall application a high-risk proposition.
Wet weather in May and June also bumps the nitrogen-loss risk up substantially, however, and N-Serve applied with spring ammonia reduces that risk, he says.
May through June is the prime time for nitrogen loss in the Corn Belt. Scharf advises growers to closely watch crop progress.
“If it’s been wet and corn is a light green or yellow, you’ve probably lost nitrogen and a rescue application may be called for,” he says. “That’s best done before corn is shoulder high.”
Aerial inspection is the best way to identify low nitrogen conditions in growing corn, he says.
Online, Scharf publishes “Nitrogen Watch” during May and June. The Web site tracks spring rainfall and identifies areas in the Midwest vulnerable to nitrogen loss due to soil type and weather conditions.
Locate the site by doing a Web search for “University of Missouri Nitrogen Watch.”
When it comes to nitrogen, economic and environmental success overlap and there are two forms of nitrogen-stabilizer products that can play a role, Scharf says:
Volatilization inhibitors that impede the action of urease, which converts ammonium to ammonia
Nitrification inhibitors that prevent soil microbes from converting ammonium to nitrate.
Some of the most widely used products farmers employ to protect their nitrogen include the following:
Agrotain: Protecting Urea
While urea is a popular nitrogen source for no-tillers, volatilization loss can begin as soon as urea hits the soil surface and begins attracting moisture.
Agrotain’s active ingredient — N (n-butyl)-thiophosphoric triamide (nBTPT) — inhibits the urease enzyme that causes urea breakdown, stabilizing nitrogen for a period before rainfall.
“Basically, it buys time for the farmer,” says Greg Schwab, director of agronomy for Koch Agronomic Services. “The research data says that Agrotain buys at least 10 days before a rain, but even at 20 days, nitrogen loss is reduced. The breakeven point is about 2½ days.”
Agrotain fits well into a no-till system, Schwab says, because surface residue can increase the potential for nitrogen loss. In a corn-soybean no-till system, the amount of soybean residue on the surface may not appear to be enough to cause a problem, but recent research indicates that soybean residue has a higher concentration of the urease enzyme that causes urea loss.
Urease activity is higher on plant and organic surfaces than soil. If a UAN solution is applied with flat-fan nozzles, more nitrogen can get hung up on residue, setting non-stabilized nitrogen up for volatilization.
Containing both a urease inhibitor and a nitrification inhibitor, Agrotain Plus is designed to protect liquid nitrogen from denitrification as well as volatilization.
The addition of a nitrification inhibitor may fit no-till systems well, Schwab says, because the loss process is often more pronounced in wetter soils. Additionally, the product won’t harm biological life in the no-till environment.
In weather conditions ideal for nitrogen loss, Schwab cites corn production increases of 15 to 25 bushels per acre.
Agrotain Plus is only for UAN solutions, but the same technology is available in ready-to-use granular form as SuperU. Agrotain Ultra is a more concentrated form of Agrotain with the rate reduced from 4 to 3 quarts per ton for urea and from 3 to 1½ quarts per ton for UAN.
Tallula, Ill., strip-tiller Mike Reichart uses Agrotain with 28% UAN solution. Custom-applied, the Agrotain and fertilizer are mixed with herbicide and broadcast after planting.
“I look at it as good insurance,” Reichart says. “I think it’s a no-brainer any time you’re putting on 28% in the spring. You might get a nice rain shortly after you put your nitrogen down, but you might not. It buys me some peace of mind.”
Reichart, who grows 600 acres of corn and soybeans and has been no-tilling since 1988, has also used Agrotain with sidedress applications. Although he hasn’t done his own side-by-side comparisons, he’s seen plenty of data that convinces him that he’s getting a return on his investment.
“We’ve had conditions that were ideal for nitrogen loss and I felt like we didn’t suffer from it,” Reichart says. “Excessive nitrogen loss is something we can’t afford.”