Production Blog

Don't Rush the Anhydrous Season

Pamela Smith
By  Pamela Smith , Crops Technology Editor
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Nutrient reduction loss starts now by postponing any fall applications of nitrogen until soil temperatures fall. (DTN photo by Jim Patrico)

This fall, I saw the first evidence of fall anhydrous applications long before the soil temperatures dipped into the safety zone -- again.

The reasons for rushing the season are as volatile as the product itself. There are thoughts that the price of anhydrous ammonia, which was running about $1400 per ton recently, might be cheap come spring if natural gas prices move higher. Fears of supply shortages and deals that require fall delivery add to the hurry. Good conditions for application make exercising patience difficult.

Still, waiting to apply nitrogen (N) until soil temperatures are consistently below 50 degrees Fahrenheit is critical to reducing loss. In Illinois, where I live, a decade of Nutrient Reduction and Education Council (NREC) research conducted in actual fields over tile drainage has shown no yield penalty for applying N in the fall. But those studies have also shown fall applied N loses up to 12 pounds more per acre than N applied in the spring.

Daniel Schaefer is involved in much of that research in his role of director of stewardship for the Illinois Fertilizer and Chemical Association. "In tile-drained fields of many parts of Illinois, it's not about the farmer economics on the amount of N lost, but that the fall application accounts for 30% of the tile nitrate load," said Schaefer.

"We are applying more that what's needed, and the loss is not seen in the yield," he added.

Funded by a 75-cent-per-ton assessment on bulk fertilizer sold in Illinois, NREC's goal is to prove and encourage adoption of practices that address these kinds of environmental concerns. The end goal is to avoid mandatory restrictions on farm fertilizer use by encouraging voluntary practices to limit downstream runoff, while still meeting soil fertility needs.

The best management practices developed through this research are part of what is called the Illinois Nutrient Loss Reduction Strategy and the recommendations also come from the University of Illinois.

Leading those recommendations is waiting until soil temperatures dip and hold. DTN Ag Meteorologist John Baranick said air and soil temperatures are on a downward trajectory, but they swing wildly in the fall.

"What could be cold soils today could be pretty warm in the next couple of days. And if you want to limit your losses, a look at the forecast over the next couple of weeks may only provide so much help," Baranick said. "With the upper-level pattern being variable over the next two weeks, the forecast is likely to change going into early November, no matter where you are in the country.

"Going deeper into November, we are expecting a more stable pattern that should provide a more consistent warmer-than normal west and colder-than normal east look to it, but even that could have some variability. These swings could bring temperatures well over that 50-degree mark for the next several weeks," Baranick continued.

"Of course, the farther north you are, the quicker you'll see that change to being consistently below 50, and the farther south you are, the greater the risk you have of them coming back up above 50 depending on a pattern change into December," he said.

These best management practices were provided to DTN by the Illinois Fertilizer and Chemical Association:

-- Use the right nitrogen rate and do not apply the full rate in the fall. Recommendations are to save 30-40% of the rate to be applied pre-plant or side-dress. This helps to manage both environmental and agronomic risk since we do not know what the weather will be during the next six months. The Illinois Nitrogen Rate Calculator (which was developed in collaboration with and available from: Iowa State University, Purdue, Michigan State, University of Minnesota, University of Wisconsin, and The Ohio State University) is updated each year with the results of dozens of nitrogen rate trials.

-- Wait until mid-day soil temperatures in bare soil at the 4-inch depth is 50 F and the weather forecast indicates temperatures will not rebound, but rather will continue to go lower. It is always recommended you take the soil temperature in the field yourself. Soil temperature maps can be a guide, but aren't always specific to the field.

-- Use a U.S. Environmental Protection Agency (EPA) labeled nitrification inhibitor with all fall-applied ammonia. These products are registered as pesticides because they inhibit bacterial activity that can convert ammonium to nitrate. These bacteria are active until the soil freezes. The inhibitor is intended to provide protection against nitrification in the late fall, early winter, and spring. Protecting ammonia with a nitrification inhibitor helps a great deal, but when soils remain warm that protection is much less effective.

-- Consider applying nitrogen in the spring only in fields located in priority watersheds that provide. Nitrate levels continue to rise in late winter and early spring in many of watersheds. Protecting lakes that supply drinking water is a priority.

KJ Johnson, IFCA president, noted that Illinois took additional steps this year by requiring that all growers and grower farm operators who transport or apply anhydrous ammonia, or maintain anhydrous ammonia, be certified, and participate in a refresher course every three years. The training addressed handling safety and best management practices.

"IFCA understands these guidelines can create economic challenges for retailers and farmers," Johnson told DTN. "We also understand that ag retailers are under immense pressure from farmers to apply ammonia this fall with threats of nitrogen prices growing in the spring. But we must keep in mind there are many eyes on our industry, and honor commitments to adhere to voluntary measures to reduce nutrient losses."

For a recent column on how much nitrogen might be left and what that means by Emerson Nafziger, University of Illinois, go to:…

For DTN article on figuring nitrogen rates go to:…

Find the link to the nitrogen calculator for various states here:…

Learn more about nitrogen management and safety at

Find research and more information from the Illinois Nutrient Reduction and Education Council here:…

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