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Think twice before fall anhydrous ammonia injection

Think twice before fall anhydrous ammonia injection
Where you live may determine if fall applications of nitrogen make sense.

A farmer told Danny Greene he was thinking about injecting anhydrous ammonia on land that flooded out and was abandoned. Greene, owner of Greene Crop Consulting, Inc., Franklin, and an Indiana Certified Crops Adviser, threw up plenty of red flags.

Related: Do You Plan To Apply Nitrogen This Fall?

"First, if you farm south of I-70, I wouldn't recommend fall-applied anhydrous ammonia. The risk of loss is too great," he said, because soils stay too warm.

"Even if you're in the northern half of the state, recognize N losses still occur. If you're going to do it, use an inhibitor."

Risk this? This field got too tall for a spring sidedress application. However, that doesn't mean fall N application is the answer. Consider all of your options.

Greene also advised not starting until the 4-inch ground temperature drops below 50 degrees F and the forecast suggest it will remain cool the rest of the winter. Temperatures at 4 inches deep in the soil and air temperature are two different things.

Enough moisture?
If you're still in a dry pocket, you may want to think twice. There needs to be enough moisture to capture the ammonia and seal the slot, Greene says. He would also shy away from soils that are "lighter" and typically lower in organic matter, with a lower cation exchange capacity.

His best advice? "Pick only soils that can hold N, use an inhibitor and limit application to one-half or two-thirds of the planned rate. Apply the rest sidedress."

With better tools coming available, you could likely test soils for nitrate before applying next summer.

Bryan Overstreet, Purdue University Extension educator in Jasper County and also a CCA, wants to know more information. Does the field flood regularly? If it is a field that floods, he would steer clear. If it didn't flood before this year. You could put N on, he says.


The secret is to wait until temperatures are cooler so ammonium won't be converted to nitrite and nitrate as quickly, he says. Those are the forms that can be lost more easily. The warmer the temperature, the more the bacteria work and cause this conversion to occur. It's the same reason to use an inhibitor. The inhibitor slows down the conversion process, although it doesn't last forever.

Related: What Are Your Nitrogen Plans For Fall And Spring?

If you're going to put money in the ground in the fall in the form of N, Overstreet says it just makes good sense to use an inhibitor as insurance that there are better odds it will still be there.

Retreat to normal practices
Traci Bultemeier, accounts manager for DuPont Pioneer, Ft. Wayne, and a CCA, takes a unique approach.

"If your typical approach is to fall apply anhydrous ammonia, then it's a good idea and should be applied when ground temperatures are under 50 degrees," she says.

"If fall anhydrous is not the normal N management practice for your farm, don't start. There are inherent risks with fall applied N, just as there are with pre-plant, at-plant and sidedress applications."

Consider the risks of each option, she suggests. If you decide to fall apply, make sure you are applying deep enough to reach soil moisture. It plays a big role in capturing N, especially in fall applications.

TAGS: Extension
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