November 7, 2023
At a Glance
- Drought conditions persist over the Midwest into fall.
- Anhydrous ammonia needs water to stay in the soil.
- Sealing is key to safeguard nitrogen fertilizer in the ground.
In fall 2012, Scott Wilburn was in Audrain County, Mo., with a spade — chipping away at the ground and searching for any hint of moisture.
“I went relatively deep into the soil,” the MFA agronomist recalls. “It was bone dry.”
However, by November of that year, when many Missouri farmers started fall applications, the area had received some moisture, and concern over applying anhydrous ammonia disappeared. Wilburn says 2023 is shaping up to be a similar situation in the central region of the state.
As harvest wraps up, farmers are heading back out this fall to apply anhydrous ammonia, but some are questioning if there is enough moisture in the ground to hold it.
Much of the Corn Belt experienced dry conditions in October. In Missouri, about 43% of the state was in either severe or extreme drought, according to the National Drought Monitor.
Add to that the National Integrated Drought Information System maps, which show depleted soil moisture across the same region. The combination has farmers and custom applicators walking crop fields to determine if conditions are suited for anhydrous ammonia applications.
“I think we are still in good shape for fall applications of anhydrous ammonia this year,” Wilburn says. “Generally, soil moisture conditions will improve in the offseason,” he adds. “We are always mindful of field conditions so when they are less than optimal, we’ll leave that field and move on to an area where conditions are more favorable.”
Search for another ‘H’
Rain during the last week of October improved soil moisture conditions across the state as some areas receiving as much as 4 inches. While Wilburn admits the ground needs more, he contends that amount is enough for ammonia (NH3) to react on its way to becoming ammonium (NH4).
NH3, or anhydrous ammonia, is a gas and unstable.
“It's basically kept under pressure in a tank, and as soon as we release it into the soil, it is violently trying to become NH4,” Wilburn explains. “It becomes NH4 by picking up an extra H, and that mainly comes from H2O.”
In most cases, if there's any water at all in the soil, ammonia will find it. In dry conditions, with no availability of water in the soil for it to become NH4, it remains a gas and can leak back out of the ground.
Need to seal NH3 in soil
Timothy Laatsch, Koch Agronomic Services director of agronomy for North America, says the bigger issue of dry soil is not that there isn’t enough water to interact and react with the anhydrous. It is the structural and physical characteristics that it imparts to the soil.
“When farmers have had a dry growing season and come in with a fall tillage pass like a fertilizer applicator, they can get blocky chunks where the soil fractures into large size clods,” he explains. “There are big macro pore channels that go deeper into the soil and large bulky pockets of air within the soil.”
Those pockets allow ammonia gas to escape before it can react with the soil water. Laatsch notes that farmers should use the right equipment to seal the injection slot, closing it up, to reduce physical off-gassing of unreacted ammonia.
Timely fall application tips
Laatsch offers these three additional best practices for applying anhydrous ammonia into dry soils:
1. Check soil temperature. Wait for the soil to cool down — the standard is 50 degrees F — before you start anhydrous ammonia application. He notes that much of the Corn Belt reached this requirement by Nov. 1.
2. Use a stabilizer. “Any time nitrogen is going to be in the soil environment for a long period of time, it will become more subjected to loss,” Laatsch warns. Using a nitrification inhibitor will slow down the biological conversion of ammonium nitrate, hold nitrogen back as ammonium and make it less subject to loss when it reaches the nitrate form. “Nitrification inhibitors, like Centuro, ensure that nitrogen is available for the subsequent crop,” he adds.
3. Consider split application. Laatsch encourages farmers to divide their operation risk by applying some of their total nitrogen budget either at planting or in-season. “We want to make sure nitrogen is available when the crop really needs it to produce yield,” he says.
Spring can’t handle NH3 pressure
This year, should a farmer wait until spring to apply anhydrous ammonia to a field that is normally suited for fall application? Only if it is extremely dry.
The fertilizer industry, as a whole, struggles if every farmer tries to put on his or her entire needs in spring, Wilburn explains. Today, much of the transportation of NH3 is by truck. and there is only so much that can be hauled to retailers or farmers on any given day.
“When a farmer is waiting in line for tanks while the neighbors are planting,” he adds, “that’s a pretty stressful situation.”
And that is one reason Wilburn encourages farmers to stick with the plan of fall-applied anhydrous, where it makes sense, in the crop management game plan. “It just takes a little pressure off the system and the farmer,” he says.
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