Don't Burn the Corn

ROCKVILLE, Md. (DTN) -- With March limping out like a drenched little lamb, the window for corn planting is opening up in some parts of the country.

In the inevitable rush to get fields prepped, sprayed and fertilized, some growers might be tempted to push corn planting as close to anhydrous ammonia applications as possible, said Brent Tharp, agronomy and product training manager for Wyffels Hybrids.

If you're looking for a "safe" number of days to avoid giving your corn seeds a bad burn, you won't find it, Tharp said. "I've seen injury from corn planted seven days after anhydrous ammonia went on, even to 14 days," he said. "You need to focus more on the spacing between the injection point and where you plant the seed."

Keeping those two far enough apart comes down to a few key factors -- the right soil moisture, the location of your anhydrous injection tracks, proper injection depth and knowing when to make the call to switch to other forms of nitrogen.

At issue is the fact that ammonia is a powerful desiccant, Tharp explained. When it makes contact with corn seed or young corn roots, it sucks water out of the tissue rapidly, leaving a burn-like injury. Corn seeds can actually be destroyed by too much contact with ammonia, but more often, you see plants that are stunted, yellow and sickly, Tharp said.

So let's dig into how to avoid this:

1. SOILS NOT TOO WET, NOT TOO DRY

Just like Goldilocks, anhydrous ammonia, or NH3, is a picky little compound.

If it's injected into soils that are too dry, the ammonia will diffuse up through the soil too quickly and could make contact with a corn seed, Tharp said. But if soils are too soggy, mechanical issues can cause problems, too.

"If the soil is too wet while you're pulling that knife through 6 to 8 inches of soil, it can cause smearing and that knife track doesn't close or seal properly," Tharp explained. "That leaves the spot open and ammonia moves up and gets closer to the seed."

2. SWING LOW, SWEET NH3 KNIFE

Injection depth is key to avoiding ammonia burn on your corn seed, Tharp said. Aim for a minimum of 6 inches deep and up to 8 inches deep, if necessary.

Wet soils can distort your injection depth, he added. "If you're applying anhydrous in wet soils, you're pulling harder through the soil, and if the tool bar is not adjusted properly, it will float around more," Tharp warned. "And instead of injecting at 6 inches, you're at 4 inches, and your corn seed will eventually only be sitting just 2 inches higher than that."

3. GIVE THE SEED SOME SPACE

Many farmers and applicators still opt to apply anhydrous at an angle, so that the corn rows don't overlap with injections sites as often and the risk of ammonia burn drops.

That's still a good option, but with GPS on most equipment, many growers can now precisely offset their fertilizer tracks 4 to 6 inches away from their corn rows, Tharp pointed out. That's close enough for corn roots to access nitrates eventually, but far away enough to avoid any ammonia burn risk.

"If you use GPS to offset tracks, and all goes well, you can plant the same day," Tharp said.

4. CHECK THOSE TRACKS

Be sure to stop at least once to check that your tracks are sealing properly, Tharp said.

A quick visual inspection can ensure that the ground is filling back in over the injection site and sealing shut, but use all your senses. When ammonia meets with the air, it will form a brief cloud of vapor that is easily visible -- "smoke" as it is commonly called. It also emits a distinct odor.

"You may see and smell it on field ends when you're lifting up your tool bar, but generally, out in the field, you don't want to see or smell ammonia to any extent," Tharp said.

5. BE OPEN TO SWITCHING THE GAME PLAN

Between the wet fall and recent flooding, this spring is sure to offer tight planting windows to large swaths of the country this year.

"If it keeps raining this spring and we get close to the ideal planting window and suddenly the soil is fit for planting, you really, really want to be planting then -- and not putting on nitrogen," Tharp said. "And that may mean you have to adjust your original plan."

One option is to drop your anhydrous ammonia rate, which can help you minimize the time between application and planting, by reducing the amount of ammonia in the soil, Tharp said. "If you cut the rate in half, you will have to make it up at some point in time in a sidedress application," he cautioned.

Another option is to switch to an alternative nitrogen source, such as urea or UAN, he added.

For more details on these options, see Tharp's article on this topic here: http://www.wyffels.com/….

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com

Follow her on Twitter @Emily_Unglesbee

(PS/AG)

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