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Corn+Soybean Digest

Smokeless Sidedressing

If you come up behind an anhydrous rig on a road west of Washington, IA, and there's a chain dragging behind every injector, you'll know it's one of the Reed brothers.

The Reeds, long-time no-tillers, believe that supplemental nitrogen needs to be applied as close to the time their corn needs it as possible. That means they sidedress anhydrous on every corn acre.

"We've used anhydrous as long as we've grown corn," says Nick Reed, who farms with his brothers Paul, Kevin and Ken. "It's the most economical form of nitrogen available and just as efficient, too."

Trouble was, though, they used to leave a vapor trail when they sidedressed no-till corn.

The Reeds looked at a lot of different ways of sealing up the anhydrous slits and minimizing losses. Most involved more aggressive loosening of the soil, so they had no appeal to the brothers. They considered adding knives, but in addition to more soil disturbance, that meant more horsepower, more fuel use and the potential for more compaction from pulling the toolbar.

After a few years of experimentation, they came up with a system that's been working since 1993.

The brothers inject nitrogen in every other row middle. Originally, in order to apply enough anhydrous for two rows, they were setting the pressure at 70 psi.

"Summertime pressures are always higher and harder to seal than if you're applying in the fall, simply because of the higher summer air temperatures," Reed explains. "So we were seeing some very high pressures while sidedressing the proper amount of nitrogen for two rows through one injector.

"If you pumped your air compressor up to 70 psi and blew air into the soil, the dust would really fly. That's what happens with anhydrous at high pressure, too. It blows the soil away from the injector and that makes it harder to seal it in the soil."

So first they simply added a second delivery tube to each injector. That allowed them to put on as much anhydrous at half the pressure.

They were using covering disks behind each injector to throw loose soil back over the slit, but some nitrogen still escaped before the disks could do their job. If the disks were set close enough to cover the slit before some anhydrous escaped, they weren't able to recover the soil loosened by the injector. They decided that filling the slot just above the anhydrous knife outlet was better than working the soil on the surface. Reed went to work with his welder and fastened a length of twisted chain from tractor tire chains behind the knife. It took several prototypes to land on the right one, but the idea worked. He says the chain is attached on only one end so it drags out its full length straight behind the knife.

"The links in the chain fill with soil, and they're wider than the anhydrous injector," says Reed. "That seals the area right above the outlet, so the anhydrous spreads into the soil rather than vaporizing and shooting out the open slit."

No doubt, the small amount of soil the chain loosens also helps close the slit below the surface. And that, in combination with the closing disks above, keeps the nitrogen in the soil. Because it works so well, they're able to run the injectors shallower, which means even less soil disturbance and lower horsepower requirements.

Reed says the most difficult parts were figuring out how to fasten the chain to the knife and how high to mount it. To attach the chain, he uses a long, straight chain link from the side chain on salvaged road grader tire chains. He cut the end off the link, threaded it through a length of 1" twisted-link chain, and welded the straight link on the injector about 2" up from the tube.

The twisted-link drag chain is a crossbar from the same salvaged tire chains. He figures these should be at least 1' long - long enough to extend back behind the covering disks, so they've thrown soil back over a specific spot before the chain has completely passed under it.

Nitrogen losses through volatilization should be a concern whenever anhydrous ammonia is applied, says Alfred Blackmer, extension soils specialist at Iowa State University.

"If soils are friable, losses due to volatilization aren't usually significant," he says. Blackmer adds, though, that wetter, firmer soils, as is often the case in no-till, may not close back up behind the knife, leaving a poor seal and meaning higher losses.

"Taking steps to ensure a good seal is important, particularly when nitrogen application rates are high on a per-knife basis," he says. ?

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