Arthur says these coulter-only anhydrous bars started getting play around 2008, as farmers searched for a faster way to inject the unstable gas of anhydrous ammonia. Because coulters penetrate only the top 3 to 5 in. of soil, they can be pulled as fast as 10 to 12 mph, manufacturers say. Knives, which go deeper, are limited to about 5 to 6 mph.

Makers of these tools cite other advantages, too. They displace less soil than knives, which reduces erosion and helps keep moisture in the ground. When being used for side-dress application, coulter units allow for application at earlier growth stages without the risk of covering the small plants, says Thompson, Yetter’s regional sales manager. And because of their shallow working depth, they have lower draft requirements, which can save on fuel costs.

Like knives, coulter injectors can apply not only anhydrous but liquid and granular formations as well, and, in some cases, manure. And they are designed to work three seasons — fall, before planting, and mid-season once the crop has emerged — so that the same tool can be used year-round.

“In the anhydrous market, disc-style applicators are definitely getting some play,” says Pauley Bradley, nutrient application product manager with John Deere, which makes the 2510H high-speed applicator.