Despite their popularity, the applicators also have their detractors. Companies that have stayed with the same tried-and-true knife-based toolbar say that unless field conditions are perfect, coulter-only applicators don’t go deep enough for the anhydrous to be sealed in the soil. 

“You can drive around the fields all day and cut nice grooves,” says Rob Zemenchik, Case IH tillage marketing manager for Case IH. “But if the gas doesn’t seal, then we’ve lost money and yield not to mention environmental and safety issues, and that is the rub.”  

He cites a 2005 study conducted by Iowa State University to support his claim. The study measured nitrogen (N) loss from a “prototype” single-disc injector and a conventional knife injector. Researchers reported that NH3 losses during application with the single-disc injector were 3 to 7% in finer-textured soils (clay loam, silty clay loam, and loam) and 21 to 52% in a coarser-textured fine sandy loam soil, indicating the need for better sealing mechanisms. In comparison, applying with a knife injector at deeper depth resulted in losses of 1 to 2% across all soil types.

In a more recent study conducted over three crop seasons (2007 to 2009), crop scientists from the University of Illinois, Iowa State University and Kansas State University found that corn yield between the two systems were similar, except at the highest rate of N (200 lbs. N/acre), where HSLD applicators showed a 11-bu./acre disadvantage.

The testing was done in Iowa, Illinois, and Kansas using a prototype John Deere 2510H high-speed low-draft applicator and a John Deere traditional anhydrous ammonia mole-knife injection applicator. Nutrients were applied at different rates in worst-case scenarios: nitrogen applied over the crop row in no-till soybean stubble.

Researchers reported that the drop in yield was the result of seedling injury for the spring preplant application in 2008 and 2009 in Iowa, and canopy damage by ammonia losses during side-dress application in Kansas in 2009. “Across all site-years, we observed that the TRAD [traditional] system allowed higher rates of application with less N loss compared to the HSLD system,” the researchers state.