The manifold for a nine-knife applicator has nine outlets, evenly spaced around the ring. People buy one manifold and expect it to put out a real small amount of NH3, then turn around and put out a lot. That doesn't work. But we can tailor the vertical dam manifold with different rings. You can use one ring for fall nitrogen at high rates and a different ring for side-dressing.
Anhydrous ammonia comes out of nurse tanks as a combination of vapor and liquid.
Unfortunately, the vapor doesn't carry much nitrogen. Worse yet, in old-style manifolds it seems to get in the way during the distribution process. Tom Colvin, an ag engineer at the USDA-ARS National Soil Tilth Laboratory in Ames, Iowa, and Richard Hartwig, an agricultural science research technician with the Tilth Laboratory, have been studying nitrogen application or misapplication for several years. The key attribute of the vertical dam manifold is that it separates the vapor portion of NH3 from the liquid, much like a cream separator separates cream from milk and a cyclone separates air from grain. The vertical dam manifold also uses three sets of orifices to raise pressure in the manifold.