“Banding with incorporation is obviously the best alternative, but even with 28% or 32% UAN, not all of the N is in a form that is subject to loss,” Kaiser says. “Only half the nitrogen is in the urea form, which is most susceptible to volatilization.”

Since UAN solutions contain about 50% of their N as urea, expect some losses from surface UAN application without incorporation. Agrotain is the only product that’s consistently proven to reduce nitrogen volatilization loss in university tests. There’s not a product that has proven effective to reduce N volatilization from liquid solutions, says the University of Minnesota Extension.

Surface-applied urea fertilizers are at risk for nitrogen volatilization; even more so at higher soil-pH levels. Rainfall of 0.25 in. or more is generally adequate to sufficiently incorporate urea into the soil.

Injecting UAN at least 4 inches deep insures that corn roots will reach the nitrogen and is preferred to broadcast and surface-dribbling UAN solutions, according to the University of Illinois Extension.

Anhydrous ammonia is another preferred nirogen form for sidedressing, says the University of Illinois Extension.  The ideal application depth for it hinges on soil type, because its ability to move from application site depends on soil structure. The more clay or organic matter, the more tightly the positive NH4+ ion binds to the negative clay soil ions. Therefore, knife at these depths:

6-8 inches for silt-loams

8-10 inches deep for sandy soils