Diffusion is more upward than down with the width of the band increasing as the rate increases. Most bands are 2 to 5 inches in diameter depending upon application rate, soil type, and soil moisture. Anhydrous ammonia reacts quickly with soil moisture to form ammonium cations which are held tightly to soil particles and are subject to little loss until converted to the nitrate form of N. Loss of ammonia as a gas can be significant if proper application techniques are not followed or soil conditions are too dry or wet. The latter condition is a common problem on Fond du Lac County soils where pre-plant applications are made in the early spring. Too much soil moisture prevents the soil from sealing behind the applicator knives.
Research shows that an application depth of at least six inches is needed to inhibit loss.
Some type of knife slot-covering apparatus is also recommended. The high pH and nitrite concentration in the anhydrous ammonia band makes it toxic to soil microorganisms. Research on this topic shows microorganism numbers declining rapidly in the band shortly after application. However, populations rapidly increase within one week and are essentially the same as non-treated areas within five weeks after application. The negative effects on soil fungi is somewhat longer lasting than bacteria but still localized to the band and not considered to be permanent.