Current trends in the fertilizer industry indicate a shift to greater production of ammonium forms of nitrogen fertilizer in comparison to nitrate forms. Reasons for these trends are many, but both economic and energy conservation are major factors. Generally, ammonium forms are produced with less, total energy and have higher nitrogen contents that permits lower production and transportation costs per unit of N. Agronomically, ammonium forms are less readily leached from soils, but produce acid as they are converted to nitrates by soil microorganisms. Thus, ammonium sources of nitrogen have both advantages and disadvantages as fertilizers for crops.
Sims, J. L.; Atkinson, W. O.; and Wells, Kenneth L., "Effect of Lime and Source of Nitrogen Fertilizer on Yield and Chemical Composition of Burley Tobacco" (1977). Agronomy Notes. 118.