l'he nitrogen recognized as one of the most important elements for plants, if not the most necessary, is being studied and discussed by many investigators ana among them the opinion is quite general that there is a considerable difference between the various forms of nitrogen. this is particularly true of soil nitrogen. Wile in some soils the nitrogen is readily ammonified and furter ifled and further oxidized to nitrites and nitrates, it does not undergo those processes in other soils. In other words, soil nitrogen is available or can easily be made available for plants in some cases, in others not. The problem of the availability of soil nitrogen is, with suitable physical and bacteriological conditions in the soil, closely associated with the question of the chemical nature of soil organic nitrogen. Evidently, some organic nitrogenous compounds readily ammonify, others do not. For this very reason , researches into the nature and character of organic nitrogenous compounds present in soils are of great moment.
Jodidi, S. L.
"Amino acids and acid amides as sources of ammonia in soils,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 1
, Article 1.
Available at: http://lib.dr.iastate.edu/researchbulletin/vol1/iss9/1