554 PRINCIPLES OF SOIL MICROBIOLOGY 



exaggerated. 46 Losses of nitrogen were found possible only when con- 

 siderable amounts of organic matter are added together with the nitrate, 

 but this is not commonly done. Pfeiffer and Lemmermann" demon- 

 strated that very little actual denitrification takes place in the soil as a 

 result of addition of manure. The lack of nitrogen often observed is 

 due to other causes rather than to the actual loss of nitrogen. Nitrate 

 reduction sets in when the soil is saturated with water. Only in the 

 presence of a great abundance of organic manures is there any fear of 

 loss of nitrate-nitrogen from the soil in a gaseous form. 48 



Great losses of nitrogen may take place in a humid, hot climate; 49 

 the rate of loss was found to be much increased by liming; bare fallows 

 in rainy season were found to be especially wasteful because of the 

 leaching of nitrates in drainage waters. There is little danger from 

 denitrification in normal soils. 50 The partial reduction of nitrates to 

 nitrites and ammonia, which is more extensive and carried out by larger 

 numbers of microorganisms does not involve any actual losses of nitro- 

 gen. The nitrates may completely disappear from the medium without 

 any actual loss of nitrogen. 51 The products formed from the nitrates 

 (nitrites and ammonia) can be further acted upon by nitrifying bacteria; 

 the part of the nitrate assimilated by microorganisms is merely stored 

 away in the soil in an organic form. 52 



46 Burri, R., Herfeldt, E., and Stutzer, A. Bakteriologisch-chemische Forsch- 

 ungen fiber die Ursachen der Stickstoffverluste in faulenden organischen Stoffe, 

 insbesondere im Stallmist und in der Jauche. Jour. Landw., 42: 329-384. 1894. 



47 Pfeiffer, Th., and Lemmermann, O. tlber Denitrifikationsvorgange. 

 Landw. Vers. Sta., 50: 115-142. 1898; Lemmermann and Wichers, 1914 (p. 

 551). 



48 Stoklasa, J. Treten Stickstoffverluste im Boden ein bei Diingung mit 

 Chilisalpeter? Centrbl. Bakt. II, 17: 27-33. 1906; Fischer, H. Versuche 

 iiber Stickstoffumsetzung in verschiedenen Boden. Landw. Jahrb., 41: 755- 

 822. 1911. 



49 Meggitt, A. A. Studies of an acid soil in Assam. II. Mem. Dept. Agr. 

 India, 7: 31-53. 1923. 



60 Voorhees, E. B. Investigations relative to the use of nitrogenous materials. 

 N. J. Agr. Exp. Sta. Rpts., 12: 97-119. 1899; 13: 88-110. 1900; 14: 144-154, 

 183-211. 1901; 15: 133. 1902; 16: 148. 1903; 17: 191. 1904. 



61 Lemmermann, O. Kritische Studien liber Denitrifikationsvorgange. (Hab- 

 ilitationsschrift), Jena. 1900. 



62 Gerlach and Vogel. Ueber eiweissbildende Bakterien. Centrbl. Bakt. 

 II, 7: 609-623. 1901; Ueber Nitrifikation und Denitrifikation in der Ackererde. 

 Centrbl. Bakt. II, 13: 706-715. 1904; Lohnis, F. Beitriige zur Kenntnis der 

 Stickstoffbakterien. Ibid., 14: 5S2-604, 713-723. 1905. 



