SOILS FEBTILIZEES. 21 



21S4; Chem. A'bs., 7 (191S), No. S, p. 527). — Another account of these investiga- 

 tions is noted above. 



Studies in soil bacteriology. — V, Nitrifying and ammonifying powers of 

 North Carolina soils, F. L. Stevens, W. A. Withers, et ai.. {North Carolina 

 Sta. Rpt. 1912, pp. 67-84, figs. S). — These investigations have already been noted 

 from another source (E. S. R., 27, p. 517). 



Studies in soil bacteriology. — VI, Miscellaneous nitrification experiments, 

 F. L. Stevens, W. A. Withers, et al. (North Carolina Sta. Rpt. 1912, pp. 

 85-104, figs. 3). — This is a report of miscellaneous experiments made during 

 the course of a series of investigations on the nitrifying and ammonifying pow- 

 ers of different types of North Carolina soils (see above). The experiments 

 include determinations of (1) the inhibiting effect of ammonia sulphate in soil 

 and in solution, (2) the migration of nitrifying bacteria in soil. (3) the effect 

 of diying upon nitrifying efficiency and nitrogen inoculating power, (4) the 

 nitrifying power of soils as determined by the Kellerman and Robinson and by 

 the Stevens and Withers methods, (5) the effect on nitrification of various 

 amounts of ammonium sulphate in the soil, (6) the relative nitrifying efficiency 

 of soils in the incubator room, and in the field, and (7) the effect of lime, cow 

 manure, and a vigorous nitrifying soil on nitrification. 



The results in general showed that additions of 0.5 per cent or more of am- 

 monium sulphate retarded nitrification in the soil. "At the end of 12 weeks 

 decided retardation is evident when there was ' additional ' ammonia to the 

 amount of 0.5 per cent or more and complete inhibition resulted from the pres- 

 ence of 5 per cent." In solutions at the end of 12 weeks retardation was evi- 

 dent with additions of 1 per cent or more of ammonium sulphate. 



There was little or possibly no migration of the nitrifying organisms in the 

 soil. Nitrifying efficiency was much lower in solution than in soil culture. 



There was general agreement in the results obtained by the different methods 

 of determining the nitrifying power of soils. The best results as regards nitri- 

 fication were obtained when ammoniacal nitrogen (in form of ammonium sul- 

 phate) was added at the rate of 120 mg. of nitrogen to 400 gm. of soil. A much 

 higher nitrifying efficiency was obtained in flasks kept in the incubation room 

 than in those buried in the soil. A somewhat higher efficiency was obtained in 

 buried flasks than in buried tubes. These results indicate " that soil tests in 

 order to give us knowledge of the phenomena as they occur in the field must 

 be made under conditions of the field." The addition of lime and cow manure 

 increased nitrification, especially during the first month. The results when a 

 vigorous nitrifying soil was added were inconclusive. 



The intensity of nitrification in arid soils, R. Stewart (Cenfbl. Bakt. 

 [etc.], 2. Abt., 36 {1913), No. 19-25, pp. 477-^90).— This article cites data 

 already reported in part in bulletins of the Utah Experiment Station (E. S. R., 

 24, p. 422; 26, p. 616) in support of the conclusion that " there is no reason to 

 assume that the accumulation of nitrates in arid alkali soil indicates a rapid 

 bacterial action at the present time. These accumulations indicate a concen- 

 tration of the nitrates already in the soil formed by slow bacterial action in the 

 remote past. The application of the irrigation water has simply furnished a 

 medium by which the nitrates may move, or be moved, from one place to 

 another." 



From a study of soils of Colorado and Utah, containing large amounts of 

 nitrates, as well as of the materials from which the soils have been derived, 

 the author concludes " that the nitrate accumulations found in these soils are 

 undoubtedly of marine origin. . . . These nitrate accumulations always occur 

 in connection with other water-soluble salts, such as sodium chlorid and gyp- 



