^16 fiXPERlMElTT STATION RECORD. [Vol. 4S 



or no nitrification. Such amounts of dried blood as are used in practice pro- 

 duced active uitrilication. An addition of bone meal equal in nitrogen content 

 to an addition of 1 per cent of dried blood was apparently toxic to nitritica- 

 tion. Experience with a great diversity of soils from different localities showed 

 that the incapacity t« nitrify 1 per cent dried blood is not limited to any par- 

 ticular type of soil. 



The conclusion is therefore drawn that California soils in general are capable 

 of actively nitrifying the amounts of dried blood used in agricultural practice. 

 Studies of the influence of alkali salts upon nitritication showed t^iat the 

 presence of 0.05 per cent sodium carbonate interfered with the nitrification of 

 1 per cent of dried blood, while 0.4 per cent sodium carbonate had no effect on 

 0.1 per cent of dried blood. The presence of 0.1 per cent of sodium carbonate 

 was toxic to the nitrification of 0.15 per cent of ammonium sulphate, but was 

 stimulating to the nitrification of 0.0625 per cent of ammonium sulphate. 



In general, additions of an excess of nitrogenous substances resulted in an 

 accumulation of nitrates. 



A list of 35 references to literature bearing on the subject is included. 



Some soil studies, W. P. Headden (Proc. Soc. Prom. A(jr. Set., 39 {1919), pp. 

 22-38).- — Data on excessive nitrate accumulation obtained from studies of beeE 

 and wheat crops and the soils growing them at the Colorado Experiment Station 

 are reviewed. It is concluded that " no refutation has as yet been made of the 

 theory that the nitrogen of these nitrates is derived from the atmosphere through 

 bacterial agencies." 



The isolation and study of nitrifying bacteria, W. M. Gicbs {Soil Sci., 8 

 {1919), No. 6, pp. i27--'f81, fifls. 6). — Investigations conducted at the Idaho Ex- 

 periment Station are reported, which were planned to study primarily the rela- 

 tions of the nitrifying bacteria in soils to their environment. The report deals 

 with the work of isolation and the morphology of the organisms and presents the 

 methods emploj^ed. 



Pure cultures of Nitrosomonas and Nitrobacter were isolated from soil and 

 cultivated on artificial media. Both developed readily on plates of washed agar 

 or silicic acid gel. The latter medium was more satisfactory in the work of 

 isolation, disregarding its difficulty of preparation, but after pure cultures were 

 secured washed agar was used with success. The colonies which developed on 

 the plates were extremely small, and required the iise of the microscope in the 

 study of their characteristics. Isolated colonies were removed from the medium 

 by means of a modification of the Barber apparatus. 



It was found that pure cultures of either Nitrosomonas or Nitrobacter will 

 produce no visible growth when inoculated into bouillon. In using bouillon as a 

 purity test 0.5 cc. of the culture must be used as inoculum to give reliable results. 

 Pure cultures of these organisms can be maintained in liquid medium for an 

 indefinite period of time. Ttte enrichment process with both Nitrosomonas and 

 Nitrobacter can be continued for an indefinite period of time without the slightest 

 loss of activity of the organisms. The F52 enrichment showed as great activity 

 as any of the preceding generations. Neither the enrichment process nor the 

 securing of superenrichment cultures will yield a pure culture of Nitrosomonas or 

 Nitrobacter without the use of suitable solid media. By careful manipulation the 

 number of nitrifying organisms in the enrichment cultures can be increased 

 from relatively few to a number greater than 10,000,000 per cubic centimeter of 

 the culture solution. Soil extract used to prepare the nutrient solutions for the 

 cultivation of both Nitrosomonas and Nitrobacter did not prove toxic in either 

 case. Sodium chlorid in a concentration of 1 per cent was very toxic toward 

 Nitrosomonas. 



A list of 67 references to works byothers bearing on the subject is included. 



