142 University of California Publications in Agricultural Sciences [Vol. 1 



culture were selected for the experiments: B. mesentericus vul- 

 gatus, Ps. putida, B. vulgatus, B. megatherium, B. mycoides, B. 

 s^ibtiUs, B. tumescens, Sarchm lutea, B. proteus vulgaris, B. 

 icteroides, B. ramosiis, Streptothrix, sp., Fs. fluorescens, B. vul- 

 garis (Novy strain), Mic. tetragenus. The organic materials 

 experimented with were dried blood (13.16% N), tankage 

 (9.62% N), cottonseed meal (5.5% N), sheep and goat manure 

 (2.13% N), peptone (14.14% N), fish guano (8.63% N), and bat 

 guano (3.96% N). 



Method of Experiments 



Fifty-gram portions of soil were placed in tumblers and 

 thoroughly mixed with the organic material to be tested. The 

 tumblers were covered with Petri dish covers and sterilized in 

 the antoclave at a pressure of thirty pounds for three hours. 

 After cooling, the soils were each inoculated with a 1 cc. suspen- 

 sion of the organisms to be tested, made up by shaking with some 

 sterile water a young slope culture grown on bouillon agar. 

 The soil was then stirred with a sterile spatula after enough 

 sterile water had been added to make a moisture content in the 

 soil about equal to the optimum. The soil cultures thus pre- 

 pared were incubated at 28° to 30° C for twelve days. After 

 the incubation period the soils were transferred to copper dis- 

 tilling flasks, 400 cc. of distilled water and an excess of j\Ig 

 added, and distilled into standard H/10 HCl. The ammonia 

 was then determined in the usual way. 



No attempt was made to run all the series with the different 

 forms or organic matter at the same time, because only the 

 relative powers of the different organisms to produce ammonia 

 were sought. For the same reason amounts of organic matter 

 were chosen in the different series which would least affect the 

 physical conditions obtaining in the cultures rather than amounts 

 employed which would make the total amount of nitrogen added 

 the same in all series. 



For the reasons above given, therefore, the effects of the 

 various organisms on any given form of organic material will 

 be treated below as a separate series in the case of each soil and 



