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



to be explained. If, therefore, the readiness of the transformation 

 of its nitrogen into ammonia by pure cultures of ammonifiers is 

 to be taken as a criterion, sheep and goat manure must be 

 adjudged to contain a relatively unavailable form of nitrogen. 

 The most amazing evidence portrayed in Table VII is the 

 very high availability of the nitrogen of bat guano, which is a 

 phosphatic guano. While without question the fact of the large 

 amount of the guano used, as well as its low content of nitrogen, 

 preclude an accurate and wholly justifiable comparison of it with 

 the other nitrogenous materials, one cannot help being struck 

 by the large transformation of its nitrogen into ammonia which 

 nearly all of the organisms tested can accomplish. In many 

 ways, the transformation of the nitrogen of bat guano into 

 ammonia resembles that of the transformation of peptone 

 nitrogen. The differences between the ammonifying powers of 

 the different organisms are, however, unquestionably more 

 marked in the case of the bat guano. In its efficiency as an 

 ammonifier of bat guano nitrogen, B. mycoides appears for the 

 firet time in all the series studied to be distinctly superior to all 

 the other organisms tested. B. vulgaris easily takes second place. 

 Not far behind, however, and about equal in efficiency, are B. 

 megatherium, B. vulgatus, B. tumescens, and Mic. tetragemis. 

 In the third class are B. ramosus, B. suhtilis, and Ps. putida, B. 

 proteus vulgaris, and B. mesentericus. In the fourth class are 

 Streptothrix, sp., Sarcina lutea, B. icteroides, and Ps. fluorescens. 



A Comparison op the ReLx\.tive Availabilities op the Organic 



Materials above Employed based on the Percentage 



OF Nitrogen Contained in Them that was 



Transformed to Ammonia 



Thus far we have been considering only the relative degrees of 

 efficiency as ammonifiers of the different organisms among them- 

 selves as respecting a given organic form of nitrogen in a given 

 soil. There is possible, however, a further very interesting study 

 of the data above given as a basis. We refer to the percentage 

 of nitrogen which is transformed in the different materials into 

 ammonia so as to give them a relative rating as to availability as 



