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



The Sandy Soil 



The good ammonifying power manifested by most of the 

 organisms tested in this soil with fish giiano finds its maximum 

 in the case of B. vulgaris, which, it will be remembered, has 

 already given evidence of notable ammonifying efficiency with 

 other nitrogenous fertilizers. B. tumescens, likewise an organism 

 with a record as an ammonifier well established, is a very close 

 second to B. vulgaris in its efficiency at the ammonification of the 

 nitrogen in fish guano. Four other organisms distinctly in the 

 second class, and about alike in ammonifying efficiency in this 

 part of Series IV, are, in the order of their efficiency, Ps. putida, 

 B. vidgatus, B. ramosus, and Sarcina liitea. Peculiarly enough, 

 B. icteroides shows an ammonifying efficiency here which places 

 it in the second class, a position which it has thus far never even 

 remotely approached in the series of experiments above discussed, 

 nor, for that matter, in other series which are described below. 

 All other organisms in this part of Series IV are distinctly in 

 the third class, but nevertheles manifest notable ammonifying 

 efficiency. 



In no other series of results have we obtained such sharp 

 lines of demarcation between the classes of organisms here tested, 

 and arbitrarily grouped, in accordance with their respective 

 powers of transforming organic nitrogen into ammonia. 



The Clay-Loam Soil 



The change in the physical condition of the soil from the sand 

 to the clay loam shows a marked effect on the ammonifying 

 power of the same organisms. Nevertheless we find, on the whole, 

 the best set of results thus far obtained with the clay loam when 

 the series with fish guano is studied. In a class by itself under 

 these conditions is B. megatherium, which is markedly superior 

 to all other organisms in this part of Series IV, except B. mcsen- 

 fericus, which is a close second. The organism, however, which 

 takes third place, B. vulgaris, falls about 20 per cent short of 

 attaining the efficiency of B. megatherium under these conditions. 

 Distinctly lower in efficiency in this part of Series IV are, in 

 the order of their importance, but only slightly different from 



