156 University of Calif orniu Publications in Agricultural Sciences [Vol. 1 



with much greater rapidity than has heretofore been believed. 

 The next striking fact brought out in these results is the clearly 

 indicated superiority of the clay-adobe soil to the clay-loam soil 

 as a medium for the ammonification of the nitrogen in cottonseed 

 meal. The third point worthy of mention in Series III is the fact 

 that we find again in it, as in the preceding series, only a few 

 of the fifteen organisms tested which show marked ammonifying 

 efficiency. 



The culture of Ps. fluorescens died in the midst of these 

 investigations and was not replaced. 



Series IV. Fish Guano 



Fish guano, in accordance with the teachings of Voorhees and 

 other agricultural chemists, has always been e.steemed a good 

 source of available nitrogen; in the words of Voorhees," "rank- 

 ing in availability well up to blood and tankage." It seemed to 

 us therefore of importance to compare in these pure culture 

 studies fish guano with the other organic materials discussed 

 above. Accordingly a series was started similar to those above 

 described, except that li/o grams of finely sifted fish guano was 

 the ammonifiable material used per 50 grams of soil. The fish 

 guano used contained 8.63 per cent nitrogen. The results 

 obtained are shown in Table VI. 



The data in Table VI not only seem to confirm the opinion of 

 Voorhees as above stated, if ammonia production by pure cul- 

 tures may be taken as a criterion for determining the availability 

 of fish guano, but they indicate in most striking fashion what 

 was not shown in any of the foregoing series for the fertilizers, 

 and particularly in the sandy soil, namely, the obliteration of 

 the marked physiological difl:'erences obtaining in other series 

 between the different organisms. Of the four nitrogenous fer- 

 tilizers thus far discussed, fish guano seems to contain the form 

 of nitrogen most generally ammonified by a large group of 

 bacteria. 



