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



regards the work of pure cultures. The columns on availability 

 of the various tables show a comparison in different soils of all 

 the materials as attacked by the same organisms, and give the 

 percentages of nitrogen in those materials which were trans- 

 formed to ammonia. In Table VIII all of the columns indicating 

 percentages of nitrogen of different fertilizers made available 

 are brought together from the other tables and one is enabled to 

 compare with much greater ease the different materials on the 

 basis of availability in the same soil and with the same organism 

 and in different soils, with different organisms. 



The Sandy Soil 



So far as this soil is concerned, the data in Table VIII 

 indicate clearly the superiority, from the point of view of the 

 availability of its nitrogen, of cottonseed meal to the other organic 

 nitrogenous fertilizers with which it is compared. Not only are 

 the absolute amounts of ammonia produced in most cases larger 

 from cottonseed meal nitrogen than from other forms, but there 

 are more organisms of the fifteen tested which can vigorously 

 ammonify this form of nitrogen. So that to illustrate, there are 

 but five organisms which have shown the power to transform 

 15 per cent or more of the nitrogen of dried blood into ammonia 

 in the sandy soil. Under similar conditions there are ten 

 organisms which hold such a record for cottonseed meal. Tank- 

 age shows itself to be the next important nitrogenous fertilizer 

 to cottonseed meal from the point of view of the availability of 

 its nitrogen. Thus, comparing it with dried blood as above, we 

 find that there are nine organisms which transform 15 per cent 

 or more of the nitrogen of tankage into ammonia. No such high 

 availability is obtained at all in the case of the fish guano. 



When we consider these nitrogenous fertilizers from the point 

 of view of the transformation of 10 per cent or more of their 

 nitrogen into ammonia, we find that there are thirteen of the 

 fifteen organisms tested which possess that power as regards 

 cottonseed meal nitrogen and another comes very close to that 

 point. In the case of tankage nitrogen there are thirteen organ- 

 isms with a similar power. In the case of dried-blood nitrogen 



