Recent Developments and Perspectives 27 



obligatory pure culture method and upon the reactions carried out 

 by these cultures under various conditions. In view of the fact that 

 a specific organism has to compete in a certain process in the soil 

 with numerous other organisms, some of which are much more active 

 and more specialized, the ability of a given organism to carry out a 

 certain function under laboratory conditions and in pure culture is 

 no proof that the organism will carry out the same function in the 

 soil. Stress should be laid on the crude cultures of an elective char- 

 acter, arranged in a manner to allow the observation of the biological 

 acti\"ities in the soil itself. 



It thus becomes evident that the scope of soil microbiology can- 

 not be narrowed down to one or two specific methods for determin- 

 ing the nature and abundance of the microbiological population, or 

 to one or two processes for measuring the activities of one or more 

 members of this population. The scope of the science is much 

 broader. It avails itself of the methods of the botanist, the zoologist, 

 the mycologist, and the bacteriologist, for determining the nature 

 of the organisms present in the soil and their abundance. It avails 

 itself of the methods of the chemist and of the physicist, for measur- 

 ing the nature of the processes carried out by these organisms. It 

 attempts to correlate the information thus obtained with that of the 

 soil chemist, the soU physicist, and the agronomist, thus contributing 

 its share to the building up of our knowledge of the science of the 

 soil. 



Like every other science, soil microbiology calls upon some of 

 the older and some of the closely related sciences for specific methods 

 and for the elucidation of its results. Soil microbiology is not and 

 cannot be merely a theoretical or a strictly applied science, as be- 

 lieved by some. It is a science in itself with many theoretical phases 

 and practical applications. From this point of view, one is hardly 

 justified in saying that up to now we have had only contributions to 

 general microbiology and that the applied science of soil micro- 

 biology is still to come. One might be more justified in saying that 

 up to now the general ecological and biochemical phases of soil 

 microbiology have been dominant and that the application of this 

 science to our knowledge of the soil is still of limited significance. 

 Even this, however, would hardly be fully justified, since consider- 

 able information has been accumulated concerning the interrelations 

 between the soil processes and the microscopic population of the 

 soil. 



