NON-SYMBIOTIC NITROGEN FIXATION 151 



ties and with a source of carbon which is not far different from 

 that found in the soil. Russell, however, after carefully review- 

 ing all of the experimental evidence on the subject, concludes: 

 "There is no evidence that ^humogen' possesses any special agri- 

 cultural value. There is not the least indication that it is fifty 

 times as effective as farmyard manure, to quote an oft-repeated 

 statement, and there is nothing to show that it is any better than 

 any other organic manure with the same nitrogen content." 

 Furthermore, he concludes that there is no definite evidence that 

 "bacterization" really adds to the value of peat. 



The conclusion is evident that soil inoculation in order to be 

 successful must be accompanied by the rendering of the physical 

 and chemical properties of the soil ideal for the growth of the 

 specific organisms to be added. A few organisms placed in a 

 new environment already containing millions can never hope to 

 gain the ascendancy over the organism^ naturally occurring in the 

 soil, for they have been struggling for countless generations to 

 adapt themselves to the environment, and only those which are 

 fitted have survived. The problem becomes even more compli- 

 cated when we recall the findings of Lipman that the bacterial 

 flora of a soil is in many cases entirely changed by climatic con- 

 ditions. On this account it would appear that to ever make soil 

 inoculation a success the chemical, physical, and even the biologi- 

 cal condition must be made suitable for the growth of the specific 

 organism added. Furthermore, strains of the organism must 

 be used which have been evolved under similar climatic con- 

 ditions. 



Soil Gains in Nitrogen. — It is well established that many 

 forms of microorganisms possess the power of fixing nitrogen 

 either when grown alone or in combination with other micro- 

 organisms of the soil. Many of these have been obtained in pure 

 culture and their morphology and physiology carefully studied. 

 The most favorable conditions for their maximum nitrogen fixa- 

 tion in pure cultures in liquid solutions have been accurately de- 

 termined. Some of the conditions requisite for their activity in 

 soils are known, but on this phase of the subject there are many 



