286 AZOFICATION 



Azotobacter, the results are that they rapidly multiply and compete 

 with the higher plants for the limited available plant-food. If, 

 however, the carbohydrates are applied in the autumn directly 

 after the removal of the crop, when the soil is warm, Azotobacter 

 are active, with the result that sufficient nitrogen is fixed to produce 

 an increased crop the following season. 



If the same quantity of carbohydrates per unit of nitrogen fixed 

 be required by the organism under natural conditions, as are found 

 necessary in laboratory experiments, enormous quantities would be 

 required for the fixation of any considerable quantity of nitrogen; 

 but it is possible that in the soil they are more economical with their 

 energy or they may live in symbiosis with other organisms which 

 furnish them part of their carbon. 



Many workers have noted either no effect or even a detrimental 

 influence when soils are treated with the carbohydrates and then 

 inoculated with Azotobacter. This may be due in a great measure to 

 any or all of the following factors: (a) Absence of a suitable 

 environment, as temperature, moisture, aeration, food and alkalinity; 

 (6) absence of a suitable host from which Azotobacter may obtain 

 part of its carbon; (c) injurious effects due to the decomposition 

 products of the carbohydrate added. 



There is considerable interest in the work of Bottomley who 

 uses bacterized peat, or humogen. The bacterizing process consists 

 of three stages : (a) Treatment of peat with a culture solution of the 

 special "humating" bacteria and an incubation of it at constant 

 temperature for a week or ten days, during which period soluble 

 humates are formed; (b) destruction of the humating bacteria by 

 sterilization with live steam; (c) treatment of this sterilized peat 

 with mixed cultures of nitrogen-fixing organisms Azotobacter 

 chroococcum and Bacillus radicicola and an incubation at 20 C. for 

 a few days, after which it is ready for use. 



Theoretically, there is much in this process which recommends it, 

 for there is no abrupt change in environmental conditions for the 

 organism added, as would be the case when added from laboratory 

 culture. Moreover, they are added in enormous quantities and 

 with a source of carbon which is not far different from that found in 

 the soil. Russell, however, after carefully reviewing all of the 

 experimental evidence on the subject, concludes: 'There is no 

 evidence that humogen possesses any special agricultural value. 

 There is not the least indication that it is fifty times as effective as 

 farmyard manure, to quote an often 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 con- 

 cludes 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 



