462 SOILS: PROPERTIES AND MANAGEMENT 



another culture to be used for inoculating the soil. Care- 

 ful investigation of this method showed that its weakness 

 lay in drying the cultures on the absorbent cotton, which 

 frequently resulted in the death of the organisms. More 

 recently, liquid cultures have been placed on the market 

 in this country, and these have, in the main, proved to 

 be more successful, notably those sent out by the United 

 States Department of Agriculture. Another very suc- 

 cessful culture medium, now being distributed by the 

 Department of Plant Physiology at Cornell University, is 

 steamed soil. The process of steaming under a pressure 

 of two or three atmospheres increases greatly the solu- 

 bility of both organic and inorganic matter, and produces 

 a medium highly favorable to the development of the 

 organisms isolated from the nodules of legumes. 



Liquid cultures for legume inoculation have now been 

 prepared and distributed by the United States Depart- 

 ment of Agriculture for seven years, and during this time 

 a record has been kept of the results so far as it has been 

 possible to do this. These are summarized by Keller- 

 man 1 as follows : average percentage of success, 76 ; 

 average percentage of failure, 24. If, however, the doubt- 

 ful reports are included with the failures, the percentage 

 of success is reduced to 38. Kellerman states as his 

 opinion that inoculation with pure liquid cultures is as 

 certain a means of infection as is inoculation with soil 

 from fields on which legumes have been successfully grown 

 for extended periods, if the soil to be infected is one well 

 adapted to the leguminous crop; but on soils not well 

 suited to legumes, the use of soil from old fields is a much 

 more satisfactory medium with which to attempt inocula- 



1 Kellerman, K. F. The Present Status of Soil Inoculation. 

 Centrlb. f. Bakt., II, Band 34, Seite 42-50. 1912. 



