CHAPTER XXIII 

 SOIL-INOCULA TION 



THE discovery that the fixation of atmospheric 

 nitrogen by legumes is accomplished with the aid of 

 bacteria suggested the artificial introduction of the 

 latter into soils liable to be deficient in them. Such arti- 

 ficial addition of bacteria to the soil, designated now as 

 soil-inoculation, was already resorted to by Hellriegel 

 and Wilfarth, as well as by other investigators in their 

 studies of nodule-formation. When they employed 

 sterile soils, they were obliged to use soil-leachings in 

 order to make possible the formation of nodules on the 

 roots. In other words, they inoculated their soils with 

 the bacteria present in the leachings. The principle 

 established by them was soon applied in a practical 

 way. 



Having learned that legume-nodules are caused by 

 bacteria, men began to wonder whether all soils are 

 sufficiently provided with the proper numbers and 

 kinds of bacteria. There was a possibility that the failure 

 of leguminous crops might be due to the lack of nodule- 

 bacteria. Accordingly, some experiments to test this 

 point were begun as early as 1887 at the Moore Experi- 

 ment Station at Bremen, Germany. The conditions were 

 particularly favorable for the success of inoculation, 



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