FIXATION OF ATMOSPHERIC NITROGEN. 281 



The first inoculation experiments in a large way were those made in 

 1887 at the Moor Soil Experiment Station, Bremen, Germany, where earth 

 taken from fields that had borne luxuriant crops of various legumes was 

 scattered over reclaimed heath or swamp soils upon which legumes had 

 not previously grown, with the result that in every instance the yield on the 

 inoculated portions of land was greater than on the uninoculated plots. 

 After such favorable results, it was but a natural step to try the effect 



FIG. 72. Roots of plant B with nodules (.Fig. 70). 



of similar applications of soil rich in the nodule-forming bacteria to 

 ordinary cultivated soils of varying character. While results in some cases 

 were eminently satisfactory in others there was no increase in the vigor or 

 amount of the crop as a result of the inoculation. 



METHODS OF SOIL INOCULATION. From these early experimental 

 results there evolved two general methods of inoculation, namely, the 

 application of soil from an already inoculated field, and the application 

 of pure cultures of the nodule-forming bacteria to the seed before sowing. 



