102 Influence of Plant Residues on Nitrogen Fixation 



May 4th, 1911. Although growth in the pots of the same sets was very 

 similar, that of the different sets varied greatly. During the first few 

 weeks after sowing those plants in the control pots (sand alone) were 

 distinctly superior to any of the others, there being little to choose 

 between the rest. Towards the end of June, however, the barley in the 

 sand inoculated with Azotobacter began to improve rapidly and at the 

 end of three months appeared to be the best crop; this was subsequently 



Sand alone 



Sand + Hay + Putrefactive 

 Organisms 



Sand + Hay 

 (sterile) 



Sand + Hay + Putrefactive 

 Organisms + Azotobacter 



Fig. 2. Pot experiments on the utilisation of bay dust for nitrogen fixation. 

 Production of dry matter by first crop (Barley), 



confirmed by actual weighings of the dry crop. The next plants to 

 improve were those in sand to which putrefactive organisms had been 

 added, but those in sand (with hay) without introduced organisms re- 

 mained comparatively small and weakly during the whole vegetation 

 period. 



A second crop of rye was then sown in all the pots and here again 

 the pots with Azotobacter possessed the most vigorous vegetation; in 



