SOIL ORGANISMS 



419 



Table XC 



NITRATE ACCUMULATION ON HEAVILY MANURED AND ON UN- 

 MANURED SOIL. 



aerated soils. Both were kept at the same temperature and 

 moisture content in the greenhouse, but no plants were grown 

 on them. The accumulation of nitrates was as follows: 



Table XCI 



It has often been assumed that carbon dioxide is a detri- 

 mental factor in biological activity in two respects: by the 

 replacement of oxygen and by a toxic influence on the organ- 



