Evolution of CO.. from Soil Humus 



155 



With this apparatus, one can list the rate of CO;, evolution day 

 hy day o\or a season, or hour by hoiu- through some special period. 

 It recjuires no abstruse calculation but makes a demand for a con- 

 tinuous suction with a steady source of power; it also calls for regular 

 attention. 



100 

 90 



Carbohydrates-aerobi^ 

 erotiic 



Carbohydrates-anaerobic ^____^— — - 



Lignin-anaerobic 



405 



498 



Fig. 67. 



205 



Days of decomposition 



Influence of aeration upon decomposition of alfalfa plant (from Tenney 

 and Waksman). 



This procedure has weaknesses such as the small size of the col- 

 lecting box; the continuous position that interrupts processes that 

 go on near or on the surface; the irregularity of suction apparatus; 

 and inability to adjust absorbent, rate of flow, and frequency of 

 changes to the great changes in rate of COo evolution brought about 

 by some types of fertilization. It is probably most valuable in fol- 

 lowing the effects of some soil treatment from the time of applica- 

 tion for a period limited to a few days. 



Smith and Brown emphasized that COo diffuses downward into 

 the soil from the area of biological activity as well as upward into 



