436 



THE PRINCIPLES OF SOIL MANAGEMENT 



Ramann states that the percentage of carbon dioxid 

 in the soil air has the following relations: 



The carbon dioxid increases with the depth. 



In general the percentage of carbon dioxid rises and 

 falls with the temperature, being higher in the warm 

 months and lower in the cold months. 



r-^ 



Fig. 116. Disc cultivator fitted with fenders. 



Changes in temperature and air pressure change the 

 percentage of carbon dioxid. 



In the same soil the content of carbon dioxid varies 

 greatly from year to year. 



An increase of moisture in the soil increases the per- 

 centage of carbon dioxid. 



The amount of carbon dioxid varies in different parts 

 of the soil. 



301. Escape of carbon dioxid as affecting composition. 



