SOIL AIR 



253 



cumTilation seem to fluctuate with the carbon dioxide, while 

 the oxygen curve is almost the exact reciprocal. Other in- 

 fluences of a minor nature enter in, such as the character of 

 the crop growing on the soil, heavy rainfall, oxygen dissolved 

 in the rain, and rapid changes of temperature. (See Fig. 

 48.) 



While plowing, application of lime, drainage, and other 

 practices have a great influence on the proportion of oxygen 



FEBR. MARCH APRIU 



Fig. 48. — Carbon dioxide in air from Dunkirk clay loam bare and from 

 the same soil cropped to oats, 1918. (After Tnrpin.) 



and carbon dioxide in the soil air, the addition of organic 

 matter seems to have the most profound effect. At the 

 Eothamsted Experiment Station,^ the carbon dioxide content 

 of the air from two soils was studied. One soil (Broadbalk 

 field) had been manured for a number of years while the other 

 (Hoos) had not received such a treatment: 



^EusseU, E. J., and Appleyard, A., The AtmospJiere of iTie Soil: Its 

 Compositiorh and the Causes of Variation; Jonr. Agr. Sci., Vol. Til, 

 Part 1, p. 25, 1915. 



