248 NATUEE AND PROPERTIES OF SOILS 



correspondingly smaller amount of oxygen, and slightly larger 

 qnantities of other gases, including ammonia, methane, hydro- 

 gen sulfide, and the like, formed by the decomposition of 

 organic matter. The percentage of nitrogen is practically the 

 same in all cases. The following average data quoted from 

 three different sources show the comparative compositions 

 as far as the carbon dioxide, oxygen, and nitrogen are con- 

 cerned. All other gases are included with the nitrogen fig- 

 ures.^ 



TABLE LII 



AVERAGE COMPOSITION OF SOIL AIR AND ATMOSPHERIC AIR 



Location 



Peecentage by Volume 





COj 



0. 



N, 



Soil Air 



Germany ^ 



Iowa ^ 



.20 

 .20 

 .25 



.03 



20.60 

 20.40 

 20.65 



20.97 



79.20 

 79.40 



England* 



Atmospheric Air 

 England * 



79.20 

 79.0 



Eussell and Appleyard,'' in their study of the soil atmo- 

 sphere, found that there are really two types of soil air. The 

 first one occupies the portion of the pore space not taken 



^ Atmospliere air carries about .93 per cent, of argon, with very small 

 amounts of other inert gases such as krypton, xenon, helium and neon. 

 These gases are of course present in the soil. 



^Lau, E., Beitrage zur Kenntnis der Zusammensetzimg der im Acker- 

 loden tefindUcJien Luft; Inaug. Diss., Eostock, 1906. 



^Jodidi, S. L., and Wells, A. A., Infliience of VarioiiS Factors on 

 DeoompoBitioid of So'il Organio Matter; la. Agr. Exp. Sta., Bes. BuL 

 No. 3, Oct. 1911. 



"* Russell, E. J., and Appleyard, A., The Atmospliere of the Soil: Its 

 Composition and the Causes of Variation; Jour. Agr. Sci., 7ol. VII, 

 Part 1, pp. 1-48, 1915. 



^Russell, E. J., and Appleyard, A., The Atmosphere of the Soil: Its 

 Composition and the Causes of Variation; Jour. Agr. Sex., Vol VII, 

 Part 1, pp. 148, 1915. 



