478 SOILS: PROPJSBTIES AND MANAGEMENT 



Characteb 

 OF Soil 



Sandy subsoil of forest . 

 Loamy subsoil of forest . 

 Surface soil of forest . . 



Clay soil 



Soil of asparagus bed not 



manured for one year . 

 Soil of asparagus bed 



freshly manured . . 

 Sandy soil, six days after 



manuring 



Sandy soil, ten days after 



manuring (three days 



of rain) 



Vegetable mold compost 



Volume in One 



Acre of Soil to 



Depth of 14 



Inches 



Air 

 (Cu. ft.) 



4,416 



3,530 



5,891 



10,310 



11,182 



11,182 



11,783 



11,783 

 21,049 



Carbon 

 Dioxide 

 (Cu.ft.) 



28 

 57 

 71 



86 



172 



257 



1,144 



772 



Composition of 100 Paets 

 OP Soil Air by Volume 



Carbon 

 Dioxide 



0.24 

 0.79 

 0.87 

 0.66 



0.74 



1.54 



2.21 



9.74 

 3.64 



Oxygen 



19.66 

 19.61 

 19.99 



19.02 



18.80 



10.35 

 16.45 



Nitrogen 



79.55 

 79.52 

 79.35 



80.24 



79.66 



79.91 

 79.91 



There are several factors that influence the composi- 

 tion of the soil air, those of greatest importance being 

 the production and escape of carbon dioxide. 



396. Sources of carbon dioxide in soil air. — The 

 presence of carbon dioxide in soils is due in small part 

 to infiltration from the atmospheric air, there being a 

 tendency for the carbon dioxide, which is heavier than 

 oxygen and nitrogen, to settle out. It may also have a 

 purely chemical origin. But in much greater measure 

 is the carbon dioxide a product of biological processes 

 that occur in the soil. At one time it was believed that 

 the formation of carbon dioxide in soils was a purely 

 chemical process of oxidation, and possibly a part of the 

 gas is formed in that way. It has already been seen that 

 there is a condensation of gases in the manifold pores 



