COMPOSITION OF SOIL AIR 

 Table LXV 



435 



Character 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 

 dioxid 



Cu. ft. 

 14 

 28 

 57 

 71 



80 



172 



257 



1,144 



772 



Composition of 100 parts 

 soil-air by volume 



Carbon 

 dioxid 



0.24 

 0.79 

 0.87 

 0.66 



0.74 



1.54 



2.21 



9.74 

 3.64 



Oxygen 



Nitro- 

 gen 



19.66 

 19.61 

 19.99 



19.02 



18.80 



10.35 

 16.45 



79.55 

 79.52 

 79.35 



80.24 



79.66 



79.91 

 79.91 



less influence is the excretion of carbon dioxid and utili- 

 zation of oxygen by plant roots. 



300. Production of carbon dioxid as affecting com- 

 position. -Although the formation of carbon dioxid 

 in the soil depends upon the decomposition of organic 

 matter, it is not always proportional to the quantity 

 of organic matter present. The rate of decomposition 

 varies greatly, and where this is depressed, as is some- 

 times seen in muck or forest soils, the content of carbon 

 dioxid is low. A high percentage of organic matter is in 

 itself likely to prevent a proportional formation of carbon 

 dioxid by the accumulation of the gas inhibiting further 

 activity of the decomposing organisms. 



