400 NATURE AND PEOPEETIES OF SOILS 



aid in the initial transformation, being particularly effective 

 in decomposing cellulose. The actmomyces, present in such 

 large numbers, seem to be especially fitted for the breaking 

 down of such resistant material. 



The result of these complex decomposition processes is the 

 formation of a partially decayed group of carbon-bearmg 

 material, some being™ quite simple while others are extremely 

 complicated. The change is accompanied through its entire 

 course by the formation of carbon dioxide and water, the end- 

 products of carbohydrate decay. The same heterogeneous 

 group of soil organisms, which initiate the simplification of 

 carbonaceous materials, seem to continue the process until 

 only the end products and the more resistant portions of the 

 original tissue remain. 



The transformations above discussed are not the only 

 sources of carbon dioxide within the soil. Some carbon diox- 

 ide is broughjb down in rain-water, while still more is given off 

 by the roots of living plants (see par. 156). Moreover some 

 carbon dioxide is obtained from the inorganic matter of the 

 soil, especially if the land has recently received an applica- 

 tion of limestone. The reactions within the soil seem to de- 

 compose such carbonates rather readily, carbon dioxide being 

 given off (see par. 201). 



220. The loss of carbon from the soil. — Carbon diox- 

 ide, the importance of which has already been fully discussed 

 (par 132), may suffer transformation in a number of ways 

 in the soil. It may be lost (1) to the atmospheric airj (2) 

 it may react with the mineral constituents of the soil and be 

 held at least temporarily by the soil mass; or (3) it may be 

 removed by leaching. Since the soil-water is always more or 

 less charged with carbon dioxide and since 'it carries car- 

 bonate and bicarbonate salts, considerable carbon is continu- 

 ally being removed in this way. In this regard the figures 

 from the Cornel lysimeter tanks ^ are especially interesting. 



^ Unpublished data, Cornell Agr. Exp. Sta., Ithaca, N". Y* 



