SOIL AIR 255 



Biochemical oxidation, however, is usually rapid and is a 

 much more impox'tant factor in the oxygen control of the air. 

 Not only do all bacteria require oxygen for their growth, but 

 they are contmually producing compounds that require oxy- 

 gen in their molecules. Carbon dioxide is an oxidation 

 product. Its formation reduces the oxygen of the air and its 

 presence causes a dilution. Sulfofication and nitrification are 

 well known examples The reactions for the process of nitri- 

 fication illustrate in addition the production of carbon dioxide 

 by chemical means : 



2NH3 + 3O2 = 2HNO2 + 2H2O 



2HNO2 + CaCOa = Ca(N0,)2 -f H^O + CO^ 



CaCNO^)^ + O2 = Ca(N0,)2 



132. Function of the carbon dioxide of the soil. — The 



solvent action of carbon dioxide is probably one of its most 

 important functions in the soil. Constant biological activities, 

 combined with the seasonal cropping influences, maintain this 

 solvent and keep it continually in contact with the solution 

 surfaces of the soil. Although a very weak acid when dis- 

 solved in water, its rapid formation and continuous action is 

 productive of marked effects. 



The availability of almost all of the plant nutrients is due 

 either directly or indirectly to the action of carbon dioxide. 

 Its influence on the potash of orthoclase, the phosphoric acid 

 of tri-calcium phosphate and the calcium of calcium carbonate 

 are well known examples : 



2KAlSi308 + 2H2O + CO2 = H^Al^Si^Oe + 4Si02 + K^COa 



CagCPOJ^ + 2H2O + 2CO2 = CaH,(P0j2 + 2CaC03 



CaCOg -f H2O + CO2 = CaHaCCOs)^ 



Stoeklasa^ has correlated the carbon dioxide production 



^Stoklasa, J., Mefhoden zur BesUmnmng der Atmungsintensitat der 

 Baktenen im Boden; Zeit. f. d. Landw. Versuelisweseix m Oesterreicli, 

 Band 14, Seite 1243-79, 1911. 



