ACTIVITIES OF SOIL MICROORGANISMS 
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Nitrogen: — Ammonia or ammonium compounds oxidized to 
oxides of nitrogen, to nitrites, to nitrates, by various stages 
or directly in order to secure growth energy, usually for the 
assimilation of carbon dioxide. 
Bacterial term — Nitrification. 
Sulfur : — Free sulfur or hydrogen sulfide oxidized to sulfites 
or sulfates. 
Bacterial term — sulfofication. 
REDUCTION : — Aerobic or anaerobic processes by which com- 
pounds are reduced to furnish oxygen. 
Carbon : — Occasionally a part of assimilation, part of the 
carbon may be reduced while another is oxidized. 
No designation of bacterial action. 
Nitrogen Primarily anaerobic ; end products, reduced nitro- 
gen compounds or free nitrogen. 
Bacterial term — Denitrification or deazofication. 
Sulfur : — The reduction of sulfates and sulfites. 
Bacterial term — - Desulfofication. 
Agricultural Experiment Station, 
Iowa State College. 
