STIMULATED DENITRIFICATION IN THE MICROENVIRONMENT OF A BIODEGRADABLE ORGANIC WASTE INJECTED INTO SOIL

Denitrification and the associated processes of nitrification, mineralization, and respiration were studied in the zone around the injection slit in which two fermentation wastes were injected into soil. All processes were stimulated apparently due to the greater availability of N and C and the increased anaerobiosis caused by the greatly enhanced respiration. Under field conditions, denitrification rates as high as 4. 9 and 2. 3 mu g cm** minus **2 h** minus **1 were measured from the cell waste and the spent growth medium, respectively. If extrapolated over the 73-d period after application, the accelerated denitrification would remove over one-half of the added N. The rate of CO//2 production explained 31. 4 to 46. 8% of the variation in denitrification, whereas soil moisture explained only 3. 6 to 18. 9% of the variation. This suggests that respiratory activity created an anaerobic microenvironment making conditions favorable for denitrification. Under laboratory conditions, the loss of N due to denitrification of the cell waste could be reduced by 68% with surface incorporation rather than injection.