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 µg cm −2 h −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. This was probably due to the cell waste material being applied to a greater volume of soil, thus reducing both the temporal and spatial zones of anaerobiosis. Samples 5 cm away from the injection slit did not have enhanced denitrification rates nor NO ‐ 3 concentrations, suggesting little lateral movement of the applied waste material. The enhanced denitrification response to cell waste C addition emphasizes the importance of respiratory O 2 consumption by heterotrophs on denitrification. These results are expected to hold for any waste that is reasonably biodegradable and has a medium to low C/N ratio.
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Rice et al. (1988) studied this question.