Contribution of denitrification and autotrophic and heterotrophic nitrification to nitrous oxide production in andosols
1996
Inubushi, K. | Naganuma, H. | Kitahara, S.
To quantify the contribution of denitrification and autotrophic and heterotrophic nitrification to N2O production in Andosols with a relatively high organic matter content, we first examined the effect of C2H2 concentrations on N2O production and on changes in mineral N contents. The optimum C2H2 concentration for inhibiting autotrophic nitrification was 10 Pa. Secondly, and Andosol taken from an arable field was incubated for 32 days at 30 degrees C at 60, 80, and 100% water-holding capacity with or without the addition of NH4 or NO3 (200 mg N kg-1), and subsamples collected every 4-8 days were further incubated for 24 h with or without C2H2 (10 Pa). At 60 and 80% water-holding capacity with NH4+ added, 87-92% of N2O produced (200-250 microgram N2O-N kg-1) was derived from autotrophic nitrification. In contrast, at 100% water-holding capacity with or without added NO3, enormous amounts of N2O (29-90 mg N2O-N kg-1) were produced rapidly, mostly by denitrification (96-98% of total production). Thirdly, to examine N2O production by heterotrophic nitrification, the Andosol was amended with peptone or NH4 (both 1000 mg N kg-1)+citric acid (20 g C kg-1) and with or without dicyandiamide (200 mg N kg-1). Treatment with citric acid alone or with citric acid+dicyandiamide suppressed N2O production. In contrast, peptone increased N2O production (5.66 mg N2O-N kg-1) mainly by denitrification (80% of total production). However, dicyandiamide reduced N2O production to 1.1 mg N2O-N kg-1. These results indicate that autotrophic nitrification was the main process for N2O production except at 100% water-holding capacity where denitrification became dominant and that heterotrophic nitrification had a lesser importance in the soils examine.
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