ISSN:
1432-0789
Keywords:
Key words Denitrification
;
N2-fixation
;
Fermentation
;
N2O/N2 ratio
;
C-availability
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Geosciences
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract Nitrate and glucose additions were investigated for their role in the C and N dynamics during anaerobic incubation of soil. A gas-flow soil core method was used, in which the net production of N2, N2O, NO, CO2, and CH4 under a He atmosphere could be monitored both accurately and frequently. In all experiments clayey silt loam soil samples were incubated for 9 days at 25°C. Addition of nitrate (50 mg KNO3-N kg–1 soil) had no effect on total denitrification and CO2 production rates, while the N2O/N2 ratio was affected considerably. The cumulative N2O production exceeded the cumulative N2 production for 6 days in the treatment with nitrate addition, compared to 1.2 days in the unamended treatment. Glucose addition stimulated the microbial activity considerably. The denitrification rates were limited by the growth rate of the denitrifying population. During denitrification no significant differences were observed between the treatments with 700 mg glucose-C kg–1 and 4200 mg glucose-C kg–1, both in combination with 50 mg KNO3-N kg–1. The N2 production rates were remarkably low, until NO3 – exhaustion caused rapid reduction of N2O to N2 at day 2. During the denitrification period 15–18 mg N kg–1 was immobilised in the growing biomass. After NO3 – shortage, a second microbial population, capable of N2-fixation, became increasingly important. This change was clearly reflected in the CO2 production rates. Net volatile fatty acid (VFA) production was monitored during the net N2-fixation period with acetate as the dominant product. N2-fixation faded out, probably due to N2 shortage, followed by increased VFA production. In the high C treatment butyrate became the most important VFA, while in the low C treatment acetate and butyrate were produced at equal rates. During denitrification no VFA accumulation occurred; this does not prove, however, that denitrification and fermentation appeared sequentially. The experiments illustrate clearly the interactions of C-availability, microbial population and nitrate availability as influencing factors on denitrification and fermentation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00335949
Permalink
