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Abstract:
NO production and consumption rates as well as N2O accumulation rates
were measured in a loamy cambisol which was incubated under different
conditions (i.e. soil moisture content, addition of nitrogen fertilizer
and/or glucose, aerobic or anaerobic gas phase). Inhibition of
nitrification with acetylene allowed us to distinguish between
nitrification and denitrification as sources of NO and N2). Under
aerobic conditions untreated soil showed very low release of NO and N2O
but high consumption of NO. Fertilization with NH4+ or urea stimulated
both NO and N2O production by nitrification. Addition of glucose at high
soil moisture contents led to increased N2 and N2O production by
denitrification, but not to increased NO production rates. Anaerobic
conditions, however, stimulated both NO and N2O production by
denitrification. The production of NO and N2O was further stimulated at
low moisture contents and after addition of glucose or NO3-. Anaerobic
consumption of NO by denitrification followed Michaelis-Menten kinetics
and was stimulated by addition of glucose and NO3-Aerobic consumption of
NO followed first-order kinetics up to mixing ratios of at least 14 ppmv
NO, was inhibited by autoclaving but not by acetylene, and decreased
with increasing soil moisture content. The high NO-consumption activity
and the effects of soil moisture on the apparent rates of anaerobic and
aerobic production and consumption of NO suggest that diffusional
constraints have an important influence on the release of NO, and may be
a reason for the different behaviour of NO release vs N2O release.
