J. Bauhus et al., EFFECT OF THE INHIBITORS NITRAPYRIN AND SODIUM-CHLORATE ON NITRIFICATION AND N2O FORMATION IN AN ACID FOREST SOIL, Biology and fertility of soils, 22(4), 1996, pp. 318-325
An acid forest soil from beech forest gaps, which were either limed or
unlimed, and the undisturbed forest was investigated for the type of
nitrifying populations and the process of N2O evolution. To see whethe
r nitrifiers were of heterotrophic or autotrophic origin, the nitrific
ation inhibitors nitrapyrin and sodium chlorate were applied to distur
bed soil samples which underwent laboratory incubations. Nitrapyrin in
hibits autotrophic nitrification. In different studies, sodium chlorat
e has been identified as an inhibitor either of autotrophic or of hete
rotrophic nitrification. In the samples investigated only nitrapyrin i
nhibited the autotrophic nitrification occurring in the limed soil. So
dium chlorate effectively inhibited heterotrophic nitrification. In th
e Limed forest floor samples, where most autotrophic nitrification occ
ured, sodium chlorate showed no inhibitory effect. In another laborato
ry incubation experiment, N2O evolution from undisturbed soil columns,
to which the above inhibitors were applied, was investigated. In thos
e samples, in which nitrification had been reduced, neither inhibitor
significantly reduced N2O evolution. Thus it was concluded that the co
ntribution of nitrification to N2O losses is negligible, and that N2O
evolution arises from the activity of denitrifying organisms. Microbia
l biomass and respiration measurements showed that the inhibitors did
not affect microflora negatively.