NITRIFICATION AND NITROUS-OXIDE PRODUCTION POTENTIALS IN AEROBIC SOILSAMPLES FROM THE SOIL-PROFILE OF A FINNISH CONIFEROUS SITE RECEIVING HIGH AMMONIUM DEPOSITION
Pj. Martikainen et al., NITRIFICATION AND NITROUS-OXIDE PRODUCTION POTENTIALS IN AEROBIC SOILSAMPLES FROM THE SOIL-PROFILE OF A FINNISH CONIFEROUS SITE RECEIVING HIGH AMMONIUM DEPOSITION, FEMS microbiology, ecology, 13(2), 1993, pp. 113-121
Using aerobic soil slurry technique nitrification and nitrous oxide pr
oduction were studied in samples from a pine site in Western Finland.
The site received atmospheric ammonium deposition of 7-33 kg N ha(-1)
a(-1) from a mink farm. The experiments with soil slurries showed that
the nitrification potential in the litter layer was higher at pH 6 th
an at pH 4. However, the nitrification potentials in the samples from
the organic and mineral horizons at pH 6 and 4 were almost equal. Also
N2O was produced at a higher rate at pH 6 than at pH 4 in slurries of
the litter layer samples. The reverse was true for samples from the o
rganic and mineral horizons. The highest N2O production and nitrificat
ion rates were measured in the suspensions of litter layer samples. Ni
trification activity in field-moist soil samples was lower than the ac
tivity in the slurries indicating that the availability of ammonium li
mited nitrification in these soils. Acetylene (2.5 kPa) retarded nitri
fication activity (70-100%) and N2O production (40-90%) in soil slurri
es. Acetylene inhibited the N2O production by 40-60% during the first
3 days after its addition to field-moist samples incubated in aerobic
atmosphere. After 3 days the inhibition became much lower (4-5%). The
results indicate that, in soil profiles of boreal coniferous forests r
eceiving ammonium deposition, chemolithotrophic nitrification may have
importance in the N2O production, and that changes in soil pH affect
differently nitrification as well as N2O production in litter and deep
er soil layers.