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Soil Compaction and Fertilization Effects on Nitrous Oxide
and Methane Fluxes in Potato Fields
R. Ruser, H. Flessa,* R. Schilling, H. Steindl, and F. Beese
ABSTRACT
from soils are well known from a number of laboratory
studies reviewed by Granli and Bøckman (1994). On
arable land, N2O emissions are strongly influenced by N
fertilization. Several studies reviewed by Eichner (1990)
and Bouwman (1994) have shown increasing N2O emission with an increasing application rate of N fertilizers.
In addition to fertilizer application, several other management practices affect N2O release. Tillage and soil
compaction (Staley et al., 1990; Hansen et al., 1993),
management of plant residues (Flessa and Beese, 1995),
and irrigation and drainage (Mosier et al., 1986) are
further measures that influence the emission rates of
N2O. The data sets that are currently used by the Intergovernmental Panel on Climate Change (1996) to estimate the global fertilizer-induced N2O emission are primarily based on results from grasslands and maize (Zea
mays L.) (Bouwman, 1994). This approach does not
consider the effects of different crops on N2O emission.
Since cropping practices and soil N dynamics may be
very different depending on the cultivated crop, it is
likely that specific crop-related patterns of N2O emission
exist. No data are available on the N2O losses from soils
planted with potato. The cultivation of the potato differs
markedly from that of cereals because potato is usually
cultivated using ridge culture. As a result of the ridgetill practice, potato fields are a very heterogeneous soil
physical system. The different bulk density and poresize distribution in the ridge soil, the uncompacted interrow soil, and the interrow soil compacted by tractor
traffic may significantly affect the N2O release by these
fields. This spatial variability in soil properties produced
by tillage practice must be considered in the estimation
of the total N2O release from potato fields. This can be
achieved either by flux measurements integrating larger
areas or by separately monitoring the N2O fluxes originating from these differently compacted areas. The latter procedure enables a more detailed investigation of
the tillage-induced effects on the emissions of N2O.
The tillage-induced changes in soil physical properties
may also influence the uptake of atmospheric CH4 in
potato fields. In soils, methane is oxidized by methanotrophic bacteria, but chemolithotrophic, NH4-oxidizing
bacteria are also able to oxidize methane (Knowles,
1993). Studies on CH4 consumption in well-drained mineral soils suggest that diffusion of atmospheric CH4 into
the soil is the primary factor limiting the rates of CH4
oxidation (Striegl, 1993). Soil compaction by tractor
traffic can significantly reduce the uptake rates of CH4
in arable soils (Hansen et al., 1993). Methane uptake can
also be inhibited by NH4–N fertilization. This inhibitory
effect of NH41–N addition was observed in forest ecosystems (Schnell and King, 1994), in grasslands (Mosier et
al., 1991), and in arable soils (Hütsch et al., 1993). The
inhibition was attributed to methane monooxygenase
This study was conducted to determine the effect of soil compaction
and N fertilization on the fluxes of N2O and CH4 in a soil (fine-silty
Dystric Eutrochrept) planted with potato (Solanum tuberosum L.).
Fluxes of N2O and CH4 were measured weekly for 1 yr on two differently fertilized (50 and 150 kg N ha21) fields. For the potato cropping
period (May–September) these fluxes were quantified separately for
the ridges (soil bulk density rb 5 1.05 Mg m23) covering two-thirds
of the total field area, and for the uncompacted (rb 5 1.26 Mg m23)
and the tractor-traffic-compacted (rb 5 1.56 Mg m23) interrow soils,
each of which made up one-sixth of the field area. The annual N2O–N
emissions for the low and the high rates of N fertilization were 8 and
16 kg ha21, respectively. The major part (68%) of the total N2O release
from the fields during the cropping period was emitted from the
compacted tractor tramlines; emissions from the ridges made up only
23%. The annual CH4–C uptake was 140 and 118 g ha21 for the low
and high levels of fertilization, respectively. The ridge soil and the
uncompacted interrow had mean CH4–C oxidation rates of 3.8 and
0.8 mg m22 h21, respectively; however, the tractor-compacted soil
released CH4 at 2.1 mg CH4–C m22 h21. The results indicate that soil
compaction was probably the main reason for increased N2O emission
and reduced CH4 uptake of potato-cropped fields.
T
he atmospheric concentrations of the radiative
active trace gases N2O and CH4 are increasing at a
current rate of ≈0.25 and ≈0.8% per year, respectively
(Intergovernmental Panel on Climate Change, 1994).
The contribution of these gases to the current anthropogenically derived radiative forcing is estimated to be
≈6% for N2O and ≈19% for CH4. Moreover, N2O is
involved in the ozone depletion process in the stratosphere (Crutzen, 1981). Since increasing atmospheric
concentrations of N2O and CH4 are expected to alter
the earth’s climate, there is a growing interest in the
sources and sinks of these gases, and in the influence
of anthropogenic activities on the exchange rates.
Nitrous oxide emissions from agriculture are estimated to account for .75% of the total global anthropogenic sources (Isermann, 1994). The biological CH4 oxidation in aerobic soils is estimated to comprise 3 to 9%
of the global atmospheric CH4 sink (Prather et al., 1995).
Nitrous oxide is produced in soils as an intermediate
during nitrification and denitrification. The emission
rates are controlled by environmental factors affecting
the rates of these processes and the relative fractions of
N2O evolved during these processes (Davidson, 1991).
The principle factors that influence N2O emissions
R. Ruser, R. Schilling, and H. Steindl, GSF-Forschungszentrum, Inst.
für Bodenökologie, Neuherberg, P.O.B. 1129, D-85758 Oberschleißheim, Germany; H. Flessa and F. Beese, Univ. of Göttingen,
Inst. of Soil Science and Forest Nutrition, Büsgenweg 2, D-37077
Göttingen, Germany. Received 19 Aug. 1997. *Corresponding author
([email protected]).
Published in Soil Sci. Soc. Am. J. 62:1587–1595 (1998).
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