H. Flessa et al., SEASONAL-VARIATION OF N2O AND CH4 FLUXES IN DIFFERENTLY MANAGED ARABLE SOILS IN SOUTHERN GERMANY, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 100(D11), 1995, pp. 23115-23124
Agricultural practices are assumed to contribute significantly to the
increase in atmospheric nitrous oxide (N2O) concentrations observed in
the last decades, and they might influence the consumption of atmosph
eric methane (CH4) by soil. The aim of this study was to quantify the
effects of management intensity, soil type, and frost periods on the e
mission of N2O and the consumption of CH4 in rotations in southern Ger
many. Fluxes of N2O and CH4 were monitored over 12 months, using a clo
sed chamber technique. The extensively managed system was cropped to s
unflower and fertilized with farmyard manure (12 t ha(-1)). The intens
ively managed field was planted with spring wheat and fertilized with
a total of 190 kg N ha(-1) given as calcium ammonium nitrate (30 kg N)
and urea-NH4NO3 solution (160 kg N). Variation in the N2O emissions w
ith time was extremely high, with flux rates ranging from 0 to 2700 mu
g m(-2) h(-1). The N2O fluxes were influenced by soil properties, man
agement practices, and weather. The highest release rates were measure
d in the winter during thawing of the frozen soil. During the growing
season, N2O emission was highest after heavy precipitation. No strong
relationship was found between N2O emission rates and soil factors suc
h as soil temperature, soil moisture, and soil nitrate content. Annual
fluxes of N2O from the extensively managed field were 9.4 and 12.9 kg
N2O-N ha(-1) yr(-1) for a sandy soil and a clay soil, respectively. T
otal N2O-N losses from the intensively fertilized field amounted to 9.
6 kg ha(-1) yr(-1) for a silty soil with a tendency to waterlogging du
ring wintertime and to 16.8 kg ha(-1) yr(-1) for a loamy colluvial soi
l. Up to 46% of the annual N2O evolution was emitted during December a
nd January when frost/thaw cycles induced extremely high N2O productio
n. The application of urea-NH4NO3 solution significantly increased N2O
emission rates. Of the 160 kg N applied, 2.9 kg N or 1.8% was lost as
N2O within a period of 8 weeks. Rates of CH4-C uptake varied from 0 t
o 17 mu g m(-2) h(-1). Soil temperature correlated positively and soil
moisture correlated negatively with the CH4 consumption. Stepwise mul
tiple linear regression, including these soil factors, explained up to
44% of the variation in CH4 fluxes. Annual CH4-C uptake was rather si
milar for the intensively and extensively managed Eutrochrepts, rangin
g from 348 to 395 g ha(-1). Significantly higher CH4-C consumption of
567 g ha(-1) yr(-1) occurred in the colluvial soil (Typic Udifluvent).
N fertilizers had no effect on the CH4 flux rates.