soil - Lublin

ha -1 day -1 ) than between slits (207 µg N m -2 h -1 or 49 g N ha -1 day -1 ) (Ball et al.,
1999). Knowledge of the small-scale spatial variability helps better estimates of the
emissions over large scale (Mummey et al., 1997). Under potato field N 2 O emission
is spatially variable due to specific configuration and soil compaction (Fig. 3).
The most pronounced dynamics in ridges is ascribed to soil temperature and increased
soil respiration, which casues an increased anaerobic volume in which
denitrification takes place (Flessa et al., 2002b) The mean share of the ridges, uncompacted
interrows and tractor-compacted interrows in the total field N 2 O emission
in this study was 66%, 10% and 24%, respectively.
N 2 O emissions from grasslands depend on soil compaction by livestock hooves
and associated high inputs of of excretal N. The effects of both factors resulted in
large temporal and spatial variability of the N 2 O flux.
Given spatial patterns of N 2 O fluxes often persist for short time and diurnal
changes are largely influenced by cycles in soil temperature (Smith et al., 1998;
Williams et al., 1999; Choudhary et al., 2002; Flessa et al., 2002a) and rainfall and
irrigation events through effects on air-filled porosity (Stępniewska et al., 2000).
-2 -1
2
µg N m h )
N O flux (
1000
750
500
250
a
Ridge
Interrow
Compacted interrow
250
200
150
100
50
WFPS (%)
0
80
60
40
20
b
0
0
May/17 Jun/7 Jun/28 Jul /19 Aug /9 Aug/30
Fig. 3. N 2 O fluxes and water-filled pore space (WFPS) during the potato growing period
(after Flessa et al., 2002b).
23