Agriculture Reference
In-Depth Information
Fig. 4.12.1.
Fluxes of N
2
O during the 25 days growing period of spring barley plants under
N
0
(ACO
2
) (/), N
1
(ACO
2
) (
r
), N
0
(ECO
2
) (
t
), N
1
(ECO
2
) (
{
). Error bars correspond to the standard
error of means from the two-way ANOVA analysis.
and wetting of the soil during the establishment of the experiment.
Wetting-up of soils has been reported to cause a significant increase in C
and N availability as well as a physical impact on O
2
diffusion, resulting in a
transient period when NO and N
2
O production may rise by a factor of
between 2 and 20 (Davidson, 1991). Gas fluxes in our experiment declined
sharply after 24 h.
Fluxes of N
2
O (Fig. 4.12.1) were concentrated in relatively short
periods (~5 days) following N fertilization, with significant differences
(
P
< 0.001) between the two N levels applied at all times. The average N
2
O
production rates for the entire measurement period after the first N
application (days 3-16) were of 10.3
±
2.8 and 17.3
±
6.4
µ
gN
2
O-N
m
−2
h
−1
for N
0
(ACO
2
) and N
0
(ECO
2
), respectively, and of 143
±
19 and
gN
2
O-N m
−2
h
−1
for N
1
(ACO
2
) and N
1
(ECO
2
), respectively.
With the second N application, enriched CO
2
atmosphere caused the rate
of N
2
O efflux in high N input to increase gradually from 11 to 74% at
the end of the experiment. However, those effects were not statistically
significant due to a high variability in the data.
Total N
2
O emissions of 50.1
140
±
22
µ
16.3 mg N
2
O-N m
−2
for
N
1
(ACO
2
) and N
1
(ECO
2
), respectively, represented 0.26 and 0.34% of the
fertilizer N applied. These results were in the range of N
2
O emissions
reported by Clayton
et al
. (1997) for grassland in Scotland fertilized with
ammonium nitrate. Ineson
et al
. (1998) in a free air enrichment experiment
±
9.8 and 57.4
±
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