Agriculture Reference
In-Depth Information
N
2
O in agriculture. These practices are
fertilizer type, timing, placement, and rate
of fertilizer application, as well as coordi-
nating the time of application with irriga-
tion and rainfall events. Each direct
nitrogen management practice infl uences
nitrous oxide emissions.
(a)
Type of fertilizer:
Nitrous oxide produc-
tion can be affected by the form of fertil-
izer applied. Venterea et al. (
2005
)
observed that plots amended with anhy-
drous ammonia emit N
2
O at rates
2-4 times greater than from those
amended with urea, ammonium nitrate,
or broadcast urea. Tenuta and
Beauchamp (
2003
) found that the rela-
tive magnitude of total emissions was
greater from urea than from ammonium
sulfate, which in turn was greater than
that from calcium ammonium nitrate.
The nitrate-based fertilizer resulted in
signifi cantly lower emissions of N
2
O
than ammonium-based fertilizer. Snyder
et al. (
2007
) demonstrated that slow,
control release and stabilized N fertilizer
can enhance crop productivity and mini-
mize the N
2
O emissions. Emissions of
N
2
O were signifi cantly higher from a
soil fertilized with urea compared to
NH
4
NO
3
(McTaggart et al.
1994
).
NH
4
NO
3
was benefi cial in reducing the
volatilization of NH
3
and the emission
of N
2
O. Another compound, NH
4
HCO
3
,
when used as basal fertilizer, contributed
less to N
2
O in contrast to urea.
the US area cropped to corn is fertilized
in autumn (CAST
2004
). Therefore,
large emissions of N
2
O could potentially
be avoided by fertilizing in spring rather
than autumn. Hultgreen and Leduc
(
2003
) showed that emissions of N
2
O
were lower following spring N fertilizer
application
compared
to
autumn
(c)
Fertilizer N placement
: Placement of N
fertilizer into the soil near the zone of
active root uptake may reduce surface
N loss and increase plant N use result-
ing in a reduction in N
2
O emissions
(CAST
2004
). Liu et al. (
2006
) found
that injection of liquid urea ammonium
nitrate at a deeper level in soil profi le
(10-15 cm) resulted in 40-70 % lower
emission of N
2
O compared to shallow
injection (5 cm) or surface application.
Hultgreen and Leduc (
2003
) reported
that the N
2
O emissions were reduced
when urea was broadcast in mid-row
rather than side-banded.
(d)
Fertilizer N rate
: The emission of N
2
O
correlates well with fertilizer N rate
(Drury et al.
2008
). Millar et al. (
2010
)
also report that increasing the amount
of N applied to soil resulted in increas-
ing emissions of N
2
O.
Global warming potential in a no-N
treatment of conventional transplanted
rice was 1,419 kg CO
2
e ha
−1
, whereas
GWP under traditional nutrient appli-
cation of NPK was 6,730 kg CO
2
e ha
−1
(Pathak
2010
). The loss in yield was
not signifi cant.
Millar et al. (
2010
) suggested that
the incentive for N
2
O emission reduc-
tion by application of lower nitrogen
application rates within a profi table
range ultimately could be fi nancially
remunerated through a carbon or nutri-
ent market. That would bring economic
and environmental advantages to
compensate for lost productivity ben-
efi ts due to the use of higher nitrogen
application rates.
application.
(b)
Fertilizer N timing
: Synchronous timing
of N fertilizer application with N demand
from plants is an important factor in
determining the emissions of N
2
O from
row crop cultivation. Crop nitrogen
intake capacity is generally low at the
beginning of the growing season,
increasing rapidly during vegetative
growth, and dropping sharply as the crop
nears maturity. Prior to spring crop plant-
ing results in increased soil N with poor
plant N uptake, and therefore, it results in
increased N
2
O emissions. About 30 % of
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