Nitrous oxide fluxes from Malagasy agricultural soils
L. Chapuis-Lardy
a,
⁎, A. Metay
a,b, 1
, M. Martinet
b
, M. Rabenarivo
a
, J. Toucet
c
, J.M. Douzet
d
, T. Razafimbelo
e
,
L. Rabeharisoa
e
, J. Rakotoarisoa
f
a
UR SeqBio IRD, c/o LRI, Université d Antananarivo, BP 434, 101 Antananarivo, Madagascar
b
ISTOM, 32 boulevard du Port, 95094 Cergy-Pontoise, Cedex 5, France
c
UR SeqBio IRD, ENSAM, 2 place Viala, bât. 12, 34060 Montpellier Cedex 2, France
d
URP SCRiD CIRAD c/o SRR FOFIFA B.P. 230, Antsirabe, Madagascar
e
LRI-SRA, Laboratoire des Radio-isotopes, Université d'Antananarivo, Route d'Andraisoro, BP 3383, 101 Antananarivo, Madagascar
f
URP SCRiD FOFIFA c/o SRR FOFIFA B.P. 230, Antsirabe, Madagascar
abstract article info
Article history:
Received 17 April 2008
Received in revised form 11 September 2008
Accepted 14 November 2008
Available online 6 December 2008
Keywords:
Tropical soil
No-tillage
N
2
O emissions
Soil mineral N
WFPS
IPCC N
2
O emission factor
In Madagascar, no-tillage practices were developed since the early 90s to prevent soil erosion and improve
soil fertility. Although such practices have helped to restore soil carbon in most cases, the impact on N
2
O
emissions has not been investigated yet. The soil N
2
O fluxes and concentrations were measured during the
growing season of an intercropping maize-soybean on a clayey soil of the Malagasy Highlands. Management
treatments consisted of direct seeding mulch based cropping system (DMC) and traditional hand-ploughing
after the preceding crop residues were harvested (HP), both with low N inputs (55–57 kg N ha
- 1
). No
significant difference in N
2
O emissions was observed between treatments (DMC vs. HP). The N
2
O fluxes
were weakly correlated to soil mineral N contents (R
2
= 0.13; P = 0.03) while no relationship was emphasized
with soil water filled pore space (WFPS). N
2
O concentrations in the soil atmosphere were correlated to
fluxes at the soil surface and to soil WFPS. N
2
O emissions at the soil surface were low ranging from 0 to
8.84 g N-N
2
O ha
- 1
d
- 1
, probably due to the low mineral N content of soil. The cumulative annual N
2
O
emission was 0.26 kg N ha
- 1
for both systems. The corresponding N loss as N
2
O-N was around 0.5% of
applied N. This is in the uncertainty range of IPCC N
2
O emission factor (EF), but the IPCC EF mean estimate
(1%) would overestimate true N
2
O emissions for the soil under evaluation.
© 2008 Elsevier B.V. All rights reserved.
1. Introduction
In the last few centuries, human activities such as industry, trans-
port and agriculture have directly or indirectly contributed to the
increase in concentrations of the major greenhouse gases in the at-
mosphere (Intergovernmental Panel on Climate Change, 2001). Three
of the principal gases of interest are nitrous oxide (N
2
O), carbon
dioxide (CO
2
) and methane (CH
4
). Both N
2
O and CO
2
are emitted from
the soil, whereas CH
4
is normally oxidized by aerobic soils, making
them sinks for atmospheric CH
4
(Hütsch, 2001). Agricultural soils
contribute about 60% of the global anthropogenic N
2
O flux, which is
equivalent to a global warming potential of 2.8 Gt CO
2
eq yr
- 1
(In-
tergovernmental Panel on Climate Change, 2007). N
2
O is produced
during numerous nitrogen transformations in soils (Robertson and
Tiedje, 1987), but on most occasions denitrification and nitrification
are the main sources. A synthesis of results on N oxide (N
2
O+NO)
fluxes from natural or unfertilized systems in the humid tropics
indicates that the fluxes are positively correlated with some measure
of N availability (soil inorganic N) and with soil water-filled pore space
(WFPS) (Granli and Bøckman, 1995; Verchot et al., 1999; Davidson et al.,
2000). Theory suggests that the relationship between N inputs and N
2
O
flux may be more complex, and in particular that N
2
O flux may exhibit a
threshold response to N inputs and soil biota (Erickson et al., 2001).
Nitrogen often limits both plant growth and N
2
O production in
terrestrial ecosystems, so that where plants are competing with
microbes for soil N, N
2
O production will be suppressed until plant N
demands have been fully satisfied. The IPCC protocols calculate
agriculture's contribution to atmospheric N
2
O loading as a simple
percentage of total N inputs: 1% of added N is estimated to be lost as
N
2
O based on fluxes from fertilized vs. unfertilized field plots
(Intergovernmental Panel on Climate Change, 2006). While fertilization
rate may be low in tropical countries, responses of N
2
O fluxes to low
levels of N inputs are unknown for many tropical soils. The number of
published measurements of N
2
O emissions from soils is increasing
steadily at mid-latitudes (Europe and North America) but there are still
few flux data from tropical and sub-tropical regions (Bouwman et al.,
2002; Stehfest and Bouwman, 2006). The representation of tropical
Geoderma 148 (2009) 421–427
⁎ Corresponding author.
E-mail address: lydie.lardy@ird.fr (L. Chapuis-Lardy).
1
Current affiliation: SupAgro, UMR SYSTEM (INRA-CIRAD-SupAgro), 2 place Viala,
Bât. 27, 34060 Montpellier Cedex 2, France.
0016-7061/$ – see front matter © 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.geoderma.2008.11.015
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