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N2O EMISSIONS FROM A MAIZE CROP IN SOUTHERN
ITALY
S. Ranucci1,2, L. Ottaiano1,3, T. Bertolini1, P. Di Tommasi1, M. Oliva1, L. Vitale1, A. Forte2,
V. Magliulo1, A. Fierro 2
1
CNR- ISAFoM, Via C. Patacca, 85 80056, Ercolano(Na); , [email protected]
Dipartimento di Biologia Strutturale e Funzionale, Università Degli Studi di NapoliFederico II, via Cinthia,
80126, Napoli.
3
Dipartimento di Ingegneria Agraria e Agronomia del territorio, Università degli Studi di Napoli Federico II,
via Università 100, Portici (Na).
2
Introduction
Agricultural practices contribute to the atmospheric N2O increase being the major source of
this gas and accounting for 24% of the global annual emission (IPCC 2007).
Soil nitrification and denitrification are the microbial processes liable for the production of
N2O, which also depends on soil characteristics and management. These processes are
controlled by different factors, such as soil moisture and soil temperature (Han Jian-gang et
al, 2007). Addition of N to the soil via mineral fertilisers, animal manure, crop residues,
sewage sludge generally increases N2O evolution (Boeckx et al, 2001).
The IPCC (2007) provides a description of the methods and equation to be adopted for the
inventory of nitrous oxide emissions from managed soils.
Few experiments aimed at evaluating N2O exchange from cropland in Mediterranean climate
showed that peak emissions follows N application and irrigation events (Lee et al, 2008).
The aim of this study was to investigate N2O evolution under different agronomic
management in a Mediterranean area.
Materials and Methods
The experimental field (18ha) is located in the Piana del Sele (Borgo Cioffi, Eboli; Salerno)
about 25 km from Salerno (4486080 N, 496470 E). The permanent study site is part of
CarboEurope and NitroEurope networks and it is located in a typical Mediterranean area,
with a climate characterized by dry summers and mild rainy winters.
N2O fluxes have been monitored during two subsequent growing season of Zea mays L.
(2007 and 2008) under intensive and reduced management. Weekly measurements were
conducted by means of 8 static manual chambers placed on a transect along the main wind
direction. Samples were collected in vials at regular intervals following chamber closure and
analysed by a gas chromatograph equipped with an ECD detector.
Results
During the first year (2007) nitrous oxide peaked 30 days after nitrogen fertilizer spreading
(Fig.1-a), while during the second year (2008) the peak was anticipated to about 15 days
following fertilization (Fig.1-b). This time delay likely probably due to the nitrification
inhibitor (DMPP) added to the fertilizer in 2007.
For both years, soon after each irrigation event N2O evolution increased, while under water
stress condition a consistent drop in measured fluxes could be detected. Cumulative N2O
fluxes (Fig.2) evidence that management played an important role. In 2007 we observed
cumulative fluxes of 2.15 N2O-N, kg-1 ha-1 while in 2008 the emissions were about 68%
lower, with fluxes of 0.69 N2O-N kg-1 ha-1. This difference was likely due to different crop
management – since less intensive soil cultivation was made in the second year - and the
lower irrigation gifts. Mosier et al (2006) reported that tillage has an effect on N2O emission,
since intensive tillage determines a flux increase linearly correlated with the amount of N
fertilizer added. The different crop sequence (fennel-corn in 2007 and grass-corn in 2008),
might also have played a role. The emission factor (EF1, (IPCC, 2006), that refers to the
amount of N2O emitted from the various synthetic and organic N applications to soils,
confirm the difference between the two years of study, being equal to 0.87% in 2007 and
0.26% in 2008, both consistently lower than the reference IPCC value of 1%.
Fig. 1
Fig. 2
300
a
60
N2O
2.5
200
40
150
30
100
20
50
10
0
0
250
2007
2008
1.5
1
0.5
0
130
150
170
190
210
230
250
DOY
40
b
N2O
R ain+Ir r .
Fertilization
2
kg N2O-N/ha
50
Rain+Irrigation(mm)
m g N2O-N/m2h
R ain+Ir r .
250
35
mg N2O-N/m2h
30
25
150
20
100
15
10
50
Rain+Irrigation(mm)
200
Fig. 1 N2O fluxes from soil(left) rain and irrigation
(right) at Borgo Cioffi site during maize crop season
2007(a) and 2008(b).
Fig. 2 Cumulative N2O fluxes during 2007 and
2008. The fertilization events, at sowing and sidedressed, are represented by arrows.
5
0
125
145
165
185
205
225
0
245
DOY
Conclusions
Soil management is key factor in the balance of N2O. This study shows that a reduced tillage
and drier water regime can play a positive role in the mitigation of the N 2O emissions from
the soil. The high variability of the EF should be further investigated by means of high
frequency measurements (i.e. real time autochambers), which may also contribute to quantify
the role played by other biophysical factor.
References
Boeckx et al, 2001. Estimates of N2O and CH4 fluxes from agricultural lands in various regions in Europe.
Borbe et al. 2009. Soil greenhouse gas fluxes and global warming potential in four high-yealding maize
systems. Global Change Biology, 13:1972-1988.
IPCC, 2006. 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Prepared by the National
Greenhouse Gas Inventories Programme, Eggleston H.S., Buendia L., Miwa K., Ngara T. and Tanabe K. (eds).
Published: IGES, Japan.
IPCC, 2007. Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change [B. Metz, O.R. Davidson, P.R. Bosch, R. Dave,
Lee et al. 2009.Tillage and seasonal emissions of CO2, andN2O and NO across a seed bed and at the field scale
in a Mediterranean climate. Agriculture, Ecosystems and environments, 129: 378-390
Mosier et al. 2006. Net Global Warming Potential and Greenhouse Gas Intensity in Irrigated Cropping Systems
in Northeastern Colorado. Published online July 6, 2006