Download Management options for soil carbon sequestration in Nordic

1/5/2017
Management options for soil carbon sequestration in Nordic agroecosystems
Thomas Kätterer
Swedish University of Agricultural Sciences, SLU
The soil plays a central role in the global carbon cycle (Pg C; billion tons)
750 +4.4 per year
550
1 500
(1m depth) 40 000
Sediments, coal, gas, oil
Kätterer, 1998
2
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Antropogenic CO2 emissions and sinks (2005‐2014)
3,4 Pg/yr
16 Pg/yr
Deforestation
33 Pg/yr
+
44%
10,9 Pg/yr
C sequestration
30%
9,5 Pg/yr
26%
Source: CDIAC; NOAA‐ESRL; Houghton et al 2012; Giglio et al 2013; Le Quéré et al 2015; Global Carbon Budget 2015
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Soil carbon sequestration
Kätterer, 2011
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Time scale of C sequestration
Long‐term agricultural field experiments – indispensable for quantifying management effects on soil properties
• About 50 experiments > 20 years
• The oldest were started 1936
• Focus on organic amendments, fertilization, cropping systems, crop rotations, tillage
• Valuable for model calibration/validation
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Soil C % (0-20cm)
Ultuna frame trial
Example: Ultuna frame trial
4
M
I
O
K
J
3
N
G
L
2
H
F
1
E
C
0
1955
D
B
1975
1995
2015A
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Soil inventories:
I (1988‐97), II (2001‐07), III (2010‐17)
C% in soil 2015
2 3 4
Swedish inventories of agricultural soils
2.4 Mton
CO2/year
Rel. Increase ley area
Sweden average
3 4 C% in soil 1995
30% 40% 50%
Ley % of agr. area
Kol % i marken
C% in topsoil
2,4 2,5 2,6 2,7
2
Rel. Increase horse poplulation
1980 2000 2020 Poeplau et al. 2015 Biogeosciences 12: 3241–3251
Swedish case study: Land use change effects on soil C
Topsoil C (Mg ha-1)
3 adjacent fields, Kungsängen, Sweden
Grassland
ΔC= n.s.
90
80
70
60
ΔC=30% 75 yrs‐1
ΔC=0.4 Mg C ha‐1 yr‐1
Arable
since1860
50
40
1930
ΔC= n.s.
1950
1970
1990
Arable 18601970,
grassland
thereafter
2010
Kätterer et al. 2008. Nutr. Cycl. Agroecosys. 81:145–155 4
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Frequency of annual crops vs. perennial leys affecting SOC
(Bolinder et al. 2010, AGEE 38: 335–342; Bolinder et al., 2012, Can J. Soil Sci. 92: 821‐833) 3 LTEs in Northern Sweden
6 year rotations: ley and annual crops
Soil organic C% (0-20 cm)
5
5 yrs ley
3 yrs ley
2 yrs ley
1 yr ley
4,5
4
3,5
3
2,5
∆SOC: 0.4 – 0.8 Mg ha‐1 yr‐1
2
1955
1960
1965
1970
1975
1980
1985
1990
Cover crops and strips with perennial vegetation for reduced N leaching and for C sequestration
Results from long‐term experiments: 1.1 Mg CO2 ha‐1 yr‐1 with cover crop
(Poeplau et al., 2015. Geoderma Regional 4: 126–133)
Photo: Gunnar Torstensson.
Timothy and English Ryegrass
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Effect of N fertilization on soil carbon
Topsoil C%
3
2,5
Topsoil C after 50 years, Soil fertility exp., 2
N0
1,5
1
N3
0,5
0
16 long‐term experiments >40 years
In average 1 kg higher SOC for each kg N fertilizer
Kätterer et al., 2012. Acta Agric. Scand. 62, 181‐198
Low yields (e.g. organic farming)
‐> deforestation ‐> lower soil carbon stocks
Arable land is a limiting
resource
Intensive production
Extensive production
Bioeconomy
Forest/Nature
Soil C
Forest/Nature
Soil C
Sustainable intensification is mandatory for providing
food for a growing human population
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Soil conservation in Iceland
Restauration of degraded grassland resulted in soil sequestration of 0.6 Mg C /ha /year in average during 50 years (Arnalds et al., 2000)
Most drained organic soils are emitting GHG but they are fertile. If set aside – food has to be produced somehwere else
Örjan Berglund
2 m subsidence during 90 years (Bälinge, Sweden) 7
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Drained organic soils
800
Cultivated
Set aside
600
CO2
400
200
2
-2
FCO (g m )
Cultivated
0
-200
-400
-600
jan
jul
jan
2012
jul
Set aside
jul
jan
2014
jul
jan
2015
jul
jan
2016
CH4 uptake > 200 kg CO2eq yr‐1
0
-5
-2
FCH (g m )
jan
2013
4
-10
-15
-20
-25
maj
sep
jan
maj
sep
jan
maj
2012 - 2014
Reduced tillage or deep ploughing?
In average no effect of reduced tillage on SOC in 25 experiments > 10 years (Meurer et al., manuscript)
RT‐CT (0‐30 cm); n=25
Δ SOC (Mg ha‐1)
10
5
0
1
3
5
7
9
11 13 15 17 19 21 23 25
‐5
‐10
Effect probably climate dependent
Deep ploughing (1m deep) in Germany • 42% higher SOC stocks after 45 years
• 15% lower C% in topsoil – potential for more sequestration.
Alcantara et al., GCB 2016
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Future prospects: Plant breeding – perennial wheat
Jerry Glover (Land Institute, Kansas) Roots of wheat and “intermediate wheatgrass”
Glover et al. 2010. AGEE 137: 3–12
Summary:
It is possible to increase soil carbon stocks
• Plant cover as long as possible (perennials, cover crops, agroforestry etc.)
• Reclamation of eroded land
• High production per area increases soil carbon and reduces deforestation
• Avoid drainage of organic soils
• Plant breeding – perennial wheat?
• The IPCC‐method accounts only for emissions. The huge fixation of CO2 accomplished by agriculture should also be considered.
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Agriculture in the North
• Few alternatives to dairy and meat production in northern parts of Scandinavia and Finland
• High standards for animal welfare, EU:s lowest use of
antibiotics
• More moose than dairy cows in Sweden
• Sweden is importing > 50% of its food (often produced
with higher climate footprint) • Agricultural area is decreasing – emissions occur
somewhere else
• Food security is becoming a political issue
• Semi‐natural grassland are hotspots of biodiversity
• Good natural conditions for expansion of agriculture
and soil carbon storage
Thanks for your attention!
Photo: G. Börjesson
Foto: M Gerentz
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