Management options for soil carbon

sequestration in Nordic croplands

Thomas Kätterer Swedish University of Agricultural Sciences

Definintion of Soil Carbon Sequestration (SCS)

Net transfer of C from atmosphere to soil at the global scale

• Only changes in present management will result in SCS

• Local net accumulation of soil C (e.g. due to manure application) does not necessarily lead to SCS

• SCS is not necessarily the best mitigation strategy - alternative use (bio-energi) must be valuated

• Changes in management practices that reduce CO2 emissions from soils compared to status quo will contribute to mitigation even if this will not lead to SCS

Crop harvested Crop residues Rhizodeposition

Decomposition

Soil C

Products

Soil C

Extensified agriculture

Intensified agriculture

Biofuel

Forest Forest

Land use options C cycling in soil-plant-systems

Carbon cycling in agricultural systems is driven by management decisions

Plant species Management

Residues Root systems

Manure treatment Waste treatment Bioenergi residues (biochar)

Tillage Water managment

NPP

Kätterer et al., 2012. Acta Agric. Scand.

Feed-back

Land use change and soil C change in temperate climates

Poeplau et al, 2011. GCB

Case study: Land use change - effects on soil C

40

50

60

70

80

90

1930 1950 1970 1990 2010

Tops

oil C

(Mg

ha-1

) Grassland Arable until 1970, grassland thereafter Arable since1860

3 adjacent fields, Kungsängen, Sweden

Kätterer et al. 2008. Nutr. Cycl. Agroecosys. 81:145–155

ΔC=0.1 Mg C ha-1 yr-1

ΔC=0.4 Mg C ha-1 yr-1

ΔC=0.2 Mg C ha-1 yr-1

ΔC=30% 75 yrs-1

Soil C sequestration is finite, reversible and dependent on climate

0

10

20

30

40

50

60

70

0 50 100 150 200

Soil

C de

rived

from

man

ure

(Mg

ha-1

)

Years since 1852

Model Hoosfield

Data Hoosfield

Model Nigeria

Data from Johnston et al., 2009. Adv. Agron. 101

90% of the effect will be realised within • 100 years in Nordic climates • 20 years under tropical conditions

C sequestration - less effective in warm/moist climates

Soil

carb

on s

tock

Time

Grassland New management

C sequestration

Cropland 35 t manure ha-1 yr-1

Temporal grassland: Frequency of annual vs. perennial crops affecting the soil C balance

2

2.5

3

3.5

4

4.5

5

1955 1960 1965 1970 1975 1980 1985 1990

Soil

orga

nic

C%

(0-2

0 cm

)

3 LTEs in Northern Sweden 6 year rotations: ley and annual crops

5 yrs ley 3 yrs ley 2 yrs ley 1 yr ley

Bolinder et al. 2010, AGEE 38: 335–342; Ericson & Mattsson, 2000

∆SOC: 0.4 – 0.8 Mg ha-1 yr-1

Annual vs. perennial crops and fertilization LTE in Estonia 1965-1997 (established on a poor subsoil)

Kätterer et al., 2012. Acta Agric. Scand. Original data and photo: Viiralt, 1998

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 1000 2000 3000 4000 5000

∆SO

C(M

g C

ha-1

yr-1)

Mean dry matter yield (kg ha-1 yr-1)

Fallow

Barley

Grass

Clover

Grass/clover

Grass/clover+faeces

Grass/clover+faeces+GM

Site Country Duration Depth ΔC a Reference (years) (cm) (Mg ha-1

yr-1)

Saint-Lambert Canada 10 20 0.8 Quenum et al. (2004) Elora Canada 20 40 0.33 Yang and Kay (2001) Woodslee Canada 35 70 1.1 VandenBygaart et al. (2003) Erika I Estonia 40 60 0.27 Reintam (2007) Erika II b Estonia 28 20 0.66 Viiralt (1998) Ås Norway 30 20 0.40 Uhlen (1991) Röbäck I c Sweden 30 25 0.40 Bolinder et al. (2010) Offer c Sweden 52 25 0.36 Bolinder et al. (2010) Ås c Sweden 30 25 0.87 Bolinder et al. (2010) Röbäck II Sweden 27 20 0.54 Unpublished data Lanna Sweden 27 20 0.42 Unpublished data Lönnstorp Sweden 27 20 0.60 Unpublished data Säby Sweden 37 20 0.45 Unpublished data Rothamsted UK 36 23 0.3 Johnston et al. (2009) Woburn UK 58 25 0.3 Johnston et al. (2009) a Only one or two figures are quoted indicating the uncertainty of the calculations b Difference between barley receiving no N fertilizer and grass/clover + faeces + green manure c Farmyard manure was applied in ley rotations but not in arable cropping system

Changes in SOC stocks in ley-arable rotations (some with manure) as compared to continuous annual cereal cropping in 15 long-term experiments (≥ 10 years)

Median ∆SOC = 0.4 Mg ha-1 yr-1

y = -0.009x + 0.7204 R² = 0.3072

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 10 20 30 40 50 60 70

∆SO

C (M

g C

ha-1

yr-1

20c

m-1

dep

th)

Duriation (years)

SOC affected by rotations with ley vs. annual cropping

Kätterer et al. (EGF 2013)

Photo: Gunnar Torstensson. Timothy and English Ryegrass

Annual cropping mimicking perennial systems Cover crops and shelterbelts for C sequestration,

reduced leaching and erosion

Average change rate: 0.32±0.08 Mg ha-1 yr-1

Huge scatter was hardly explicable by environmental parameters (High share of short-term studies) RothC steady state for “average cropland” predicted a total SOC stock change of 16.7±1.5 Mg ha-1

Extrapolation to 50% of global cropland area would compensate for 8% of GHG emissions from agriculture.

Poeplau et al., submitted

Cover crops: Meta-analysis comprising 37 sites and 139 plots

Ultuna frame trial since 1956

The same amount of carbon is added every second year in different organic amendments +/- mineral N fertilizers 15 treatments, 4 replicates, 60 plots Clay loam, Eutric Cambisol Kätterer et al., 2011. AGEE 141: 184-192.

Soil archive

0

1

2

3

4

5

1950 1960 1970 1980 1990 2000 2010 2020

Soil

C %

(0-2

0cm

)

M

I

O

K

J

N

G

L

H

F

E

C

D

B

A

Changes in topsoil C over time in the Ultuna frame trial

Bare fallow Control

Calcium nitrate

Straw

Straw + N

Green manure

Farmyard manure

Peat

Saw dust

Sewage sludge FYM + P

Saw dust + N

Ammonium sulfate

Calcium cyanamid

Peat + N

Kätterer et al. (2011) Agric. Ecosys. Environ. 141, 184-192

Effect of organic amendments and N fertilization on soil C

• C retention differs considerably between C sources

• Retention of root-derived C is 2.3 times higher than for above-ground residues

• N fertilization results in higher root production and consequently in higher soil C stocks

Kätterer et al., AGEE 2011, Kätterer et al. ACTA 2012

Ultuna, Sweden, after 53 years C mass k*C ΣHj*Ij

SOC in Swedish soil fertility experiments

0

0.5

1

1.5

2

2.5

3

Tops

oil C

%

N0N3

Topsoil C after 50 years (only annual crops, no manure)

C stocks in Ap-horizon increased by about 1 kg C for each kg N applied

Kätterer et al., 2012. Acta Agric. Scand.

No N

High N

Significant SOC changes in upper subsoil (to 40 cm) in long-term experiments

About 30% of SOC accumulation occurred below maximum ploughing depth (25 cm)

Kirchmann et al., 2013; Kätterer et al., 2014;

50 years 30 years

Results from 16 long-term experiments (4 series): Each kg of N applied resulted in 1.1 kg C extra in the topsoil (0-20 cm)

• Additional SOC change in subsoil: About 0.5 kg C kg-1 N • Total SOC change: 1.6 Mg C kg-1 N (6 kg CO2-equ.)

Stabilization of crop residue C is controlled by soil texture and nutrient availability

• 18 pairs of straw incorporated vs. removed • 7 long-term field experiments 27-58 years Poeplau et al. (Geoderma, in press)

Manzoni et al. 2008 Science 321, 684-686 N Kirkby et al. 2014 SBB 68, 402-409

Increasing clay content

0

0.5

1

1.5

2

2.5

1940 1960 1980 2000 2020

SOC%

0-2

0cm

Ultuna frame trial

y = 0.0038x - 6.52 R² = 0.24

60%

70%

80%

90%

100%

110%

120%

130%

140%

1950 1960 1970 1980 1990 2000 2010 2020

Rela

tive

yiel

d Yield increase due to straw addition

C sequestration is not always the best mitigation option

’Green’ N fertilizer (Ahlgren et al. 2009. Biores Tech 99, 8034−8041) • Energy from 1 ha winter wheat straw can be used to produce

1.6 Mg N fertilizer. • Energy from 1 ha salix would yield 3.9 Mg N fertilizer

Pyrolysis of harvest residues – gas and biochar Soil fertility has to be considered Optimal mitigation options may differ between regions

Straw added Straw removed

Reduced tillage for C sequestration?

Etana, et al., 2013. SCS

Different stratification of SOC but no differences in SOC stocks between mouldboard ploughing and shallow tillage after 35 years at Ultuna, Sweden (1974-2009)

Effects are not conclusive due to interactions with • Crop yields • Climate

Previous estimates (up to 0.8 Mg ha-1 yr-1; Freibauer et al., 2004) were too optimistic Main benefits: • Less fuel and labor • Erosion control • Moisture preservation • But benefits may partly be offset by

higher N2O-emissions

Reduced tillage for C sequestration?

Virto et al. 2012 Biogeochem. 108:17-26

Ogle et al. 2012. AGEE 149, 37– 49

Sustainable intensification

Biochar filter for P and pesticids

Topsoil

Subsoil

Subsoil losening and injection of organic material for improved soil structure, root extension and more efficient nutrient aquisition.

Sedimentation Drainage

Increasing efficiency through crop-specific placement of fertilizer

Long-term experiments are essential for model calibration and validation, e.g. for national GHG reporting

-1,5

-1

-0,5

0

0,5

M to

n CO

2

Mineral soils

0.5 -0.5

• Meteorological data • Agricultural statistics • Soil monitoring • Soil database • Long-term field exp.

(calibration)

ICBM_region model

Andrén & Kätterer 2008 Nutr. Cycl. Agroecosys. 81:129–144 Lokupitiya et al. 2012 Biogeochem. 107:207–225 Borgen et al., 2012 GHG Meas. Managem. 2:1, 5-21

Tg CO2 1990 2000 2012

ICBM applications

On-going work: Model validation using data from 3 inventories (1990-2014)

Preliminary result: Slight increases in SOC in most regions On-goin work: Idendification of drivers for observed change

Regions (län)

Soil inventories 1990th, 2000th, 2010th

Implementing ICBM at farm scale

Kröbel et al., 2014

Conclusions: Strategies för C sequestration • Perennial crops instead of annuals: about 0.4 Mg C ha-1 yr-1

• Catch crop/intercropping: about 0.3 Mg C ha-1 yr-1 • Recycling of products that are not recycled today • Plant breeding for higher root/shoot ratios? Retention of root-

C is higher than that of above-ground residues. • Subsoil managment for increasing yields and SCS • Long-term field experiments are essential for quantifying SOC

changes (model calibration and validation) • Stabilization of crop residue-C is controlled by soil texture and

N availability • 1-2 kg SOC for each kg N applied given that there is a yield gap • Extensification of production will lead to decreasing SOC and

further deforestation

Crop harvested Crop residues Rhizodeposition

Decomposition

Soil C

Products

Soil C

Extensified agriculture

Intensified agriculture

Biofuel

Forest Forest

Land use options C cycling in soil-plant-systems

NPP is the main driver for C sequestration and for prevention of further deforestation and land degradation

Plant species Management

Residues Root systems

Manure treatment Waste treatment Bioenergi residues

Tillage Water managment

NPP

Kätterer et al., 2012. Acta Agric. Scand.

Feed-back

Thank’s for your attention!

Foto: M Gerentz

Photo: G. Börjesson