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  • Management options for soil carbon

    sequestration in Nordic croplands

    Thomas Ktterer 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

    Ktterer 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, Kungsngen, Sweden

    Ktterer et al. 2008. Nutr. Cycl. Agroecosys. 81:145155

    C=0.1 Mg C ha-1 yr-1

    C=0.4 Mg C ha-1 yr-1

    C=0.2 Mg C ha-1 yr-1

    C=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: 335342; 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)

    Ktterer 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 C 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) s Norway 30 20 0.40 Uhlen (1991) Rbck I c Sweden 30 25 0.40 Bolinder et al. (2010) Offer c Sweden 52 25 0.36 Bolinder et al. (2010) s c Sweden 30 25 0.87 Bolinder et al. (2010) Rbck II Sweden 27 20 0.54 Unpublished data Lanna Sweden 27 20 0.42 Unpublished data Lnnstorp Sweden 27 20 0.60 Unpublished data Sby 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 R = 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

    Ktterer 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: 0.320.08 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 16.71.5 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 Ktterer 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

    Ktterer 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

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

    Ultuna, Sweden, after 53 years C mass k*C Hj*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

    Ktterer 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; Ktterer 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 R = 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, 80348041) 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 h

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