Assessing the potential of soil organic carbon sequestration in African soils

Razafimbelo T. M*., Bernoux M., Badiane Ndour N.Y., Sabir M., Aholoukpe H., Amadji G., Balarabe O., Hien E., Koné A., Taisso M., Gallali T., Sall S., Andriamananjara A.,

Razakamanarivo H., Blanchart E., Barthès B., Rakotovao N., Masse D., Albrecht A., Abgassi A., Guibert H., Brossard M.

University of Antananarivo, Laboratoire des RadioIsotopesMadagascar

March, 22nd 2017, Red Room,FAO, Rome, Italy

FAO-UNESCO, 1978

African soil main constraints

FerralsolsAcrisols, Cambisol

Regosols, Arenosols and Podzols

Ferric and Plinthic Luvisol

Fluvisols, Gleysols, Histosols

Low nutrient content, weathered, Al and Mn toxicity, High P-fixation, low nutrients and water retention, susceptible to erosion

Mainly quartz, low water and nutrient holding capacity, wind erosion, poor soils with nutrient leaching

Low nutrient content

Poor to moderate drainage

o Restauration of degraded soils

o Mantaining soil fertility and productivity of agricultural soils

o Limitation or preservation from erosion

o Safety of ecosystemic services provided by soils

Importance of soil carbon sequestration in Africa

Factors controlling soil C sequestration

C INPUTResidues, Mulch,Compost, Amendment,Deposition

C OUTPUTErosionDecompositionLeaching Harvest

Soil carbon

f [Climate, Altitude, Soil properties (texture, mineralogy, mineral reserve), Landscape position]

f [Climate, Altitude, Soil properties (texture, mineralogy, mineral reserve), Topography]

Climate

Altitude

Soil properties

Topography

Oladimeji I. Oladele, Ademola K. Braimoh, 2015

Factors controlling the maximum of soil C sequestration

f [Climate, Altitude, Soil properties (texture, mineralogy, mineral reserve), Topography]

Climate

Altitude

Soil properties

TopographySoil Carbon (Mg/ha)

Soil 0-100 cm

Altit

ude

Rakotonarivo, 2010

SO= South WesternNE= North East

Factors controlling the maximum of soil C sequestration

Factors controlling the maximum of soil C sequestration

f [Climate, Altitude, Soil properties (texture, mineralogy, mineral reserve), Topography]

Climate

Altitude

Soil properties

Topography

Clay + Fine silt (%)

Potential Soil Carbon sequestration (?)

0

20

40

60

80

0 20 40 60 80 100

Vegetação pereneSistema melhoradoCultura permanente

Perennial vegetationImproved systems (+MO)Annual crops (-MO)

Feller and Beare, 1997

Changes in management / practices

Conservation agriculture

Organic fertilizers

Improved Rice practices

Crop rotation/ association

Agroforestry

Potential techniques for soil carbon sequestration

Use or Improvement of existing traditional practices

Zai holes

Improved fallows

Half-moon holes

Potential techniques for soil carbon sequestration

Potential C-sequestration technological options for humid and semi-arid climates

Marks et al.,2009Modified from Lal, 2004

CaSA Network

Soil Carbon for Sustainable Agriculture in Africa

http://reseau-carbone-sol-afrique.org

21 teams, 11 african and european countries

AlgeriaBeninBurkina FasoCameroonCôte d’IvoireMaliMadagascarMorrocoSenegalTunisiaFrance

To replace Soil and Soil Carbon as centers of the sustainability of

Agricultural Systems

C sequestration values ... Conservation agriculture

Photos : Husson O.

Madagascar

% Clay0 20 40 60 80

Gleysoil (Gl)Ferralsol 1 (Fr1)Ferralsol 2 (Fr2)

XHumid tropical climate (2500mm, 19°C)

XX

Subtropical climate (1300mm, 17°C) Ferralsol 3 (Fr3) X

Tropical climate (1200mm, 20°C)Ferralic Cambisol (Cf)

Fluvisol (Fl)X

X

Some C sequestration values ... Conservation agriculture

Razafimbelo et al., 2010

Madagascar

Some C sequestration values ... Conservation agriculture

Razafimbelo et al., 2010

Main crop Legume Inputs DC in kgC/ha/yr

Hum

id tr

opic

alTr

opic

alSu

btro

p

Rice Stylosanthes guy. 0Gl. (20%) 803

Rice Stylosanthes guy. Mineral Gl. (20%) 1816*

Fr1 (45%) Rice Stylosanthes guy. 0 527

Fr2 (30%) Rice Stylosanthes guy. Mineral 0

Maize Vigna unguic. ManureCf (20%) 137

Rice Vigna unguic. ManureFl (15%) 727*

Maize Vigna unguic.Cf (20%) 220Manure Mineral

Rice Vigna unguic.Fl (15%) 600Manure Mineral

SoybeanMaizeFr3(65%) 324Manure Mineral

Roose et al., 1999

• «To wake up early»

• A microcatchment

system• A local supply of organic matter

15

Photos : Hien E.

Zai practicesSome C sequestration values ...

Hien E.

Burkina Faso

Masse et al., 2011

No significant differences in 0-10cm

SOC higher in Zai holes

Effect of duration

More effects in holes than in ”between Holes”

Soil organic carbon changes in zaï systems

Zai practicesSome C sequestration values ... Burkina Faso

Mucuna Pruriens© Joseph G. Mureithi, KARI, Kenya

*

Maize + mucuna vs Maïze + NPK

11 years0-40 cm depthNitisol, sandy loam textured

Mucuna cover effect*

SOC

(Mg.

ha-1)

SOC : Mucuna>Maize+NPK>Maize No fert.

Barthès et al., 2004

Legume useSome C sequestration values ...

DC = 1.35 MgC/ha/yr

Benin

Manure

Organic urban waste

Compost

Manure – Urban organic waste - CompostFerralsol, clayey (40%)8 years0-30cm depth

MgC/ha/yr

Organic fertilizerSome C sequestration values ...

44

46

48

50

SOC 2006SOC 2012

DC1 = 21 ‰ DC2 = 86 ‰ DC3 = 103 ‰

MgC

/ h

aDC1 = 0.158 DC2 = 0.609 DC3 = 0.752

Madagascar

Rafolisy et al., in prep

Agroforestry systemsSome C sequestration values ... Madagascar

0

10

20

30

40

50

60

70

80

90

100

SOC

(Mg.

ha-1)

20

DC = 200 ‰

DC = 0.631 MgC/ha/yr

Cloves + Rice vs Rice Slash and burn

- Simple: less than 200 cloves / ha- Complex : 200 to 400 cloves / ha

24 years0-40 cm depthNitisol, sandy loam textured

* *

*

Agroforestry systems

Some C sequestration values ...

Madagascar

Andriamananjara et al., 2016

21

Conclusions …

• Amount of C sequestration is/will be different according :

systems, but also climate and soil type and topography => main factors controlling carbon sequestration

• Values are affected by great variability. => Need of appropriate method for SOC changes measurement.

• Sustainable practices will be efficient for SOC sequestration by the way that carbon content will be maintained => all increases will be considered as fully positive ...

• Sustainable practices exist, but they have to be adopted by farmers and developed with them…

http://reseau-carbone-sol-afrique.org

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Misaotra tompoko

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