enhancing soc sequestration: myth or reality in africa?

Enhancing SOC sequestration:

myth or reality in Africa?

Rolf Sommerr.sommer@cgiar.org

21 March 2017Rome, Italy

CGIAR Consortium

IFPRI

CIMMYT

CIP

BIOVERSITYINTERNATIONAL

AFRICA RICE IITA

ILRI

ICRAF

ICARDAICRISAT

IWMI

IRRI

CIFORWORLD FISH

ILRI

Placing Sustainability at the Heart of Agricultural Development

From the Symposium webpage:…large losses of soil organic matter …have occurred in soils from various global agroecosystems … where losses ranged between 25–75 % of their original SOC pool. These losses provide an opportunity: the recoverable carbon reserve capacity of the world’s agricultural and degraded soils is estimated to be between 21 to 51 Gt of carbon.

Soil organic carbon sequestration aspirations

How much is recoverable, where, and how long would it take and then last?

Total emissions worldwide

(2012) 51,840 Mt CO2 EQ

=

14.14 Gt C

Source: EcoFys 2016

Losses of SOC in response to Land use (change)

Source:Don et al. 2011 Global Change Biology 17, 1658–1670

Losses of SOC in response to Land use (change) Source: Kinjangi, 2008 (PhD thesis, redrawn)

Forest to cropland (Western Kenya)

0

2

4

6

8

0 30 60 90 120

kg C

/m²/1

0 to

12

cm

Years since native forest conservation

Heavy-texturedNorth Nandi

Heavy-texturedSouth Nandi

Medium-texturedKakamega

Losses of SOC in response to Land use (change)

Forest to permanent pastures (French Guiana Amazonia)

Pasture age (yrs)

Primary forest

Source:Stahl et al. 2016, Global Change Biology doi:10.1111/gcb.13573

Observed SOC changes over time under "improved" land use

In SSA increases were between 0.28 and 0.96 Mg C ha-1 yr-1, but with much greater variation and a significant number of cases with no measurable increase. …CA should be promoted on the basis of these factors and any climate change mitigation regarded as an additional benefit, not a major policy driver for its adoption.

… data from 125 on-farm validation trials across 23 sites in Malawi, Mozambique, Zambia and Zimbabwe. … No consistent differences in bulk density and soil C concentrations were found. … These results … indicate that there is a limited potential for conservation agriculture to significantly increase soil C stocks after up to 7 years of conservation agriculture

Observed SOC changes over time under "improved" land useSource: Sommer et al. submitted for publicationCIAT long-term trials, Western Kenya:

ISFM

17

19

21

23

25

1/Jan/05 1/Jan/08 1/Jan/11 1/Jan/14

SOC

(g/k

g)

FYM+ R+

FYM+ R-

FYM- R+

FYM- R-

LSD

Conservation Agriculture

17

19

21

23

25

1/Jan/05 1/Jan/08 1/Jan/11 1/Jan/14

0T R+

CT R+

CT R-

0T R-

LSDs, same level of tillage

Instead of C-sequestration, we detect losses in both systems!

Observed SOC changes over time under "improved" land use

Source:Don et al. 2011 Global Change Biology 17, 1658–1670

Food for thought• True C-sequestration or only "avoided losses"?• How transferrable are results to other tropical agro-ecosystems?• Importance of land use history!?• Importance of climate, "base" SOC levels / landscapes / clay

content and other soil properties…

SOC

cont

ent

Time

Improved management

Common practice

?

05/03/2023 13

A fundamental shift in global agriculture is required where sustainability constitutes the core strategy for agricultural

development.

Rockström et al. Ambio (2017) 46: 4. doi:10.1007/s13280-016-0793-6

Create the right enabling environment and incentives for change: policy and institutional

New systems and approaches: to motivate behavior change and enable the right responses

Innovation: to tackle new coincidences of problems

Multi-scale delivery that manages trade-offs and build synergies

Collaboration across research and development communities is key!

Moving from Opportunity to Reality: What’s needed?

Photo © G. Smith

• Revisit the individual "best bet" cases (above all grasslands)

• In sub-Saharan Africa food security and sustaining soil fertility comes first, SOC sequestration is a co-benefit only!

• Very different type of cropping systems are required for "carbon" farmers

• Avoid deforestation!

• Avoid draining wetlands and peatlands!

Holistic view

16

Thank you!Photo © A. Notenbaert