PhD research presentation at the workshop of the Climate Food and Farming Network, Dec. 2-4 at Aarhus University, Foulum. The Climate Food and Farming Network is an initiative of Copenhagen U., Aarhus U., and the CGIAR Research Program on Climate Change, Agriculture and Food Security.

1. Soil Carbon Sequestration Potentials of Semiarid soils at the CCAFS Site in Wote, Makueni
County
Presented by Fredrick M. Wandera- University of Eldoret
Supervisors;
1.
Prof. (Dr.) Klaus Butterbach-Bahl
2.
Pro. Wilson Ng’etich
3.
Dr. David Pelster

2. Introduction
Carbon sequestration potential is the process of estimating the
capacity of a system to capture and store carbon dioxide for a
long time , in order to reduce its contribution to global
warming
 Soils are the largest carbon reservoir of the terrestrial carbon
cycle. The total C in terrestrial ecosystem is approximately
3170 gigatons(GT), with nearly 80%(2500GT) is found in soil(Lal
2008).
 Soil carbon is either organic(1550GT) or inorganic(950GT). The
soil carbon pool is approximately 3.1 times larger than the
atmospheric pool of 800GT(Oelkers & Cole 2008). Only the
ocean has a larger pool of about 38,400GT of carbon, mostly in
inorganic forms( Houghton 2007).


3. Soil Carbon Sequestration in Drylands

47 percent of the surface of the earth can be classified as dryland
(UNEP, 1992) which are considered to be areas where average rainfall
is less than the potential moisture losses through evaporation and
transpiration.

In semi arid lands, soil carbon sequestration is low due to low primary
production, high land degradation, land use change, high demand for
grazing land and poor land management techniques

Drylands exhibit chemical degradation of the soil; loss of vegetation
cover, loss of topsoil infiltration capacity, reduction in soil water
storage, loss of SOM, fertility and structure, loss of natural
regeneration; and lowering of the water table

Globally, the potential to sequester carbon by improving grassland
practices or rehabilitating degraded grasslands is substantial – of the
same order as that of agricultural and forestry sequestration( FA0

4. Objectives





To determine soil carbon sequestration potentials in semiarid soils
To provide an inventory of the soil organic carbon stocks
for semi- arid grasslands under different land use/ land
use change
To show the relationship between land use/land use
change and soil carbon stocks depletion
To estimate soil carbon recovery rates through bush land
rehabilitation
To provide data and information on the capacity of semi
arid to sequester carbon

5. Methodology

The study site measures 10 by 10 square kilometers. It lies
in the lower eastern region of Kenya characterized by dry
climate. It has bimodal rainfall pattern with annual
rainfall of 250-500mm. Rainfall is uncertain in the region
with a 66% rainfall reliability ranging between 150- 200
mm and 100-150 mm.

The main soil types Ferralsols, Acrisols, Luvisols and
Arenosols(FAO 2006) characterized by low nutrient levels,
low water holding capacities, easily eroded, low in SOM
and are mostly loose friable sands.

The major vegetation is grasslands consisting of shrubs,
scattered tree species, grass species and cultivated crops(

6. Wote CCAFS
site

7. Rehabilitated bushland

8. Degraded bushland by overgrazing

9. Cont.’

Major land use are peasant mixed livestock and crop production on
small size of land of 2.5 acres with no use of fertilizer, use organic
manure, low soil moisture, crop failure, charcoal burning

Analysis of Satellite imagery and aerial photographs of the study site
to show land use change over time and space

Stratification of land use, land use change and rehabilitated
grasslands( IPCC 2006)

Soil sampling will be done to a depth of 1 meter below the soil at
depths of 0-30cm, 30-60cm and 60-100cm using the Eijkelkamp soil
sampling kit.

Analysis of bulk density, Total carbon, SOM, SOM aggregates fractions,
SOM isotopic signatures and SOC at ILRI and KIT-IFU Laboratories

10. Outcomes

To provide information that may enhance soil
carbon sequestration with changes in land use and
soil management.

To help design mitigation and adaptation
strategies that will reduce emission of greenhouse
gases, particularly CO2

To write a MSc thesis and upgrade it into a PhD

To use data obtained from the study to publish 4
papers in international soil science journals

11. Conclusion

The intension of this study is to generate information on
the carbon sequestration potential of dry lands ( semi arid
lands). This information should persuade researchers,
donors and governments to evaluate dry lands as
alternatives sinks for carbon dioxide in addition to
forestry and agro-forestry which have received major
attention.