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Soil Carbon Sequestration Potentials of Semi-arid soils at the CCAFS Site in Wote, Makueni County


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Presentation of Fredrick Wandera at 2013 workshop of the Climate Food and Farming Network:

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Soil Carbon Sequestration Potentials of Semi-arid soils at the CCAFS Site in Wote, Makueni County

  1. 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. 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. 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. 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. 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. 6. Wote CCAFS site
  7. 7. Rehabilitated bushland
  8. 8. Degraded bushland by overgrazing
  9. 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. 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. 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.