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Tropentag 2023, September 20 - 22, Berlin, Germany

"Competing pathways for equitable food systems transformation: trade-offs and synergies."


Storage and distribution of soil organic carbon, total nitrogen and CO2 emissions in semi-arid soils

Chukwuebuka Christopher Okolo1, Girmay Gebresamuel2, Amanuel Zenebe2, Mitiku Haile2, Jephter Ebuka Orji3, Chinyere Blessing Okebalama4, Chinedu Emmanuel Eze5, Emmanuel Eze6, Peter Ndubuisi Eze7

1Jimma University, Natural Resources Management, Ethiopia
2Mekelle University, Dept. of Land Res. Manag. and Environ. Protection, Ethiopia
3Alex Ekwueme Federal University Ndufu-Alike, Dept. of Agriculture, Nigeria
4University of Nigeria, Dept. of Soil Science, Nigeria
5Michael Okpara University of Agriculture, Dept. of Agronomy, Nigeria
6University of Education Heidelberg, Dept. of Geography ‑ Research Group for Earth Observation (rgeo), UNESCO Chair On World Heritage & Biosphere Reserve Observation and Education, Germany
7Botswana International University of Science & Technology, Dept. of Earth & Environmental Science , Botswana


Abstract


This study aims to investigate soil organic carbon (SOC) and total nitrogen (TN) contents and stocks, and CO2 emissions in croplands, grazing lands, exclosures and forest lands of semi-arid Ethiopia. Sampling was done at 0-30, 30-60 and 60-90 cm soil depth and concentration and stocks of SOC, TN and selected soil properties were determined using routine laboratory procedures. There were variations in distribution of SOC and TN stock over 90 cm depth across land use types and locations, decreasing from topsoils to subsoil, with average values ranging from 48.68 Mg C ha-1 and 4.80 Mg N ha-1 in Hugumburda cropland to 303.53 Mg C ha-1 and 24.99 Mg N ha-1 in Desa’a forest respectively. Forest sequestered significant higher SOC and TN stock, decreasing with depth, compared with other land uses. In Desa'a and Hugumburda, the conversion of forest to cropland resulted in a total loss of SOC stock of 9.04 Mg C ha-1 and 2.05 Mg C ha-1, respectively, and an increase in CO2 emission of 33.16 Mg C ha-1 and 7 .52 Mg C ha-1 yr-1, respectively. The establishment of 10-year (Geregera) and 6-year (Haikihelet) exclosures on degraded grazing land increased SOC stock by 13% and 37% 1 respectively. Clay content and precipitation partly modulated SOC distribution, with high SOC content recorded in soils with high clay content and precipitation. Exclosure establishment on degraded ecosystem has shown to be a sustainable restoration pathway with significant improvement in soil properties and C sequestration. Loss of SOC stocks associated with land use conversion can be reversed in degraded croplands with the introduction of sustainable soil management practices (residue retention, integrated soil nutrient management, reduced tillage impact) in view of mitigating climate change impact.


Keywords: Cambisols, land use change, soil organic carbon sequestration, soil processes, vertisols


Contact Address: Chukwuebuka Christopher Okolo, Jimma University, Natural Resources Management, Jimma, Ethiopia, e-mail: okolochukwuebuka@gmail.com


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