Shifting cultivation maintains but its conversion to mono-cropping decreases soil carbon and nitrogen stocks compared to natural forest in Western Ethiopia
This study was conducted to assess the effects of shifting cultivation and its conversion to mono-cropping on soil organic carbon (SOC) and total nitrogen (STN).
We compared soil pH, texture, bulk density and SOC and STN contents and stocks (0–100 cm) in natural forest (NF), adjacent shifting cultivation (SC) areas (> 100 years old) having three (SC-3Y), five (SC-5Y) and seven (SC-7Y)-year-old fallowing, and 10 year-old mono-cropping field (MCF) converted from shifting cultivation in Western Ethiopia.
There was no significant difference in soil pH in NF and all shifting cultivation areas. However, MCF had lower soil pH compared to SC-3Y and SC-5Y. There was no or very little difference in soil texture and bulk density across the study sites. Shifting cultivation did not affect SOC and STN stocks. However, conversion of shifting cultivation to mono-cropping decreased SOC (45–50% over 10 years; loss of 11.6 ± 0.2 Mg C ha−1 yr.−1) and STN stocks (18–45% over 10 years; loss of 0.6 ± 0.1 Mg N ha−1 yr.−1).
While shifting cultivation maintained SOC and STN, its conversion to mono-cropping decreased them, potentially contributing to global warming and decreasing soil fertility.
KeywordsNatural forest Shifting cultivation Mono-cropping Soil bulk density Soil organic carbon Soil nitrogen
The authors wish to thank the farmers and staff of Gudeya Bila Wereda administrations and sectors, especially Development Agents members of Zengi station who allowed and supported us to conduct the study. We are also grateful to Weyinshet Aferik and Alima Gibiril for assisting in field and laboratory work, Habitamu Taddese for creating a map of the study areas and Zebene Asfaw, Fantaw Yimer, Mulugeta Limenih, Robert Sturtevant, Tracy Beedy, and Demel Teketay for constructive and valuable comments in the earlier manuscript. Financial support was provided by African Forest Forum, MRV project of Wondo Genet College of Forestry and Natural Resources, International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP D1 50.16) Minimizing Farming Impacts on Climate Change by Enhancing Carbon and Nitrogen Capture and Storage in Agro-Ecosystems and Korea International Cooperation Agency (KOICA) project (NO. 2018-004) Strengthening the Capacity to Address Climate Change on Forestry Sector in Ethiopia.
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