Low black carbon concentration in agricultural soils of central and northern Ethiopia

Markku Yli-Halla; Karoliina Rimhanen; Johanna Muurinen; Janne Kaseva; Helena Kahiluoto

doi:10.1016/j.scitotenv.2018.02.284

Low black carbon concentration in agricultural soils of central and northern Ethiopia

Sci Total Environ. 2018 Aug 1:631-632:1-6. doi: 10.1016/j.scitotenv.2018.02.284. Epub 2018 Mar 5.

Authors

Markku Yli-Halla¹, Karoliina Rimhanen², Johanna Muurinen³, Janne Kaseva⁴, Helena Kahiluoto⁵

Affiliations

¹ Environmental Soil Science, Faculty of Agriculture and Forestry, P.O. Box 56, 00014 University of Helsinki, Finland. Electronic address: Markku.Yli-Halla@helsinki.fi.
² Natural Resources Institute Finland, Latokartanonkaari 9, 00790 Helsinki, Finland.
³ Environmental Soil Science, Faculty of Agriculture and Forestry, P.O. Box 56, 00014 University of Helsinki, Finland.
⁴ Natural Resources Institute Finland, 31600 Jokioinen, Finland.
⁵ Lappeenranta University of Technology, Saimaankatu 11, 15140 Lahti, Finland.

PMID: 29518722
DOI: 10.1016/j.scitotenv.2018.02.284

Abstract

Soil carbon (C) represents the largest terrestrial carbon stock and is key for soil productivity. Major fractions of soil C consist of organic C, carbonates and black C. The turnover rate of black C is lower than that of organic C, and black C abundance decreases the vulnerablility of soil C stock to decomposition under climate change. The aim of this study was to determine the distribution of soil C in different pools and impact of agricultural management on the abundance of different species. Soil C fractions were quantified in the topsoils (0-15cm) of 23 sites in the tropical highlands of Ethiopia. The sites in central Ethiopia represented paired plots of agroforestry and adjacent control plots where cereal crops were traditionally grown in clayey soils. In the sandy loam and loam soils of northern Ethiopia, the pairs represented restrained grazing with adjacent control plots with free grazing, and terracing with cereal-based cropping with adjacent control plots without terracing. Soil C contained in carbonates, organic matter and black C along with total C was determined. The total C median was 1.5% (range 0.3-3.6%). The median proportion of organic C was 85% (range 53-94%), 6% (0-41%) for carbonate C and 6% (4-21%) for black C. An increase was observed in the organic C and black C fractions attributable to agroforestry and restrained grazing. The very low concentration of the relatively stable black C fraction and the dominance of organic C in these Ethiopian soils suggest vulnerability to degradation and the necessity for cultivation practices maintaining the C stock.

Keywords: Biochar; Black carbon; Carbonates; Ethiopia; Soil organic matter.