Agroforestry Systems

, Volume 91, Issue 1, pp 137–148 | Cite as

Effects of Acacia seyal and biochar on soil properties and sorghum yield in agroforestry systems in South Sudan

  • Biar Deng
  • Priit Tammeorg
  • Olavi Luukkanen
  • Juha Helenius
  • Mike Starr


We studied the effects of Acacia seyal Del. intercropping and biochar soil amendment on soil physico-chemical properties and sorghum (Sorghum bicolor L.) yields in a two-year field experiment conducted on a silt loam site near Renk in South Sudan. A split-plot design with three replications was used. The main factor was tree-cropping system (dense acacia + sorghum, scattered acacia + sorghum, and sole sorghum) and biochar (0 and 10 Mg ha−1) was the subplot factor. The two acacia systems had lower soil pH, N and higher C/N ratios compared to the sole sorghum system. Biochar significantly increased soil C, exchangeable K+ contents, field capacity and available water content, but reduced soil exchangeable Ca2+ and effective CEC, and had no effect on soil pH. Acacia intercropping significantly reduced sorghum grain yields while biochar had no significant effect on sorghum yields. The land equivalent ratio (LER) for sorghum yield was 0.3 for both acacia systems in 2011, with or without biochar, but increased in 2012 to 0.6 for the scattered acacia system when combined with biochar. The reduction in sorghum yields by the A. seyal trees was probably due to a combination of competition for water and nutrients and shading. The lack of a yield response to biochar maybe due to insufficient time or too low a dosage. Further research is needed to test for the effects of tree intercropping and biochar and their interactions on soil properties and crop yields in drylands.


Acacia seyal Biochar Land equivalent ratio (LER) Savanna Tree intercropping 



We acknowledge funding support from the Landscape Management Planning and Training for the Environment in Southern Sudan (LAMPTESS) project, and Department of Agricultural Sciences, Faculty of Agricultural and Forestry, University of Helsinki. We also are indebted to the staff of faculties of Agricultural and Forestry, University of Upper Nile, South Sudan for their help and facilitation in the field work. The technical assistance in the laboratory during the chemical analysis of the samples at the University of Helsinki, Finland by Prof. Markku Yli-Halla and laboratory technician Marjut Wallner are appreciated.


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Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  • Biar Deng
    • 1
  • Priit Tammeorg
    • 1
  • Olavi Luukkanen
    • 2
  • Juha Helenius
    • 1
  • Mike Starr
    • 2
  1. 1.Department of Agricultural SciencesUniversity of HelsinkiHelsinkiFinland
  2. 2.Department of Forest SciencesUniversity of HelsinkiHelsinkiFinland

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