In situ charcoal production in Acacia decurrens-based taungya system improved soil properties and productivity of three agricultural crops in the highlands of Ethiopia

Short-term in situ charcoal production-induced changes in soil properties and crop productivity of acidic soil in Acacia decurrens-based taungya system were assessed in the Guder watershed of northwestern Ethiopia. Data were collected through field study, pot experiment and interviews with local farmers. The field study involved a survey of 36 paired charcoal production kiln sites and adjacent reference sites in 18 croplands to analyse soil physicochemical properties and productivity of tef (Eragrostis tef), barley (Hordeum vulgare) and wheat (Triticum aestivum). A pot experiment was undertaken with wheat to investigate seed germination and chemical fertilizer needs at charcoal production sites. Local farmers were interviewed for their perceptions and management practices. The production and short-term presence of charcoal in kiln sites significantly increased sand fraction, pH, organic carbon, available phosphorous, exchangeable Mg2+ and exchangeable K+ compared with the reference sites. Charcoal production practice raised pH by 0.83 units, organic carbon, available P and exchangeable K+ by 40%, 92% and 303%, respectively. Exchangeable acidity and exchangeable Al(3+ )were lowered by over 80% at kiln sites. Both aboveground biomass and grain yield of tef, barley and wheat were, on average, 135% higher at kiln sites than at the reference sites. Furthermore, crops grown at kiln sites were taller and had greener and larger leaves. Farmers' responses indicated higher crop productivity and reduced inorganic fertilizer application at kiln sites. Results from the pot experiment provided evidence of faster seed germination, enhanced crop productivity and reduced inorganic fertilizer needs in charcoal-treated soils. The study suggests that the inclusion of charcoal remnants and heating can increase carbon storage, improve soil properties which promote crop productivity and reduce the need for inorganic fertilizer in degraded, acidic agricultural soil.