Desalegn Tadele’s research while affiliated with Bahir Dar University and other places

Following land degradation and the associated reduction in crop production, smallholder farmers in the highlands of northwestern Ethiopia have recently practiced Acacia decurrens ‐based fallow system. Despite the rapid expansion of this new cropping system, its effect on soil properties and crop productivity has never been exhaustively studied. We assessed the effects of A. decurrens ‐based fallow system on soil properties and tef ( Eragrostis tef ) productivity under the existing production environment on farmers' fields using: (i) tef cultivation under the fallow system in two rotations which represent 5 and 10 years of continuous fallow period (fallowed lands); (ii) conventional tef cultivation system (ST system); (iii) tef cultivation on fallowed lands in the first rotation for two consecutive years; (iv) ST system adjoining a 4‐year‐old acacia woodlot; and (v) interview with local farmers. The results showed that fallowed lands in the first and second rotations improved soil properties and tef productivity with greater effects in the second rotation. Compared to the ST system, fallowed lands in both rotations significantly increased soil pH, soil organic carbon (SOC), available P, total N and cation exchange capacity (CEC), but decreased exchangeable Al ³⁺ . Tef aboveground biomass and grain yields were increased by 74% and 93% in the first rotation and 103% and 167% in the second rotation over the ST system, respectively. Similarly, height was increased by 9% in the first rotation and 17% in the second rotation. Fallowed lands sustained positive effects on soil fertility and tef productivity over two successive production years highlighting that the fallow system can benefit farmers through the cultivation of two annual crops in 2 years. Significant tef yield reductions occurred over the first 10 m distance from the acacia woodlot. Soil moisture, pH, SOC, available P, total N and CEC were higher at croplands close to the acacia woodlot. According to the farmers, the fallow system can improve tef productivity and reduce the need for inorganic fertilizer by 50%. Overall, the results demonstrated that fallowing with A. decurrens can reduce soil acidity and restore nutrients for sustainable crop production; and the shading effect could be the limiting factor for tef production on croplands adjacent to the acacia woodlots.

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 Mg ²⁺ 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.