The impact and cost of mineral fertilizers as well as their associated risks on the environmental safety is becoming unaffordable. To alleviate these problems, integrating mineral fertilizers with easily available and an environmental friendly soil amendment, such as biochar is of paramount importance towards meeting our goal of increasing agricultural production and ensuring food security. The experiment was conducted at Wondo Genet Agricultural Research Center in 2013 and 2014 cropping seasons to investigate the effects of biochar application rate on selected soil properties, growth, and yield of lemon grass (Cymbopogon citratuc L.). The treatments consisting of coffee husk and bagasse derived biochars were applied at the rates of 5, 10, 15 and 20 tons ha-1 each, and a control treatment without amendment, with 9 treatments. The treatments were laid out in randomized complete blocked design with three replications. Application of both biochars at different rates improved soil pH, soil organic carbon (OC), total nitrogen (N), available phosphorus (P), cation exchange capacity (CEC) and exchangeable cations. Fresh biomass, dry matter yield, number of leaf per hill and essential oil yield of lemon grass were significantly increased due to the application of biochars. Over two years, the highest mean fresh biomass and total dray matter, number of leaf per hill and moisture content were obtained by the application of 15 t ha-1 coffee husk biochar followed by the same rate of bagasse biochar. However, the highest mean essential oil yield was obtained from the application of 15 t ha-1 bagasse biochar followed by the same rate of coffee husk biochar. To conclude, coffee husk biochar at the rate of 15 t ha-1 could be recommended as the best treatment followed by bagasse biochar with the same rate to achieve optimum lemon grass yield in Wondo Genet and similar areas. Therefore, application of biochar is very imperative to improve soil fertility and crop yield.
