Effects of biochar and vermicompost on nutrient bioavailability, potato growth and phytoremediation of copper contaminated Soil Haramaya District, Eastern Ethiopia

Sustainable production necessitates the meticulous management of agricultural soil, which is a nonrenewable natural resource. However, in eastern Ethiopia, fungicides are widely used to prevent the loss of Khat and vegetables, which can lead to the distribution of heavy metals in the soil environment. The purpose of this study was to examine how biochar and vermicompost made from agricultural waste and invasive weeds affect nutrient bioavailability, soil fertility, potato growth, and phytotoxicity remediation in artificially contaminated soil. The contaminated soil with 300 mg kg-1 Cu was treated with biochar (0, 2.5, 5, 7.5, and 10 tha-1) and vermicompost (0, 5, and 10 tha-1) at three replicates and incubated for 120 days. The improved soil was planted with potato plants (Solanum tuberosum) until maturity for 120 days. The experimental results revealed that the addition of biochar and vermicompost significantly improved the soil pH, OM, OC, TN, K and Av.P. Furthermore, these amendments significantly reduced Cu solubility in exchangeable pots (83.7%), physiologically based extraction tests (86.31%), and the leachability of heavy metals surrounding the environment (93.5%) compared with those in the untreated pots. Phytotoxicity remediation tests demonstrated that the addition of biochar and vermicompost considerably increased potato biomass. This study revealed that the use of biochar and vermicompost lowered the nutrient bioavailability of Cu by immobilizing it in more stable forms, which might reduce plant uptake. The potato plants in the control treatment group absorbed more of the material than did those in the other groups. Therefore, the use of these amendments is useful for improving soil contaminated with heavy metals and enhancing fertility and productivity.