Impact of Biochar and Lime on Phytoavailability of Pb and Cd in a Contaminated Soil

Current study was conducted to evaluate the efficiency of water hyacinth (Echhornia crassipes) biochar and lime to remediate cadmium (Cd) and lead (Pb) contaminated soils. A pot experiment was carried out treating soil with Cd and Pb (both separately and in combination) at the rates of 3, 6, 9 mg/kg and 250, 500, 750 mg/kg, respectively. Biochar and lime were applied separately to the metal spiked soils at the rate of 5.54 g/kg and 2.77 g/kg, respectively. After growing metal accumulator plant Eleusine indica for five months, metal contents were examined in plant biomass (composite sample prepared mixing equal amount of both root and shoot). Water hyacinth biochar had higher efficiency (up to 72%) to reduce phytoavailability of Pb compared to Cd for E. indica when applied in metal spiked soil. However, lime application restricted the availability of Cd to E. indica up to 38.8% compared to control. Documented greater microbial biomass carbon (MBC) and chlorophyll content under application of water hyacinth biochar than lime indicates its higher efficacy for growth of plants and microbes in Pb and Cd contaminated soil due to supply of nutrient in the soil. Therefore, the water hyacinth biochar and lime have potential to reduce bioavailability of Pb and Cd in contaminated soil.