Enhancing microbe assisted remediation of nickel contaminated soil by using biochar and chitosan as immobilizing agents

Different vegetable crops grown on heavy metal contaminated soil showed marked difference in metal accumulation, their uptake and distribution pattern. Spinach is a common vegetable used for human consumption and metal accumulation in its edible parts is a serious risk for human health. Nickel (Ni) contamination is a widespread problem in the era of industrial development. Nickel toxicity is harmful for plants and it can affect many metabolic processes resulting in reduced growth and yield. Different ways are being sought to reduce Ni bioavailability and toxicity. Pot experiment was conducted to explore the role of interactive effect of endophytic bacteria (Burkholderia phytofirmans PsJN) and immobilizing amendments (biochar and chitosan), on growth and biomass of spinach in Ni contaminated soil. Soil was artificially contaminated with Ni up to 100 ppm by using nickel sulfate hexahydrate salt. Biochar and chitosan were applied at the rate of 1 % (w/w) in soil. Results revealed that application of biochar and chitosan (0.5% each) combined with endophytic bacteria significantly increased leaves dry weight, photosynthetic rate and transpiration rate up to 66%, 25% and 75%, respectively, as compared to control. Maximum decrease 35% and 51% of Ni in root and leaves, respectively, was observed by combined application of biochar, chitosan and Burkholderia phytofirmans PsJN, over control. Regarding the quality parameters of spinach leaves, protein, fat and fiber content were increased up to 27%, 43% and 29%, respectively, by combined application of immobilizing amendments (biochar and chitosan) along with Burkholderia phytofirmans PsJN, over control. However, these studies shows the immobilizing effect of integrated use of biochar, chitosan and Burkholderia phytojirmans PsJN and reduce the risk involved in use of spinach leaves for human consumption, grown in Ni contaminated soil.