Microbe-assisted remediation of lead, nickel and cadmium contaminated soil in association with biochar and okra (Abelmoschus esculentus L.)

Heavy metal contamination of soil has become a global environmental concern in industrial and urbanized areas all around the world. The assessment of potential bioavailable nickel (Ni), lead (Pb) and cadmium (Cd) fraction in soil is a great concern because this fraction is the most important due to its harmful effect on soil quality and ultimately toxicity in the environment. With the aim to maximize okra (Abelmoschus esculentus L.) growth and yield under heavy metals (Ni, Cd and Pb) contaminated soil, a pot experiment was conducted at wire house of the Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad. The soil was spiked with heavy metals at the rate of 550 , 80 and 70 ppm by using Pb(NO3)2 , NiSO4, Cd(NO3)2 salts respectively. Biochar was applied at the rate of 1 and 2% biochar in each pots containing 10 kg soil. Three different strains of endophytic bacteria i.e. FD-17, KS-54 and PsJN were also applied for growth evaluation of okra in metal contaminated soil. Okra variety 'Punjab 8' was used as test crop. The maximum increase in shoot weight, root weight, okra grain weight up to 50%, 59%, and 58%, over control were recorded by co-inoculation with FD-17 and KS-54 in heavy metal contaminated soil amended with 2% biochar. Quality parameters like protein, ash, fat and fiber were also improved up to 44, 83, 88 and 90% by combined application of FD-17 and KS-54 in 2% biochar amended soil. Heavy metals such as Ni, Cd and Pb were decreased up to 66 ,48, 52 in grain, 40, 59 and 14 % in soil, 39, 20, 49% in root, and 35, 60, 58% in shoots respectively, over control, by combined application of FD-17 and KS-54 in 2% biochar amended soil. It was concluded that combination application of biochar and endophytic bacteria showed positive effect on growth, yield and immobilization of Ni, Cd and Pb in metal contaminated soil.