|Title||Role of Fungal-bacterial Biofilm and Woody Biochar on Soil Enzyme Activities and Ni Immobilization in Serpentine Soil|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Vithanage, Meththika, Bandara Tharanga, Hewage Bhagya, Herath Indika, Seneviratne Mihiri, Kumarathilaka Prasanna, Yapa Priyantha, Wekumbura Chandima, Rajakaruna Prasanna, Dissanayaka Shiromi, and Seneviratne Gamini|
Serpentine surrounding soil systems containing high amounts of heavy metals may be unfavorable environments for crop growth and soil microorganisms. The application of biofilm (BF) and biochar (BC) was examined as potential bioamendments on the activity of soil microorganisms and Ni bioavailability in serpentine soil. Bacteria were isolated from serpentine soil combined with a garden soil fungus to form a fungal bacterial biofilm. The BCs (BC300, BC500, BC700) were prepared by slow pyrolysis of Gliricidia sepium biomass at three different temperatures (i.e. 300, 500, 700 o C) with a holding time of 2 h. A pot experiment was conducted with tomato (Lycopersicon esculentum L.) by adding BCs at three different percentages, 1, 2.5, 5% (w/w) with and without fungal-bacterial biofilm. The bioavailability of Ni was assessed by 0.01 M CaCl2 extraction. Polyphenol oxidase and dehydrogenase enzyme activities were determined by iodometric and spectrophotometric methods respectively. The biomass of tomato plants grown in the 5% BC700 treatment with BF was 10-fold higher than that of the control. The bioavailability of Ni and polyphenol oxidase activity showed a decrease at BCs of increasing temperature. The maximum bioavailability reduction of Ni in 5% BC700 was 90% compared to the control, whereas the addition of BF showed no considerable change. Dehydrogenase activity showed no pattern and the maximum was found in 2.5% BC300 without BF which was 91-fold higher than the control. Results suggest that the addition of BC together with BF into serpentine soil immobilizes Ni significantly, while decreasing soil enzyme activities.