Effect of two contrasting biochars on soil microbiota in the humid tropics of Peninsular Malaysia

Abstract

Report on soil microbial community in tropical soil of humid tropics remained limited despite the current research interest in biochar-microbe study in various climatic regions. A field-trial spanning three consecutive crop cycles of Zea mays var. Masmadu was conducted in tropical Acrisols of Peninsular Malaysia. Palm kernel shell and rice husk biochars of different feedstock and pyrolysis conditions were used for amendment. Soil samples were collected during maize harvesting and were analyzed for physicochemical properties (pH, CEC, organic C, labile active C), microbial biomass (C, N), and seven C-cycle enzymes activity (total cellulase, endoglucanase, β-glucosidase, xylanase, invertase, phenol oxidase, peroxidase). Total soil genomic DNA was extracted and subjected to the analysis of bacterial 16S rRNA and fungal ITS gene abundance quantification. Microbial genetic profiling was fingerprinted by using DGGE. Significant increases of all measured soil physicochemical properties, microbial biomass C, microbial biomass N, and gene abundances were observed in all biochar amended soils. Significant changes of total cellulase, endoglucanase, phenol oxidase, and peroxidase were not detected. A significant shift in microbial genotypic and enzymatic functional diversity based on microbial C-cycle enzymes was not detected. Correlation data revealed significant linkages of soil microbial biomasses and gene abundances with all measured soil physicochemical properties. The biochar influences the microbial community by elevating microbial habitat potential to a more favorable state and increasing labile active carbon sources in the field trial.