Role of Coconut Shell Biochar on Soil Properties, Microbial Diversity and Nitrogen Mineralization in Tropical Latosol

Biochar is a promising material to improve soil quality. Effects of coconut shell biochar on tropical soil nitrogen mineralization and microbial community were less reported. The incubation experiment was conducted to observe the required effects. Biochar rates in latosol were 0%, 1%, 2% and 5% (w/w), respectively. Results showed: (1) soil pH and CEC improved with biochar rate; (2) urease activity was increased at the lower biochar rate (<2%) but reduced at the 5% rate, while acid phosphatase activity was not changed by biochar; (3) biochar addition reduced soil microbial diversity. The bacterial population like Proteobacteria, Gemmatimonadetes, Planctomycetes, Verrucomicrobia and Bacteroidetes enhanced by more biochar addition, while Actinobacteria and Chloroflexi were found less at the high biochar rate. Fungal strains like Ascomycota decreased by biochar addition, but Basidiomycota and Chytridiomycota increased at high biochar rates. Genus of Haematonectria, Chaetomium, Gibberella, Aspergillus, Fusarium and Eupenicillium decreased effectively under biochar addition; (4) soil nitrogen mineralization with biochar amendment was described well by the exponential model (R-2>0.95, P<0.01), but soil nitrogen mineralization potential was found to be less due to biochar application. Thus, the addition of biochar derived from coconut shells had positive effects on soil characteristics, microorganisms, and nitrogen mineralization.