Microbial Community Response to Different Biochar Amendments in Sugarcane and Rice Soils.

ABSTRACT Biochar has been proposed to enhance crop yield and decrease greenhouse gas emission. In this study, we investigated the effects of biochar made from different feedstocks on soil microbial community under subtropical sugarcane and rice production in Louisiana. Field experiments were established in Duson and Crowley, LA, respectively, with sugarcane or rice biochar made from respective harvest residue was applied. In addition, wood biochar was applied at the both sites.  Soil samples were collected at the end of growth season and were characterized for microbial community using phospholipid fatty acids (PLFA) method and principle component analysis (PCA). Total biomass and different biomarker ratios including fungi: bacterial PLFAs (FBR), Gram- negative and gram-positive ratio (G+/G-), saturated: monounsaturated PLFA (S/M), and cyclopropane: precursor PLFAs (cy/pre) were quantified. Principle component analysis (PCA) was used for statistics. Results showed that biochar addition significantly increased total microbial biomass in both sugarcane and rice soils, and wood biochar tended to have stronger effect. Biochar amendment generally decreased fungi abundance.  In sugarcane soil, application of biochar decreased G+/G-, but increased the ratio in rice soil. Stress indicators,  S/M ratio and cy/pre ratio, were higher with biochar addition in both soils. Overall, these results indicated significant shifts in microbial community structure in response to biochar amendment and the differences between the two cropping systems.

Keywords: biochar; soil microbiology; subtropical crop.