MICROBIAL COMMUNITY DIVERSITY INFLUENCED BY ORGANIC CARBON SOURCES IN RICE-RAPE ROTATION FARMLAND

The present study was intended to characterize the responses of soil microbial community to organic carbon sources in rice-rape rotation farmland in Erhai Basin, Yunnan, China. The farmland was supplemented with nitrogen fertilizer alone, nitrogen fertilizer plus organic carbon source materials (Vicia faba straw, corn straw, or composting pine needles) or not fertilized; the soil physical and chemical properties, carbon and nitrogen hydrolases (beta -1,4-glucosidase, N -acetyl -beta - D- glucosidase)were quantitatively investigated. The composition and diversity of soil microbial community were scrutinized by Illumina high-throughput sequencing technology. The effects of soil physicochemical properties on soil microbial community were revealed by redundancy analysis (RDA). It turned out that when compared with no fertilization, the organic fertilizers plus nitrogen fertilizer significantly increased organic matter, total nitrogen, carbon to nitrogen ratio (C / N ratio) in soils and the activities of carbon/nitrogen hydrolases by 7%, 3%, 5% and 22%/9%, respectively. The results of high- throughput sequencing showed that organic carbon source materials combined with nitrogen fertilizer significantly altered the composition and diversity of soil microbial community; Actinoplanes, Rhizobiales, Sordariales, Chaetomiaceae and Labilithrix, which were able to degrade organic matter and fix nitrogen, were substantially increased in their relative abundance. RDA showed that the rhizosphere microbial community was significantly affected by pH, organic matter, total nitrogen and C / N ratio (p<0.05), and Labilithrix, Sordariales, Actinoplanes, and Chaetomiaceae showed a significantly positive correlation with total nitrogen, organic matter and C / N ratio. This study indicates that organic carbon source materials combined with nitrogen fertilizer could increase the contents of soil organic matter and total nitrogen, enhance the activities of carbon/nitrogen hydrolases, and significantly increase the relative abundance of microorganisms capable of degrading organic matter and promoting nitrogen cycle in soils.