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IMPACTS OF LONG-TERM FERTILIZATION ON BACTERIAL COMMUNITY STRUCTURE, SOIL MICROBIAL BIOMASS, AND GRAIN YIELDS IN RED PADDY SOIL IN CHINA

Bacteria play essential roles in soil ecosystems. This study aims to investigate rice rhizosphere bacterial communities, soil nutrition, and grain yield affected by long-term (30 years) fertilization practices. Four fertilizations were applied to experimental red paddy soils: no fertilizer (NF), chemical fertilizer (CF), harvested residue returned to soil (HRR), and 60% organic manure plus chemical fertilizer (OCF). Bacterial communities were then assessed by means of denaturing gradient gel electrophoresis (DGGE) targeting 16S rRNA genes. Results showed that the bacterial community structure of OCF was similar to HRR, which was the most diverse and stable compared to the other treatments. Moreover, CF’s effects were similar to NF, which was markedly less diverse. Eight bacterial phyla were identified by sequence analysis of the DGGE bands from rhizosphere inhabitants in the red paddy soils. In addition, soil microbial biomass C and N were significantly higher in HRR and OCF than in CF and NF. Furthermore, double rice grain yield and dry matter in OCF plots were significantly highest (P < 0.05). Long-term treatment of organic matter containing fertilizers promoted rhizospheric bacterial diversity and soil quality. The combination of inorganic and organic fertilizers (OCF) improved grain yields more than solely inorganic (CF) or organic (HRR) fertilizers.