Pyrosequencing analysis of bacterial community diversity in long-term fertilized paddy field soil

Analysis of soil bacterial community and its diversity in conditions of intensive fertilization using high-throughput sequencing in paddy field soil has to date, not been extensive. Using 454 pyrosequencing of 16S rRNA genes, the current study investigated how bacterial succession changed under seven different fertilizer regimes (NP, NK, PK, NPK, compost, NPK + compost and unfertilized) in a 45-year old paddy field trial. Of the selected treatment variables the application of compost best enhanced soil fertility. Unexpectedly, long-term fertilization had no significant effects on soil microbial structure in paddy soils. The bacterial communities were dominated by Proteobacteria and Chloroflexi. Actinobacteria and Firmicutes were substantially abundant in the compost and NPK + compost treatments. Our findings highlight the fact that organic fertilizer amendment activates diverse groups of Gram-positive microorganisms when compared to conventionally used chemical fertilizers. Abundance of Rhizobiales that directly influences rice growth through symbiosis or indirectly through nutrient cycling, and Methylococcales that combat greenhouse gas (methane) emissions, were high in treatments that received compost, in comparison to inorganic fertilizer amended and unfertilized treatments. Consequently, the application of long-term organic fertilizer has a reasonable and beneficial impact on the bacterial community inhabiting the soil, and can lead to a good crop yield.