Characteristics and driving factors of soil bacterial and archaeal communities under long-term fertilization regimes in black soil

【Objectives】 This paper was aimed to investigate the characteristics of soil bacterial community shifts under long-term fertilization regimes of black soil in northeast China. Combined with the soil physiochemical characteristics, the main driving factors would be determined. 【Methods】 Five treatments including CK(without fertilizer), application of combined NP(nitrogen-phosphorus), NK(nitrogen-potassium), PK(phosphorus-potassium) and NPK(nitrogen-phosphorus-potassium) were sampled. Ten cores (2.5 cm in diameter) were randomly collected from the plough layer (5-20 cm) of each plot of experimental field and mixed together. The changes of bacterial communities and soil nutrients were investigated via pyrosequencing and conventional chemical analysis, respectively. A correlation analysis was carried out to determine the main important factors influencing bacterial community composition. 【Results】 1) Compared to CK, NP and NPK treatments increased the richness of soil microorganisms while they decreased under PK treatment. NPK treatment increased the biodiversity of soil microorganisms while NK treatment decreased. Different fertilization practices greatly changed the soil bacterial community structures. All the fertilized treatments decreased the relative abundances of Acidobacteria, Cyanobacteria, Planctomycetacia and Chloroflexi, and increased Gemmatimonadetes and Firmicutes, compared to the unfertilized treatment, while others varied differently in different fertilization treatments. These results mentioned above showed soil bacterial communities have significantly changed under long-term fertilization regimes. 2)The use of urea significantly changed the soil physiochemical conditions. Soil total N, available N and organic matter in N-containing treatments were significant higher than those in N-deficiency treatment, while pH was lower. 3)There were significant correlations between soil microorganisms and physiochemical characteristics. The change of soil pH, resulted from continuous nitrogen fertilizer application, was approved to be the most important factor determining bacterial community composition, and pH contributed 66.5% of variation. All the physiochemical characteristics being exploited contributed to 100% of the variations. 【Conclusions】 Our research demonstrated the effects of long-term different fertilization on bacterial community, and found pH was the most important factor determining bacterial community structures. The results may provide a new insight in understanding of the microorganisms in black soil, and will be very meaningful to the rational utilization of fertilizer and agricultural sustainable development.