| Abstract | KB  Full paper
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Background, Aim and Scope:
Knowledge about shifts of microbial community structure and diversity following different agricultural management practices could improve our understanding of soil processes and thus help to develop sound management strategies. A long-term fertilization experiment was established in 1989 at Fengqiu (35o00’N, 114o24’E) in central China. The soil (sandy loam) is classified as aquic inceptisols and has received continuous fertilization treatments since then. The fertilization treatments included control (CK, no fertilizer), chemical fertilizers nitrogen (N) and potassium (K) (NK), phosphorous (P) and K (PK), NP, NPK, organic manure (OM), and half chemical fertilizers NPK plus half organic manure (1/2NPKOM). The objectives of this study were to examine if the microbial community structure and diversity were affected by the long-term fertilization regimes.
Materials and Methods:
Soil samples were collected from the long-term experimental plots with seven treatments and four replications in April 2006. Microbial DNAs were extracted from the soil samples and the 16S rRNA genes were PCR amplified. The PCR products were analysed by DGGE, cloning and sequencing. The bacterial community structures and diversity were assessed using the DGGE profiles and the clone libraries constructed from the excised DGGE bands.
Results:
The bacterial community structure of the OM and PK treatments were significantly different from those of all other treatments. The bacterial community structures of the four N-containing treatments (NK, NP, NPK and 1/2NPKOM) as well as CK were more similar to each other. The changes in bacterial community structures of the OM and PK treatments showed higher richness, abundance and diversity. Phylogenetic analyses indicated that Proteobacteria (30.5%) was the dominant taxonomic group of the soil, followed by Acidobacteria (15.3%), Gemmatimonadetes (12.7%), etc.
Discussion:
Irrespective of the two fertilization treatments of OM and PK, the cluster analysis showed that bacterial communities of the rest five treatments of CK, NK, NP, NPK and 1/2NPKOM seemed to be more similar each other, which indicated the relative weak effects of the four N-based treatments on soil bacterial communities. N fertilizer may consider as a key factor to counteract the effects of other fertilizers on microbial communities.
Conclusions:
Our results show that long-term fertilization regimes can affect bacterial community structure and diversity of an agricultural soil. The OM and PK treatments showed a trend towards distinct community structures, higher richness, abundance and diversity when compared to the other treatments. Contrasting to the significant positive effects of OM and PK treatments on the bacterial communities, N fertilizer could be considered as a key factor in the soil to counteract the effects of other fertilizers on soil microbial communities.
Recommendations and
Perspectives:
Because of the extremely high abundance and diversity of microorganisms in soil and the high heterogeneity of the soil, it is necessary to further examine the effects of fertilization regimes on microbial community and diversity in different type soils for comprehensive understanding their effects through the appropriate combination of molecular approaches.
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