Abstract
Soil microorganism plays an important role in nitrogen (N) fixation process of paddy field, but the related information about how soil microorganism that drive N fixation process response to change of soil phy-chemical characteristics under the double-cropping rice (Oryza sativa L.) paddy field in southern of China is need to further study. Therefore, the impacts of 34-years different long-term fertilization system on soil N-fixing bacteria community under the double-cropping rice paddy field in southern of China were investigated by taken chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method in this paper. The field experiment were set up four different fertilizer treatments: chemical fertilizer alone (MF), rice straw and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (OM), and unfertilized as a control (CK). This results showed that compared with CK treatment, the diversity index of cbbLR and nifH genes with OM and RF treatments were significantly increased (p<0.05), respectively. Meanwhile, the abundance of cbbLR gene with OM, RF and MF treatments were increased by 23.94, 12.19 and 6.70×107 copies g-1 compared to CK treatment, respectively. Compared with CK treatment, the abundance of nifH gene with OM, RF and MF treatments were increased by 23.90, 8.82 and 5.40×109 copies g-1, respectively. This results indicated that compared with CK treatment, the soil autotrophic azotobacter and nitrogenase activities with OM and RF treatments were also significantly increased (p<0.05), respectively. There were an obvious difference in features of soil N-fixing bacteria community between application of inorganic fertilizer and organic manure treatments. Therefore, this results demonstrated that abundance of soil N-fixing bacteria community in the double-cropping rice paddy field were increased by long-term applied with organic manure and crop residue managements.
Highlights
The results indicated that soil nitrogenase activity with MF treatment were significantly higher (p
Regarding the different fertilizer treatments, this study demonstrated that soil nitrogenase activity with OM treatment were higher than that of MF, RF and CK treatments, which suggested that soil organic carbon (SOC) content was a vital factor for promoting the growth of soil nitrogenase
The soil C and N contents in paddy field may be the most important factor affecting on community structure of soil N-fixing bacterial. These results indicated that more molecular diversity and phylogenetic analysis of cbbLR and nifH genes in different geochemical environments were found by using polymerase chain reaction (PCR) method, which were provided more abundant of uncultivated cbbLR and nifH gene sequences for researcher [9,12,27]
Summary
The aim of this research was: (1) to explore the diversity of soil N-fixing bacteria in paddy field under different long-term fertilization conditions; (2) to analyses the soil diversity of cbbLR and nifH genes and its phylogenetic with different fertilizer regime in a double-cropping rice system by using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method
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