| The peanut is one of the main oil-bearing and economic crops in low-hilly red soil region of south China. Recently, with the rapid intensification and large-scale planting of peanuts, the continuous cropping obstacle of peanuts is getting increasingly serious. Currently, there are several methods applied to alleviate the continuous cropping obstacle, such as intercrop and rotation crop, using continuous cropping resistant varieties, rational application of fertilizers and microbial agents. By analyzing how fertilizers and microbial agents influence the growth of continuous cropping peanuts and microbial community structure, we can provide rational fertilizer and microbial agents application methods for alleviating continuous cropping obstacle. Through carrying out field experiments and Pot experiments, we can compare the influence of different fertilizers and different microbial agents on the growth characteristics of continuous cropping peanuts; The total community DNA was extracted from soil using the direct lysis method, then bacterial universal primers and fungal universal primers were used to amplify16S rDNA V3region fragments of bacteria and18S rDNA of fungi respectively; the DGGE method was implemented to analyze microbial community structures of different samples; By isolating pure bacillus strains from different soil samples, we employed RFLP to analyze the diversity of these bacillus species.In the field experiments, the resuLts showed that the growth status of peanuts was the best when jointly applied compound fertilizer, organic fertilizer and microelement fertilizer (T7). Which yield was increased by53.99%compared to the control (T8). Among fertilizers for peanut growth, compound fertilizer was the most important, organic fertilizer followed by and microelement fertilizer had the minimum importance. The microbial agents also couLd increase the output of peanuts to some extent, which rose by32.14%compared with the control. The microbial count results revealed that the quantity of bacteria and actinomycetes in some soil samples that imLplied with microbial agents had increased, however the amount of fungi had declined. Through analyzing the DGGE profiles between different samples showed that the bacterial and fungal species of all treated samples were abundant, the soil samples after treated by microbial agents, the species of bacteria increased while the species of fungi decreased. Cluster analysis indicated that soil samples that treated with microbial agents were in the same cluster and there was little difference between the different fertilizer treatments of microbial community structure in different soil samples. By dint of the PCR-RFLP in analyzing16S rDNA, we found seven OUTs restriction endonuclease types out of the twelve gene libraries. The diversity of bacillus in soils that applied with bacillus agents was relatively lower, while others were more or less the same. The results of16S rDNA sequencing suggested that the major bacillus types in all soils were B. cereus, B. subtilis, B. pumilus and B. megaterium. The proportion of the B. cereus in soil samples that treated with bacillus agents was approximately15%higher than the other treatments.In the pot experiments, the effects of the microbial agents to peanut grown in the concentration of1010cfu/mL were better than that of109cfu/mL, and it was the best to use the mixed fertilizer to Bacillus and photosynthetic bacteria. The soil samples with1010cfu/mL microbial agents had more bacteria and less fungus, and the soil sample with mixed fertilizer of Bacillus and photosynthetic bacteria were the most significant. DGGE profiles of different samples revealed that some bacteria and fungi species were relatively abundant. The cluster analysis indicated that almost all the soil samples were in the same cluster. Compared with the control, the soil samples with1010cfu/mL microbial agents had the most difference in microbial community structure among all the treatments. Through PCR-RFLP analysis of16S rDNA, we identified seven gene libraries including6OUTs restriction endonuclease types. Overall, the diversity of bacillus in soil samples that treated with bacillus agents was relatively low as a whole. The results of16S rDNA sequencing suggested that the dominant bacillus species in all the soil samples were B. cereus, B. subtilis, B. pumilus and B. megaterium. The proportion of the B. cereus in soil samples treated with1010cfu/mL bacillus agents had slightly risen. |
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