| Many problems have been brought in the main apple planting areas of loess plateau because of perennial extensive management,such as the replantation diseases caused by the soil degradation,and the decrease of the quality of apple by the excessive pesticide,which are seriously threatened the sustainable and steady development of the apple industry.In this study,a microbial compound fertilizer was developed on the basis of the screening of microbial strains of PGPR from the apple tree and the soil fundamental fertility of the orchards.The fertilizer efficiency was evaluated by the yield,optimal fruit rate,weight of single fruit,sugar content and hardness,while the change of the soil microbial flora was assessed by high-throughput sequencing after fertilization in order to provide the theoretical basis and data support for further researches.The F162 strain,screened from the orchard soil,showed the excellent ability of dissolving the inorganic or organic phosphorus.The available phosphorous content was up to 65.930 mg/L after inoculated F162 to inorganic phosphorus medium.The ability of potassium solubilizing of one bacteria,named YA-07 stored in our laboratory,was measured,and its potassium rate was up to 17%.The strains of F162 and YA-07 were identified as Aspergillus niger and Paenibacillus mucilaginosus respectively through their morphological,physiological and biochemical experiments and 16s rDNA or ITS sequences.It was found that the two strains were co-inoculated in the same medium growing well and no suppressing each other.The number of the two strains F162 and YA-07 were up to 9.0×108cfu/g and 1.58×109cfu/g respectively by the optimization of solid fermentation conditions.The formula of the fertilizer named F25 was designed in according to the soil fundamental nutrient of ten orchards in the main apple planting areas of loess plateau,pH and the demand characteristics of the processes of apple growth.According to high-throughput sequencing results,the microbial community in the soil was changed obviously after applying the microbial compound fertilizer;It was showed that approximately 227 species of fungi and 266 species of bacterium were declined sharply or even disappeared,while the abundance of 224 fungi and 261 bacteria species increased significantly after the fertilization.The significant differences of flora were found in 44 genera of fungi and 7 genera of bacteria.To be specific,Bradyrhizohium,Sebacinales and Pseudonocardiaceae increased significantly,while a common pathogenic bacteria in agriculture Ralstonia spp.decreased significantly.The microbial community richness in the soil presented certain decline after the fertilization,while the soil fungal diversity increased and the bacterial diversity decreased based on the α,β diversity analysis results.Besides,the fertilization had a more significant effect on the soil restoration of aged orchards.The investigation results of the apple production and quality showed that the microbial compound fertilizer could not only promote the growth and development of apple,but also increase the yield and quality of apples.The yield,optimal fruit rate,weight of single fruit,sugar content and hardness of applying the microbial compound fertilizer were increased by 24.84%,24.73%,9.15%,8.14%,1.46%respectively compared to the control fertilizer.The production value of per tree was increased by 82.58 yuan and the input-output ratio was 1:1.95 after fertilization this F25 fertilizer.It was demonstrate that the fertilizer not only could improve the soil micro-ecological environment,but also could enhance the quality and yields of apples,and increase the income of farmers,according to the results of the changes of the microbial flora and the evaluation of the fertilizer efficiency.Therefore,this fertilizer is worth to be widely used in apple planting areas. |
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