Abstract:Taking the soil of old apple orchard in Mengyin, Laizhou and Qixia, Shandong Province as the object, this study is to explore the effects of freezing-thawing on the number of the soil microbial and enzymatic activity of old apple Orchard, and to provide a theoretical basis for the measures to alleviate the apple replant disease in production. After cleaning the three old apple orchard, two deep trenches were dug at the original location of the fruit trees, and the soil of 0-30 cm and 30-60 cm soil were placed on both sides of the deep ditch separately. The soil sampling was carried out before winter and in spring, and then the soil physical and chemical properties, soil microbial population, soil enzyme activity and soil cation exchange capacity were determine. After freezing-thawing treatment, The numbers of soil bacteria, fungi and actinomycetes in each layer decreased significantly, and the upper soil decreased the most significant. The numbers of soil bacteria, fungi and actinomycetes in the upper of Mengyin apple orchard decreased by 40.6%, 43.6% and 55.7 % respectively, and the ratio of soil bacteria/fungi in 3 old apple orchard was greatly increased; At the same time soil F. oxysporum gene copy number was detected by using real-time fluorescence quantitative technique and found that the copy number of F. oxysporum in each layer decreased significantly after freezing-thawing treatment, The activities of urease, phosphatase and invertase in each soil layer decreased significantly,and there was a significant difference; The change of the soil?cation?exchange?capacity?(CEC) of the three old apple orchard was significantly different, The upper soil CEC in Mengyin apple orchard decreased by 41.7%, the lower layer soil CEC increased by 19.2%, whereas that in Qixia was opposite. In conclusion, after the freezing-thawing treatment, the number of soil microbes in the upper and lower layers were reduced significantly, and the soil microbial community structure was optimized. These results are helpful to alleviate the apple replant diseases.