Effects Of Soil Layer Replacement After Air Drying With Freezing-thawing On Microorganism Of Apple Replant Orchard Soil

The experiment was conducted from2012to2013in the apple orchard of Mengyin, Laizhou and Qixia, which has the apple replant disease(ARD).Effectss of air drying with freezing-thawing and soil layer replacement on soil microbial quantity,soil enzyme and soil cation exchange capacity was studied. Malus hupehensis Rehd was chosen as the experimental material to show the effects of soil layer replacement on the growth of Malus hupehensis Rehd seedlings.. The main results are as follows:1.After the treatment of air drying with freezing-thawing, the fungi amount of topsoil and subsoil in Qixia apple orchard decreased for52%and54.5%,40.8%and72%in Laizhou,35.9%and47.3%in Mengyin. The bacterial population of topsoil in Qixia apple orchard decreased for52%and54.5%,64.8%and36.6%in Laizhou,23.3%and93.8%in Mengyin. The number of actinomycetes was also significantly decreased. Drying and freeing-thawing treatment obviously decreased the amount of fungi, bacterial and actinomycetes in soil. The treatment increased the ratio of bacteria to fungi.2.The treatment of drying and freezing-thawing also decreased the activity of urease, invertease and phosphatase obviously. The activity of urease, invertease and phosphatase had a positive relationship with the quantity of soil microbiological. And the treatment also changed pH of different soil in different layer of different orchards. The treatment increased the pH of Acidic soil orchard and decreased the pH of Alkaline soil orchard.3.In September, the amount of fungi in topsoil of different orchards after soil layer replacement(SLR) was23.8%、7.5%and11.9%lower than the CK.The bacterial amount was55.9%、2.1%and18.7%higher than CK. The amount of fungi and bacterial in subsoil was the same change trend as that in topsoil. The soil layer replacement(SLR) treatment increased the amount of bacterial and decreased the amount of fungi, also increased the ratio of bacteria to fungi. The treatment of SLR has little effectss on the amount of actinomycetes.4. Soil layer replacement(SLR) improved the plant high, stem diameter, dry and fresh weight and also the net photosynthetic rate of Malus hupehensis Rehd. After soil layer replacement(SLR), the average plant high, stem diameter, dry and fresh weight of Malus hupehensis Rehd in three orchards was10.6%、17.7%、20.3%and16.5%higher than that of CK, and it’s significant difference dry and fresh weight.The net photosynthetic rate of Malus hupehensis Rehd increased for22.9%、21.2%and32.2%with the treatment of SLR.This treatment was an effectsive way of promoting the growth of Malus hupehensis Rehd in replant orchard. 5. Air drying with freezing-thawing and soil layer replacement were effectsive ways of overcoming apple replant disease. With the study of soil cation exchange capacity after treatment, we can figure out that the air drying with freezing-thawing effected the soil cation exchange capacity complicated. The soil cation exchange capacity decreased or increased after the treatment. The soil layer replacement increased the cation exchange capacity of the topsoil of three orchards for8%,20%and54%, which improved the soil abilities of water and fertility retention. The treatment of SLR effected the CEC of subsoil complicated.