The Growth And Declining Of Soil Microbe Amount In Root Zone And Their Influence To The Plant Replantation In The Apple Orchard Of Loess Plateau

Orchard replant problem has been a worldwide difficult problem that hinder the development of fruit industry , so the study of the mechanism and prevention of replant disease is also an important content of fruit farming research. The test regarded the tivated loessial soils of Weibei highland as the objects, studied the spatial changes of soil microbe amount and enzymatic activity in the red fuji tree's root zone which was divided by different layers and different level distance, then with the pot experiment, investigated the growth of replant breedlings influenced by the soil of different root zone spatial, The aim was to explore the main occurrence mechanism of fruit replant problem in our regional ,while to provide reference for its solvion. Results are as follows:(1) in the tree root zone of Weibei highland orchard, change of the microbe amount has a certain rule with increasing depth of soil layers or distance level from tree base: in the vertical profile of the soil, bacteria,fungi,actinomycetes mainly distribute in the layer of 0-40cm, being gradually less with the increasing depth of soil layers; in the level distance, from tree base to the outward in the range of 200cm, the amount of bacteria become gradually more, the amount of fungi become gradually less while the amount of actinomycetes first reduce then increase , the actinomycetes is distribute more in 0-100cm where has a great dense of root stubble.(2) both soil urease and invertase have a most significant positive correlation with bacteria and actinomycetes. in the vertical profile of the soil, activities of urease and invertase are reduced with the increment of soil depth, in the level distance, from tree base to the orchard row(distance is 200cm), activity of invertase has a increased tendency,activity of urease was first increased and then decreased,the changes of catalase are not significant in the the spatial of root zone, and the correlation between microbe and catalase was not very significant(p<0.05).(3) the pot experiment show that the plant height, new shoot length, new shoot diameter, quantity of the new shoot and single leaf area of the seedlings replanted in the soil collected from region of 0-40cm layer, 100-200cm level distance are decreased less than that planted in unreplant soil, while seedlings replanted in region of 20-40cm layer, 100-150cm level distance show least severe replant disease, the apple seedlings planted in the soil collected from of 0-20cm or 60-80cm layer, 0-100cm level distance show the poorest growth.(4) when we replanted apple seedlings in the old orchard after the old apple trees were removed, the young trees replanted in the old orchard rows would show less serious replant disease, the suitable distance for the replant site from the tree base is 100-200cm.