Abstract:

Soil nutrient distribution and imbalance were studied in the root zone of 0～80 cm layer and far from the trunk 0-200 cm in Weibei highland orchard, while the replant diseases of potted apple plants were analyzed. Results indicated that soil nutrients advanced along with increasing of the tree root base distance in level distribution；In vertical direction，other soil nutrients dropped along with deepening of the soil layer except for available Ca and Mg. Available P, Ca, Mg, Zn, Mn were deficit in orchard soils and N/P, K/P, Ca/P, Ca/Mg, Ca/Mn, Ca/Zn were imbalance in the root zone. The average of replant plant height, shoot length and rough, leaf area and root-activity were reduced 44.93%，34.46%，23.88%，49.48% and 11.40% separately, which represented replant disease evidently, and which aggravated follow comply with deepening of the layer and lighten as far from the tree trunk in orchard. To sum up, deficiency of Zn and imbalance of Ca/Zn were one of main factors to cause replant diseases; The replant diseases were lighter relatively in the zone of 0～40 cm layer and far from the trunk 100-200 cm, where Soil nutrients were concentrated, which will provide some reference to solve replant diseases in old orchard.

Key words: apple, root zone, nutrient, replant disease