| Weibei area in shaanxi province is one of the most suitable area for planting apple trees. The natural environment in this area is best for growing apple trees such as the high attitude, sufficient illumination, and the big temperature difference. Meanwhile, the thick soil layer and appropriate soil texture are other suitable conditions. The soil is rich in Potassium, Magnesium, Calcium, Zinc, and Selenium and so on. However, many serious problems appear in orchard as the planting age increased, such as fruit trees accelerated aging and deciduous. Fruit trees can live for several dozens or hundreds years which are different from annual or perennial crops. Planting fruit trees can have accumulated effect on soil quality since the fruit roots can extend widely and absorb tons of nutrients from soil every year. Soil fatigue usually exsists in orchard which may have negative effects on health growth of fruit trees.Apple quality and Storability deterioration is also appears frequently. Therefore, it is a problem demanding prompt solution to research on evolution of orchard soil quality and explores the mechanism of fruit senescence for sustainable development of fruit industry.In this study try to find soil quality index which is sensitive for planting fruit trees through analyze soil physics and chemistry indicators in different planting-age orchards, Moreover, the accumulate of mineral nitrogen in order to reveal nutrient depletion and accumulation and provide evidence for orchard management. Following is the results:1. Planting fruit trees had dual effects on soil physics conditions. It protected and improved the surface soil but concealment degrades on subsurface soil physics condition.The study of different aged orchards (<10 yr, 10-20 yr, >20 yr) in the Weibei Region showed that soil bulk density in the 0~30 cm soil layer decreased as orchard age increased. However, increased in 30~60cm soil layer to more than 1.30 gï¹’cm-3 which is the upper limit for healthy garden soil. Soil bulk density in the 10~30 cm soil layer was less in orchards than cropland. Soil hardness increased rapidly in 30~45cm, almost up to 1000 kPa which is the upper limit for healthy root growth. Soil hardness closely related to soil water content. Soil water content was higher in 0~30cm but lower in 30~60cm soil layer which caused the problem of Soil desiccation, one of the reasons to lead to soil hardness with no irragation. Subsurface soil hardness had negative effect on the increase of moisture content in deep soil. Physical clay(<0.01mm)and clay(<0.001mm) content have different degree eluviation and deposition in 0~80cm soil profile. The depth of soil profile which clay eluviation and deposition increased as planting-age increased. It showed that the hardness of orchard soil in weibei area was caused by clay eluviation and deposition and drought.Soil aggregation was poor throughout the entire profile of the orchard soils. Most water stable aggregates in the orchard soils were in the 0.25~0.50 mm size class. The amount of >0.25 mm water-stable aggregates increased as orchard age increased. The amount of water-stable aggregates in 20 yr old orchards was two times greater than in 10 yr old orchards. Fruit trees had a dual effect on soil physical conditions. Soil physical condition improved in the topsoil but worsened in the subsoil as orchard age increased.2. Soil fertility quality degrades significantly.Exchangeable Ca2+ and degree of Ca saturature are both soil index of health orchard soil. The exchangeable Ca2+content in 0~60cm surface soil increased as the depth of soil layer increased. That means decalcification happened in orchard soil in weibei area. The eluviation and deposition of Ca2+ was significant, especially in >20yr old orchards and the amount of exchangeable Ca2+ increased as the soil depth increased in 0~60cm soil layer. The amount of exchangeable Ca2+ decreased as planting-age increased in 0~100 soil layer (above the caliche). The distribution of water-solution Ca2+ and exchangeable Ca2+ was consistent in soil profile. Water-solution Ca2+increased as soil depth increased in 0~60cm soil layer. According to the soil quality health index (calcium degree>80%), 47.6% soil calcium degree did not reach that index, which means unsaturated exchangeable Ca2+ exists even in limy soil layer, moreover, more soil layer with unsaturated exchangeable Ca2+ as the increase of planting-age. Planting apple trees has no significant effect on CEC, which was relatively smaller in full fruit period orchard. Orchard soil quality in weibei area was significantly worse as the planting-age increased.According to the character of orchard soil fertilization, Alkali-hydrolyzable nitrogen appeared no significant difference in soil profile of three different horizon levels under fruit crown of different planting-age orchards. Alkali-hydrolyzable nitrogen mainly distributed in 0~60cm soil layer and decreased as the soil depth increased. The amount of alkali-hydrolyzable nitrogen depleted significantly in >20yr old orchard, especially in 0~100cm soil layer, higher than it was in 10~20yr old orchard. Alkali-hydrolyzable nitrogen in 100~150cm soil layer increased as the planting-age increased, but the difference was not significant. Alkali-hydrolysable nitrogen accumulated remarkably in different soil layer of different planting-age orchards. The variability of available P was significant between soil layers. The amount of available P in 0~20cm soil layer was higher, and it decreased as the soil depth increased. The available P content was more than 50 mgï¹’kg-1 and had potential environmental risk. The amount of available P in soil profiles accumulated significantly in the three space levels, especially in the soil layer below 40cm, the variability of available P content was more significant in >20yr old orchard than in other two planting-age orchards, which means that the available P gradually migrate downward and accumulated in deeper soil layer as the planting-age increased.Nitrate nitrogen content in orchards increased as planting-age increased. The amount of nitrate nitrogen was higher in the horizontal level which was 100cm from stem in >20yr and <10yr old orchard, however, nitrate nitrogen was higher in horizontal level which was 150cm from stem in 10~20yr old orchard. There was no significant difference in soil ammonium nitrogen content which means no correlationship among soil ammonium nitrogen content, planting-age, fertilization and human management. Soil mineral nitrogen content increased as planting-age increased. The difference was significant between horizontal levels in <10yr old orchard, however, this did not appear in 10~20yr old orchard and >20yr old orchard. Soil ammonium nitrogen content increased as planting-age decreased. The content keep stable in 60~150cm soil layer and there was no significant difference in different planting-age orchard. Applying moderate N fertilizer in orchard soil is important in orchard soil nutrient management.
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