在渭北果区选择不同园龄(<10年、10～20年、>20年)果园,分层测定0～60 cm土层土壤容重、土壤坚实度、土壤含水量以及表层土壤团聚体组成等物理性状,进一步分析了果园土壤物理性状随园龄的变化特征.结果表明:土壤容重在0～30 cm土层随园龄增长而降低;在30 cm以下土层随园龄增长而增加,超过了健康园艺土壤的质量标准1.30 g·cm-3;与休闲农田相比,种植果树可降低10～30 cm土层土壤容重;但30 cm以下土层土壤坚实度急剧增大,接近或达到了限制根系延伸的土壤质量标准1 000 kPa;与休闲农田相比,种植果树对于降低17.5～27.5 cm土层的坚实度具有明显作用.果园表层土壤团聚体状况整体较差,水稳性优势团聚体直径为0.5～0.25 mm,>0.25 mm水稳性团聚体含量随园龄增加而增大,>20年果园比<10年果园高1倍.种植果树对表层土壤具有明显的保护和改善作用,却在深层发生着紧实化和坚硬化过程.果树对土壤物理状况的双重效应体现在对0～30 cm土层土壤结构具有改善作用,对30 cm以下土层土壤结构有破坏作用.果园土壤"深层的隐蔽性退化过程"影响着果树根系健康生长,应当给予极大关注.%Soil bulk density, hardness, moisture and surface soil aggregation composition were measured in ＜10-, 10～20- and ＞20-year-old orchards in Weibei Region. The results showed that soil bulk density in the 0～30 cm soil layer decreased with increasing orchard age. However, bulk density below the 30 cm layer increased with increasing orchard age, exceeding the 1.30 g·cm-3 upper limit for healthy garden soils. Soil bulk density in the 10～30 cm soil layer was lower in orchards than in croplands. Soil hardness increased sharply below the 30 cm soil layer, almost reaching the 1 000 kPa upper limit of soil quality standard for healthy root growth. Soil hardness in the 17.5～27.5 cm soil layer is lower in orchards than in croplands. Soil aggregation status was poor in surface soil of orchards. Most water-stable aggregates in the orchard soils were in 0.5～0.25 mm range class. Contents of water-stable soil aggregates ＞0.25 mm increased with increasing age of orchards. Water-stable soil aggregates contents in 20-year-old orchards were two times higher than those in 10-year-old orchards. Fruit trees have a dual effect on soil physical characteristics. Soil physical conditions was generally improved in topsoil (0～30 cm), but worsen in subsoil (＜30 cm) with increasing orchard age. As latent degradation of subsoil in orchards affected the healthy growth of fruit trees, any such degradation should be carefully monitored.
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