渭北旱塬苹果园土壤紧实化现状及成因

本研究通过分析渭北旱塬苹果园土壤的紧实化现状及其诱导因素,找出影响当地苹果园健康发展的土壤退化隐性因素,为果园科学管理提供理论依据。分别选取种植年限＜10年(4～6年)、10～20年(14～16年)和＞20年(24～26年)的苹果园各4个,分析0～60 cm土层土壤容重和紧实度随土层深度的变化规律,探明果园土壤内部紧实化发生的部位和退化程度,同时,通过分析土壤团聚体数量及其稳定性、土壤黏粒和有机质含量,揭示引起渭北果园土壤内部紧实化的原因。结果表明: 渭北果园0～60 cm土层土壤容重和紧实度均随植果年限和土层深度的增加而显著增大。以20 cm土层为界,渭北各园龄段苹果园土壤具有明显的“上松下实”变异特征,20 cm以上土层上述各指标基本满足苹果树的正常生长需求,20 cm以下土层土壤则已超出了苹果树健康生长的阈值。造成渭北苹果园亚表层以下土壤紧实化的原因主要是土壤团聚作用差、有机质含量低,加之植果期间人为扰动少,土壤中分散的黏粒会向下层移动。此外,随着植果年限的增加,土壤紧实化过程更加明显。

Status and causes of soil compaction at apple orchards in the Weibei Dry Highland,Northwest China

To find out the recessive factors of soil degradation threatening the healthy development of Weibei apple orchards, we examined soil compaction status and its inducing factors. This study could provide a theoretical basis for apple orchard scientific management. We evalua-ted the changes of soil bulk density and compaction with the depth of soil layer in 0-60 cm in four apple orchards with various planting period, including <10 years(4-6 years), 10-20 years(14-16 years) and >20 years(24-26 years). The location and degradation degree of soil compaction in orchard were investigated. Through analyzing the number of soil aggregates and the stability, soil clay and organic matter contents, we tried to find the reasons for the internal compacting of soil in Weibei orchards. The results showed that soil bulk density and compactness in the 0-60 cm soil layer significantly increased with increasing planting years and soil depth. With the 20 cm soil layer as a boundary, soil of Weibei orchards in different planting years showed obvious variation characteristics of loose in upper and compact in lower. The above indicators in soil layer above 20 cm basically met the normal requirements of apple trees, whereas soil layer below 20 cm exceeded the threshold for healthy growth of apple trees. The main reasons for soil compaction below the subsurface layer were poor soil aggregation, the lack of soil organic matter, less human disturbance during fruit planting, and the movement of scattered clay particles to the lower layer. With increasing years of fruit planting, soil compaction became more severe.