种植苹果树对渭北果园土壤胶结物质分布的影响

本研究通过系统研究种植果树对土壤胶结性物质的演化规律及其与土壤团聚体稳定性之间关系的影响,探索影响果园土壤团聚体状态的因素,以期为果园科学管理提供理论依据。在渭北旱塬苹果主产区分别选取10 a、20 a的苹果园和农田(冬小麦-夏玉米轮作,对照)各4个,在果树冠层投影范围内距树干2/3处逐层采集0~100 cm土层土壤样品和0~50 cm土层原状土壤样品,研究不同植果年限果园及农田土壤剖面黏粒、有机质、CaCO_3等团聚体胶结物质的分布及其与团聚体稳定性之间的关系。结果发现:在0~100 cm土层范围内,各果园土壤黏粒含量基本随土层深度的增加而递增,且在0~40 cm土层表现为农田10 a果园20 a果园,40 cm以下土层则呈现相反的态势;种植果树相比农田可显著增加0~100 cm土层土壤有机质总储量,但随着种植果树年限的增加,土壤有机质总储量呈递减趋势;在0~100 cm土层土壤CaCO_3总储量表现为10 a果园农田20a果园,但在0~40 cm土层CaCO_3含量及储量表现为10 a果园农田20 a果园,而40~100 cm土层则为20 a果园10 a农田。皮尔森相关分析发现(29)0.25 mm土壤团聚体的数量和平均重量直径(MWD)与土壤黏粒、有机质和CaCO_3含量密切相关,其中机械稳定性团聚体的数量和稳定性主要受土壤中CaCO_3、有机质含量的影响,水稳性团聚体的数量和稳定性主要受土壤中黏粒和CaCO_3的影响。总之,植果显著改变了土壤中黏粒、有机质、CaCO_3的演化过程和趋势,随植果年限增加,果园土壤黏粒和CaCO_3在土壤较深土层淋溶淀积明显;各果园土壤有机质总储量虽然高于农田,但随植果年限增加,有逐渐减少的趋势。可见植果明显加速了渭北黄土塬地土壤的残积黏化和钙化过程,影响着表层土壤团聚作用和底层土壤的紧实化和坚硬化程度。

Effects of planting apple trees on distribution of soil cementing materials in Weibei apple orchards

The aim of this study was to explore the effects of planting apple trees on soil cementation substances, to determine the relationship between soil aggregate stability and soil cementation substances, to reveal the factors affecting soil aggregate state and to build theoretical basis for the scientific management of apple orchard in Weibei Plateau. Four replicates of 10-year-old and 20-year-old orchards and four farmlands (wheat-corn rotation, CK) were selected for the experiment in Binxian County, Shaanxi Province. Soil samples within two-thirds of the radius of apple tree canopy were collected. Four replicates of undisturbed core samples were taken by driving volumetric rings (100 cm³) into the 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm and 40-50 cm soil layers to determine soil aggregates. Another four replicates were collected from 10 cm and 20 cm intervals respectively over a depth of 0-60 cm and 60-100 cm in each plot to determine the soil contents of clay, organic matter (SOM) and calcium carbonate (CaCO₃) contents. The results showed that soil clay content increased with increasing depth in the 0-100 cm soil layer. The increase was in the order of farmland > 10-year-old orchard > 20-year-old orchard for the 0-40 cm soil layer and reverse order was noted for the 40-100 cm soil layer. Planting apple trees increased SOM content in the 0-100 cm soil layer of the orchard. However, SOM content decreased with increasing planting age of orchard. The content of soil CaCO₃ was in the order of 10-year-old orchard > farmland > 20-year-old orchard for the 0-40 cm soil layer, 20-year-old orchard > 10-year-old orchard > farmland for the 40-100 cm soil layer, and 10-year-old orchard > farmland > 20-year-old orchard for the 0-100 cm soil layer. Pearson correlation analysis showed that the quantity and mean weight diameter (MWD) of > 0.25 mm soil aggregates were closely link to soil clay, SOM and CaCO₃ contents. Macro aggregates (> 0.25 mm) and MWD of mechanically stable aggregates were mainly affected by CaCO₃ and SOM contents. However, the quantity and stability of water stable aggregates were mainly affected by soil clay and CaCO₃ contents. Overall, planting apple trees changed the evolution processes of soil clay, SOM and CaCO₃. Soil clay and CaCO₃ migrated to deep soil with increasing age of orchard. The total storage of SOM in orchard was higher than that in farmland, but decreased with increasing planting age. It was concluded that planting apple trees enhanced soil residual viscosity and calcification, which affected aggregation of surface soil and compaction and hardness of bottom soil.