用分形理论评价长期施肥对土壤理化性质的影响

为探讨不同施肥处理对土壤理化性质和团聚体分形特征的影响以及用分形特征评价长期施肥对土壤理化性质尤其是土壤团聚体稳定性的影响,采用1个现存的分形模型作为主要研究手段。结果表明,有机肥-化肥混施分形维数较小,单施化肥则较大。分形维数与团聚体平均质量直径(MWD)、几何平均直径(GMD)呈显著负相关,因此,分形维数能同时反映团聚体粒径分布和土壤结构稳定性。另外,分形维数越高,黏粒含量越高,土壤容重越大,有机质含量越少;反之,分形维数越低,大团聚体和有机质含量越高,土壤容重越小。分形维数高时,易导致大孔隙分布少,微小孔隙分布多,不利于水肥移动;分形维数低时孔隙分配较合理,水肥能得到有效利用。因此,在农业生产中应当强调有机肥和化肥配施,有机肥肥源较缺的地区应当重视秸秆还田。

Effects of Long-term Fertilization on Soil Properties Using Fractal Theory

This study investigated the effects of different fertilization practices on soil physical properties and fractal features of aggregates,and evaluated the effects of fractal features on soil physical properties especially on aggregate stability using an existing fractal model.The results showed that the fractal dimension(D) seemed smaller under treatments applying organic materials than under treatment applying chemical fertilizer alone.The fractal dimension had significantly negative correlation with mean weight diameter (MWD) and geometric mean diameter(GMD),so it could reflect aggregate size distribution as well as soil structure stability.Besides,higher D often indicated higher clay content,higher soil bulk density,and lower organic matter content,while lower D indicated more macroaggregates,lower soil bulk density,and higher organic matter content.The former often induced less macro-pores and more micro-pores,which were bad for soil water and nutrition availability,and vice versa.It was concluded that integrated application of organic and chemical fertilizers was essential for maintaining high soil quality.Under conditions where there were limited organic fertilizers,it was necessary to return crop residues into the field.