(土壤学）第六章-土壤结构和 与力学性质-土壤颗粒和质地.pptVIP

4、植树种草，培肥改土 在过砂或过粘的土壤上，种植适生的乔灌木树种或耐贫瘠的草本植物可改良土壤质地、培肥土壤。 * * * * ISSS:INTERNATIONAL SOCIETY OF SOIL SCIENCE USDA:UNITED STATES DEPARTMENT OF AGRICULTURE * * * * * * * * An example of its use is shown for a sample with 15 percent sand, 35 percent silt, and 50 percent clay: find 15 percent on the sand axis and draw a line up, parallel to the silt axis; find 35 percent on the silt axis and draw a line down, parallel to the clay axis; then find 50 percent on the clay axis and draw a line to the right parallel to the sand axis. Where these three lines intersect identifies the texture class-in this case as clay. * Considering the great importance of soil texture, it is valuable to know how to measure soil texture. There are two general ways to do this: one method can be done quickly in the field without special equipment (texture-by-feel); texture-by-feel is easy to do, but requires practice and experience to do well. another method is done in a lab, which is more accurate but requires more time and specialized equipment. * * * A more quantitative and accurate means of determining the textural class of a soil sample is to use a laboratory procedure. The general steps are to separate them by sieving and sedimentation. Sedimentation can be used to separates particles of different size because the velocity of settling is proportional to the square of particle diameters. Mathematically, this is described by stoke laws. * In this case a hydrometer is used to read the particle density directly. The value in the hydrometer stem represent the amount of silt and clay. * * * * * 华中农业大学资源与环境学院 华中农业大学资源与环境学院 第一节 土壤颗粒和质地 Soils Sustain Life 一、土壤粒级 土粒的种类 单粒、复粒 矿质、有机 土壤矿物质是不同粒径颗粒的组成 按土粒的大小将土壤单粒分为若干组，这些组称为土壤粒级(particle size fraction) 石砾、砂粒、粉粒、粘粒 、胶粒 Soils Sustain Life 土壤颗粒组成 Soils Sustain Life 二、土壤粒级分类 常见的土壤粒级制 ISSS 粘粒 粉粒 砂粒 石砾 USDA 粘粒 粉粒 砂粒 极粗砂粒 石砾 C. 物理性粘粒 物理性砂粒 石砾 CN 粘粒 粉粒 砂粒 石砾 0.002 0.02 2.0 0.05 1.0 0.01 0.002 0.05 0.002 2.0 1.0 1.0 Soils Sustain Life 三、土壤粒级的性质 粗 →