矿质土粒( soil particle) 土壤颗粒绝非标准球形,是各种不规格形状的,那么,粒径的 含义就并非它们的真实直径或半径。--当量直径 当量直径(有效直径) equivalent diameter or effective diameter of soil particle∶与同质的标准球形颗粒沉降速度相同的土粒直径 或半径(建立在颗粒分析方法上) 3.粒级分类制( classification systems of soil separates) 土壤颗粒大小是连续分布的,要确定土壤颗粒的分级需要硏究土壤颗粒大小 和性状间关系,找到由量变到质变分界点,突变点,就可以作为化分类别的依 据。受人为因素的影响,当前土壤立即分类制有 Size is a continuous variable. Although dividing particle size into discrete size ranges is arbitrary, it is also useful. Individual soil particles range in size from boulders that are meters in diameter to clay particles that are less than 0. 002mm(less than 2 um)in diameter Particles so different in size also have different properties. The terms used to divide the continuous size variable, diameter into discrete units are considered next一.矿质土粒 （soil particle） 土壤颗粒绝非标准球形，是各种不规格形状的，那么，粒径的 含义就并非它们的真实直径或半径。-----当量直径 当量直径（有效直径）equivalent diameter or effective diameter of soil particle : 与同质的标准球形颗粒沉降速度相同的土粒直径 或半径（建立在颗粒分析方法上） 3. 粒级分类制（classification systems of soil separates) 土壤颗粒大小是连续分布的，要确定土壤颗粒的分级需要研究土壤颗粒大小 和性状间关系，找到由量变到质变分界点，突变点，就可以作为化分类别的依 据。受人为因素的影响，当前土壤立即分类制有： Size is a continuous variable .Although dividing particle size into discrete size ranges is arbitrary, it is also useful. Individual soil particles range in size from boulders that are meters in diameter to clay particles that are less than 0.002mm (less than 2 m）in diameter .Particles so different in size also have different properties. The terms used to divide the continuous size variable, diameter, into discrete units are considered next