低活性富铁层黏粒阳离子交换量诊断标准的土壤学基础和指标修订研究

Ferrosols is specific soil order in Chinese Soil Taxonomy (CST). LAC-ferric horizon is the diagnostic horizon with clay CEC7 <24 cmol(+)/kg as one of the definitions in which clay CEC7 is calculated by soil CEC7×1000/clay content, not directly measured from clays themselves. However, the calculated value is higher than the measured one, which often lead the misjudgment some red soil types in CST. Revising clay CEC7 definition of LAC-ferric horizon is necessary and urgent.. In this project application, we will collect a series of different red soil samples, measure clay CEC7, soil CEC7 and soil other properties of the samples, compared and analyze the difference and the correlation of clay CEC7 and soil CEC7 as well as explore the inner pedological mechnism , determine the contribution of different soil properties to soil CEC7, set up the new calculating formula for clay CEC7 on the easily-measured soil properties, and finally validate and revise the value of clay CEC7 in the definition of LAC-ferric horizon.

中国土壤系统分类中设有富铁土纲，诊断层为低活性富铁层，其划分依据之一是黏粒CEC7<24 cmol(+)/kg，但不是实测的黏粒CEC7，而是依据细土CEC7×1000/黏粒含量换算得到，但这一换算值远高于实测值，会导致依据换算值得出的土壤系统分类高级单元出现误判。关于修订现有黏粒CEC7这一指标的呼声极为迫切。. 为此本申请项目旨在是通过获取大量的南方红壤样品，在实测细土CEC7和颗粒组成、pH、有机质和黏土矿物组成等关键属性，提取黏粒实测黏粒CEC7；在此基础上比较黏粒CEC7和细土CEC7差异以及分析形成这种差异的内在土壤学特别是土壤矿物学成因，定量剖析我国南方红壤系列成土因素和土壤不同属性对细土CEC7的贡献，建立基于细土CEC7和其他土壤易测属性的黏粒CEC7新算法，修订CST中低活性富铁层黏粒CEC7划分标准。

中国土壤系统分类中，粘粒阳离子交换量(CECclay)采用土壤CEC/黏粒含量×1000的算法，会导致结果偏高，从而热带或亚热带地区的一些富铁土误判为淋溶土或雏形土，亟待修订。为此，本项目针对我国热带和亚热带地区的可变电荷和酸性土壤，建立了不同情形下CECclay的新算法。建立的CECclay新算法主要如下：.1、基于CECsoil和土壤其他易测属性的新算法.（1）CECclay=0.441CECsoil/Clay.（2）CECclay=7.289log(CECsoil/Caly).（3）CECclay=16.958+0.811CECsoil-0.879pH-0.284SOM+0.128Slit-0.103Clay.2、基于实测CECclay、CECsoil和土壤其他易测属性的新算法.（1）CECclay=10.32-0.14pH-0.05SOM-0.11FeO+0.01Silt-0.01Clay+1.17CECsoil.（2）CECclay=−3.40+0.01Sand+0.02Silt+1.05CECsoil.3、基于乙酸铵(pH7.0)交换法与BaCl2-MSO4强迫交换法测定的新算法. CECclay=2.3114×CEC1soil**1.14961/clay×1000.4、基于区域性（江西省）的新算法.（1）高有机质. 1）黏土类，CECclay=[CECsoil-0.510SOM+0.899]/Clay×1000. 2）粘壤土类，CECclay=[CECsoil-0.817SOM+1.316]/Clay×1000. 3）壤土类，CECclay=[CECsoil-(2.492SOM-15.665)]/Clay×1000.（2）低有机质. CECclay=[CECsoil-0.853CECslit-0.899]/Clay×1000. CECclay=CECsoil-1.2804L-1.4441T-1.5141pH+69.1305]/Clay×1000. 其中，L和T分别为纬度和年均气温。