Thickness Of Cumulic Epipedon And Its Effects On Soil Taxnonmy Of Lou Soil

Lou soil is one of the most important agricultural soils in Guanzhong area,which has formed obvious cushion layer on the surface of the original soil because of the long-term artificial soil manure mound.In order to understand the soil forming characteristics and systematic classification of Lou soil,18 typical Lou soil profiles in Guanzhong area were selected,and the classification of Lou soil in advanced and grass-roots classification units were determined according to the Chinese soil system classification scheme through field soil forming factors,profile shape investigation and soil sample analysis.At present,there are few descriptions of the spatial differentiation of Lou soil.Based on the semi variance function simulation and interpolation analysis of 288 Lou soil mound data in Guanzhong Lou soil area,the spatial differentiation characteristics of Lou soil mound thickness in Guanzhong area are obtained.The results show that:?1?The thickness of Lou mound in Guanzhong area is between 5?100 cm,with an average of 53.53 cm.Generally,the thick cushion in the East is widely distributed,and the thickness in the southwest is relatively thin.Through the interpolation of the optimal semi variance function model,the classification areas of different thickness of the cushion are:60?70 cm,>70 cm,50?60 cm,40?50 cm,20?40 cm,0?20 cm.Mainly concentrated in60-70 cm,accounting for 51.68%of the total area of Guanzhong.In general,the area of Guanzhong is more than 90%,and the thickness of Lou soil mound is more than 50 cm.?2?The test section consists of 9 diagnostic layers and diagnostic characteristics,including the surface layer,the clay layer and the calcium accumulation layer,belonging to 5subclasses,among which 3 sections are the calcium accumulation soil,2 sections are the mottled soil,8 sections are the common soil,4 sections are the pile accumulation soil,1 section is the common simple cultivation soil,which is the rudiment soil According to the standard,it can be divided into 9 Tu groups,including 13 sections with clay particle size and 5 sections with loamy;16 sections with siliceous mixed mineralogical type,2 sections with mixed soil temperature,14 sections with calcareous and 4 sections without acid;according to the standard of soil system division,18 sections can be divided into 18 different soil systems.The statistical results of 71 profiles of Lou soil in related literatures show that the thickness of the cushion layer is between 17 cm and 97 cm,and the average thickness is 50.07 cm.Therefore,the 50cm thickness of the surface layer of the cushion layer is suitable for the classification of typical Lou soil.In order to further improve the classification of soil system in China,and strengthen the ability to distinguish and classify the rudiment soil with the phenomenon of stacking and bedding,it is suggested to add the subspecies of stacking and drying and moistening rudiment soil.?3?The profile color of artificial soil,eluvial soil and rudimentary soil is mainly turbid yellow brown;the new soil body is mainly composed of clay plastic film and humus plastic film;the eluvial soil is mainly composed of clay plastic film;no new soil body is found in rudimentary soil.The artificial soil is mainly composed of silty clay and silty soil,and the eluvial soil is mainly composed of silty clay.Only one texture appears in the rudimentary soil,which is silty soil.Soil pH increased with the increase of CaCO₃content,which had a great relationship with loess parent material.