Study On Genetic Characteristics And Taxonomy Of Limestone Soils In Chongqing

Soil is the material basis on which people live and is an indispensable natural resource.Soil classification is the foundation of understanding soil and the basic method of studying soil.Currently,soil classification in China has entered the stage of quantitative and systematic classification,and its development trend is quantitative,standardized and standardized.Soil systematic classification has been carried out in many provinces and a series of achievements have been made.Soil systematic classification in chongqing is also under way.Of limestone soil in chongqing,has proven the happening of the characteristics of the advanced system of this kind of soil classification and basic classification unit,this paper takes chongqing 17 typical individuals of limestone soil as the research object,through data collection and field investigation,stratified sampling,laboratory analysis and other methods to achieve the selected typical individuals of soil environment,soil profile morphological characteristics and the basic physical and chemical properties and other relevant information and indicators,referring to the principles and methods of the Chinese soil taxonomic classification,specific diagnosis of typical individuals of the tested soil layer and diagnostic characteristics,the senior delimit the system classification and classification units at the grass-roots level,The limestone soil genetic classification and systematic classification in chongqing were compared to provide reference for the two classification systems.The main research results are as follows:?1?Among many factors of soil formation,parent material,topography,soil moisture and human activities have profound influence on the occurrence characteristics and quantitative indexes of limestone soil in chongqing.Chongqing limestone soil due to carbon dioxide and water solution for a long time,its process and characteristics of soil and rocks close connection of the weathering and leaching of carbonate,mainly for called chaotu Triassic limestone,dolomite,siliceous rock weathering residual deposit,distribution between 300¹150 m low hilly land,at low elevation area generally Mosaic and yellow soil,and another seven section below cushion material for the whole piece of limestone;Through different land use modes,human activities act on soil forming factors,change the formation process of soil,and change the original soil structure,water retention and air permeability through cultivation.The seasonal change of rainfall changes the movement and morphology of iron in soil.In the dry/wet state,the tested section color was mainly turbid yellow-orange,turbid yellow-brown,turbid yellow,yellow-brown,olive brown,turbid brown,bright brown,brown and so on.The soil texture of most limestone soils is dominated by silty clay and silty clay loam,as well as loam,sandy loam and clay.The soil structure is mostly massive,and a few are granular.?2?According to“the Keys to Chinese soil taxonomy?third edition?”,a total of1 diagnostic surface horizons was retrieved from the limestone soil in Chongqing:Ochric epipedon.Three diagnostic subsurface horizons:argic horizon,cambic horizon and calcipan;8 diagnostic characteristics:L.C.of carbonate rocks,lithic contact,soil moisture regimes,redox features,soil temperature regimes,humic property,ferric property and calcaric property.One diagnostic evidence:calcic evidence.?3?According to“the Keys to Chinese soil taxonomy?third edition?”,the limestone soil in Chongqing is divided into three Ordere:Argosols,Cambosols and Primosols.There are 5 Suborder:Perudic Argosols,Udic Argosols,Perudic Cambosols,Udic Cambosols,Orthic Primosols.There are 6 Group:Carbonati-Perudic Argosols,Carbonati-Udic Argosols,Carbonati-Perudic Cambosols,Carbonati-Udic Cambosols,Ferri-Udic Cambosols,Udi-Orthic Primosols.There are 7 Subgroup:Humic Carbonati-Perudic Argosols,Typic Carbonati-Perudic Argosols,Typic Carbonati-Udic Argosols,Humic Carbonati-Perudic Cambosols,Brown Carbonati-Udic Cambosols,Typic Ferri-Udic Cambosols,Carbonatic Udi-Orthic Primosols.?4?According to“Criteria for establishment of soil family and soil series in Chinese Soil Taxonomy”,combines the condition of limestone soil field survey in Chongqing,choose the level of soil particle size,mineralogical type,calcareous and acid-base reaction level,soil temperature level as a basis for the tu division,depth and thickness,surface soil and soil texture,clastic rock in the soil,such as tuberculosis,intrusive body and so on as the basis of soil classification,divided into 16 minority and17 soil series.?5?The Chinese Soil Taxonomy?CST?references to soil genetic classification?SGC?were identified.The yellow limestone soil subgroups in GSCC were sorted into Typic Carbonati-Perudic Argosols,Typic Carbonati-Udic Argosols,Humic Carbonati-Perudic Cambosols,Brown Carbonati-Udic Cambosols,Typic Ferri-Udic Cambosols,Carbonatic Udi-Orthic Primosols.The black limestone soil subgroups in GSCC were sorted into Typic Carbonati-Perudic Argosols,Brown Carbonati-Udic Cambosols,Carbonatic Udi-Orthic Primosols.It can be seen that there is no simple and single correspondence between soil types and soil phylogenetic classification.The same subclass in soil phylogenetic classification can correspond to different subclasses in soil phylogenetic classification,and the same subclass in soil phylogenetic classification can also correspond to different subclasses in soil phylogenetic classification.The reference between the two is only an approximate reference,which cannot be simply one-to-one correspondence.Due to the difference between the two system classifications,the corresponding relationship has complexity and uncertainty.?6?In the systematic classification of limestone soil,some considerations were made that the nodules of calcium carbonate did not participate in the determination and analysis of the content of calcium carbonate,resulting in the lower content of the experimental data than the equivalent of CaCO₃ in the actual soil layer,which would affect the determination of calcic deposit and calcic deposit.It is suggested to revise the retrieval criteria of calcic deposits and calcic deposits,and to consider the priority of comminution grinding or secondary carbonate retrieval of CaCO₃ equivalents.The steep topography has an important influence on the classification of soil classes.In the karst areas in southeast Chongqing with an altitude of less than 1,000 m,the higher the altitude is,the better the water condition will be,and the more prone to the formation of clay layer.If the elevation is roughly the same,the slope is the primary factor affecting the formation of clay layer in the soil.A finer texture is recommended when differentiating soil systems by texture.On the basis of strengthening systematic classification research,China's soil systematic classification can improve the application technology,expand the application scope,provide help for solving practical production problems,and play a greater role in social development.