The Research Of Soil Diagnostic Characteristics And Systematic Classification In Arid And Semi-arid Grasslands In Inner Mongolia

With the refinement of land use methods,soil system classification with quantitative,standardized and international characteristics has become the trend of international soil classification.At present,the soil classification data of Inner Mongolia are mostly classified data of soil occurrence and lack of classified data of soil system.This study is based on the soil of arid and semi-arid grassland in Inner Mongolia.Through the methods of field investigation and indoor analysis,were used to study the soil physical and chemical properties and genetic characteristics of the soil tested in the study area were analyzed and described.In addition,there are gypsum and salt deposits in some parts of the arid area of Inner Mongolia,and the indoor analysis of water soluble salt and gypsum in the soil of the arid grassland is carried out.According to"Chinese Soil Taxonomy?Third Edition?"and"Chinese Soil Taxonomy-the principles and standards of family of soil and soil series are established?using the draft?",the diagnostic horizon,diagnostic characteristics,Diagnosis of phenomenon,Order,Suborder,Groups,subgroup,and family of soil and soil series were retrieved and partitioned.The results showed that:?1?The soil layer of the semi-arid grassland is between 120¹70cm.The surface color of the soil is mostly black brown,turbid yellow brown,dark brown and brown ash.The color of the subsurface layer is mostly turbid yellow brown,turbid yellow orange,gray brown,dark brown and brown ash.The soil structure is mostly lump,the soil texture is sandy loam and loamy soil,soil is soft and a few sections have lime reaction.In response,the sections 15-008and 15-030 have calcic horizon.The soil layer of the arid grassland is between 90¹56cm,the surface color is mostly turbid brown and turbid orange,the subsurface layer color is turbid yellow orange,orange white and turbid orange,the soil texture is sandy loam and loam,the soil structure is lump,soil is hard,profile have lime reaction,and many sections have calcic horizon.?2?The content of soil clay particles is low,soil viscosity is weak,soil sand content is the highest,silt content is the second,clay content is the lowest,soil is salt based saturated soil,exchangeable base ion is Ca²⁺and Mg²⁺mainly,soil total nitrogen content is less than 4 g kg^-1,C/N<10.Most of the soils in the semi-arid grassland are mostly neutral and microalkaline,and the cation exchange and organic carbon content of the soil are higher.Most of the soil is alkaline,and the amount of cation exchange and organic carbon in the soil is low.The tested soil contains a small amount of stone paste and water soluble salt,and its content is low.?3?The tested soil has 2 diagnostic surfaces horizons,2 diagnostic subsurfaces horizons,2diagnostic evidence,and 7 diagnostic characteristics.According to the Chinese Soil Taxonomic?Third Edition?,3 order,5 suborders,6 groups and 6 Subgroups were retrieved from the tested soil,and 6 subcategories:the typic haply-ustic isohumosols,the typic haply-udic isohumosols,the typic haply-ustic cambisols,the typic bori-udic isohumosols,the typic haply-udic isohumosols,and the calcaric aridi-orthic primosols.The classification of soil system and the classification of soil occurrence in the study area were approximated,and the subclasses of the same subclass in the soil system classification were found.The subclasses of the classification were meadow,calcareous soil,chestnut soil,light chestnut soil,brown calcium soil and light brown calcium soil.The tested soil is divided into 13 soil family and 18 soil series.?4?According to the Chinese Soil Taxonomy?Third Edition?,there are some problems in it:?1?According to the Penman formula in Chinese Soil Taxonomy?Third Edition?,the soil moisture in the semi-arid grassland is not in conformity with the actual soil moisture status.?2?Because of the lack of aridic epipedon,it can not be divided into aridsols.It is considered that the classification criteria for"aridic epipedon"in Chinese Soil Taxonomy?Third Edition?are too strict.?3?it is obvious that it is inappropriate to retrieve the udic cambosols.This is not suitable.It is suggested that further study and discussion should be carried out on the criteria for the division of"aridic epipedon".It is suggested to add calcium accumulation to calci-ustic cambosols Chinese Soil Taxonomy?Third Edition?.