Pedogenesis Characteristics Of Typical Cropland Soils In Central Hunan And Their Attribution In Chinese Soil Taxonomy

In this paper,21 typical soil profiles in central Hunan are studied.According to Keys to Chinese Soil Taxonomy(3rd edition)and Criteria for establishment of Soil Family and Soil Series in Chinese Soil Taxonomy,based on the soil field investigation,this paper study the characteristics of soil profiles,the physical and chemical properties of these soil profiles,and determines the diagnostic and diagnostic characteristics of typical soil profile,establishes a new soil system.The main results are as follows:(1)There is a significant difference between different types of soil profiles developed in different parent materials in central Hunan.The soil color is different of profiles developed in 6 different parent materials.And the soil color developed from same parent material with different development degree was also different.The depth of soil profile developed in different parent materials is deep or shallow.The porosity of sandstone and granite weathered soils is higher than that of other parent soils.It can be found by comparison that the limestone weathered soil is more likely to form clay iron-manganese gel film or ferromanganese nodules than other parent soils,but it is difficult for sandstone weathered soil to produce soil neovasites,such as porphyry or colloidal film.(2)The soil texture is related to parent materials.The content of soil clay developed from limestone weathering,purple rock weathering,slate weathering and quaternary red clay is higher,the texture is mostly silt clay and clay.Granite weathering material and sandstone weathered soil silt content is higher,texture is mostly silt,clay loam.(3)The soils derived from granite,slate and quaternary red clay in the test soil are acidic or strongly acidic;The soils of limestone,sandstone and purple rocks are acidic and have lime reaction.The soil profile developed by limestone,sandstone,slate and quaternary red clay have poor soil exchange performance.There is a great difference between the layers of soil clay CEC7 in the two parent material development profiles of purple rock and granite.The content of total iron in different parent materials changed greatly,but the content and degree of free iron in soil were higher,which reflected the characteristics of high weathering.(4)The content of soil organic carbon decreased with increasing section depth and varied among different levels.The soil fertility level in different sections is different,but the content of soil potassium in purple rock and granite is relatively high,and phosphorus and potassium are relatively deficient.(5)According to Keys to Chinese Soil Taxonomy(3rd edition),three diagnostic surface layers were identified in the study area,4 diagnosis table lower layer,8 diagnostic characteristics,1 diagnosis.(6)The soil in the study area is divided into 4 soil classes:iron-rich soil,leaching soil,embryonic earth and newly formed soil,5 sub-classes,10 soil types,13 sub-classes,21 soil families and 21 soil series.(7)The classification results of Chinese soil taxonomy and soil genetic classification are not corresponding,even if the soil dimensions of the individual purple soils correspond to the soil classes in the system classification,they do not correspond in the low-level classification units.