Taxonomic Classification Of Purple Soil In Chongqing

With the development of soil science,the trend of the development of soil classification is the quantitative,standardized and normalization soil taxonomy.So,it's necessary to have a comprehensive research to help national and regional soil taxonomy,which can help to promote the combination of soil science and production.At present,China has carried on the soil taxonomic classification in many provinces such as Fujian,Hubei,Hunan,Zhejiang and other regions.While the study on soil systematic classification of Chongqing has just started.In order to understand the types and distribution characteristics of purple soil in Chongqing integrally and establish complete soil series.The study collected forty-two soil profiles of purple soil,through field investigation and sampling analysis,obtained the soil forming conditions,the morphological characteristics and the physical and chemical properties of purple soil in Chongqing,according to the principles and methods of Chinese soil taxonomy,established diagnostic horizons and diagnostic characteristics of soil,designated soil taxonomy,and had a reference between genetic classification and soil taxonomy classification.The main results are as follows:(1)The differences of climate,vegetation,topography,parent material and so on have great influence on the morphological characteristics and physical and chemical properties.Purple soil had large proportion of silt and sand,higher gravel concentration.The physical weathering of purple soil was stronger,while the chemical weathering was weaker.The diagram of purple soil was 10RP~2.5Y,there had been little change of dry diagram and moist diagram.Compared to moist value and dry value,almost all decreased 1 and the chroma variation of different levels was small.The effect of removing silicon and aluminum in the process of occurrence and development of purple soil was not strong.(2)According to Chinese Soil Taxonomy(3rd edition),study area identified one diagnostic surface horizon: Ochric epipedon,three diagnostic subsurface horizons: Cambic horizon,Argic horizon and Glossic horizon,one diagnostic evidence: Alic evidence,eight diagnostic characteristics: Soil moisture regimes,Soil moisture regimes,Paralithic contact,Calcaric property,Anthroturbic layer,Redox features,Ferric property and Lithologic characters.(3)According to Chinese Soil Taxonomy(3rd edition),purple soil in Chongqing have been divided into three Orders: Cambosols,Argosols and Primosols,five Suborders: Perudic Cambosols,Udic Cambosols,Udic Argosols,Anthric Primosols and Orthic Primosols,ten Group and seventeen subgroup.(4)According to Criteria for Establishment of Soil Family and Soil Series in Chinese Soil Taxonomy and the actual situation of purple soil investigation in Chongqing,choosing the size of particles,mineral composition,pH,soil temperature as the basis of Soil Family.Considering the depth and thickness of selected horizon,the texture of surface soil,rock and fragments,concretion,intrusions,organic matter of surface soil,source of material,the color of soil and other soil properties as the basis of Soil Series.There were thirty-six Soil Family and forty-two Soil Series.(5)Reference soil genetic classification with soil taxonomic classification approximately,seven soil genus in soil genetic classification correspond seventeen Subgroup in soil taxonomic classification of forty-two purple soil in Chongqing.It can be seen,soil taxonomy and genetic classification were not a simple,single correspondence,the same Subgroup in soil taxonomic classification correspond different genus in soil genetic classification.Reference result is approximate,is must not simply one-to-one correspondence.