Study On Genetic Characteristics And Taxonomy Of Soils In Ningxia

Soil classification is the premise and foundation for pedology research.It is also the reflection of the development level of soil science,the carrier of soil information,the foundation of soil resource investigation,and the medium for the transfer of agricultural technology.In order to study genetic characteristics and taxonomy of soils in Ningxia,the paper selected G1~G10 representative soil profiles in Ningxia irrigation district,M1~M10 representative soil profiles in middle parts,S1~S10representative soil profiles in North and South Mountains.In geomorphic units with similar soil forming environment and soil forming process to analyze the soil environmental information,morphological characterization,particle composition and other physicochemical properties,the paper carried on the research of genetic characteristics of typical soils in Ningxia,then detenmined the diagnostic horizons and characteristics to establish the soil classification system in Ningxia,at the same time tried to divide soil series.The main conclusions are as follows:(1)It was learnt that the main soil forming processes of the typical soils in irrigation district were mellowing processes triggered by artificial cultivation,redox process caused jointly by irrigation and groundwater,sedimentation of silt in irrigation water,and salinization process,as well,in some areas.The main soil forming processes of the typical soils in middle parts involved weak humus accumulation process,weak eluviation-illuviation processes and clayification.Also the altitude has an obviously influence on the development characteristics of the soil in mountains of Ningxia,as with the increase of altitude: the accumulation process of humus is gradually obvious,the leaching process is increased and the lime reaction is gradually weakened until disappeared,the soil moisture regime is gradually improved,and a weak redox reaction is happened in the bottom of the soil with high altitude and the soil p H value is gradually decreased,and soil acidity and alkalinity have had a certain change.(2)By referring to and identification in line with“the Keys to the Chinese Soil Taxonomy(third Edition)”,it was found that the thirty profiles had the following diagnostic horizons and characteristics:siltigic epipedon,fimic epipedon,Cumulic epipedon,mollic epipedon,ochric epipedon,aridic epipedon,argic horizon,cambic horizon,salic horizon,calcipan,ustic/aridic/udic soil moisture regim,frigid/mesic temperature regime,calcaric property,redox features,sodic property,isohumic property,loess and loess-like deposits,calcic and anthrostagnic evidence.Affected by the soil forming environment and factors,the diagnostic horizons and characteristics showed the same vertical changes with the altitude rising,as a manifestation of vertical zonal development of soil.Among them,the diagnostic surface horizons is change from mollic epipedon into ochric epipedon,the soil moisture regime changes through aridic/ustic soil moisture regime to udic soil moisture regime,and the soil temperature regime changes from mesic soil temperature regime to frigid soil temperature regime.(3)In the Chinese Soil Taxonomy,the 30 soil profiles could tentatively be sorted into 6 soil order,8suborder,12 soil group and 16 subgroup,they were Siltigi Fimi-Orthic Anthrosols,Anthrostagnic Siltigi-Orthic Anthrosols,Mottlic Siltigi-Orthic Anthrosols,Typic Siltigi-Orthic Anthrosols,Parasalic Earth-cumuli-Orthic Anthrosols,Mottlic Earth-cumuli-Orthic Anthrosols,Sodic Argi-Orthic Aridosols,Sodic Hapli-Orthic Aridosols,Mottlic Hapli-Udic Isohumosols,Typic Hapli-Boric Argosols,Recalcaric Hapli-Ustic Argosols,Typic Hapli-Ustic Argosols,Typic Molli-Ustic Cambosols,Typic Hapli-Ustic Cambosols,Mollic Bori-Udic Cambosols,Calcaric Aridi-Orthic Primosols.(4)The particle size level of the typical profiles include clay,clay-loamy,loamy,sandy,coarse bone sandy,loamy-sandy,sandy-coarse bone sandy.The mineralogy classes of the typical profiles include illite mixture,feldspar mixture,silica mixture,feldspar,mixture.The calcareous and category of acid-base of the typical profiles include non-acid and calcareous.Soil temperature grade includes frigid and mesic temperature condition.Then the combination of the above 4 indicators includes 15 types,such as clay illite mixture calcareous mesic,clay-loamy feldspar typical calcareous mesic,loamy silica mixture calcareous mesic,loamy feldspar mixture calcareous mesic.According to the standard for classification of soil families in the Chinese Soil Taxonomy,the 30 soil profiles could tentatively be sorted into 27 soil families,among them G8 and G9 alongs to clay-loamy mixture calcareous mesicMottlic Earth-cumuli-Orthic Anthrosols,M2 and M9 alongs to loamy silica mixture calcareous mesicTypic Hapli-Ustic Cambosols,M6 and M10 alongs to loamy feldspar mixture calcareous mesic-Typic Hapli-Ustic Argosols.(5)Finally,according to the standard for classification of soil series in the Chinese Soil Taxonomy,the30 soil profiles could tentatively be sorted into 29 soil series,such as G1 Chengguan series,G2 Xigang series,G3 Jinji series,G4 Xinbao series,G5 Yingshuiqiao series,G8-G9 Quchong series and so on.For the same soil families(G8 and G9,M2 and M9,M6 and M10)was divided by the anlysis of the deferences in the characteristic soil layer and attribute,the arrangement of soil layer,the color of surface,soil texture and the intrusion status.(6)The reference studies show that between the two soil classification systems,the Chinese Soil Genetic Classification and the Chinese Soil Taxonomy,does not exist any simple one to one relationship.While the same types of soil in the Genetic Classification System may correspond with several type in the Chinese Soil Taxonmy.The quantitative norms in the Chinese Soil Taxonomy make soil classification more quantified,thus improving the accuracy of soil classification and eliminating the phenomena of different soils having the same soil name.