The Pedogenetic Characteristics Of Sierozem And Cumulated Irrigated Soil In The Ningxia Hui Autonomous Region And Their Attribution In Chinese Soil Taxonomy

Soil classification laid the foundation of soil science, and formed the basis of soil mapping, rational use and conservation of soil resources, distribution of agricultural production and improving ecological environment. It is well known that, soil taxonomy was still in the process of constantly development and improvement, and there are many limitations in every classification methods. As an example, soil genetic classification, which has a profound impact on soil taxonomy, pour attention into soil-forming conditions and highlighted the role of a single factor, but ignored the effects of the other soil-forming factors. In addition, soil genetic classification lack of quantitative indexes and made the classification boundaries and soil locations in classification system confused. Soil taxonomic classification, which divides the soil based on the properties of itself and quantitatively, remedied the deficiencies of genetic classification and guide the tendency of soil classification. Chinese Soil Taxonomy, the soil classification in line with international standards and which was under the popularization and application, has been established according the soil characteristics of our country.In this research,25 Sierozem and 10 Irrigation silting soil profiles in Ningxia were studied, and the physicochemical properties and the forming environments of these soils were analyzed. Combined with the theory and methods of Chinese Soil Taxonomy, we discovered the diagnostic characteristics and established the taxonomy system of Sierozem and Irrigation silting soils. These results confirmed location of the tested soil samples in Soil Taxonomy system, and provided a reference for the soil classification in Ningxia. The main conclusions are as follows:(1) Based on ?Keys to Chinese Soil Taxonomy? (3rd edition), the main Diagnostic Horizons of sierozem were Ochric epipedon, Aridic epipedon, Cambic horizon, Argic horizon, Calcic horizon. The main Diagnostic phenomena were Alkalic evidence, Calcic evidence, Sodic evidence, and the Diagnostic Features were Lithologic characters, Paralithic contact, Isohumic property, Sodic property, Calcaric property, Base saturation. The main Diagnostic Horizons of Irrigation silting soil were Siltigic epipedon, Fimic epipedon, Cambic horizon, Argic horizon, Anthrostagnic epipedon. The main Diagnostic phenomena were Anthrostagnic evidence, Alkalic evidence, Calcic evidence, Sodic evidence, and the Diagnostic Features were Redoxic features, Sodic property, Calcaric property, Base saturation.(2) According to the diagnostic horizons and characteristics, sierozem could be divided into Cambisols, Aridisols and Luvisols three Orders, four Suborders, including Ustic Cambisols and so on,6 Groups of Hap-Ustic Cambisols and so on,8 Subgroups of Typ-Hap-Ustic Cambisols and so on. Samples of Irrigation silting soil could be divided into Anthrosols,1 Suborder of Orthic Anthrosols,1 Groups of Sil-Orthic Anthrosols,4 Subgroups of Mot-Sil-Orthic Anthrosols and so on.(3) In accordance with classification principles and standards of Soil Families and Series, combined with profiles characteristics, Sierozem could be divided into 15 Soil Familys and 12 soil Series, and Irrigation silting soil could be divided into 7 Soil Familys and 10 soil Series.(4) There is a corresponding relation between CSGC and CST, and the relationship, usually was "many-to-one" or "one-to-many", is relatively complex in high categories. But the relationship is simpler, in the main was "one-to-one" and "one-to-many", in the basic categories of soil classification with.