Genetic Characteristics And Taxonomic Classification Of The Representative Paddy And Grassland Soils In Guizhou Province

To understand the placement soils of Guizhou Province in the Chinese Soil Taxonomy Classification,eighteen paddy soil and twenty-nine grassland soil profiles were collected from different sites of the province.The environmental conditions and soil properties of the soil profiles were analyzed in detail.The soils were classified according to the Chinese Soil Taxonomic Classification,and the corresponding relationships between the soil types of Chinese Genetic Classification System and those of the Chinese Soil Taxonomic Classification were discussed.The results indicated that:(1)The 18 paddy soils under the study had obvious profile differentiation with deep soil depth.Soil colors were mainly yellowish brown,their lightness and chroma had great variation,the soil texture was dominated by clayey loam and loamy.The clay content of most soil profiles increased with the increase of soil depths,but the soil organic matter content decreased with the increase of soil depths.The soils were mainly neutral and acidic.Iron oxide in the surface had been leached and deposited in subsoil;There was an increasing tendency in the total Fe and free Fe from the topsoil to the bottom,The vertical distribution of total Fe and Mn were similar,but the ratio of Mnd/Mnt was commonly higher than hiaf of Fed/Fet.(2)There were obvious difference in the degree of profile development among the 29 grassland soils under the study.Besides some soils had relatively shallow development,the most of soils had deep soil depth.The soil texture was dominated by clay loam and sandy loam,the main color of soils in their moisture state were brown and black.High amount of organic matter was accumulated in surface soils,and organic matter is the grassland soils was generally higher than that of in the paddy soils,the soils were mainly acidic to strong acid.Influenced by the parent materials,the free Fe of the studied soils varied greatly,but most soil profiles were an increasing tendency in the free Fe from the A layer to the B layer.The studied soils had relatively rich nitrogen and the total phosphorus,but lacked of the available phosphorus and potassium.The total nitrogen content decreased with the increase of soil depths;the total phosphorus distribution was more uniform in the profiles,and the available phosphorus had obvious accumulated in surface soils;the total potassium had no obvious feature in the profiles,but there was an increasing tendency in the available potassium from the bottom to the topsoil.(3)According to the Keys to Chinese Soil Taxonomy(3rd edition),the eighteen studied paddy soils and twenty-nine grassland soils were identified eight diagnostic horizons and ten diagnostic characteristics.The eight diagnostic horizons is Anthrostagnic epipedon,Hydragric horizon,Mollic epipedon,Umbric epipedon,Ochric epipedon,Argic horizon,Albic horizon,Cambic horizon;The ten diagnostic characteristics is Lithic contact,Paralithic contact,Isohumic property,L.C.of carbonate rocks,Ferric property,Gleyic features,Redox features,Base saturation,Soil temperature regimes,Soil moisture regimes.Based on the diagnostic requirements,the studied soil profiles could be sorted into six Orders:Anthrosols,Gleyosols,Isohumosols,Argosols,Primosols,and eight suborders,twelve groups and nineteen subgroups,and,thereinto,eighteen paddy soils could be sorted into one order,one suborder,three groups and five subgroups,twenty-nine grassland soils could be sorted into five order,seven suborders,nine groups and fourteen subgroups.(4)The results obtained according to the classification correlation study,There was not a one-to-one correspondence of the soil types between Chinese soil genetic classification system and Chinese soil taxonomy system,The relationship between the two classification systems is more complex.and the reference difficulty is relatively large,but a comparative relationship for some dominant soils existed.