| In the present, soil erosion has done severely harm to living and development forhuman being. Ferrisols, located in South China, are the most important food productionarea. It was being seriously eroded by water because of long-term's unreasonableutilization and weak ecological system, which harmed the development of nationaleconomic greatly. So, the study for aggregate stability and its impact factors is to beimportant to deducing water erosion danger, stabilizing and improving agriculturalproduction, preserving soil resources and balancing soil ecological system. Nine typicaleroded red soils, which developed from three parent materials at Hubei Xianning, HubeiChibi and Hunan Changsha, are used in this paper. Analyse the type and content ofIron-Aluminum Oxides and Clay minerals in designated size aggregates(＞4mm, 2mm-4mm, 1mm-2mm, 0.5mm-1mm, 0.25mm-0.5mm) get by wet screening and dryscreening from the test soil. Discussion of different forms of Iron-Aluminum Oxides andClay Minerals and the stability of Aggregates in Eroded Ultisols of the relationshipbetween. The main results as followed:1. As for the basic properties of the tested red soil, the pH changes in between4.41-4.92, the CEC goes from 15.53cmol·kg-1-66.96cmol·kg-1 and Clay surface area(SSA) in the range of 51.45m2·g-1-51.93m2·g-1. they change with the increasing oferosion degree but the regularity is not very obvious. The Clay content (Clay％) and theOrganic matter content (OM) is reduced with the increasing of erosion and the Clay％debases from 34.90％to 10.29％, the OM reduces from 34.58 g·kg-1to 3.68g·kg-1.2. Land use can usually affects the physical and chaemical properties of soil, and then itcan promote the formation of the aggregates and delay the damage indirectly. As for heaggregates in the soil of tea garden and bosk, the Organic matter content (OM) between20.91 g·kg-1-34.58 g·kg-1, the Clay content (Clay％) between 20.91％-34.58％. but in theweeds or bare land soil, it's Organic matter content (OM) just between 20.91g·kg-1-34.58 g·kg-1, the Clay content (Clay％) only between 20.91％-34.58％.3. The Micro-Aggregate size in tested soil distribution mainly in the range of0.002mm-0.05mm and its weight percentage are all above 20％. With the increasing ofthe Erosion, the content of the Micro-Aggregates size between 0.002mm-0.05mm reducesfrom 23.25％to 20.49％and the stability of the tested soil reduces too, the Dispersion ratio (DR) increases from 35.11 to 54.80, the Clay dispersion index (CDI) increases from20.09 to 43.74.4. The distribution of Aggregates (＞0.25mm) in Ultisols were mainly in＞4mm, 2-4mmand 1-2mm. the weight percentage is of more than 70％. After wet sieving, the waterstable Aggregates content (WSA％) are also mainly located in the areas 1mm-4mm. Withthe increasing of the Erosion, weight percentage of water stable Aggregates located in＞4mm and 2mm-4mm reducing, weight percentage of water stable Aggregates located in0.25-0.5mm and＜0.25mm increasing. With the increasing of the Erosion, the Dispersionratio (DR) of the Aggregates down. With the increasing of the Depth, the Mean WeightDiameter (MWD) of the Aggregates increasing and the DR of Aggregates sizes in＞1mmreducing, stability of it increasing.5. The content of Chelated Iron (Fep) and flee Iron (Fed) is closely related to theanti-erosion index of Aggregates in Ultisols. They raise the Clay content to promote theformation and stability of aggregates. With the increasing of the Erosion, the content ofChelated Iron (Fep) goes down from 0.25 g·kg-1 to 0.10 g·kg-1, and then to 0.08 g·kg-1,the content of free Iron (Fed) increase from 63.69g·kg-1 to 47.94 g·kg-1 and then to 93.58g·kg-1. With the depth increasing, the content of Chelated Iron (Fep) and flee Iron (Fed)is reduces. The content of Chelated Aluminum (Alp) is always higher than the content ofChelated Iron (Fep), which indicates that Al is more active than Fe during the complexwith organic matter. With the increasing of the Erosion, the content of Chelated Iron (Fep)and free Iron (Fed) in Aggregates locateing in＞4mm, 2-4mm and 1-2mm is more relatedto the water stable Aggregates content (WSA％). the content of Chelated Iron (Fep) andflee Iron (Fed) has a negative correlated relations with the Dispersion Rate (DR) ofAggregates, but it more related to Clay flocculation Index (CFI), and Clay Content(Clay％).6. The Clay Minerals style in the test soil is 1.4nm intergrade Mineral, Hydromica andKaolinite. With the increasing of the Erosion, the content of Kaolinite is closely related tothe content of water stable Aggregates content (WSA％) and free Iron (Fed). Kaolinitehas some ontribution to maintain stability of Aggregates but the other two typs of ClayMinerals seem have no obvious contribution on it.
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