Characteristics and classification of anthropogenic soils with earth-cumulic horizon in Wei River valley of China

The Wei River valley is regarded as the origin of dry farming in northern China. Area has received application of the earth-mixed manure for hundreds of years, and that has resulted in the formation of an important anthropogenic soil, named Lou soil, with earth-cumulic horizon. Survey and genetic classification of the Lou soil were done since 1930; however, the characterization and designation in soil taxonomy need further attention. In this study, 18 typical Lou soil profiles were selected and 61 soil samples were collected. Natural soil-forming factors, morphologies, and physiochemical properties were studied. Diagnostic horizons and characteristics of the selected soil profiles were determined, and their designation in the Chinese soil taxonomy (CST) was defined. The selected Lou soil profiles were found to have 2 diagnostic surface horizons, 3 diagnostic subsurface horizons, and 6 diagnostic characteristics. Thickness of the earth-cumulic horizon was the key indicator for determining designation of the Lou soil at the order level. Thirteen profiles were attributed to Orthic Anthrosols with a corresponding cumulic epipedon diagnostic horizon, while other 4 and 1 profiles were attributed to Ustic Argosols and Ustic Cambosols respectively with the thickness of earth-cumulic horizon ranged from 20 ~ 50 cm. Three subgroups identified were Calcic Earth-cumuli-Orthic Anthrosols, Mottlic Earth-cumuli-Orthic Anthrosols, and typic Earth-cumuli-Orthic Anthrosols in the Orthic Anthrosols. Subgroup of Cumulic Hapli-Ustic Argosols and subgroup of Typic Hapli-Ustic Cambosols were identified in the Ustic Argosols and Ustic Cambosols, respectively. We suggest that the new soil group of Cumulic-Ustic Cambosols under suborder Ustic Cambosols should be included in the CST classification system.