Abstract: To understand the geographical distribution of soils with “albic horizon”, identify accurately the “albic horizon”in the fields and provide the scientific basis for soil investigation and mapping, twenty-five soil profiles with white color horizon were collected from Zhejiang, Fujian, and Guizhou provinces in the southern China. The characteristics of the white color horizon in the region and their relationships with landform and parent materials were analyzed. The results showed that great variations in texture, free iron oxide and organic matter were found in the soils with white color horizon in the southern China. According to the soil color and vertical distribution characteristics of soil free iron oxide, the twenty-five soil profiles were divided into 3 types, i.e., white color horizons affected by parent materials, affected by composite soil processes, and formed by iron removal. The white color horizons affected by the parent materials were not the result of the iron removal, but were related to the low free iron oxide in their parent materials or superimposed parent materials of soil profile. Color for the white color horizons affected by the composite soil processes were not consistent with their free iron oxide profile distribution, as the white color was the result of iron removal in the former soil formation stage, and the iron oxide deposition on the soil structure in the later formation stage covered the iron removal characteristics of the bleach horizon. The white color horizon formed by the action of iron removal was an “albic horizon”, which could be really used for soil classification. The free iron oxide content in the horizon was obviously lower than that of the overlying or the underlying soil. The distribution of the soils with “albic horizon” was most concentrated in the valley plain, gentle slope of hilly mountain and hill ridge, and its micro topography was characterized by the slope and low concave surface, and it was easy to accept the water flow from the height. But their surface generally did not accumulate surface water, with the characteristics of the inner side to the drainage. In order to distinguish from the white color horizon affected by the parent materials, it was suggested that additional diagnostic requirements for the “albic horizon” should be added. The proposed additional diagnostic requirement was that the free iron oxide content of the “albic horizon” was less than 75% of that in its overlying or underlying soil.

Key words: white color horizon, albic horizon, parent material, landform, free iron oxide, iron removal process