Application of "Classification of Cultivated Soils in Japan, Third Approximation" to the Existing Soil Maps

NAKAI Makoto, HASHIMOTO Hitoshi, YAMADA Nobuaki, SAGE Yoshifusa, INOUE Matatsugu, HAMAZAKI Tadao

doi:10.18920/pedologist.43.1_28

"Classification of Cultivated Soils in Japan, third approximation" was examined to be applied to soil maps of cultivated field in which the second approximation was used for mapping. The existing soil profile descriptions and soil analysis values in Hokkaido and Toyama Prefecture were also used for examination. On the way of applying the third approximation to the soil maps, there occurred some problems, e.g. all item did not answer the card of soil profile descriptions, the differentiating criteria were different from the third approximation, and the soil analysis values were not accurate. It could be solved considerably by using the existing data as much as possible, and adding presumption and prediction. Moreover, soil maps were already different from the current state because of the change of the soil which was mainly caused by the farm land consolidation. Farm land consolidated can be comparatively easy to be specified, and the soil can be classified through using a simplified soil survey method. The third approximation had also some problems; 1) Some soil name of the second approximation was changed, for example, Andosols to Lowland soils or Volcanogenous Regosols. This is a result from using the quantitative definition and "keyout" method, which is unavoidable for a precise and objective classification, 2) As for dressed peat soils, the limit of the inorganic surface would be too thin, 3) Shapes of mottle used for definition of the hydromorphic soils such as Lowland soils is difficult to say to generalize. The definition of shape would be popular by means of publishing such a manual, 4) A quantitative boundary of the upland and the mountain is not definite, 5) It is necessary to examine parent materials quantitatively, and to treat properly the pumicious flow and the pyroclastic flow deposit, 6) The subsurface soil is not defined when it consists of two or more layers, 7) It is necessary to eliminate the contradiction on a soil code, and on the names of soil subgroups and soil series groups. It is necessary to organize the committee that authorizes the modification of the system of the cultivated soil classification systematically.

Application of "Classification of Cultivated Soils in Japan, Third Approximation" to the Existing Soil Maps

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