A scheme for soil classification of paddy fields in Japan with special reference to mineral paddy soils

An approximation to establish a unified comprehensive classification system for Japanese soils

“…Common to Terrestrial and Semi-terrestrial paddy soil orders, the Surface-water type is characterized by the presence of the Bg horizon, in which iron and manganese mottlings are illuviated as the effect of leaching by irrigation water (46,47). This type can be correlated with KYUMA and KAWAGUCHI'S Aquorizem (44).…”

“…It can be correlated with KAMOSHITA'S Brown lowland soils (48) and UCHI-YAMA'S Brown oxidized type (49). The fiuctuated groundwater subgroup is the synonym of KANNO'S Intermediate type (46). It is characterized by the presence of the Bg(r) horizon which can be identified by gleyed mottles and specific haloed tubular mottles (47).…”

Historical aspects of soil classification in Japan

“…Thus, a classification system of paddy soils was developed according to several kinds of proposals such as those of Uchiyama (1949), Kanno (1956Kanno ( , 1962a, Yamazaki (1962), Matsui et al (1961), and the Subcommittee on the Paddy Soil Classification (1969) of the Group of Japanese Pedo10gists. The key principle for the classification of paddy soils was based on soil morphological properties affected not only by the changes in the level of the groundwater table with the topographical sequence level but also by the influence of irrigation water under rice cultivation.…”

“…Matsui et al (1961) proposed a tentative system of classification for paddy soils on alluvial plains. They followed Kanno's soil classification (Kanno 1956) and Yamazaki's soil classification (Yamazaki 1962), and developed a modified classification system by adding organic soils under rice cultivation to the proposed classification system and improving the method of subdivision of lower categories. This tentative classification system was consisted of four categories.…”

“…It should be noted that Uchiyama realized that the infiltration rate of inigation water within the soil profile might be playing a key role in the morphological development characteristic of paddy soils. Kanno (1956) proposed a soil classification of mineral soils under paddy production based on soil surveys conducted in Fukuoka and Kumamoto Prefectures, southwestern Japan. He recognized the basic morphological characteristics of paddy soils according to horizon sequences reflecting the reduction-oxidation conditions of soils.…”