Outline of comprehensive soil classification system of Japan, first approximation

The characteristics of Japanese soil were developed by wide paddy field farming, the influence of volcanic ash on soil, and a perudic moisture regime under temperate climatic conditions. Major soil classifications in Japan have developed in line with public work projects and soils in Japan have tended to be classified independently depending on the land use, such as cultivated area, forest, and so forth. Consequently, there is no available soil map drawn with a single framework of soil classification on a practical map scale, which hampers the progress of environmental studies such as watershed-level nutrient cycling, carbon sequestration and so on. In response, we published the Comprehensive Soil Classification System of Japan – First Approximation; a more practical system that enables the nationwide classification of soils. In it, we defined the following categories: soil great group, soil group, soil subgroup, and soil series group, determined by dichotomous keys. The proposed system contains 27 soil groups, 116 soil subgroups and 381 soil series groups. Setting these 4 category levels renders the system usable for both general outlines and detailed descriptions, and to create soil maps and soil information on various scales. Discipline: Soils, fertilizers and plant nutrition Additional key words: Ando soils, Paddy soils, Upland soils *Corresponding author: e-mail obara@affrc.go.jp Received 12 December 2013; accepted 10 November 2014. Introduction Soil is a natural body that covers the thin surface layer of the Earth. It provides nutrients and water to plants and supports plant bodies. Soil is also a living space and habitat for animals and microorganisms. Although soils have common general properties, their figure and properties vary considerably depending on the soil forming factors. Soils are the end product of the collective influence of climate, relief, organisms, parent materials and time. Understanding soil varieties and classifying them while keeping their different characteristics in mind is crucial to recognizing the environment, managing soils and keeping land sustainable. In Japan, these differences in soils were recognized and old documents of agricultural guidance from the Edo era (1600 – 1868) have emerged. More recently, the first national soil survey program was launched in the 1870s, using a European agro-geological soil classification introduced by Dr. Fesca from Germany, following which certain soil survey programs have been carried out for agricultural land, forest land, and other land use to date. Soil classification systems were also developed to order data and publish survey reports, referring to the development of soil classification systems overseas and international organizations such as FAO and IUSS. The characteristics of Japanese soil emerged through wide paddy field farming, the influence of volcanic ash on soil, and a perudic moisture regime under temperate climatic conditions. The soil classifications of Japan were developed to identify soils with peculiar characteristics under those conditions, and group soils in meaningful ways for agricultural, and forestry production. In this paper, we would like to introduce soil classification of major soils in Japan and provide an outline of the latest soil classification; namely “the Comprehensive Soil Classification System of Japan – First Approximation”. 1. General view of the soil classification of major soils in Japan The soil classification in Japan has proactively developed in three fields, namely paddy soils, volcanic ash soils,