Consideration of Suffix Symbol on Soil Taxonomy and World Reference Base for Soil Resources Classification

Abstract

There is a difference between ST and WRB in distinguishing the master horizon. When a pedologists investigate a soil profile, it is difficult to determine which classification method to choose including the master horizon, add a prefix, suffix, etc. to the horizon name. The suffix symbol for groundwater level uses 'g' for ST and 'l' or 'r' for WRB. The suffix symbol 'r' represents a strong reduction state, and 'l' is used in a state where oxidation is much progressed. However, in the real agricultural field, the groundwater level is lowered so that the oxidized part of the profile is classified based on < 2%, 2 -20%, > 20%. In addition, there are soils with a mottle quantity of 20 to 49%. ST classifies this as one like 'g', and WRB distinguishes it. However, since only the presence of a mottle is determined, a refinement is required.

Comparison of Soil Taxonomy (2022) and WRB (2022) Systems for Classifying Paddy Soils with Different Drainage Grades in South Korea

“…In general, the main color of soil can change according to its redox state. That is, moderately well-drained soils do not have reduced-colored mottles (i.e., grey spots), whereas poorly drained soils have oxidized-colored mottles (i.e., red spots) on the reduced-colored background [4]. Hence, this suggests that the color and quantity of mottle in soil horizon can be an indicator of classifying soil drainage grade which is an important factor for recommending land use.…”

“…), determining the properties of the soil (e.g., pH, soil organic matter, base saturation, cation exchange capacity, extractable bases, particle size distribution, etc. ), and organizing these results to create a soil map [4]. Subsequently, for various land use purposes, the assembled data and the created soil map can be used by scientists or land owners to predict and evaluate the suitability, limitation, and potential of soil behavior [5,6] that are the key consideration for successful agricultural activities.…”

“…Moreover, the collected soil samples and related databases via the soil survey are of great importance for the conservation of soil resources, as well as further application in estimating soil carbon stock, water capacity, and soil loss [7], thereby contributing to sustainable agriculture. Soil classification is performed using a soil profile description through visual observation and determining the physicochemical characteristics of each soil layer [3,4]. Soil classification is aimed at clearly understanding the characteristics of soil and helping soil management through soil commentary; therefore, an accurate investigation and classification of the soil are essential.…”

“…Then, the Rural Development Administration (RDA) developed a soil information system using soil database and soil maps accumulated over 40 years of soil surveys across the country, which was digitized and provided to the public online in 2006 [7]. Currently, RDA soil researchers are performing to rework soil classification according to the updated ST and WRB systems, in order to publicize soil classification information globally [2,4,12]. Nevertheless, with the lack of existing classification data and the recent changes in land use and consumption, vegetation, and climate, it is not possible to satisfy most of the classification criteria that conform to the current ST and WRB systems [2,15].…”

Quantification of Drainage Classes of Korean Soils as Morphological Characteristics

“…조사방법이 ST에서는 'g'만으로 구별하고 있고 WRB에서는 'r'과 'l'을 사용하여 그 표현을 달리하고 있다 (Sonn et al, 2019). 그 기준은 Table 2에 나 타나 있고 이에 따른 토양통은 모암 (모재)지대별로 Table 5에 나타나 있다.…”