Kyushu University Academic Staff Educational and Research Activities Database
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Syuntaro Hiradate Last modified date:2022.07.25

Professor / Division of Bioproduction Environmental Sciences
Department of Agro-environmental Sciences
Faculty of Agriculture

Graduate School
Undergraduate School

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Academic Staff Educational and Research Activities Database .
Academic Degree
Ph.D. (Agriculture)
Country of degree conferring institution (Overseas)
Field of Specialization
Soil Science
Total Priod of education and research career in the foreign country
Outline Activities
Based on soil science, I perform education and research activities to establish suitable and sustainable management system of agricultural soils, develop soil evaluation methods, clarify soil chemical reactions, conserve biodiversity, clarify material cycling in ecosystems, etc. In laboratory experiment, I try to analyze soils using cutting-edge analytical techniques, such as nuclear magnetic resonance spectroscopy and mass spectroscopy in addition to general chemical analyses. Also, I conduct field survey on Ogasawara Islands and Aso-Kuju National Parks, etc., for their conservation research.
Research Interests
  • Research on the soil formation processes and soil classification based on soil survey
    keyword : pedorogy
  • Characterization of the ecosystems of Ogasawara Islands by material cycle including soil systems
    keyword : feral goats
  • Estimation of the rate of soil carbon sequestration
    keyword : soil organic carbon, 14C dating
  • Regulation of soil environment for the conservation of biodiversity and ecosystems
    keyword : avalable phosphate in soils, exchangeable acidity, alien plants, endemic plants
  • Interactions between soil components and plant essential elements
    keyword : Phosphorous,31P Nuclear Magnetic Resonance
Academic Activities
1. Jithya Nawodi Wijesinghe, Jun Koarashi, Mariko Atarashi-Andoh, Yoko Saito-Kokubu, Noriko Yamaguchi, Takashi Sase, Mamoru Hosono, Yudzuru Inoue, Yuki Mori, Syuntaro Hiradate, Formation and mobility of soil organic carbon in a buried humic horizon of a volcanic ash soil, GEODERMA, 10.1016/j.geoderma.2020.114417, 374, 2020.09, [URL], A buried humic horizon (C-14 age between 5.4 and 6.8 kyr BP) of a volcanic ash soil in Aomori, Japan, which was collected from the depth between 147 and 187 cm at 5 cm-interval (total eight sub-horizon samples), was investigated to clarify the degree of biological transformation and mobility of soil organic carbon (SOC) fractions. The SOC fractions were prepared from each sub-horizon sample by extraction and precipitation procedures with controlling pH of the extracted solution, resulting in humin, humic acid (HA), and four fulvic acid (FA) fractions (two hydrophilic FA fractions: FA(1) and FA(2), and two hydrophobic FA fractions: FA(3) and FA(IHss)). The prepared SOC fractions were characterized by C-14 age and stable isotopic ratios of C-13 (delta C-13) and N-15 (delta N-15). The hydrophilic FA fractions showed the highest delta C-13 and delta N-15 values, indicating that these SOC fractions had been most enriched with C-13 and N-15 by biological metabolic processes. On the other hand, the HA fraction showed the lowest delta C-13 and delta N-15 values, therefore this fraction would have been less-metabolized, although HA fraction has been regarded as well-processed in general. The C-14 age of the HA fraction was almost same as the deposition age of the corresponding sub-horizon, indicating that the C in the HA fraction would have been fixed in situ right after photosynthesis by plants at the early stage of soil formation and chemically stabilized at soil surface, by fire event, etc. The average rates of vertical translocation of the SOC fractions were low (humin and HA fractions: < 1 mm per century, FA fractions: 1-4 mm per century), implying that the vertical translocation of SOC would not be the main mechanisms for forming thick humic horizons. The present study showed strong evidence of the in situ formation of SOC on soil surface, and successive up-building accumulation of soil particles containing SOC would contribute to the formation of the thick humic horizons..
2. Syuntaro HIRADATE, Properties of Soils of the Ogasawara Islands: Keys to Understand Past Nature and Find Adequate Management for Future, Global Environmental Research, 23, 1&2, 29-36, 2019.12, [URL], Soil profiles under natural forest vegetation on four islands of the Ogasawara Islands, Japan, were compiled and evaluated based on chemical analysis to learn about the natural habitats of the past and determine adequate management measures for conserving the respective ecosystems. The majority of the soils could be characterized as high acidity (high exchangeable acidity, low pH(H2O) with low pH(KCl)), high cation exchange capacity (CEC) and high proportions of exchangeable Mg over exchangeable Ca and K, and those soils are in fairly early stages of weathering, differing from “laterite” and/or “laterite-like soils.” Available P for plants in the soils is bimodal: very low or very high. The very high level of soil-available P was caused by seabird activities in the past. The high proportion of exchangeable Mg would induce Ca and K deficiency in plants, and this situation would have prevailed in the Ogasawara Islands. Available N for plants in the surface horizons of the soils is generally high and does not limit the ecosystem productivity in many cases of natural forest. Soil erosion would cause fatal effects on the ecosystem by removing the surface horizons and exposing subsoil horizons with extremely high levels of soil acidity, high proportions of exchangeable Mg and low levels of available P and N, with inappropriate permeability and aeration ability for plant growth. Such subsoil horizons would provide very poor conditions for growing plants. Conserving soils is essential and important to the recovery and restoration of the natural vegetation and ecosystems..
Membership in Academic Society
  • Japanese Society of Pedology
  • Japanese Society of Soil Science and Plant Nutrition
  • The Clay Science Society of Japan
  • Japan Humic Substances Society
  • American Society of Agronomy
  • Soil Science Society of America
Educational Activities
I teach students soil functions and roles, fundamental soil constituents, soil organisms, soil formation and taxonomy, soil analytical methods, etc. Based on the fundamental knowledge of soil science, I performed education activity on environmental science, agricultural production science, ecology, conservation, etc.