2023 Fiscal Year Final Research Report

Soil environmental condition of the ginger field converted from paddy and its relationship to disease infection in the mountainous region of Kochi Prefecture

Research Project

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Project/Area Number	21K05328
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Review Section	Basic Section 38010:Plant nutrition and soil science-related
Research Institution	Kochi University
Principal Investigator	Sota Tanaka 高知大学, 教育研究部総合科学系黒潮圏科学部門, 教授 (10304669)
Co-Investigator(Kenkyū-buntansha)	森塚直樹高知大学, 教育研究部総合科学系生命環境医学部門, 准教授 (10554975) 大西浩平高知大学, 教育研究部総合科学系生命環境医学部門, 教授 (50211800)
Project Period (FY)	2021-04-01 – 2024-03-31
Keywords	ショウガ / 音地 / 中山間地 / 土壌の空間変異 / 根茎腐敗病
Outline of Final Research Achievements	Simanto Town in Kochi Prefecture is the center of ginger production in Japan. However, disease infection is serious problem in the production. This study investigated spatial variability in soil environmental condition within each ginger field in order to clarify the soil conditions which would exacerbate the disease occurrence and damages. The effect of soil fumigation seemed to reach to sufficient soil depth. However, in case of the fields where drainage could not keep out the rainwater inflow from outside, it is suggested that surviving pathogens in deep soils could move up toward surface soils with rising soil water levels during rainy season, resulting in the infection to ginger roots. There were the Akaonji layer found at subsoils in some fields, a volcanic ash layer derived from the Kikai Caldera eruption. The Akaonji layer had extremely high water holding capacity to play a role of impermeable layer, probably exacerbating the disease occurrence and damages of ginger plants.
Free Research Field	土壌肥沃度・特性評価
Academic Significance and Societal Importance of the Research Achievements	ショウガ栽培についての作物病理学研究や防除に関する研究は高知県などにより行われてきたが、それらの成果を実際のフィールドに適用するための研究知見は皆無であった。本研究では、圃場間のみならず圃場内での立地・土壌環境の変異と病害発生の関係を調べるとともに、音地土壌の理化学性や物理性、鉱物性を詳細に検討することにより、病害発生とその程度は赤音地層の有無のような下層土の状況に起因している可能性が高いことを示した。これらの結果をもとに、立地・土壌条件を類型化し、病害発生の原因となる圃場の排水に関係する対策や消毒方法の選択に関する試案を策定して、生産者や行政に提案した。