On-soil decomposition of organic matter, and its contribution to formation of course debris in tea-plantation

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K06335
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 41050:Environmental agriculture-related
• Research Institution: Shizuoka University
• Principal Investigator: Nagumo Toshiyuki 静岡大学, 農学部, 准教授 (70362184)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 茶園 / 土壌炭素貯留 / 整枝・せん枝残渣 / 分解

Outline of Final Research Achievements

We studied the organic carbon dynamics in tea-plantation soil, where soil organic carbon is a major storage form for carbon dioxide sink. As a result, the tea plantations had a higher organic carbon content in the soil and a higher carbon storage capacity, compared to adjacent fields such as arable, orchards and thicket with the same geological and meteorological conditions. Tea-plantation soil contains many low crystallinity minerals, which are dissolved and extracted by acid oxalate. These minerals may form an organo-mineral complex with soil organic matter, thereby stabilize it. On the other hand, there are many pruning residues in the tea plantation. In particular, the leaves were rapidly fragmented with the help of soil animals, and it was speculated that they were one of the sources of soil organic carbon.

Free Research Field

環境土壌学

Academic Significance and Societal Importance of the Research Achievements

茶園は硝酸汚染源であり，温室効果ガスであるN2O排出源の主要な排出源である。一方，研究代表者である南雲は，炭素収支に注目するとN2O排出を加味しても正味CO2吸収源として働いている可能性を示した。ただし，茶園での炭素動態はほとんど未解明のままであった。茶園は，森林の落葉落枝に相当する人工的リターと言える整枝せん枝残渣に加え，通常の農地と同様に敷き藁や堆肥・有機肥料も施用されるため有機物投入が極めて多い，一方その土壌は多用される窒素肥料の硝化によって強酸性を示すという特殊環境である。本研究の成果は，この茶園環境下での炭素貯留メカニズムの解明を試みた。