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Chinese Agricultural Science Bulletin ›› 2025, Vol. 41 ›› Issue (28): 78-86.doi: 10.11924/j.issn.1000-6850.casb2025-0101

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Response of Different Organic Carbon Fractions to Organic Carbon Accumulation in Typical Paddy Soils

YE Chengcheng1(), ZHU Jie1, LI Zicheng1, ZHANG Mingkui2()   

  1. 1 Wenzhou Plant Protection and Soil Fertilizer Management Station, Wenzhou, Zhejiang 325000
    2 College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058
  • Received:2025-02-10 Revised:2025-06-11 Online:2025-10-05 Published:2025-10-10

Abstract:

To investigate the characteristics of soil organic carbon accumulation and its relationship with organic carbon fractions, 25 surface soil samples from each of 7 representative paddy fields (paddy soils) in Zhejiang Province were selected to determine the composition of different soil organic carbon forms. The response of each form of organic carbon to soil carbon accumulation was analyzed, and the saturation mechanism of soil organic carbon accumulation was explored. The results showed that with the accumulation of soil organic carbon, the content of humic acid, fulvic acid, humic acid carbon and humic acid carbon in various types of the soils showed an initial increase followed by a trend towards equilibrium. The content of these organic carbon components at equilibrium was positively correlated with the content of soil clay, silt and amorphous iron oxide. Free organic carbon increased linearly with the accumulation of soil organic carbon, and continued to increase when the soil organic carbon was at high level. In this case, the accumulated organic carbon in the soils was mainly in the form of free organic carbon. Results suggested that the saturation phenomenon of soil organic carbon was related to the form of organic carbon. The accumulation of humic acid, fulvic acid, humin carbon, and humic acid carbon closely associated with soil inorganic components was limited by the ability of mineral adsorption protection, and their contents increased with the increase of total soil organic carbon, but they tended to equilibrium when the mineral adsorption sites were saturated. The free organic carbon, mainly driven by the input amount of organic matter, was not obviously affected by soil physical protection, and it increased linearly with the accumulation of organic carbon, and its saturation phenomenon was not obvious. This study reveals the different contribution patterns of different forms of organic carbon components to the accumulation of organic carbon in paddy soil, which provides a theoretical basis for the development of accurate organic material input and soil fertilization strategies for regional paddy soil, and also provides a scientific reference for the sustainable management of paddy soil.

Key words: paddy soil, organic carbon, humus carbon, response, saturation value