台灣北部不同耕作方式對土壤有機碳型態分布的影響

Abstract

增加土壤碳匯不僅能提升土壤肥力，亦能減緩溫室效應。農田中不同耕作方式會影響作物產量與土壤中有機碳含量，但僅量測有機碳含量無法判斷土壤中的有機碳是否能穩定保存。因此將有機碳藉由分解的難易度，區分成具有不同物理化學特性的型態，能判斷有機碳在土壤中的周轉速率，了解土壤有機碳品質。然而，目前台灣農田土壤的有機碳型態之相關研究不足。因此，本研究目的為研究台灣北部地區旱田在不同施肥以及水田土壤在不同水分管理下，計算作物生產量與土壤碳匯含量，以及有機碳型態在含量與分布上的變化，以了解台灣農田土壤有機碳的品質。研究區域位於新北市新店區台大實驗農場安康分場，種植狼尾草 (旱田) 以及水稻 (水田)。採集土壤樣品進行有機碳型態分離，分別是低密度態、高密度態、可氧化態及非可氧化態，並分析團粒穩定度、有機碳官能基與微生物之活性。研究結果顯示，在旱田中，化學肥料可提升地上部作物產量，而有機肥料施用則增加了最多的土壤有機碳含量。混合施用有機肥料與硝化抑制劑可維持較佳的團粒穩定度和微生物生長，並提供持續的碳源。在水田不同水分管理下，慣行灌溉具有較高水稻產量，而雨養管理有較高的團粒穩定度和微生物量。在不同水分管理下，土壤有機碳型態分布具有相同趨勢，主要以重密度態儲存。綜合評估地上部產量與土壤有機碳匯及其穩定度，建議旱田採用有機肥料與化學肥料混合施用，水田採用雨養管理，以提升台灣農田土壤有機碳品質。

Increasing soil carbon sequestration not only enhances soil fertility but also mitigates the greenhouse effect. Measuring total organic carbon content cannot accurately reflect the quality of soil carbon sequestration. Therefore, organic carbon is divided into different fractions based on its decomposition difficulty. These fractions exhibit distinct physical and chemical properties in the soil, allowing us to assess the stability of soil organic carbon and understand its quality. However, there is still a lack of research on the organic carbon fractions of farmland soils in Taiwan. Therefore, this study aims to investigate the crop yield and soil carbon sequestration content in uplands under different fertilization practices and in paddy fields under different water management practices in northern Taiwan. The study also aims to analyze the changes in the content and distribution of various organic carbon fractions to understand the quality of soil organic carbon in Taiwanese farmlands. The study area is located in the farmland of the Ankang Branch of NTU Farm, Xindian District, New Taipei City, and is planted with Pennisetum (upland field) and rice (paddy field). Soil samples were collected regularly to separate the fractions of organic carbon, which were the light fraction, heavy fraction, oxidizable fraction, and non-oxidizable fraction. And analyze the aggregate stability, organic matter functional groups, and microbial biomass carbon. The results showed that in the upland, chemical fertilizers increased the yield of aboveground crops, while organic fertilizers increased soil carbon sinks. A mixed application of organic fertilizers with nitrification inhibitors maintains optimal aggregate stability and microbial activity and provides a sustainable source of carbon. Under different water management practices in paddy fields, conventional irrigation had higher rice yields, while rainfed management led to higher aggregate stability and microbial biomass. The distribution of soil organic carbon forms exhibits the same trend under different water management practices, with the majority stored in the heavy fraction. Considering both above-ground yield and the sequestration and stability of soil organic carbon, it is recommended to use a combination of organic and chemical fertilizers in upland fields and adopt rainfed management in paddy fields to enhance the quality of soil organic carbon in Taiwanese farmlands.