以功能基因定序探討不同水稻田栽培管理對土壤脫氮微生物群落的影響

Abstract

氣候變遷和全球暖化是當今人類廣泛關注的問題。全球暖化的主要原因是大氣層中溫室氣體（GHG）濃度的增加。氧化亞氮（N2O）是主要的溫室氣體之一，與CO2相比，它們在100年的時間內具有較高的溫室氣體暖化潛勢。在導致溫室氣體排放的原因當中，人為活動產生N2O排放主要與農業活動有關，水稻栽培是來源之一，這是由於化肥的廣泛使用和長期厭氧土壤條件的形成。因此，減少農業活動的N2O排放對於緩解全球暖化至關重要。 為了研究各種理化因子對微生物的影響，進而推測不同條件下N2O排放量的變化，本研究在臺灣新北市新店區進行了一項田間實驗。實驗地點同時進行四種不同的水稻種植方式。第一個為對照組（C），第二塊稻田則採用節水灌溉技術（WS），另一塊稻田採用稻稈還田技術（S），最後則是同時採用兩種技術的稻田（S+WS）。研究主要從四片稻田收集土壤樣本，並且分析其物理和化學特性，包括土壤含水量和pH值等物理特性，以及NH4+和NO3-等化學特性。此外，本研究還會利用16S rRNA基因以及nirS脫氮基因的次世代定序分析土壤微生物群落。 從巨觀規模來說，有進行稻稈還田處理的土壤總溶解性有機碳SbOC較高。而在不同的稻田中，不同的灌溉方法對於微生物群落的影響較大，此外，因為季節變化溫度下降導致的微生物各基因豐度下降也十分明顯。qPCR以及nirS基因定序的結果則顯示慣行灌溉與稻稈還田可以增加nosZ/nir，nosZ/nir的上升則可能會減少稻田的N2O排放量。因此，慣行灌溉與稻稈還田值得進一步研究並推廣以期能夠達到永續環境的目的。

Climate change and global warming are widespread concerns for humanity today. The primary cause of global warming is the increased concentration of greenhouse gases (GHGs) in the atmosphere. Nitrous oxide (N2O) are major greenhouse gases with high global warming potential over a 100-year time horizon compared to CO2 . Anthropogenic N2O emissions are predominantly associated with agricultural activities, with rice cultivation being one of the sources, due to the extensive use of chemical fertilizers and the creation of prolonged anaerobic soil conditions. Therefore, it is crucial to reduce N2O emissions from agricultural activities to mitigate global warming. To investigate the effects the effects of various physicochemical factors on microorganisms, and to predict the changes of N2O emissions under different plantations, a field experiment was conducted in Xindian District, New Taipei City, Taiwan. Four different rice cultivation practices were carried out simultaneously in the experimental site. One rice field was irrigated using water-saving techniques (WS), another was planted with returned rice straw to the farmland (S), a third received both treatments (S+WS), and the last field served as the control treatment (C). Soil samples were collected from the four rice plantations to analyze their physical and chemical properties, including physical properties such as soil water content and pH, and chemical properties such as NH4+ and NO3- .Additionally, soil microbial communities were analyzed using next-generation sequencing of 16S rRNA genes and nirS genes. At a macro scale, Soils treated with straw return had higher total soluble organic carbon (SbOC). In different rice plantations, different irrigation methods had a greater effect on microbial community, and the seasonal temperature drop led to a noticeable decrease in the abundance of various microbial genes. qPCR and sequencing of the nirS gene showed that customary irrigation and straw returning could increase nosZ/nir, and that an increase in nosZ/nir might reduce N2O emissions from rice fields. Therefore, customary irrigation and straw returning are worthy of further study and promotion to achieve environmental sustainability.