Investigation which Arable Land is the Main Contributor to Global Warming between Paddy and Upland Field under Nitrogen Fertilization?

다국어 초록 (Multilingual Abstract)

Methane (CH₄) and nitrous oxide (N₂O) have been considered as two of the major greenhouse gases (GHGs) from agricultural land, out of which CH₄ is normally emitted from water-logged paddy fields while N₂O is emitted from aerobic upland soils. Both of these arable lands are thought to be the major GHGs emission sites, however, it has not been studied yet which land is responsible for higher contribution to GHGs emissions in the same region. A two year field study was conducted to calculate the contribution for global warming made by rice paddy fields and red pepper cultivation in upland soil under different nitrogen (N) fertilization levels. The urea as a source of nitrogen was applied at four different levels (0, 50, 100, and 200% of recommended doses for cultivation), and rice and red pepper were cultivated for paddy and upland fields, respectively during May to October. The CH₄ and N₂O were measured from both arable lands to quantify GHGs fluxes. The CH₄ emission was increased in a quadratic response with increasing nitrogen application level at rice paddy field and upland soil, but rice paddy has significantly higher CH₄ emission than red pepper upland soils. In contrast, N₂O emission showed a correlation of linear regression with N fertilization level increasing at both of the arable lands, however, upland soil showed significantly higher N₂O emission than rice paddy field. The rice paddy field has much higher global warming potential (GWP) than upland soil under lower levels of N fertilization (below 265 kg N ha<SUP>-1</SUP>) using carbon dioxide (CO₂) equivalent comparison. However, upland soil showed clearly higher GWP than rice paddy field under higher N fertilization. Therefore, we concluded that upland soil is a place which contribute much more to the GHGs emission caused by high N₂O fluxes under application of high N fertilizer.