Effects of Fertilizer Level on Nitrous Oxide Emission from Upland Soil in South Korea Under Climate Change Scenario (RCP-8.5): High-Resolution Modeling Approach.

Nitrous Oxide is a potent greenhouse gas that is over 298 times greater than carbon dioxide, and agricultural soils are an important source of nitrous oxide emissions, accounting for approximately half of the total anthropogenic nitrous oxide emissions. In this study, the process-based model (DNDC; DeNitrification and DeComposition) was used to estimate nitrous oxide emissions of bean cultivation for the entire South Korea paddy soil (1km² scale grid cell). For operating DNDC model, basic input parameters (daily climate data, soil pH, soil organic matter contents, soil bulk density, and soil clay contents) were obtained from domestic national organizations (Korea Meteorological Administration and Rural Development Administration). Simulations of the DNDC model were performed under four fertilizer level (0, 100, 200, and 400 kg urea-N ha^-1) and climate change scenario (RCP-8.5). Following the 5-year spin-up from 2011 to 2015, we performed an 80-year simulation from 2016 to 2095 for each grid cell using the DNDC model. The simulation results of fertilizer level for the 2020s (average 2016 to 2025) annual nitrous oxide emissions of each level decreased in the following order: 400 kg urea-N ha^-1 > 200 kg urea-N ha^-1 > 100 kg urea-N ha^-1 > 0 kg urea-N ha^-1, as expected. Nitrous oxide emissions were moderately low at fertilizer level to 200 kg urea-N ha^-1, where grain yields were maximized, after which emissions more than 40%. In the 2090s under RCP-8.5 scenario, some increase in grain yields has been confirmed. However, as the atmospheric temperature increased, nitrous oxide emissions more than doubled, with a larger increase in fertilizer level. The spatial distribution of nitrous oxide emissions ranged from 0.7 to 5.2 t CO₂-eq ha^-1 yr^-1 per each grid cell in South Korea. The nationwide distribution of nitrous oxide emissions was high in the southern region and near the coast. The regional distribution difference was expected to be due to atmospheric temperature and precipitation.