AbstractsBiology & Animal Science

Abstract The application of excessive N fertilizer is a common farming practice in Southeast Asia to ensure the optimum crop yield. However, surplus N in soil induced from higher fertilization than crop N demand is highly susceptible to loss as N2O emission and nitrate leaching during heavy rainfall events in the monsoon season. Intensive farming conducted in the Haean catchment of South Korea has received much attention due to its geographical importance as an upstream region of the Soyang River Dam, which is used as the major drinking water for urban residents (including Seoul). Taking into account the combination of monsoon climate, intensive N fertilizer use and sand dressing prior to mulching and seeding of upland fields in the Haean catchment are likely to cause significant N loss and soil erosion, which have a high potential for directly impacting on the dam water quality via the Mandae stream. The plastic mulch as well as high N fertilization is a typical agricultural management practice for upland crop cultivation in the Haean catchment. To consider effects of plastic mulch on the dynamics of soil temperature and water content, based on soil measurements, meteorological input data i.e. air temperature and precipitation were adjusted to allow the biogeochemical LandscapeDNDC model differentiating simulations of plastic mulch (row) conditions. Furthermore, the actual weather data was applied for the simulation of interrow conditions. The main parameters such as MaxTDD, Tlimit, OptYield and WUECMAX for the simulation of plant growth of major upland crops (i.e. potato, radish, soybean and cabbage) and dominant tree species (i.e. Quercus Mongolica) of the Haean catchment were newly implemented into the model. Taking into account mulching effects and different agricultural management practices, the LandscapeDNDC was validated against detailed field measurements of N2O emission, nitrate concentration, soil temperature and water content (5, 15 and 30 cm soil depth) and biomass production from potato, radish, soybean and cabbage fields. Furthermore, the LandscapeDNDC was also tested against field data of N2O emission, soil temperature and water content (10 cm soil depth) from temperate deciduous forest sites located at three different altitudes and thus different exposure to atmospheric N deposition (24 - 51 kg N ha-1). Application of the adjusted meteorological data showed better prediction of soil temperature and water content from rows covering with plastic mulch as compared to application of the actual weather data (e.g. adjusted data: r2 = 0.49; actual data: r2 = 0.18). Developmental stages of major upland crops were successfully captured by the LandscapeDNDC and separately simulated above- and belowground biomass were in good agreement with measured biomass (r2 = 0.81 - 0.98). The peak N2O emissions after N fertilization from potato, radish and cabbage fields were generally underestimated, however, with respect to high uncertainties and low frequency of measurements, temporal dynamics and magnitude of N2O…