The purpose of this study was to develop options for a more sustainable catchment management, resulting in a reduction of agricultural non-point pollution of water resources in South Korean agricultural catchments. Therefore, an N budget analysis was conducted, which related N inputs into soil under intensive agriculture to N outputs at both field and catchment scale in a mountainous catchment in South Korea. The N budget of all investigated crops was positive, with total N inputs exceeding N outputs by 2.8 times. Radish showed the highest N uptake efficiency (43-45%), whereas rice showed the lowest with 24-30%. At the catchment scale, agriculture contributed over 90% to the maximum N surplus (473. Mg). Rice and radish, with over 100. Mg. N surplus each, contributed the largest part. Comparing these results to the N export in the catchment outlet, it was found that N leaching and surface runoff were the dominant loss pathways, leading to a seasonal inorganic N export of 329. Mg. Because fertilizer N was the major N input (>50%) for all crop types except soybean, its reduction was identified as the major scope of action for N savings at the field and catchment scale. The currently observed trend of land use change from annual to perennial crops additionally assists the reduction of N surplus but shows only a spatially limited applicability for the future. Further measures like split applications, application timing to match crop needs and cover crops during the fallow complement the attempt.
Bibliographical noteFunding Information:
This study was carried out as part of the International Research Training Group TERRECO (GRK 1565/1) funded by the Deutsche Forschungsgemeinschaft (DFG) at the University of Bayreuth, Germany and the National Research Foundation of Korea (NRF) at Kangwon National University, Chuncheon, South Korea . Ji-Hyung Park was also supported by NRF project (ERC 2009-0093460). We thank Christopher L. Shope for his help with the simulations of the daily discharge at the catchment outlet. We also want to thank Jaesung Eum and Sebastian Arnhold for their help with estimations of N loss with surface runoff and Svenja Bartsch for her help with river–aquifer exchange.
- Catchment scale
- Dryland crops
- N export
- N surplus
- N use efficiency
- Rice paddy