14:15 〜 14:30
[AHW18-13] Assessment Nitrogen Budget in Detailed Spatial Pattern by Modeling Approach with Constructed Accurate Agricultural Behavior
キーワード：奈良盆地、窒素収支、地下水汚染、脱窒、Soil & Water Assessment Tool
Since the 20th century, anthropogenic factors dominated by fertilizer usage have significantly perturbation of the material cycle patterns represented by nitrogen, and probably doubling the turnover rates of the terrestrial nitrogen cycle. The changing on nitrogen cycle processes would cause serious environmental pollution, and further threated the entire biosphere integrity. As the largest distributed store of freshwater, groundwater is having very important position in the production and domestic of human society. However, there are many difficulties in the pollution assessment of groundwater. Current methodologies are mainly used to either assess the entire groundwater quality of a specific area or the process of nitrogen cycling in plants, cannot or very difficult to assessment groundwater contamination in detailed spatial pattern on a large spatial scale, such as simultaneous classification of different land-use types and soil types at catchment-scale.
This study using Soil & Water Assessment Tool (SWAT) assessed the nitrogen budget in detailed spatial pattern in a rural catchment of Nara Basin. To obtained a detailed nitrogen balance in paddy land, the model constructed a detailed agricultural behavior database to improve the accuracy of the model, and the model was fully calibrated and verified by streamflow, paddy evapotranspiration, nitrate and total nitrogen concentration of river water.
Result shows, in the Nara Basin, the nitrogen leaching in paddy fields was 42 kg/ha, account 65% of total nitrogen leaching of study catchment. The tea fields, which occupy only 0.06% of the land, contributed 1% of the nitrate leaching of catchment because it nitrogen leaching quantity was as high as 187 kg/ha. The annual nitrogen denitrification in paddy field was 7.3 kg/ha, and 85% is occurred in farming season.
Acknowledgment: This research has been supported the Asia-Pacific Network for Global Change Research (APN) under Grant No. CRRP2019-09MY-Onodera (funder ID: http://dx.doi.org/10.13039/100005536), Research promotion for the environmental creation and rehabilitation of Osaka Bay area by Osaka Bay Regional Offshore Environmental Improvement Center (Project No. 010005, 020004, 030003, PI: Mitsuyo Saito). And Grant-in-Aid for Scientific Research (A) by Japan Society for the Promotion of Science (Project No. 21KK0192, PI: Shin-ichi Onodera).
This study using Soil & Water Assessment Tool (SWAT) assessed the nitrogen budget in detailed spatial pattern in a rural catchment of Nara Basin. To obtained a detailed nitrogen balance in paddy land, the model constructed a detailed agricultural behavior database to improve the accuracy of the model, and the model was fully calibrated and verified by streamflow, paddy evapotranspiration, nitrate and total nitrogen concentration of river water.
Result shows, in the Nara Basin, the nitrogen leaching in paddy fields was 42 kg/ha, account 65% of total nitrogen leaching of study catchment. The tea fields, which occupy only 0.06% of the land, contributed 1% of the nitrate leaching of catchment because it nitrogen leaching quantity was as high as 187 kg/ha. The annual nitrogen denitrification in paddy field was 7.3 kg/ha, and 85% is occurred in farming season.
Acknowledgment: This research has been supported the Asia-Pacific Network for Global Change Research (APN) under Grant No. CRRP2019-09MY-Onodera (funder ID: http://dx.doi.org/10.13039/100005536), Research promotion for the environmental creation and rehabilitation of Osaka Bay area by Osaka Bay Regional Offshore Environmental Improvement Center (Project No. 010005, 020004, 030003, PI: Mitsuyo Saito). And Grant-in-Aid for Scientific Research (A) by Japan Society for the Promotion of Science (Project No. 21KK0192, PI: Shin-ichi Onodera).