Modeling the effect of rainfall intensity on soil-water nutrient exchange in flooded rice paddies and implications for nitrate fertilizer runoff to the Oita River in Japan
Modeling the effect of rainfall intensity on soil-water nutrient exchange in flooded rice paddies and implications for nitrate fertilizer runoff to the Oita River in Japan
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DOI：
10.1002/2013wr014643
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发表时间：
2014-11-01
影响因子：
5.4
通讯作者：
Stefan, Heinz G.
中科院分区：
文献类型：
--
作者：
Higashino, Makoto;Stefan, Heinz G.
本文研究了降雨强度对稻田土壤-水界面养分交换的影响及其对大分河硝态氮径流的影响。日本九州岛上的大分河流域全长650公里（2公里），其中11%用于农业（水稻）。在6月/ 7月的季风季节，重度施肥的稻田被淹没，大量的NO3-N排放到大分河。建立了稻田NO3-N释放模型。该模型主要考虑降雨强度的影响。它假设除了增加地表径流和入渗外，季风雨还增强了孔隙水的流动，并通过土/水界面的动压力波动导致硝酸盐从土壤中释放出来。水田NO3-N释放量由模拟的土壤/水交换速度(W)来描述，W随降雨强度和水导率的增加而增加，约为10(-2)~ 10(-6)cm/s。当河流流量因降水（季风）而增加时，NO3-N负荷几乎与河流流量成正比，且几乎没有延迟。实测的大分河单位NO3-N日负荷量和稻田m(2)与降水强度R （R-1.042）几乎成正比，因此模拟了稻田单位NO3-N释放率（R-1.095）。这一结果表明，雨滴诱导抽水是提高稻田NO3-N径流的一个重要过程，即使不是关键过程。这意味着，随着气候变化，极端降雨事件的发生增加，地表水体的养分负荷可能会增加。
This paper examines the effect of rainfall intensity on nutrient exchange at the soil-water interface of rice paddy fields and the implications to nitrate runoff to the Oita River. The Oita River Basin on Kyushu Island in Japan covers 650 km(2) of which 11% are used for agriculture (rice). During the monsoon season in June/July, the heavily fertilized paddy fields are flooded and large amounts of NO3-N are discharged to the Oita River. A model has been developed for the NO3-N release in the rice paddy fields. The model focuses on the effect of rainfall intensity. It assumes that in addition to increased surface runoff and infiltration, the monsoon rain enhances pore water flow and causes nitrate release from the soil by dynamic pressure fluctuations at the soil/water interface. The magnitude of NO3-N release from paddy fields is described by the simulated soil/water exchange velocity (W) which increases with rising rainfall intensity and hydraulic conductivity, and is on the order of 10(-2) to 10(-6) cm/s. When the river flow rises due to precipitation (monsoon), the NO3-N load rises almost proportionately to the river discharge, and with little delay. Measured unit NO3-N loads in the Oita River per day and m(2) of paddy fields were nearly proportional to precipitation intensity R (R-1.042) and so were modeled unit NO3-N release rates in the paddy fields (R-1.095). This result suggests that raindrop-induced pumping is an important if not crucial process that enhances NO3-N runoff from rice paddy fields. An implication is that the nutrient loading of surface water bodies may grow as the occurrence of extreme rainfall events increases with climate change.