不同水分管理方式下水稻生长季N2O排放量估算：模型验证和输入参数检验

利用2005～2007年我国稻田N₂O排放通量的田间原位测定资料和国际上其它地区稻田N₂O报道结果，对作者建立的不同水分管理方式下水稻生长季N₂O排放估算模型进行了验证. 结果表明，持续淹水稻田N₂O排放的拟合结果与其他地区淹水稻田N₂O通量值相一致. 淹水-烤田-淹水的水分管理方式下，稻田N₂O排放的拟合值接近于国际上同类研究结果. 淹水-烤田-淹水-湿润灌溉的水分管理方式下，稻田N₂O排放的估算模型对田间原位测定资料有很好的适切性. 为了检验模型输入参数的可信度，将本研究建立的有关我国水稻生产的相关资料数据库与以往研究报道结果进行了比较，结果表明，两者具有高度的一致性. 数据库资料表明，在20世纪50～70年代间，持续淹水稻田占20%～25%，大约75%～80%的稻田采用淹水-烤田-淹水的水分管理方式. 在20世纪80～90年代间，采用持续淹水，淹水-烤田-淹水和淹水-烤田-淹水-湿润灌溉水分管理方式的稻田分别约占12%～16%、 77%和7%～12%. 20世纪50年代水稻生长季平均每季总施氮量为87.49 kg·hm^-2，而90年代平均为224.64 kg·hm^-2. 其中，化学氮肥的施用量从20世纪50年代的37.4 kg·hm^-2增加到了90年代的198.8 kg·hm^-2，分别占水稻生长季氮输入总量的43%和88%. 在20世纪50～70年代间有机氮的输入量相对比较稳定，平均变幅在45.2～48.2 kg·hm^-2之间，随后逐步降低，有机肥料氮占氮输入总量的比例从20世纪50年代的52%降低到了90年代的9%. 作物残体N输入量从20世纪50年代的4.9 kg·hm^-2增加到了80年代的6.3 kg·hm^-2. 20世纪50～70年代水稻生长季氮肥施用量具明显的空间变异性，而80～90年代间其空间变异较小. 模型验证和输入参数检验的结果表明，该模型能较好地模拟我国不同水分管理方式下的稻田N₂O直接排放量.

Quantifying Direct N2O Emissions from Paddy Fields During Rice Growing Season in China: Model and Input Data Validation

The models on direct N₂O emissions from rice paddies under different water regimes developed by the authors were validated against field measurements in China reported in 2005-2007 and in other regions. In flooding rice paddies (F), N₂O emission predicted by the model was consistent with previous reports in other regions. Under the water regime of flooding-midseason drainage-reflooding (F-D-F), the model developed in this study was comparable to that established by using worldwide database. The models also well fitted N₂O emissions from rice paddies under the water regime of flooding-midseason drainage-reflooding-moisture but without waterlogging (F-D-F-M) in China. Consistency of rice production data derived from the database of this study with those reported in previous studies suggests that the model input data of rice production had high reliability. The input data showed that water management and nitrogen input regimes have greatly changed in rice paddies since the 1950s. During the 1950s-1970s, about 20%-25% of the rice paddy was continuous water logging, and 75%-80% under the water regime of F-D-F. Since the 1980s, about 12%-16%, 77% and 7%-12% of paddy fields were under the water regimes of F, F-D-F and F-D-F-M, respectively. Total N input during the rice growing season averaged 87.49 kg·hm^-2 in the 1950s and 224.64 kg·hm^-2 in the 1990s. Chemical N input during the rice growing season has increased from 37.4 kg·hm^-2 in the 1950s to 198.8 kg·hm^-2 in the 1990s, accounting for 43% and 88% of the seasonal total N inputs, respectively. Manure N input was applied at stable rate, ranging from 45.2 kg·hm^-2 to 48.2 kg·hm^-2 during the 1950s-1970s, but thereafter it decreased over time. The contribution of manure N to total N inputs has decreased from 52% in the 1950s to 9% in the 1990s. Crop residue N retained during the rice growing season has increased from 4.9 kg·hm^-2 in the 1950s to 6.3 kg·hm^-2 in the 1980s. A high spatial variation of nitrogen inputs during the rice growing season was found in the 1950s-1970s, while it was not pronounced in the 1980s-1990s. Overall, the results of this study suggest that the models could be used to quantify direct N₂O emissions from rice paddies under various water regimes in China.