不同水分管理方式下水稻生长季N2O排放量估算：模型应用

基于田间原位测定结果，作者建立了不同水分管理方式下稻田N₂O排放估算的统计模型. 在模型验证和输入参数检验的基础上, 本研究应用模型估算了20世纪50～90年代我国稻田水稻生长季N₂O直接排放量. 结果表明, 由于水稻种植面积和氮输入量的增加、以及水分管理方式的变化, 稻田N₂O-N季节排放量从20世纪50年代平均每年9.55 Gg增加到了90年代每年32.26 Gg, 同期伴随着水稻单产的增加. 在20世纪50～90年代间, 我国水稻生产的N₂O-N排放量以平均每10 a6.74 Gg的速度递增. 20世纪50年代和90年代稻田N₂O-N季节排放通量平均分别为0.32 kg·hm^-2和1.00 kg·hm^-2, 相当于季节氮输入总量的0.37%和0.46%. 本研究模型估算50～90年代间稻田N₂O季节排放量的不确定性为59.8%～37.5%. 就全国稻田的不同种植区域而言, 长江中下游地区稻田水稻生长季N₂O排放量占全国稻田N₂O排放总量的51%～56%. 20世纪90年代水稻生长季N₂O排放量约占我国农田N₂O年总排放量的8%～11%. 相对于旱地作物而言, 过去几十年水稻生产的发展在很大程度上减缓了我国农业生产的N₂O排放. 然而, 随着水稻生产中节水灌溉的推广和氮肥施用量的增加, 我国稻田N₂O季节排放量预计将相应增加.

Quantifying Direct N2O Emissions from Paddy Fields During Rice Growing Season in China: Model Application

Based on statistical analysis of field N₂O measurements in rice paddies in China, the models on direct N₂O emissions under different water regimes were established. After successes in model validation and input data verification, the models were used to quantify changes in direct N₂O emissions from paddy fields during the rice growing season in mainland China between the 1950s and the 1990s. Due to increases in rice planting area and nitrogen input and changes in water regime, the models predicted that seasonal N₂O-N emissions from rice paddies have increased from 9.55 Gg each year in the 1950s to 32.26 Gg N₂O-N in the 1990s, which was accompanied by the increase in rice yield over the period 1950s-1990s. During the period 1950s-1990s, seasonal N₂O-N emissions from rice paddies have increased, on average, at a rate of 6.74 Gg per decade. Seasonal N₂O fluxes in rice paddies were estimated to be 0.32 kg·hm^-2 in the 1950s and 1.00 kg·hm^-2 in the 1990s, which accounted for 0.37% and 0.46% of the seasonal total N inputs, respectively. The uncertainties in N₂O estimate were estimated to be 59.8% in the 1950s and 37.5% in the 1990s. Seasonal N₂O emissions from rice paddies in the region of middle and lower Yangtze River contributed 51%-56% to its national total. In the 1990s, N₂O emissions during the rice growing season accounted for 8%-11% of the reported annual total of N₂O emissions from croplands in China, suggesting that paddy rice development could have contributed to mitigating agricultural N₂O emissions in the past decades. However, seasonal N₂O emissions would be increased given that saving-water irrigation and nitrogen inputs are increasingly adopted in rice paddies in China.