State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, P.R. China.
College of Earth Science, University of Chinese Academy of Sciences, Beijing, P.R. China.
Glob Chang Biol. 2021 Jan;27(2):327-339. doi: 10.1111/gcb.15410. Epub 2020 Nov 15.
Increasing levels of atmospheric CO are expected to enhance crop yields and alter soil greenhouse gas fluxes from rice paddies. While elevated CO ( ) effects on CH emissions from rice paddies have been studied in some detail, little is known how might affect N O fluxes or yield-scaled emissions. Here, we report on a multi-site, multi-year in-situ FACE (free-air CO enrichment) study, aiming to determine N O fluxes and crop yields from Chinese subtropical rice systems as affected by . In this study, we tested various N fertilization and residue addition treatments, with rice being grown under either (+200 μmol/mol) or ambient control. Across the six site-years, rice straw and grain yields under were increased by 9%-40% for treatments fertilized with ≥150 kg N/ha, while seasonal N O emissions were decreased by 23%-73%. Consequently, yield-scaled N O emissions were significantly lower under . For treatments receiving insufficient fertilization (≤125 kg N/ha), however, no significant effects on N O emissions were observed. The mitigating effect of upon N O emissions is closely associated with plant N uptake and a reduction of soil N availability. Nevertheless, increases in yield-scaled N O emissions with increasing N surplus suggests that N surplus is a useful indicator for assessing N O emissions from rice paddies. Our findings indicate that with rising atmospheric CO soil N O emissions from rice paddies will decrease, given that the farmers' N fertilization is usually sufficient for crop growth. The expected decrease in N O emissions was calculated to compensate 24% of the simultaneously observed increase in CH emissions under . This shows that for an agronomic and environmental assessment of effects on rice systems, not only CH emissions, but also N O fluxes and yield-scaled emissions need to be considered for identifying most climate-friendly and economically viable options for future rice production.
大气中 CO 浓度的增加预计将提高作物产量，并改变稻田土壤温室气体通量。虽然已经对高浓度 CO（）对稻田 CH 排放的影响进行了一些详细的研究，但对于它如何影响 N O 通量或产量标准化排放知之甚少。在这里，我们报告了一项多地点、多年的现场 FACE（自由空气 CO 富集）研究，旨在确定中国亚热带水稻系统的 N O 通量和作物产量受的影响。在这项研究中，我们测试了各种氮施肥和残留添加处理，水稻在（+200 μmol/mol）或对照条件下生长。在六个地点年中，对于施肥量≥150 kg/ha 的处理，与对照相比，水稻秸秆和籽粒产量在（+200 μmol/mol）下增加了 9%-40%，而季节 N O 排放减少了 23%-73%。因此，在（+200 μmol/mol）下，产量标准化 N O 排放量显著降低。然而，对于接受施肥不足（≤125 kg/ha）的处理，没有观察到对 N O 排放的显著影响。大气 CO 浓度升高对 N O 排放的缓解作用与植物氮吸收和土壤氮供应减少密切相关。然而，随着氮盈余的增加，产量标准化 N O 排放量的增加表明氮盈余是评估稻田 N O 排放的有用指标。我们的研究结果表明，随着大气中 CO 的增加，如果农民的氮施肥通常足以满足作物生长，那么稻田土壤 N O 的排放量将会减少。预计减少的 N O 排放量计算为补偿同时观察到的在（+200 μmol/mol）下 CH 排放增加的 24%。这表明，对于评估 CO 对水稻系统的影响的农业和环境评估，不仅需要考虑 CH 排放，还需要考虑 N O 通量和产量标准化排放，以确定未来水稻生产最有利于气候和经济可行的选择。
