Purpose

Nitrous oxide (N₂O) measured simultaneously with di-nitrogen (N₂) emissions from soils are greatly uncertain due to large temporal and spatial variations. This study aims to report N₂O, N₂, N₂/N₂O, ¹⁵N-N₂O, wheat-maize annual grain yields, and yield-scaled N₂O and N₂O plus N₂ emissions on the responses to different nitrogen (N) fertilizer rates in a winter wheat-summer maize cropping system. Furthermore, this study also seeks to determine controlling factors for N₂O, N₂, and N₂/N₂O emissions and significantly investigate the relationship between the soil-climate measured factors and ¹⁵N-N₂O.

Materials and method

Three N inputs and control treatments, 0, CK; 200, LN; 400, MN; and 600, HN kg N ha⁻¹ year⁻¹ were set since 1998. Direct measurement method has been used to quantify N₂O and N₂ emissions.

Results

Our results indicated that the effects of long-term N fertilization significantly increased N₂O and N₂ and also reduced N₂/N₂O emission ratios as described by exponential functions. Using structural equation modeling (SEM), NH₄⁺, WFPS, NO₃^-, and DOC were revealed to be main controlling factors for N₂O, while N₂ by DOC, NO₃^-, WFPS, and temperature finally N₂/N₂O was positively related to temperature. Furthermore, the ¹⁵N-N₂O was positively related to N₂/N₂O ratios, indicating that denitrification is the dominant process at the study site. The yield-scaled N₂O emissions followed the order HM>MN>LN>CK, and they were 1.56, 1.47, and 1.07 times greater than CK, respectively. Total yield-scaled N₂O plus N₂ were in the order of CK>HN>MN>LN.

Conclusion

N fertilization has shown strong impact not only on N₂O, N₂, and N₂/N₂O emissions but also on yield-scaled N₂O and N₂O plus N₂ emissions. High agronomic nitrogen use efficiency (NUE), low yield-scaled N₂O emissions, and low cumulative N₂O plus N₂ emissions were observed at 200-LN treatment, suggesting this rate to be an optimum and sustainable agricultural management practice with no significant crop yield reduction as compared to the current farmers’ practice of 400 kg N ha⁻¹ year⁻¹.

中文翻译：

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温带半干旱农业生态系统中长期氮肥对N 2 O，N 2及其产量尺度排放的影响

目的

由于较大的时间和空间变化，从土壤中同时排放的一氧化二氮（N ₂ O）和二氮（N ₂）排放量非常不确定。本研究旨在报告N ₂ O，N ₂，N ₂ / N ₂ O，¹⁵ N-N ₂ O，小麦玉米的年度谷物单产以及产量定标的N ₂ O和N ₂ O以及N ₂排放对响应的响应。冬小麦-夏季玉米种植系统中不同的氮肥施用量。此外，本研究还试图确定N ₂ O，N ₂和N _2的控制因素。/ N ₂ O排放量，并研究土壤气候测量因子与¹⁵ N-N ₂ O之间的关系。

材料与方法

三个N输入和控制处理，0，CK；200，LN；MN，400；自1998年以来设定了600，HN kg N ha ^-1 year ^-1。直接测量方法已用于量化N ₂ O和N ₂排放。

结果

我们的结果表明，长期施用氮肥的效果显着增加了N ₂ O和N _2，并且还降低了N ₂ / N ₂ O的排放比，如指数函数所述。使用结构方程模型（SEM），NH ₄ ⁺，WFPS，NO ₃ ^- ，和DOC显露是对于N主要控制因素₂ O，而Ñ ₂由DOC，NO ₃ ^-，WFPS和温度最后Ñ ₂ / N ₂ O与温度呈正相关。此外，¹⁵ N-N ₂ O与N ₂正相关/ N ₂ O比值，表明反硝化作用是研究现场的主要过程。产量尺度的N ₂ O排放量按HM> MN> LN> CK的顺序排列，分别比CK大1.56、1.47和1.07倍。总产量标度的N ₂ O加N ₂的顺序为CK> HN> MN> LN。

结论

施氮不仅对N ₂ O，N ₂和N ₂ / N ₂ O排放产生了强烈影响，而且对按产量定级的N ₂ O和N ₂ O加N ₂排放也产生了强烈影响。在200 LN处理下，观察到高的农艺氮利用效率（NUE），低产量的N ₂ O排放以及低的累积N ₂ O加N ₂排放，这表明该比率是最佳且可持续的农业管理实践，没有与当前农民的400千克N ha - ¹年^-1的实践相比，农作物的单产显着降低。