Soil-emitted nitrous oxide (N₂O) and nitric oxide (NO) in crop production are harmful nitrogen (N) emissions that may contribute both directly and indirectly to global warming. Application of nitrification inhibitors, such as dicyandiamide (DCD), and urea deep placement (UDP), are considered effective approaches to reduce these emissions. This study investigated the effects of DCD and UDP, compared to urea and potassium nitrate, on emissions, nitrogen use efficiency and grain yields under direct-seeded rice. High-frequency measurements of N₂O and NO emissions were conducted using the automated closed chamber method throughout the crop-growing season and during the ratoon crop. Both UDP and DCD were effective in reducing N₂O emissions by 95% and 73%, respectively. The highest emission factor (1.53% of applied N) was observed in urea, while the lowest was in UDP (0.08%). Emission peaks were mainly associated with fertilization events and appeared within one to two weeks of fertilization. Those emission peaks contributed to 65%–98% of the total seasonal emissions. Residual effects of fertilizer treatments on the N₂O emissions from the ratoon crop were not significant; however, the urea treatment contributed 2%, whereas UDP contributed to 44% of the total annual emissions. On the other hand, cumulative NO emissions were not significant in either the rice or ratoon crops. UDP and DCD increased grain yields by 16%–19% and N recovery efficiency by 30%–40% over urea. The results suggested that the use of DCD and UDP could mitigate N₂O emissions and increase grain yields and nitrogen use efficiency under direct-seeded rice condition.

作物生产中土壤排放的一氧化二氮（N ₂ O）和一氧化氮（NO）是有害的氮（N）排放，可能直接或间接地导致全球变暖。硝化抑制剂如双氰胺（DCD）和尿素深层施用（UDP）的应用被认为是减少这些排放的有效方法。与尿素和硝酸钾相比，本研究调查了直播水稻下DCD和UDP对排放，氮素利用效率和谷物产量的影响。在整个农作物生长季节和再生作物期间，使用自动密闭室方法对N ₂ O和NO排放进行高频测量。UDP和DCD均可有效减少N ₂O排放分别为95％和73％。在尿素中观察到最高的排放因子（占施用氮的1.53％），而在UDP中观察到最低的排放因子（0.08％）。排放峰值主要与施肥事件有关，并在施肥的一到两周内出现。这些排放高峰占季节性排放总量的65％–98％。化肥处理对再生作物N ₂ O排放的残留影响不显着。然而，尿素处理贡献了2％，而UDP贡献了年度总排放量的44％。另一方面，无论是水稻还是再生作物，累积的NO排放均不显着。与尿素相比，UDP和DCD可使谷物产量提高16％–19％，氮素回收效率提高30％–40％。结果表明，使用DCD和UDP可以减轻N在直栽水稻条件下，释放₂ O并增加谷物产量和氮素利用效率。