双氰胺减少铵态氮肥施用后潮土N2O排放的机制

为探讨双氰胺（DCD）减少铵态氮肥施用后氧化亚氮（N₂O）的排放机制，通过开展好氧培养试验，研究DCD配施铵态氮（NH₄⁺-N）或亚硝态氮（NO₂^--N）对潮土土壤N₂O排放的影响，同时添加不同浓度NO₂^--N模拟NO₂^--N累积对N₂O和CO₂排放的影响。结果表明： DCD仅对NH₄⁺-N氧化过程中N₂O排放有抑制作用，对NO₂^--N还原过程中产生的N₂O没有影响；培养前7 d，DCD显著抑制NH₄⁺-N的氧化过程，降低净硝化速率，而在添加NO₂^--N土壤中加入DCD后净硝化速率显著增加，培养30 d后，DCD对NH₄⁺-N和NO₂^--N氧化过程均没有影响；添加外源NO₂^--N明显促进了N₂O排放，其排放通量显著高于不施肥的对照处理； N₂O累积排放量同NO₂^--N浓度呈正相关，CO₂累积排放量同NO₂^--N浓度呈显著负相关。研究表明，DCD可以避免NO₂^--N大量累积而产生的毒害作用，但仅对氨氧化过程N₂O减排有效果，因此亟待研发适于抑制NO₂^--N产生N₂O的新型抑制剂。

Mechanisms of underpinning the dicyandiamide-induced N2O emissions reduction in a fluvo-aquic soil after ammonium nitrogen fertilization

This study explores the mechanisms underpinning the dicyandiamide(DCD)-reducing nitrous oxide(N₂O) emissions. This was carried out using two aerobic incubation experiments to examine the effects of DCD on the production of N₂O from NO₂^--N by adding DCD combined with NH₄⁺-N or NO₂^--N. Then, the effects of NO₂^--N accumulation on N₂O emissions was determined by adding different amounts of NO₂^--N. The results showed that DCD only inhibited N₂O emissions during the oxidation of ammonium nitrogen(NH₄⁺-N) and had no effect on N₂O emissions during the reduction of NO₂^--N. DCD significantly inhibited the oxidation of NH₄⁺-N and decreased the net nitrification rate at 7 d following incubation; however, the net nitrification rate increased significantly following the addition of DCD to NO₂^--N soil. Following 30 d of culture, DCD had no effect on the oxidation of NH₄⁺-N and NO₂^--N. The addition of exogenous NO₂^--N significantly promoted N₂O emissions, and these emission rates were significantly higher than those of the control treatment. Cumulative N₂O emissions were significantly positively correlated with the NO₂^--N concentrations, whereas the cumulative CO₂ emissions demonstrated the opposite relationship. These results indicate that DCD may eliminate the toxicity caused by the accumulation of NO₂^--N, although it is only effective in reducing N₂O emissions during the oxidation of ammonia oxidation. Therefore, new inhibitors that restrict N₂O production from NO₂^--N are urgently needed.