尿素与缓释尿素配施添加DMPP对砂姜黑土氮素转化的影响

研究尿素与缓释尿素配施添加硝化抑制剂3,4-二甲基吡唑磷酸（DMPP）对砂姜黑土氮素转化的影响，为田间速效与缓释氮的合理配施提供理论依据。采用室内恒温、恒湿培养试验方法，试验设不施肥（CK）、单施尿素（N）、单施缓释尿素（S）、60%尿素+40%缓释尿素（NS）、尿素+DMPP（ND）、缓释尿素+DMPP（SD）、60%尿素+40%缓释尿素+DMPP（NSD）共七个处理，通过测定不同处理土壤中不同形态氮素含量，探究添加DMPP在单施尿素、单施缓释尿素及尿素与缓释尿素配施上对土壤氮素转化的不同影响。ND处理在培养第1~35 d内铵态氮含量均显著高于N处理（P<0.05），并有效延缓了铵态氮向硝态氮转化的时间。SD处理较之S处理在显著提高土壤中铵态氮含量的同时（P<0.05），也能有效抑制硝化作用，其硝化抑制有效作用时间在49 d左右，并且在此期间内能降低表观硝化率，提高硝化抑制率。与NS处理相比，NSD处理不仅能够显著提高土壤铵态氮含量（P<0.05），使铵态氮半衰期延长至18.6 d，硝化抑制率显著提高（P<0.05），表观硝化作用有效抑制时间延长了32 d左右。综合分析表明，尿素与缓释尿素配施添加DMPP在抑制氨氧化作用中效果明显，显著提高硝化抑制率（P<0.05），降低表观硝化率，有效延长了铵态氮在土壤中停留的时间，该措施为有效阻控农田氮素损失提供了科学依据。

Effects of Combined Application of Urea and Slow-release Urea Plus DMPP on Nitrogen Transformation in Lime Concretion Black Soil

A soil experiment was conducted to explore the influences of the combined application of urea and slow-release urea plus 3,4-dimethylpyrazole phosphate (DMPP) on nitrogen transformation in lime concretion black soil. There were seven treatments, namely (1) CK (without fertilization), (2) N (only urea), (3) S (only slow-release urea), (4) NS (60% urea and 40% slow-release urea), (5) ND (urea plus DMPP), (6) SD (slow-release urea plus DMPP), and (7) NSD (60% urea and 40% slow-release urea plus DMPP). This study mainly focused on the dynamic change of soil nitrogen forms during a 63 d incubation period. The results showed that: (1) in the treatment of ND, the contents of ammonia nitrogen were significantly higher than those in N treatment during prior 35 d incubation period (P<0.05), which indicated that the addition of DMPP could effectively delay the process of ammonium oxidation. (2) Similarly, the SD treatment also exhibited significantly higher ammonia nitrogen contents in soil than S treatment (P<0.05). Moreover, oxidation of ammonium was inhibited up to day 49 with reduced apparent nitrification rate. while the nitrification inhibition rate was enhanced. (3) Compared to NS treatment, the contents of ammonia nitrogen were significantly higher and the half-life of ammonia was extended up to 18.6 d in NSD treatment (P<0.05). In addition, the nitrification inhibition rate under NSD treatment increased significantly and the inhibition continued up to day 32 (P<0.05). Comprehensive above analysis, the ammonia oxidation processes were significant inhibited and the residence time of ammonium in soil were significantly prolonged by the addition of DMPP in the treatment of urea combined application with slow-release urea, which exhibited a relative higher nitrification inhibition rate and a relative lower apparent nitrification rate (P<0.05). These findings provide scientific reference for application of urea and slow-release urea to prevent loss of nitrogen in farmland.