尿素肥斑中氮素形态转化初探

Primary study on transformation of nitrogen forms in the urea patch

采用特制模拟容器,通过尿素扩散形成营养斑,观察斑内NH+4、NO-2和NO-3浓度变化及它们之间的相互转化。结果表明,NH+4、NO-2和NO-3浓度在距离肥斑7～8cm处的微域达到最大,尤以NO-2浓度增加较为显著,是一般土壤NO-2水平的数千倍。随培养时间增加,NO-2和NO-3最大浓度峰向施肥点移动,但两者浓度变化趋势不同,NO-2浓度在21d前随培养时间增加而增加,之后随培养时间增加而下降,而NO-3浓度随培养时间增加一直增加。结果还表明,NO-2是尿素营养斑内主要离子形态,从NH+4到NO-2的转化比较迅速,而NO-2转化为NO-3不是短暂的过程,这可能与施肥引起的土壤pH值变化有很大关系。

Special designed container was used to simulate diffusion of urea and investigate changes of NH^+_4, NO^-_2 and NO^-_3 concentrations, and their transformation. The results indicated that the highest concentrations of NH^+_4, NO^-_2, and NO^-_3 were in the microzones 7-8cm distancing from urea patch, especially NO^-_2, which was thousands times of NO^-_2 in the bulk soil. The highest peaks of NO^-_2 and NO^-_3 concentrations moved to urea with increasing time, respectively, but they differed. The former increased with time before 21d and decreased with time after 21d, but the highest concentration of NO^-_3 always increased with time. It was also seen from the results that NO^-_2 was main ion in the urea patch, and the transformation from NH^+_4 to NO^-_2 was quickly, but it was not short process from NO^-_2 to NO^-_3, which might relate to change of soil pH resulted from fertilization.