尿素与DCD和有机物料配施条件下氮素的转化和去向

Nitrogen Transformation and Fate in Soil Under the Conditions of Mixed Application of Urea with DCD or Different Organic Materials

采用好气土壤培养试验 ,研究了尿素配施有机物料和DCD条件下土壤不同氮库的动态。结果表明 ,尿素、尿素与小麦秸秆、苜蓿秸秆、鸡粪配施的条件下 ,硝化作用在 7d之内完成。DCD处理的NH4 N一直保持较高水平 ,说明DCD对土壤硝化过程有强烈的抑制作用。与单施尿素相比 ,C N高的小麦秸秆显著地降低了NH4 N、NO3 N的含量 ;C N低的苜蓿秸秆和鸡粪显著地增加了NH4 N、NO3 N的含量。土壤易矿化有机态氮不仅含量低 ,且处理之间没有显著差异。与对照相比 ,施肥后土壤微生物氮的含量有所增加 ,但处理间没有达到显著水平。15N标记结果表明 :肥料氮的回收率在 84 .1%～ 92 .0 %之间 ,加入DCD显著提高了肥料氮的回收率 ,其他处理之间没有显著差异。DCD处理肥料氮主要以有机固定态或粘粒矿物固定态存在 ,其次以NH4 N形式存在 ;其他处理肥料氮在土壤中主要以NO3 N形式存在 ,加入秸秆增加了化肥氮被土壤固定的比例 ,鸡粪中的氮素几乎全部以极易矿化的形式存在。

Dynamics of different soil nitrogen pools after application of urea with DCD or organic materials were studied by aerial incubation method. The results showed that nitrification completed in 7 days after application of urea with wheat straw, alfalfa straw and poultry manure. The NH 4 N in DCD treatment maintained high level, which illustrated that DCD had strong inhibiting effect on nitrification. High CN ratio of wheat straw significantly decreased the amount of NH 4 N and NO 3 N in soil while low CN ratio of alfalfa straw and poultry manure significantly increased the amount of them compared to urea treatment. The content of Norg was low and no significant difference among all treatments. Soil microbial biomass N increased after fertilizers application compared to control treatment but no significant difference among treatments. The 15 N labeled results showed that recovery of fertilizer nitrogen was between 84.1% and 92.0%. The recovery of fertilizer nitrogen was no significant difference among other treatments but it was significantly high in DCD treatment. The residual nitrogen existed mainly in organic form or fixed NH 4 + in DCD treatment but mainly in NO 3 N form in other treatments. The proportion of fixed nitrogen fertilizer increased with wheat straw treatment. The nitrogen in poultry manure mainly existed in easy mineralization form.