中文摘要：

在陕西省永寿县和河南省洛阳市分别设置了11和7处大田试验，分5层采集0～100cm土壤样品并测定其起始硝态氮含量。永寿试验设7个处理，分别为不施氮，硝态氮、铵态氮品种、硝态氮与铵态氮2：1组合各2个处理；洛阳试验设6个处理（硝态氮肥只有1个品种），施氮处理均施N150kg hm-2，研究小麦对铵态氮和硝态氮肥响应的差异及其与不同深度土层硝态氮累积量的关系。试验表明，同一形态不同氮肥品种之间的增产差异显著低于不同形态之间的差异。比较不同形态氮肥的小麦产量、增产量和增产率的平均值，硝态氮肥最高，硝态氮、铵态氮组合次之，铵态氮最低。氮肥增产量和增产率随土壤累积硝态氮量增加而显著下降；累积量越低，氮肥增产效果越突出，硝态氮的效果也越显著。由此可见，土壤累积的硝态氮量是决定氮肥肥效的主要因子，也是决定不同形态氮素效果的主要凼子。只有存硝态氮累积量低的土壤上，氮肥才能充分发挥作用，硝态氮也才能表现出明显的优势。

英文摘要：

Field experiments were conducted with 11 sites laid out in Yongshou,Shaanxi Province and 7 in Luoyang, Henan Province,and 5 soil samples for each site were collected in 20 cm increment to 100 cm depth ,for analysis of initial nitrate N contents. In Yongshou, each experimental site had 7 treatments,i, e. control （without N fertilization） , two kinds of nitrate N fertilizers （NN） ,two kinds of ammonium N fertilizers （AN） ,and two combinations of nitrate N ＋ ammonium N （NN ＋ AN） in a ratio of 2：1 , while in Luoyang, each experiment site had only 6 treatments with only one kind of nitrate N fertilizer. In N all treatments,the N application rate was 150 kg hm-2 as basal fertilizer, The experiments were carried out to explore wheat responses to ammonium N fertilizers and nitrate N fertilizers and their relationships with nitrate N accumu- lation in different soil layers. Results show that the difference in yield increase between the two kinds of N fertilizers with the same N form was significantly smaller than that between N fertilizers difterent in N form. Comparison between the fertil- izers different in N form in average of yield, yield increment （ kg hm 2 ） and yield increase rate （ % ） ,Treatments NN were the highest in yield and yield increment, followed by Treatments NN ＋ AN and Treatments AN in the end. In the experi- ments,yield increment and yield increase rate declined significantly with the increase in nitrate N accumulation in soil pro- file. The lower the nitrate N accumulation,the higher the crop response in yield and the more significant the effect of nitrate N fertilizer. It is,therefore,clear to see that nitrate N accumulation in soil profile is the major factor determining crop re- sponse to N fertilizer and effect of N fertilizers different in N form. Only in soils low in nitrate N accumulation,can N fertil- izer be brought into full play,and can nitrate N show its significant superiority.