Abstract: The split plot design was employed with main plot of normal N application rate(225 kg/ha,N3),reducing 20% of N application rate(180 kg/ ha,N2),reducing 30% of N application rate(157.5 kg/ ha,N1) and no N application(N0),sub-plot of 5 hybrid cultivars[Zeyu 8911(ZY8911),Weike 518(WK518), Zhengdan 958 ( ZD958), Nongda 108 (ND108) and Xianyu 508 (XY508)]in this experiment,and the changes of grain yield,N efficiency,chlorophyll fluorescence and activities of key enzymes related with N metabolism in different genotypes of maize were studied,so as to provide scientific basis for improving N efficiency and realizing high-yield and high-efficiency maize cultivation in Huang-Huai-Hai region.The results showed that the grain yield was 12.12 t/ha under the normal application rate of N.With the N application rate reduction,grain yield significantly decreased,which was 9.20 t/ha under N0 treatment.The grain yields of ZD958 and WK518 were significantly higher than those of XY508 and ND108, there was no significant difference between ZY8911 and the other genotypes.N uptake efficiency,N utilization efficiency and N efficiency significantly increased under N application reduction.Three indexes of WK518,ZD958 and ZY8911 were overall higher than those of ND108 and XY508 except that N uptake efficiency of ZY8911 was lower than that of ND108.The SPAD value in the ear leaf decreased under N application reduction,which of WK518,ZD958 and ZY8911 were overall higher than those of ND108 and XY508. Fo,Fm,Fv/ Fm and PSⅡ comprehensive performance index(PI) decreased under N application reduction, which was the highest in ND108. Nitrate reductase and glutamine synthetase activities in the ear leaf first increased and then decreased with N application reduction,which were the highest at 20 days after silking. The enzyme activities of WK518,ZD958 and ZY8911 were overall higher than those of ND108 and XY508,and the order of NR and GS activities was N2>N3>N1>N0.In conclusion,ZD958,WK518 and ZY8911 had higher SPAD value and activities of enzymes related to N metabolism,better fluorescence characters,compared with ND108 and XY508,could maintain matter accumulation and capacity of N assimilation,and hold the higher N utilization efficiency in the process of N metabolism,thereby reaching higher yield under the low N condition.However,in order to ensure the
yield,the reduction of N application rate should not be too large, and it is advisable to reduce the application rate by 20%.

Key words: Nitrogen fertilization reduction, Maize genotype, Nitrogen efficiency, Yield, Fluorescence parameter, N metabolism enzyme

摘要： 采用裂区设计，主区为正常施氮量（225 kg/hm²,N3）、减氮20%（180 kg/hm²,N2）、减氮30%（157.5 kg/hm²,N1）、不施氮(N0)4个施氮水平，副区为5个玉米主栽品种（泽玉8911、伟科518、郑单958、农大108和先玉508），研究氮肥减施下不同基因型玉米产量、氮效率、荧光参数、氮代谢关键酶活性的变化，为提高黄淮海地区玉米氮效率、实现玉米高产高效提供科学依据。结果表明，N3处理玉米籽粒产量平均为12.12 t/hm²，随着施氮量减少，籽粒产量显著下降，N0处理籽粒产量仅为9.20 t/hm²；不同基因型玉米籽粒产量表现为郑单958和伟科518较高，显著高于先玉508和农大108，泽玉8911与其他基因型之间差异不显著。氮肥减施显著提高了夏玉米的氮吸收效率、氮利用效率和氮效率，除氮吸收效率中泽玉8911低于农大108外，各基因型间的氮吸收效率、氮利用效率和氮效率总体表现为伟科518、郑单958、泽玉8911＞农大108、先玉508。氮肥减施后，玉米穗位叶SPAD值降低，不同基因型玉米SPAD值总体表现为伟科518、郑单958、泽玉8911＞农大108、先玉508。穗位叶初始荧光(Fo)、最大荧光(Fm)、最大光化学效率(Fv/Fm)、PSⅡ综合性能指数(PI)总体上均随施氮量的减少而下降，以农大108最高。吐丝后穗位叶硝酸还原酶（NR）和谷氨酰胺合成酶（GS）活性总体均呈先增加再降低的趋势，以吐丝后20 d最高，不同施肥处理间均表现为N2>N3>N1>N0，不同基因型间表现为伟科518、郑单958、泽玉8911＞农大108、先玉508。总之，氮肥减施条件下，与农大108和先玉508相比，郑单958、伟科518和泽玉8911穗位叶有较高的叶绿素含量和氮素代谢相关酶活性、较好的荧光特性，保证了植株物质积累和氮素同化能力，维持氮代谢过程中较高的氮利用效率，进而保证了在低氮条件下具有较高的产量，但为了保障产量，氮肥减少量不宜太大，以减施20%为宜。

关键词: 氮肥减施, 玉米基因型, 氮效率, 产量, 荧光参数, 氮代谢酶