Abstract: A two year experiment was conducted to investigate the differences of net photosynthetic rate（Pn）of the flag leaves,wheat yield,nitrate nitrogen（N）in soil and N fertilizer use efficiencies,including apparent recovery efficiency of applied N（REN）,agronomic efficiency of applied N（AEN）,physiological efficiency of applied N（PEN）,partial factor productivity of applied N（PFPN）for winter wheat under three treatments:no N treatment（T1）,decreasing N treatment（T2,180kg·ha-1N）and conventional N treatment（T3,315kg·ha-1N）with two different growing seasons,represented by T11,T21and T31 in 2008/2009 and T12,T22 and T32 in 2009/2010,respectively.The results showed that，（1）the differences of the photosynthesis of flag leaves（Pn）and yield of Jimai22 were not significant between T21 and T31,as well as between T22 and T32,which all significant higher than T11 and T12.（2）The content of nitrate N in 0-200cm soil layer under T22 at harvest was significant lower than that under T32 and T21,and the decreased rates were 32.2% and 26.7%,respectively.（3）REN,AEN,PEN and PFPN under T22 were significant higher than those under T32 and higher than REN,AEN and PEN except PFPN under T21 as well.For no reductions of the Pn of flag leaves and yield for Jinmai22,180kg·ha-1 N is a reasonable value for the farmer with decreasing the risk of groundwater pollution and promoting fertilizer N use efficiency compared with the conventional N treatment.The research results can provide a theoretical basis for sustainable development of high nitrogen utilization and winter wheat cultivation.

Key words: Decreasing nitrogen inputs, Wheat, Yield, Nitrate nitrogen, Nitrogen fertilizer use efficiency