Abstract: 【Objective】Water and fertilizer are the major limiting factors in crop production. At present, the utilization of water and nitrogen is not reasonable, not only giving rise to a waste of water resources, but also making a threat to the environment. In order to discuss a reasonable collocation of water and nitrogen in winter wheat and summer maize rotation system, grain yield and nitrogen uptake and utilization were analyzed based on a 5-year experiment carried out in North China Plain (NCP).【Method】In the winter wheat and summer maize rotation system, the split plot design was employed with main plot of water (limiting water and suitable water), sub-plot of nitrogen fertilizer ((0+0), (60+60), (120+120), (180+180), (240+240) and (300+300) kgN·hm^-2, respectively, for wheat and maize rotation system), and three replicates in each sup-plot. Limiting and suitable water was employed according to winter wheat and summer maize irrigation system in the piedmont plain of North China, and the irrigation treatments included two, limiting water treatment irrigated 1 water at jointing stage and suitable water treatment irrigated 2 water at jointing and blossom stages for winter wheat, while for summer maize which irrigation time was confirmed according to the different years precipitation, and 1 water before sowing, 2 water before sowing and 12 leaf, and 3 water before sowing, 12 leaf and blossom stages.【Result】When water supply was more than 609.5 mm for wheat and maize, limiting factors of effect of N fertilizer was not water, and the contribution of N fertilizer to yield was larger; while water supply was lower, the effect of N fertilizer was restrained, and the contribution of water to yield was larger. Water and N had an obvious coupling effect, the N application rate for getting a high yield were 134.8 kg·hm^-2 and 126.4 kg·hm^-2 for wheat, and 176.8 kg·hm^-2 and 127.2 kg·hm^-2 for maize under limiting and suitable water conditions, respectively. When N fertilizer rate was 300 kg·hm^-2 and 240 kg·hm^-2, respectively, under limiting and suitable water for the two seasons crop, shoot N was amounted to a higher value, but N fertilizer rate was more than 60 kg·hm^-2 for maize under two water conditions and for wheat under limiting water, and 120 kg·hm^-2 for wheat under suitable water conditions, straw residual N significantly increased. Partial productivity of N fertilizer (PPNF) decreased with the increase of nitrogen application rate, and with the years passing, PPNF decreased significantly, especially the treatments of nitrogen application rate at 60 kg·hm^-2 for wheat season, which PPNF decreased rapidly. The soil organic matter and total nitrogen content did not decrease when nitrogen application rate reached 240 kg·hm^-2 of limiting water and 120 kg·hm^-2 of suitable water treatments for winter wheat and summer maize rotation system.【Conclusion】The major factor for limiting fertilizer efficiency was water under the condition of limiting water, therefore the amount of nitrogen application should be reduced in dry years. For winter wheat and summer maize rotation system, the N application rates for getting maximum yields were 311.6 kg·hm^-2 and 253.6 kg·hm^-2 respectively, and which grain yields were 16 127.5 kg·hm^-2 and 17 272.9 kg·hm^-2, respectively, under limiting and suitable water conditions.

Key words: winter wheat, summer maize, water and nitrogen, yield, nitrogen uptake and utilization