Optimizing regulation irrigation schedule，rates and coupling with N fertigation was an effective way for realizing crop production improvement as well as water and nutrient use efficiency enhancement. The effects of drip-irrigation frequency (which controlled soil matric potential at 0.2 m depth immediately under drip emitters controlled higher than -20

-30 and -40 kPa) and nitrogen fertilizer level (0

180

225

262.5

300 and 345 kg/hm2) on the maize grain yield

water use efficiency and nitrogen use efficiency were studied by the means of using a split plot experiment with two factors. There was an obvious tendency that the plant height and LAI of maize increased with levels of water

but those decreased when the N applied rate beyond 262.5 kg/hm2. The response of dry matter weight of maize in harvest time to irrigation water was: W1 (－20 kPa)＞W2 (－30 kPa)＞W3 (－40 kPa). The effects of nitrogen fertilizer amounts on the amount nitrogen of seed in maize in harvesting dates was : N3 (262.5 kg/hm2)＞N4 (225 kg/hm2)＞N2 (300 kg/hm2)＞N5 (345 kg/hm2)＞N0 (0 kg/hm2). Both irrigation and N supply exerted a significant role on maize yield as well as yield component of kernels per row and 100 grain weight. An obvious positive interaction was obtained between water and nitrogen. Moreover，the effect of N on yield was substantially higher than that of irrigation. N fertilizer use efficiency increased with increasing N level within N supply range of 0～262.5 kg/hm2

and then dropped markedly when N rate above 262.5 kg/hm2．And in this range

it was found that the water use efficiency (WUE) and irrigation water use efficiency (IWUE) increased with increasing N level，while that decreased with increasing irrigation rate. At the suitable irrigation level of W3

the WUE，IWUE of 42.20～49.23 kg/mm and 63.31～78.00 kg/mm could be achieved. The highest yield was obtained in the combination treatments of W2N4 with the value of 20 489.06 kg/hm2. W3N3 combination treatment had the highest WUE

NRE and the yield could achieve 18 730.62 kg/hm2

which decreased 8% compared with the treatment of W2N4. In the present experiment

the optimal combination of nitrogen rate and irrigation frequency was W3N3 for the higher nitrogen fertilizer use efficiency

water use efficiency

and could achieve ideal grain yield

meanwhile

which had lower potential harm for environment.