Abstract:Trelliscultivation of custard apple (Cucumis melo var. saccharinus Naud) in open fields is a new cultivation pattern owing to advantages of high yield and high efficiency in land use. The optimum combination of irrigation and nitrogen was obtained by investigating the effects of different nitrogen(N) and irrigation(I) levels on fruit yield, quality, nitrogen utilization efficiency(NUE) and irrigation water use efficiency(IWUE) of trelliscultivated melon in extremely droughty Kashi region. The results indicate that the fruit weight is increased under the nitrogen application, and the yield is increased by 31.0%. The rotten fruit rate is increased significantly under the nitrogen level of 375 kg/ha and quantity of water close to 8250 m3/ha. The highest NUE is obtained with quantity of water in 6750-7500 m3/ha and is decreased as the increase of the N level. The highest IWUE is obtained with application of nitrogen close to 225 kg/ha. The Vc content of the pulp under N375 kg/ha is the lowest, which is 11.3% to 25.6% lower than that of N0 The flesh rate and skin rate are not influenced by the irrigation (5250-8250 m3/ha), while nitrogen application can increase the flesh rate and reduce the percentage of placenta and seeds weight. The results suggest that as the yield close to 81745 kg/ha, the optimum combination of nitrogen and irrigation is 303 kg/ha and 7405 m3/ha without lessening quality.