Abstract: 【Objective】 In view of the questions of unreasonable irrigation and nitrogen in the vegetable greenhouse in semiarid northwest area, effects of water and nitrogen supply on the growth, yield, yield components, IWUE and WUE of cucumber under fertigation were investigated in order to regulate water and fertilizer scientifically and provide scientific reference for actual production. 【Method】 ‘Bonai 9-1’ was chosen as the test cultivar, the greenhouse plot experiment was subjected to three irrigation water levels [W1 (60% ET₀), W2 (80% ET₀) and W3 (100% ET₀), the irrigation of the whole growth period of cucumber were 126,152 and 177 mm, respectively] in interaction with four nitrogen fertilization levels [N0 N1 (180 kg·hm^-2), N2 (360 kg·hm^-2), N3 (540 kg·hm^-2)], and there were 12 treatments in total. Growth indexes were measured during the growing season and yield and yield components were counted after the final harvest. 【Result】 In addition to stem diameter, irrigation and nitrogen application influenced cucumber plant height, leaf area index, dry weight, yield, yield components, IWUE and WUE significantly. Irrigation had a significant positive correlation with plant height, leaf area index, fruit number, average fruit weight and yield, whereas the impact of nitrogen fertilizer on cucumber growth and yield showed different trends due to the different nitrogen levels. The impact of nitrogen fertilizer on plant height and leaf area index showed an increasing trend first and then decreasing, reached the maximum at N₂ treatment. Dry weight was slightly different, which showed under W₁ level, reaching the maximum in N₂ treatment, decreased slightly in N₃ treatment afterwards, and there were no significant difference between the N₂ and N₃ treatments. The remaining irrigation levels showed varying degrees of increase with the increasing nitrogen fertilizer. Cucumber yield also increased with the increasing nitrogen rate. When the nitrogen rate increased to N₂ level, and continued to increase, the effect of yield showed different trends under different irrigation levels. In other words, there was no significant difference among yields when nitrogen rate increased to N₂ levels and continued to increase under W₁ and W₂ levels, while difference was significant between N₂ and N₃ treatments and N₃ improved yield by 8.4% than N₂ under W₃ level. Irrigation had a significant negative correlation effect on IWUE, and gained IWUE maximum 41.33 kg·m^-2 at W₁ level. The impact of irrigation on WUE showed an increasing trend and then decreasing, reached the maximum 55.82 kg·m^-2 at W₂ level. Nitrogen rate had a positive correlation effect on IWUE, whereas showed different trends on WUE. In W₁ and W₂ treatments, WUE showed an increasing trend and then decreasing with the increase of nitrogen rate, reached the maximum 52.34 kg·m^-2, 55.82 kg·m^-2,respectively, at N₂ levels, while in W₃ treatment, WUE was significantly increased with the increase of nitrogen rate. The maximum yield was obtained in W₃N₃ treatment, but the WUE and IWUE were significantly lower than W₂ level. Compared with W₃N_3, the treatment of W₂N₂ reduced the irrigation amount by 16.7%, nitrogen rate by 33%, yield by only 11.3%, improved IWUE by 6.5%, and WUE by 11.1%. Path analysis on yield and growth index (height, stem diameter, leaf area index, dry weight) showed that dry weight and leaf area index had the important effects on cucumber yield improvement, which can be used for the first and second indexes of high yield.【Conclusion】Reasonable irrigation and nitrogen application not only maintained good growth characteristics of cucumber, but also obtained the maximum economic benefit. In comprehensive consideration of yield, water and fertilizer conservation, W₂N₂ treatment (80% ET₀, 360 kg N·hm^-2) was better appropriate combination of water and nitrogen under the experimental conditions.

Key words: greenhouse cucumber, water and nitrogen supply, fertigation, yield, water use efficiency, path analysis