Abstract: 【Objective】The objectives of the study were to investigate the effects of different water and nitrogen supply rates on fruit yield and quality of tomato (M6088), irrigation water and nitrogen use efficiency，and to obtain the best combination of irrigation and nitrogen for maximum tomato production when a single indicator was considered and the optimal range of water and nitrogen rates for high yield and quality tomato production. 【Method】A pot experiment was conducted in greenhouse at the Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Area of Ministry of Education in Northwest A&F University in 2013. The treatments comprised three irrigation upper limitations (W1, 70%θ_f; W2, 80%θ_f; W3, 90%θ_f, θ_f is the field capacity), and three nitrogen rates (N1, N 0.24 g·kg^-1; N2, N 0.36 g·kg^-1; N3, N 0.48 g·kg^-1). And the treatments were replicated fifteen times in random complete block designs. The multivariate regression analysis was used to obtain the best combination of irrigation and nitrogen for maximum tomato production when a single indicator was considered. The spatial analysis method was further used to comprehensively evaluate the tomato yield and quality to seek optimal range of water and nitrogen rates.【Result】The amount of irrigation and rate of nitrogen significantly affected the fruit yield, fruit quality, irrigation water productivity (IWP, in kg·m^-3, kg fruit produced per cubic metre water irrigated) and partial factor productivity of nitrogen (PNP). The fruit yield per plant increased first and then decreased with the irrigation and nitrogen rates were increased (except for N1, W1 treatments). Increasing irrigation amount remedied production reduction caused by nitrogen deficiency under N1 condition; increasing nitrogen rate relieved restrain from drought on fruit yield under W1 condition. Yield and the water and nitrogen supply exhibited a binary quadratic regression relationship. The maximum yield (1 599.4 g/plant) was achieved when the irrigation and nitrogen rates were 62.3 L/plant and 0.3864 g·kg^-1 soil, respectively. When the irrigation and nitrogen rates increased constantly, the tomato yield decreased. The IWP increased with the decreasing irrigation amount and increasing nitrogen rate, while the PNP was in contrast. The rates of water and nitrogen significantly influenced fruit quality parameters. With the increasing of nitrogen rate, soluble solids and organic acid content increased while vitamin C, lycopene and soluble sugar content and sugar acid ratio first increased and then decreased. Soluble solids and vitamin C content decreased with increasing irrigation amount (excepted for N2 treatment). Lycopene and soluble sugar content and sugar acid ratio first increased and then decreased with increasing irrigation amount (except for N1 treatment). The entropy weight method was used to determine the subjective weight of single tomato quality attributes. Results indicated that the attributes were ranked based on their importance by lycopene＞soluble sugar＞sugar-acid ratio＞organic acid＞Vc＞soluble solids. 【Conclusion】Through the multivariate regression analysis and the spatial analysis methods, the results showed that acceptable yield and quality of tomato (≥95% of corresponding maximum values) were obtained within the range of irrigation upper limitation 80% θ_f and nitrogen rate 0.34-0.44 g·kg^-1 soil.

Key words: tomato, water and nitrogen supply, yield, water and nitrogen use efficiency, quality