Abstract:Aiming to implement accurate and effective water and fertilizer management for the efficient and intensive production of melons in facilities. The melon of “Qianyu No.6” was selected as test material, in a double-layer large-span greenhouse in Yangling, Shaanxi from April to July in 2020. With two factors of water and fertilizer, three irrigation levels were designed based on the crop transpiration (ETc) (W1: low water, 75%ETc, W2: medium water, 100%ETc, W3: high water,125%ETc) and three fertilization rates were calculated according to the target yield method (F1: low fertilizer 758.44kg/hm2, F2: medium fertilizer 948.05kg/hm2, F3: high fertilizer 1137.66kg/hm2). To investigate the effects of different water and fertilizer conditions on the growth, yield, quality and water and fertilizer use efficiency and the optimal irrigation and fertilization plan was determined by using a comprehensive evaluation method. The results showed that the coupling of water and fertilizer had different effects on the indicators of melon. The total of 12 indicators from four categories of growth, yield, quality, and profitability were combined and weighed based on game theory. The total yield got the largest comprehensive weight of 0.343, and the lowest weight was obtained from free amino acid content of 0.007. Comprehensive evaluation was carried out based on gray relation analysis and TOPSIS coupling model, and the compound closeness was the best under the medium levels of both irrigation and fertilization. The combined application of fertilization had a significant interaction effect on the comprehensive growth of melon, and the tendencies of irrigation and fertilization on the comprehensive growth of melon were observed first increasing and then decreasing, which was consistent with actual production. Melon had the highest comprehensive growth score when the irrigation amount was 810.52~990.64m3/hm2 and the fertilization rate was 853.25~1042.85kg/hm2, which was the optimal water and fertilization application plan. The research result can provide a basis for the scientific management of water and fertilizer in the production of melon in local greenhouse.