| As one of the top ten fruits in the world,melon is deeply loved by the market.Their cultivation in Yan’an is very broad.However,there is short of water resources and the hardness of agricultural irrigation water is high,and the EC value leads to serious soil salinization in Yan’an area.At the same time,at this stage,growers blindly follow the trend to plant varieties,apply a large amount of fertilizer and extensive management,which not only leads to the decline of melon yield and quality,but also leads to environmental pollution and further deterioration of soil physical and chemical properties.Therefore,this study carried out four crops and four groups experiments to screen suitable oriental melon varieties cultivated and reasonable water fertilizer management scheme on organic substrate in Yan’an.The treatments are as follows:(1)Comparative experiment of oriental melon varieties cultivated in protected organic substrate.In the spring of 2020 and 2021,‘Linglonghuang’,‘Zetianchunyi’,‘Zetianmeiyu’,‘Zetiansihao’,‘Zetianyouya’,‘hangtianqingya’,‘Gk-01’,‘Gk-02’,‘Gk-03’,‘Ze-04’,‘Ze-05’,‘Lx-06’,‘Lx-07’,‘Lx-08’,‘Lvbote’ and ‘Qingnonglvbao’,‘Linglonghuang’,‘Ribentianbao’,‘Qingnongcuibao’,‘Jingyu352’,‘Lingtianlvguan’,‘Gk-03’,‘Ze-04’,‘Zhongyuan9016’,‘Jindi’,‘Bingtangwangzi’,‘Zetiansihao’,‘Jichuang20B’,‘Lvbote’ were chosen as materials.Comparing and analyze 11 indexes including the nutritional quality,flavor quality,commodity quality,yield.The determinants and indexes determining the quality characters of oriental melon were screened by principal component analysis(PCA),and the yield and representative quality of oriental melon were comprehensively evaluated in combination with TOPSIS,Finally,oriental melon suitable for organic substrate culture in Yan’an area was selected.(2)Research on water and fertilizer scheme of oriental melon organic substrate cultivation.‘Qingnong Lvbao’ chosen as the test material,experiments were performed using a quadratic orthogonal rotation combination design(implemented 1/2)with three experimental factors,which are irrigation amount(W),EC,and irrigation frequency(F),at five levels,for a total of 23 treatments.And conventional treatment(0.50 L/plant,one strength Yamazaki melon nutrient solution,1 time/d)served as the control(CK).All treatments were conducted using a completely randomized block design in three replicates.Regression analysis and random forest method were used to analyze the effects of different water and fertilizer factors on the types and contents of aromatic substances in the early stage of fruit expansion,the late stage of fruit expansion,the color change stage of fruit and maturity stage of fruit,and principal component analysis was used to determine the fertilizer coupling scheme conducive to the formation of aromatic substances in oriental melon cultivated on organic substrate in Yan’an area.The main results are as follows:(1)The representative indicators of quality traits of oriental melon screened by PCA were solid acid ratio,sugar acid ratio,soluble protein,free amino acid,fruit weight and solid acid ratio,sugar acid ratio,vitamin C,pulp thickness and free amino acid.Comprehensive evaluate the yield and representative quality index of oriental melon by TOPSIS and screen out that ‘Zhongyuan 9016’,‘Jichuang 20b’,‘Jindi’ which were suitable for organic substrate cultivation in Yan’an region.(2)The regression analysis of aromatic substances in different growth stages of oriental melon showed that the amount of irrigation,nutrient solution EC and their interaction had significant effects on the content of aromatic esters in oriental melon growth stage,and the interaction between nutrient solution EC and irrigation was significantly higher than that of single factor.Through the analysis of 60 aromatic substances in the whole growth period of melon by random forest model,we found that hexyl acetate,ethyl acetate,ethyl butyrate,ethyl caproate,hexanal,octanal,and 2-nonenal were the important aromatic substances in the growth and development of oriental melon.The optimal management obtained by PCA was irrigation with 1.68 L water for seven times per day per plant and nutrient solution EC maintained 3.53 m S/cm,which can get the high yield and best flavor quality of oriental melon.(3)According to entropy weight method,the common representative indexes of oriental melon growth and development,nutrient utilization,water efficiency,fertilizer efficiency,quality and yield in autumn of 2020 and spring of 2021 were dry biomass,nitrogen agronomic efficiency(NAE),water use efficiency(WUE),fertilizer using efficiency(FUE),sugar acid ratio and yield.The difference index was nutrient absorption,and the representative indexes were plant potassium content and fruit potassium content,respectively.The values of above representative indexes were normalized,and the TOPSIS method was used for comprehensive evaluation to establish the comprehensive evaluation system of oriental melon cultured in organic substrate.The optimal treatment of Ci in autumn of 2020 was irrigation with 0.73 L water for seven times per day per plant and nutrient solution EC maintained 3.53 m S/cm,the optimal treatment of Ci in Spring of 2021 was irrigation with1.68 L of water for seven times per day and nutrient solution EC maintained 3.53 m S/cm,the optimal scheme for comprehensive Autumn and Spring seasons was irrigating with 1.20 L water for seven times per day and nutrient solution EC maintained 3.20 m S/cm.By constructing the regression model of irrigation amount,nutrient solution EC and irrigation frequency on the comprehensive Ci of oriental melon,the results showed that the irrigation amount,nutrient solution EC and irrigation frequency in the autumn of 2020 increased first and then decreased.In the spring of 2021,the irrigation amount gradually increased the comprehensive Ci of oriental melon,the EC of nutrient solution gradually decreased,and the irrigation frequency first increased and then decreased.There was interaction among irrigation amount,nutrient solution EC and irrigation frequency on comprehensive Ci of oriental melon.The nutrient solution EC was the decisive factor for the comprehensive Ci of melon. |
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