Study On The Effect Of Watermelon With Coupling Of Water And Fertilizer Under Drip Irrigation In Plastic Tunnel

Watermelon var. Nongkeda No.11was used to study the effects of water-fertilizercoupling on growth, yield and quality of watermelon and its photosynthetic characteristics inplastic tunnel. Nine treatments were designed including three irrigation amount levels (W1,450m3/hm2; W2,900m3/hm2; and W3,1350m3/hm2) and three fertilizer levels (F1, N81.53kg/hm2+P2O533.43kg/hm2+K2O101.09kg/hm2; F2, N163.05kg/hm2+P2O566.85kg/hm2+K2O202.18kg/hm2; and F3, N244.58kg/hm2+P2O5100.28kg/hm2+K2O303.27kg/hm2). This study was to set up a new model for good quality and high yield evaluation ofwater-saving watermelon cultivation in the arid regions of northwest China.1. Effects of different fertigation treatment on morphological characteristic indexes ofwatermelon were significant in plastic tunnel. Under the low fertilization level (F1) andmiddle fertilization (F2), plant height increased through improve irrigation water，but there isno change at high fertilization level(F3). F2W2treatment has been able to provide enoughmaterial and water for vegetative growth of watermelon. The main effect of fertilizatioin andirrigation level were significant on plant height and stem diameter in each growth stage ofwatermelon, and interaction effect existed between fertilization and irrigation treatment onthe place of first female flower.2. Effects of different fertigation treatment on yield and water use efficiency ofwatermelon were significant in plastic tunnel. There was interaction effect betweenfertilization and irrigation treatment on weight per melon of watermelon by variance analysisof double factors. Weight per melon increased with increasing irrigation water, and F3treatment can increase production with W3level. The water use efficiency had significantdifference among different fertigation treatment. The WUE increased with the increase offertilization, but it seems lower than before under F3level. F2W2treatment revealed arelatively high yield and WUE; yield was3.6%higher than F3W3and the highest water useefficiency (35.73%higher than F3W3) at the end of the experiment. The plant height, stemdiameter and leaves number of watermelon had significant positive correlation with yield.3. Effects of different fertigation treatment on fruit quality of watermelon weresignificant in plastic tunnel. Interaction effect existed between fertilization and irrigationtreatment on longitudinal section diameter. Content of total soluble solid, soluble protein and lycopene of F2W2treatment were best in fruits as well as good sugar acid ratio and excellettaste. F2W1treatment and F3W2treatment showed the highest soluble sugar content and totalvitamin C content (but no significant difference with F2W2), respectively. There was anobvious or significance interaction effect between fertilization and irrigation treatment on fruitqualities. Dominant component analysis is used to evaluate the quality of fruit, F2W2cametop overall.4. Effects of different fertigation treatment on photosynthetic characteristics indicators ofwatermelon leaves were significant in plastic tunnel. Compared with the other treatments,F2W2showed much higher chlorophyll content in each growth stage. Interaction effectexisted between fertilization and irrigation treatment on the photosynthetic characteristics.There was a positive correlation between photosynthetic characteristics and morphologicalindexes. Content of protein and organic acid were not significant correlation withphotosynthetic characteristics, other quality indicators of fruit had obvious or significancepositive correlation.So, when the amount of feritilizer and water was F2(N163.05kg/hm2+P2O566.85kg/hm2+K2O202.18kg/hm2) and W2(900m3/hm2), yield and WUE of watermelon wasrespectively35888kg/hm2and39.88kg/m3, the main fruit qualities of watermelon werebetter, content of center total soluble solid, soluble sugar, total vitamin C, soluble protein andlycopene was pespectively10.59%、105.06g/kg、34.51mg/kg、0.19mg/g and36.25mg/kg.F2W2treatment was recommended as the best combination of water and fertilizer for theproduction of watermelon under drip irrigation and plastic film mulch in the arid area ofnorthwest China.