Reserch Water Requirement And Irrigation Effects Of Watermelon With Drip Irrigation Under Mulch Film In Plastic Shed

With drip irrigation under mulch film in plastic shed, the treatment of different watersupply conditions（Kcp：0.5Ep,1.0Ep,1.5Ep） in watermelon different growth stages （Seedling,Flowering and Bearing, Fruit Development, Fruit Mature）was implemented. The temperature,illumination, relative humidity and pan evaporation in plastic shed were recorded, and thewater requirement rate and evapotranspiration of watermelon were measured. The relationshipbetween environmental factors and watermelon water requirement rate were studied. Theeffects of different treatment on watermelon growth physiology, yield, fruit quality, and wateruse efficiency were studied. The relationship between irrigation water amount,evapotranspiration and yield, fruit quality were analyzed. Water requirement regulation andthe best irrigation scheme were demonstrated. The main results were as follows.（1） The high correlation was found between environmental factors and water requirementrate. A very significant positive correlation between water requirement rate and daily meantemperature, daily mean illumination, daily mean pan evaporation was showed, and thecorrelation coefficients that respectively were0.935,0.894and0.878. A very significantnegative correlation between water requirement rate and daily mean humidity was also beingfound, and the correlation coefficient was-0.848. Daily mean temperature and daily meanillumination were the key factors that influenced watermelon water requirement rate. Aregression function was be established, which was shown that, Y=-18.79+0.60X₁+1.10X₅（R=0.97, F=50.12, P=0.0002）, Y as water requirement rate, mm·d^-1.X₁as daily mean temperature,℃. X₅as daily mean illumination, klx.（2） With analysis of watermelon plant’s height, leaves amount, leaves area of differenttreatments, we found Treatment5（T5） was the best for watermelon production in plastic shedthat irrigation Kcpin watermelon plant seedling stage, flowering and fruit bearing period, fruitdevelopment stage and fruit mature stage respectively were1,1,1.5,1. With analysis ofwatermelon plant photosynthesis, we found T5was also better than other treatments.（3）The order of fruit yield of different treatments was shown that，T4>T8>T5>T7>T3>T2>T9>T6>T1. The order of water use effects （WUE） of differenttreatments was shown that, T1,T5>T8>T4>T2>T6>T3>T9>T7. In view of saving water andhigh efficiency, we consider that T5was best. （4）A very significant positive correlation between irrigation water amount,evapotranspiration and fruit yield, plant fresh weight （FW）were showed, and the correlationcoefficients that respectively were0.79,0.64,0.80,0.50（P<0.05）. Correlation between plantdry weight （DW） and irrigation water amount, evapotranspiration were not being found.（5） The result of analysis of fruit quality was as follows. The fruit length of T5was thelargest, and fruit length and diameter of T1was all the smallest. Fruit Shape Index of T6washighest （1.12）. Pericarp Width of T9was the thickest, and T2was the thinnest. The content ofVitamin C of T1was the highest（11.36mg·100gFW-1）, T7secondly（8.62mg·100gFW-1）, thedifference between other treatments was not significantly（P>0.05）. The Content of TotalSoluble Protein （TSP） of T3was significantly higher than the others. The content of TotalSoluble Solid （TSS） of T5was the highest （12.10%） while T3smallest （11.07%）. Throughoverall analysis of fruit quality, T5was considered best.（6） A very significant negative correlation between vitamin C （VC） and plantevapotranspiration was showed, and the correlation coefficients was0.57（P<0.05）. Andcorrelation coefficient of total soluble protein content （TSP）and water irrigation amount infruit development and mature stage was0.60（P<0.05）. A negative correlation between totalsoluble solid （TSS） content and water irrigation amount in fruit development and mature stagewas showed, and the correlation coefficient was0.31.（7） The range of the ratios of plant evapotranspiration and evaporator’s evaporation（ET/EP） was0.37-1.59in the whole watermelon growth, and the change regulation of ratio（ET/EP） of all treatments was similar. In seedling stage the ratio was low（0.37-0.41）, butwhen flowering and fruit bearing it suddenly increased in value（0.48-0.96）, and it reaches itspeak in fruit-development stage, until fruit mature stage it significantly decline （0.77-1.00）.（8）The ratios of plant evapotranspiration and evaporator’s evaporation （ET/Ep） of T5inwatermelon plant seedling stage, flowering and fruit bearing period, fruit-development stageand fruit mature stage respectively were0.40,0.76,1.59,0.77, which was suitable forwatermelon production and can be used to provide information for watermelon precisionmanagement and scientific irrigation.