The Effect Of Irrigation Amount With Different Plastic Film Mulching On The Growth,Yield And Quality Of Greenhouse Watermelon

The early mature Watermelon var.Nongkeda No.11 was used as research object,this studywas carried on with the aim of water saving,yield increasing and higher quality.With setting 4 different amount of irrigation : 1000m3/hm2(W1),1400m3/hm2(W2),1800m3/hm2(W3),2200m3/hm2(W4)and covering 3 different plastic films: black plastic film(P1),common transparent film(P2)and silver black double color weeding film(P3),this thesis gave analyses to the effects of irrigation amount on growth,yield,irrigationwater use efficiency and yield and quality of watermelon in greenhouse in the situation of different film covering in northwest dry farming area.The results were as follows:Different irrigation amount and plastic film had significant influences on the morphological indexes of watermelon in greenhouse.The plant height of watermelon increased with the increase of irrigation amount,and the plant height under W4 irrigation amount was the highest.Under the same irrigation amount,the plant height of common transparent plastic film(P2)covered watermelon was higher than that of black plastic film(P2)and silver black weed plastic film(P3)during the whole growth period.Besides,there were differences in different growth periods.Small differences in theseedling stage,bigger in flowering and expanding stage,and smallest in mature stage.The change of stem diameter was opposite to plant height.The stem diameter was higher in the middle and low irrigation amount W1 and W2 than in the high irrigation amount.There was small effect on the steam diameter of different plastic film covering,the differences of different treatments with different plastic mulching were not obvious.Plant height and stem diameter were important indexes to evaluate the growth of watermelon and there were negative correlation existing between them.Under the level W1,the internodes of watermelon were short and the main stem was stout and under W4,the stem was thin and the vine got too long to be benefit for the growth of watermelon in greenhouse.Different irrigation amount and plastic film covering had significant effects on photosynthetic characteristics of watermelon in greenhouse.The total chlorophyll content of the plant treated with W3P2 remained high during the whole growth period.From W1 to W4 irrigation amount,the chlorophyll content of watermelon leaves showed the trend of increasing first and then decreasing,and basically reached the peak at the level of W3.Different film mulching had little effect on chlorophyll content of leaves,and there was no rule concluded among the treatments.The change trend of net photosynthetic rate with irrigation amount was the same as that of chlorophyll.From flowering to expanding to mature stage,the net photosynthetic rate reached the maximum at the W3 irrigation level,and the transparent plastic film coverage was better than the other two kinds of plastic film mulching.Under the W3 level,stomatal conductance was the biggest in each treatment,and the effects of different plastic film treatments were little.Stomatal conductance of W3P2 was very good in each period,while W1P1 was lowest in the whole growth period.Under the W3 level,the intercellular carbon dioxide concentration of all treatments remained low,and the performance was obvious from the seedling stage to the expanding stage.Of all the treatments,W3P2 showed the best growth potential,and the chlorophyll content,net photosynthetic rate and stomatal conductance of the treated plants maintained high levels in the whole growth period.Different irrigation amount and plastic film covering had significant effects on yield and irrigation water use efficiency of watermelon in greenhouse.With the increase of irrigation water,the single fruit weight of watermelon showed the trend of first rising and then decreasing,and reached the maximum value at the level of W3,becoming the inflection point.W1P3 treatment had the lowest single melon weight;W3P2 treatment had the largest single melon weight,which was significantly different from other treatments.Under the same irrigation level,the average fruit weight of Watermelon under common transparent plastic film(P2)was larger than that of black plastic film(P1),and the black plastic film was larger than the black silver black mulch film(P3).The variation trend of yield with irrigation amount was the same as that of single melon weight.The yield of W3P2 was the highest in all treatments,reaching 47.13 t/hm2.The irrigation water use efficiency of irrigation decreased with the increase of irrigation water,and the irrigation level of W1 was the highest,and W1P1 reached 38.97kg/m3.But the yield of watermelon at this time was very low,which could not meet the needs of production.Under the W2 and W3 levels,the irrigation water use efficiency of different mulching watermelon plants showed P2>P1>P3.The effects of irrigation amount and plastic film covering on the fruit quality of watermelon in greenhouse were obvious.There were no obvious differences on the watermelon skin thickness of different treatments.Different film mulching on the rind thickness had no significant difference.At the level of W3 and W4,the fruit diameter was increased;under the W1,W2 and W3 levels,the vertical diameter of Watermelon under transparent plastic film was higher than that of black film and silver black weeding film.The vertical and horizontal diameter of watermelon treated with W3P2 was the largest in all treatments.The fruit shape index of all treatments was 1.02-1.07,the fruit shape index of W1P3 was the smallest,reaching 1.02,and the fruit was nearly round;the fruit shape index of W3P2 was the largest,1.07,and the fruit was elliptical.The effects of different irrigation levels on total soluble sugar content,total vitamin Ccontent,lycopene content,soluble solids content,total soluble solids content and so on were significant.At the W3 irrigation level,the indicators of each treatment performed well;in the three kinds of plastic film,the ordinary colorless transparent film(P2)was better.In all treatments,the indexes of watermelon under W3P2 treatment was better than other treatments.Based on the above analyses,it was pointed that W3P2 treatment,that was,irrigation volume of 1800m3/hm2 with ordinary transparent film(P2)mulching,was the best solution selected in this experiment.Under this treatment,watermelon had strong growth potential,high photosynthetic capacity,high yield and good quality.It was suitable for efficient water-saving cultivation of watermelon in greenhouse in arid and semi-arid areas of Northwest china.