Effects of drip irrigation threshold on yield and quality of muskmelon in plastic greenhouse

In order to investigate the effects of different soil water content threshold on growth, yield production and irrigation water utility efficiency of muskmelon (Cucumis melo L., Yilishabai variety) in greenhouse, four treatments of soil water content thresholds (I45 with 45% field capacity, I55 with 55% field capacity, I65 with 65% field capacity, I75 with 75% field capacity) were conducted, and a furrow irrigation (G75 with 75% field capacity) as control treatment. The results showed that plant height, stem diameter, leaf area and aboveground biomass decreased with soil water content threshold declined. Values of fruit diameter, pericarp thickness and flesh thickness are the largest for treatment I75, while the index of fruit shape is the least; but the fruit length of I65 is the biggest. As to the fruit quality, total soluble solids (TSS) content ranked as: I65＞I55＞I75＞I45; soluble sugar content ranked as: I55＞I65＞I45＞I75; Vitamin C (Vc) content ranked as: I55＞I65＞I75＞I45; soluble protein content as follows: I55＞I65＞I45＞I75; free amino acid content as follows: I45＞I65＞I55＞I75. The yield and mean fruit weight are highest for I75; the value of water use efficiency for I65 is the highest among the treatments as to 29.16 kg/m3 that is 76.4% higher than that of furrow irrigation (G75), it can save irrigation water 58.1% and the mean fruit weight only declined 3.2% compared with furrow irrigation. Therefore, based on production and quality, 65% field capacity would be the most appropriate thresholds for muskmelon starting irrigation on vegetative growth stage.