Study On Water Requirement And RDI Patterns Of Watermelon In Arid-hungriness Oasis Area

The paper studied water requirement and deficit patterns of watermelon under RDI in arid-hungriness oasis area, Gansu province. The experiment was conducted in the farm of the center of agriculture and technology in Minqin county, Gansu province. The average irrigation of the area was used for the normal irrigation of experiment. 2/3, 1/2 and 1/3 of normal irrigation was used for the deficit of the experiment. According to growth characteristic of watermelon, four growth stages was use for deficit stages of the experiment, as follows: seedling-flowering, flowering-fruit bearing, fruit bearing-swelling and swelling-maturing, There were ten treatments and two repetition including one controlled treatments. The deficit of single stage and whole growth stages was used. The experiment was started from the first May to the seventeenth August, 109 days. The research fruit was as follows: (1) In the stage of seedling–flowering ,the research about diurnal change of leaf conductance, transpiration, photosynthesis and leaf WUE indicated that the leaf conductance and transpiration of full water supply were bigger than those in water deficit, that photosynthesis and leaf WUE of 2/3 of normal irrigation(treatment 4) were bigger than those of controlled treatment. In the deficit stage of fruit bearing-swelling, the photosynthesis, leaf conductance and leaf WUE of 2/3 normal irrigation (treatment 6) was bigger than those of 1/2 normal irrigation (treatment 3), and transpiration of the controlled treatment was bigger than that of the treatments of water deficit. (2) According to the research about biomass of watermelon, the compensatory effect was occurred in caudexes,root, leaves , flowers and so on, watering again after 2/3 deficit. The root/shoot was best than that of other treatments. (3) The relation of ET and irrigation was indicted that ET would become big if irrigation became big. The crop coefficient made clear that the key stage of consuming water of watermelon was the stage of fruit bearing-swelling (4) The highest production was treatment 6 whose production was higher 3.81% than controlled treatment. The treatment 6 was irrigated capacity of 2/3 normal irrigation in the stage of fruit bearing-swelling. The production of treatment 8 which was reduce water capacity was lower 5.01% than that of controlled treatment, but its water-saving was 12.92%. The relation of production with ET and irrigation wad correlative evidently. Compared to other treatments, the production WUE and IUE of treatment was the biggest. According to analyzing synthetically quality, the quality of treatment 8 was the best. After two weeks, the quality of watermelon was increased about the flesh rigidity, but the hull rigidity and soluble solids concentration were decreased. (5) The experiment was used 4 models of water-production function. The model of Jensen was the best than other models. It could reflect water-stressed sensitive index of watermelon in Minqin county, Gansu province. The order of water-stressed sensitivity of watermelon was fruit bearing-swelling, swelling-maturing, flowering-fruit bearing and seedling-flowering.