| In order to screen out the optimal combination of irrigation water volume and potassium fertilizer application amount suitable for watermelons grown in solar greenhouses in Ningxia, The experimental was designed the combinations to the irrigation amount W (1:1400 m3.hm-2, 2:80 m3.hm-2, 3:2200 m3.hm-2) with the potassium application amount K (0:0 kg.hm-2, 1:80 kg.hm-2, 2:160 kg.hm-2, 3:40 kg.hm-2), to investigate the effects of water and potassium interaction on the relative content of chlorophyll, fruit character, quality, yield, irrigation water utilization, nutrient absorption and fertilizer utilization. The results showed that the relative content of chlorophyll in watermelon leaves was higher in the facilities of high water and high potassium interaction. The effects of W2K3, W3K2 and W3K3 treatments on fruit traits and quality were more significant than those of other treatments, and the soluble solids in the central part were increased by 0.85~0.94 percentage points, 0.76~0.85 percentage points and 0.89~0.98 percentage points, respectively, compared with W1K0, W1K1 and W2K0 treatments. W1K3 treatment had the best utilization effect of irrigation water, and W3K1, W3K2 and W3K3 treatments had the most obvious effect on watermelon yield, reaching 73309.70 kg.hm-2, 73906.42 kg.hm-2, 73975.70 kg.hm-2, respectively. And the yield compared with W1K0, W1K1, W1K2, W2K0 and W2K1 treatments, it was significantly increased by 5.18% to 7.47%, 6.04% to 8.34% and 6.14% to 8.45%, respectively, but there was no significant difference with other treatments. The best potassium absorption effect was found in W3K3 treatment. High water and low potassium were conducive to potassium fertilizer utilization. The correlation analysis showed that besides total acid index, quality index, yield and potassium accumulation were positively correlated with each other, and were negatively correlated with total acid index, potassium utilization index and partial productivity of potassium fertilizer. In conclusion, the interaction of high water and high potassium can promote photosynthesis and nutrient absorption of watermelon leaves, improve fruit quality and watermelon yield, and the condition of high water and low potassium is conducive to the utilization of potassium fertilizer. |