Water and potassium utilization efficiency and yield and quality of cucumber (Cucumis sativus L.)

Efficient use of irrigation water and fertilizer is essential for the sustainable growth of vegetable crops. To optimize the yield, quality, and water and potassium (K) use efficiency of cucumber ( Cucumis sativus L.), three irrigation limits and three potassium (K) application levels were used to determine the lower irrigation limit and potassium application rate. The experiment was a 3 x 3 factorial with three K application levels and three lower limits of irrigation, to study the effects of water and K interaction on the growth and development of cucumber in greenhouse substrate cultivation. Taking W80K8 (high water and fertilizer level) treatment as a control (CK), three K application levels (K0: 0 mg & sdot; L - 1 , K4: 156 mg & sdot; L - 1 , K8: 312 mg & sdot; L - 1 ) and three lower limits of irrigation (W60: 60 % of potting substrate field water capacity, W70: 70 % of potting substrate field water capacity, W80: 80 % of potting substrate field water capacity) were set up. The experimental results showed that the lower limit of irrigation, K supply, and their interactions had different impacts on the growth and development, leaf photosynthetic characteristics, substrate enzyme activities, fruit quality, yield, and plant K accumulation of cucumber. Under the coupled water and K model, compared with CK, the chlorophyll a, chlorophyll b, carotenoid content and net photosynthetic rate of cucumber in W70K4 treatment were increased by 38.53 %, 17.66 %, 30.66 % and 14.40 %, respectively; the K utilization rate and bioproductivity and water use efficiency of cucumber treated with W70K4 increased by 54.89 %, 90.19 %, and 12.11 %, respectively. In a comprehensive comparison, the W70K4 treatment improved the chlorophyll content, net photosynthetic rate, and water and K utilization efficiency of cultivated cucumber plants, promoted growth, and reduced the use of water and fertilizer. Therefore, to ensure high yield, high quality, and water savings in cucumber cultivated in facilities, the ideal water and K coupling model for summer greenhouse substrate cultivation of cucumber is to irrigate to the lower limit of 70 % of the water holding capacity of the substrate field, and to apply K fertilizer at a concentration of 156 mg & sdot; L - 1 .