Schedule of drip irrigation under film for watermelon growth in plastic shed based on E601-B pan evaporation in northwest China

In order to find the optimum drip irrigation schedule for watermelon grown in plastic sheds using E601-B type pan evaporation, effects of different water supply conditions (K-cp: 0.5, 1.0, 1.5 Ep) on growth, photosynthesis, fruit yield, and water use efficiency during different growth stages were studied. The relationship between irrigation water amount (Ir), evapotranspiration (ET), and yield was also analysed. Results showed that treatment 5 (T5) performed best. The recommended corresponding irrigation K(cp)s were 1.00, 1.00, 1.50, and 1.00 for seedling, flowering and fruit bearing, fruit development, and fruit mature stages, respectively. For T5, the ratios of plant evapotranspiration to pan evaporation (ET/Ep) during the four stages were 0.40, 0.76, 1.59 and 0.77, respectively. Both irrigation water amount and ET positively correlated to fruit yield and plant fresh weight (FW). For FW, the correlation coefficients were 0.79, 0.64, 0.80 and 0.50 (P < 0.05), respectively. There were no correlations between plant dry weight (DW) and irrigation water amount or evapotranspiration. The data from this study provide reference information for precision management and scientific irrigation on watermelon.