Effect of deficit irrigation on physiology, plant growth, and fruit yield of cucumber cultivars

Increased water scarcity necessitates the implementation of water-conserving irrigation management practices to sustain crop production,especially in water-limited areas. A two-year field study was conducted during 2019 and 2020 to evaluate the effect of deficit irrigation on physiology, plant growth, and yield of cucumber cultivars. The experiment was conducted in a split-plot design with four irrigation levels (100% ET_c (crop evapotranspiration), 80% ET_c, 60% ET_c, and 40% ET_c) as main plot factor and two cultivars (Poinsett 76 and Marketmore 76) as subplot factor with three replications. Results showed that stomatal conductance (g_s), transpiration rate (E), photosynthesis rate (P_n), intercellular CO₂ concentration (C_i), and leaf area were significantly lower in 60% ET_c and 40% ET_c compared to 100% ET_c while stomatal limitations, intrinsic water use efficiency (WUE_i), and relative leaf temperature were significantly higher in 60% ET_c and 40% ET_c compared to 100% ET_c. The observed values of these aforementioned parameters were comparable between 100% ET_c and 80% ET_c. A decrease in leaf area, as well as a decrease in P_n, resulted in a decline in overall photosynthesis per plant in 60% ET_c and 40% ET_c compared to 100% ET_c. As a consequence of this, plant dry biomass and total fruit yield were significantly lower in 60% ET_c and 40% ET_c compared to 100% ET_c. However, photosynthesis per plant was comparable between 100% ET_c and 80% ET_c due to comparable P_n and leaf area between them. Because of comparable photosynthesis per plant, plant dry biomass and fruit yield were comparable between 100% ET_c and 80% ET_c. Marketmore 76 had significantly higher g_s, E, P_n, C_i, and leaf area and it had significantly lower stomatal limitations, WUE_i, and relative leaf temperature than Poinsett 76. Vegetative dry biomass and total above-ground dry biomass were higher in Marketmore 76 but fruit yield was higher in Poinsett 76. These results suggest that 80% ET_c irrigation level and Poinsett 76 cultivar can be recommended for successful cucumber production without causing a significant decline in fruit yield in water-limited Southern High Plains of United States.