Foliar Application of Plant Growth Hormones to Improve Growth and Yield of Drip-Irrigated Cucumber (Cucumis sativus L.) under Full and Deficit Irrigation

A field experiment was conducted at the vegetable research farm, Faculty of Agriculture, Assiut University for three summer seasons 2020, 2021 and 2022. The study aimed to improve the growth and productivity of cucumber under different water regimes using foliar application of six plant bio-stimulants during the plant growth stages. The cucumber cultivar 'F1 Hayal' was planted under three water regimes 100%, 75% and 50% of irrigation water requirements. Plant bio-stimulants were sprayed at different growth stages using the recommended concentrations of Salicylic Acid (SA at 10uM), Glycine Betaine (GlyBet at 50mM/L), Indole Acetic Acid (IAA at 100 uM), Proline at 1 mM/L, Potassium Silicate (PS at 1mM/L) and Humic Acid (HA at 1g/L). The results showed that the tested growth hormones enhanced the growth and yield parameters of cucumber under a 100% water regime. Under deficit irrigation (water regimes 75% and 50%), foliar application of PS at 1 mM/L increased length of cucumber plants (cm), plant fresh and dry weights (g), leaf area (cm2), number and weight of marketable fruits/plant, and total yield of marketable fruits (ton/fedd., 1 fedd. = 4200m2). Proline application at 1 mM/L and GlyBet at 50 mM/L came second. Plants of control treatment (sprayed with distilled water) illustrated significant reduction in growth and yield parameters under all tested water regimes (100%, 75% and 50%) as compared to the plants treated by stimulants. Potassium Silicate spraying could be recommended as a natural, environmentally friendly material during the growth stages of cucumbers that may increase growth, production, and fruit quality.