Effect of Planting Dates and Foliar Spraying with Salicylic Acid, Selenium, Chitosan and Glycine Betaine on Growth and Productivity of Garlic

Garlic is an economically important crop, but late planting exposes it to low-temperature stress, negatively affecting growth, yield and quality. This study aimed to enhance garlic tolerance to low temperatures and improve productivity through foliar application of stimulants under different planting dates. A field experiment was conducted on a private farm in Mit Fares village, Bani Ubaid district, Dakahlia Governorate, Egypt, using a split-plot design with three replications. The main plots were assigned to two planting dates (October 1st and November 1st), while the subplots were allocated to foliar spraying, including salicylic acid (150 mg L-1), selenium (5.0 mg L-1), chitosan (150 mg L-1), glycine betaine (700 mg L-1), and a control (tap water). Measurements were recorded at 100, 120, and 180 days after planting, covering vegetative growth parameters, photosynthetic pigments, biochemical contents, and yield attributes. Results revealed that early planting (October 1st) significantly enhanced plant growth, photosynthetic pigments accumulation, and bulb yield. Among the foliar treatments, selenium followed by salicylic acid exhibited the most positive effects, followed by glycine betaine and chitosan compared with the control treatment. Additionally, all stimulant applications under late planting resulted in a significant increase in marketable yield and bulb quality compared to the control. These results highlight the vital role of foliar stimulants in mitigating low-temperature stress and optimizing garlic productivity under different planting schedules.