Gibberellic Acid and Benzyl Adenine Improve Garlic Seed Cloves Sprouting and Boost Plant Growth and Productivity in Unfavorable Conditions

Garlic production in Egypt faces the challenge of increasing temperatures within the usual planting time, causing delays and uneven garlic seed cloves sprouting.  Hence, this investigation aimed to improve the sprouting of garlic seed cloves in unfavorable conditions by soaking them in gibberellic acid (GA3) and benzyl adenine (BA) solutions before planting on two different planting dates. Two trials occurred in the successive seasons of 2021-22 and 2022-23 in the experimental farm of the Horticulture Department, Faculty of Agriculture, Ain Shams University, Shoubra El-Kheima, Qalubia Governorate, Egypt, to assess the impact of soaking garlic seed cloves in solutions of 50, 100, and 200 ppm of GA3 and 25, 50, and 100 ppm of BA for 24 hours before planting on September 20 and October 15 on sprouting, plant vegetative growth characteristics, bulb properties, and yield, as well as the leaf contents of chlorophyll, nitrogen, phosphorus, and potassium. The obtained results indicated that planting the garlic seed cloves in October was more beneficial than in September for promoting the seed cloves’ sprouting percentage and rate due to the better weather conditions vs. September. Meanwhile, planting in September allowed for longer vegetative growth before bulbing onset, leading to a longer shoot, more leaf number, a higher plant dry weight, and improved bulb quality in diameter and weight. Nevertheless, bulb yield per plot and feddan were higher in October planting date due to increase plant density from increasing seed clove sprouting percentage. Moreover, the levels of chlorophyll, phosphorus, and potassium in the leaves increased when the seed cloves were planted in October, but the nitrogen content showed no significant increase between the two planting dates. Soaking the cloves in solutions of GA3 and BA increased clove sprouting, plant growth characteristics, bulb attributes, and yield, as well as an increase in leaf content of chlorophyll, nitrogen, phosphorus, and potassium compared to the control treatment. The effectiveness of GA3 was greater than that of BA. The 100 ppm GA3 solution was the most effective for improving seed cloves sprouting and all plant and yield parameters, as well as leaf chemical constituents, for both planting dates. The findings from this study may provide valuable insights for optimizing garlic production, particularly in unfavorable production conditions.