Studies of Water Requirements of Horticultural Crops: II. Influence of Drought at Different Growth Stages of Onion1

Two years of field experiments with onion crops (Allium cepa, L.) show that this plant is differentially sensitive to drought in each stage of its vegetative cycle. Drought at the seedling stage increases the rate of foliar emergence, produces a greater number of leaves, accelerates bulb formation by 15 days, and increases the final weight as compared with the check (no significant difference). When drought occurs at the beginning of the bulb formation, it causes a delay in foliar emergence, a smaller number of leaves, and a decrease in bulb weight (a significant difference as compared with the check). In other stages of the cycle (post‐transplanting, and 50 and 100% of the bb's weight), the drought does not cause significant damage to the plant's growth.