1. Onion germination period
It takes 10-15 days to germinate from seed germination to the first true leaf. Unearthed 7-8 days after sowing under suitable germination conditions. During this period, planting should be careful not to be too deep, the soil should not be too thick, and keep the soil moist during germination.
2. Onion seedling stage
It is the seedling stage from the first true leaf revealed to 4-5 true leaves. Onion seedlings grow rapidly after they are unearthed, and maintain proper temperature and humidity during the period. The growth of the root system at this stage is more important than the growth of the aerial parts. The growth of onion seedlings is slow, the amount of growth is small, and the consumption of water and fertility is not large. The suitable seedling age for planting is 5-6g per plant, 0.5-0.6cm thick pseudostem, 12-15cm tall, and 3-4 true leaves.
Seedlings are too large and prone to bolting. During the overwintering period after planting, the growth of the plant is very small. Before winter, water and fertilizer should be controlled to prevent the accumulation of dry matter caused by the long legs and reduce the plant's ability to overwinter; at the same time, it should also prevent the plant from being too large and feeling the low temperature. During the chemical stage, the first bolting phenomenon occurred in the second year.
3. Prosperous growth period
After the onion plants turn green (or after planting the overwintering onions in the seedbed), until the bulbs are enlarged, that is, from 4-5 true leaves to 8-9 functional leaves, the thickening of the base of the leaf sheath is a vigorous growth The peak period is 40-60 days. From the perspective of development stage, there is no essential difference between the vigorous growth period and the seedling stage. The lower part of the ground is sensitive to temperature, and the early growth rate is faster than that of the upper part. In the future, the growth of the aerial parts will gradually accelerate. As the leaves grow vigorously, the bulb slowly expands.
During this period, we must ensure sufficient water and fertilizer supply, especially the supply of nitrogen fertilizer, to promote the vigorous growth of the aerial part, and lay a solid foundation for the expansion of the bulb. Onions planted in spring, after planting, if seedlings are affected by adverse conditions such as low temperature (2-10 degrees), drought, etc., some plants may be tillering or early bolting, resulting in reduced production; if high temperatures and drought are encountered, Speed ​​up the aging of the root system. In the later part of this period, water and fertilizer should be properly controlled, otherwise the ground parts will grow too vigorously, which will cause the onion to become "greedy green" and delay the expansion of the bulb.
4. Bulb expansion
It takes 30-40 days from the thickening of the base of the leaf sheath until the bulb matures to the stage of bulb expansion. During this period, the onion bulbs expanded rapidly. Bulb formation is based on the material input and accumulation of nutrients, and high temperature and long daylight are necessary environmental conditions. As the temperature rises and the duration of sunshine increases, the growth of the leaf is inhibited. The nutrients in the leaf body and the upper end of the leaf sheath are transported to the base of the leaf sheath and the bud, and stored in the base of the leaf sheath and the bud. The bulb quickly expands.
The leaf body and root system tend to stagnate from slow growth. The leaf body begins to yellow, the false stem is soft, and the outer leaf pin of the bulb is film-like due to the inward movement of nutrients. At this time, it should be harvested in time. If abnormal low temperature is encountered or excessive nitrogen fertilizer is applied during the bulb expansion period, the leaf "greedy green" growth will not occur or delay lodging.
5. Sleep period
After harvesting, the onion enters the physiological dormancy period. Dormancy is an adaptation of onions to bad environments such as high temperature, strong light, and drought. The harvested product organs should be promptly put into a physiological dormant period for the purpose of storage.
The length of onion physiological dormancy period varies with the characteristics of the variety, storage conditions, and the degree of dormancy, generally 60-90 days. The longer the dormancy period, the stronger the storability.
The management points of the above onions in each growth period. During the growth period of onions, the onion diseases and insect pests must be controlled in time. Farmers must scientifically manage and master the management points of each period to achieve the purpose of high yield of onions.
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