1 Onion Growth Conditions
The growth temperature of onion is 12～26°C, and the seedlings have strong cold resistance and can withstand low temperature of -6～-7°C. The bulbs need to be 20 to 26 ° C during the rapid expansion period, which is beneficial to the formation of bulbs under long-day conditions. Onion roots are shallow, water absorption is weak, and high soil moisture is required. Its underground part is more resistant to dryness, and the relative humidity of the air is 60% to 70%. It has high requirements on the concentration of soil solution and is suitable for fertility crops. It is suitable for planting on neutral soil with fertility, looseness, water retention and fertility.
2 Fertilizer characteristics of onion growth
The leaves are the assimilated organs of the onions, and the bulbs are storage organs, so the growth of the leaves directly affects the quality and yield of the onions. Onion has a small amount of fertilizer in the seedling stage, and as the development of the aboveground part accelerates, the amount of absorbed fertilizer increases sharply. When the bulb begins to expand, the nutrients are concentrated on the onion and the leaves are lighter. From the perspective of various nutrients, potassium is most absorbed, followed by nitrogen, calcium and phosphorus. In the bulbs that store nutrients, the elemental content is the order of nitrogen, potassium, phosphorus, and calcium.
The onion roots began to grow when the average temperature in the 10 cm soil layer reached 5 °C, and the root activity began to flourish at 10-15 °C. From the point of view of nutrient absorption, the winter absorption is very small, and it will increase after the spring of March of the following year. Later, as the plant grows gradually, the amount of fertilizer absorption increases accordingly.
3 Onion Nutritional Diagnosis
Nitrogen deficiency: leaf color is light green and poor growth. Phosphorus deficiency: poor growth, no special symptoms on the leaves.
Potassium deficiency: white to brown dead spots between the veins of old leaves, similar to those of downy mildew, should be noted.
Calcium deficiency: a wide, irregularly shaped white dead spot on the top or middle of the new leaf. Heart rot occurs in the middle of the bulb.
Boron deficiency: the growth and development of new leaves is blocked, leaf deformity, chlorosis. Sulfur deficiency: the leaves of the new leaves are light.
Magnesium deficiency: light green to yellow between veins.
4 Onion Fertilization Technology
The onion nursery bed should choose loose and fertile soil with strong water retention capacity, and apply the base fertilizer. Generally, 25 to 30 kg of decomposed organic fertilizer and 0.08 to 0.15 kg of phosphorus pentoxide should be applied in the seedling nursery of 11 square meters; The water is applied to 17-20 kg of manure and manure, or 0.09 to 0.12 kg of nitrogen to promote seedling growth. The seedlings are planted in the field 15 to 18 cm before planting to form an advantageous environment for onion fertilizer. The organic fertilizer is about 20-40 tons per hectare, 450-600kg of plant ash can be applied to the acidic soil, and 55-90kg of phosphorus pentoxide is applied to the field with insufficient phosphate fertilizer. After the onion slows the seedlings and enters the stems and leaves to grow, in order to promote the formation of a good vegetative organ, it is necessary to pay close attention to the first fertilizer, 15 to 19 tons of manure per hectare, or 30 to 45 kg of nitrogen. Bulb expansion period should be applied 2 to 3 times "priming fertilizer", each time applying 45 to 60 kg of nitrogen per hectare. The method of applying inorganic fertilizer can be applied in the seedling hour, and then watered immediately, without delay. After the plants are grown and sealed, they can be combined with watering and fertilization. 30 to 50 days after planting, that is, when the bulb begins to transfer into the rapid expansion period, it is a key topdressing period, and the effect on the onion is significant. When topdressing, it is necessary to pay attention to quantity and quality, and also pay attention to the appropriate period of topdressing. If the key fertilization time is too late, the bulb will not be adequately nutritious when it is swollen rapidly, and the maturity period will be delayed. It will not be transferred to dormancy in time, affecting the yield of onion, and it is not conducive to storage. If the key topdressing is too early, the aboveground leaves are easy to grow. Therefore, it is not conducive to the expansion of the bulb.
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