1 Onion growth conditions
Onion growth temperature is 12 ~ 26 °C, seedlings are resistant to cold, can be -6 ~ -7 °C low temperature. Bulbs need rapid expansion of 20 ~ 26 °C, in the long-day conditions conducive to the formation of mature bulbs. Onion roots are shallow and have low water absorption capacity and require high soil moisture. Its basement is more resistant to dryness, and its relative humidity is 60% to 70%. High concentration of soil solution is required for hi-fertilizer crops. It is suitable for planting in fertile, loose, neutral soils with strong water retention and fertility.
2 Onion growth requires fertilizer
The leaves are the assimilation organs of the onion, and the bulbs are storage organs, so the growth of the leaves directly affects the quality and yield of the onion. The amount of fertilizer absorbed by onions at the seedling stage is very small. With the acceleration of the development of the aboveground parts, the amount of fertilizer absorption increases rapidly. When the bulb began to expand, the nutrients concentrated on the onion, and the leaves became lighter in color. From the point of view of various nutrients, the absorption of potassium is the highest, followed by nitrogen, calcium and phosphorus. In the bulbs that store nutrients, the element content is the order of nitrogen, potassium, phosphorus, and calcium.
The onion root system began to grow when the average temperature in the 10cm soil layer reached 5°C, and the activity of the root system began to flourish at 10°C to 15°C. From the aspect of nutrient absorption, the absorption in winter is very small, and it begins to increase after the spring warmth in March of the following year. After that, the plant gradually grows and the amount of sucking fertilizer increases accordingly.
3 Onion nutritional diagnosis
Nitrogen deficiency: Light green leaves, poor growth. Phosphorus deficiency: poor growth, no special symptoms on the leaf.
Deficiency of potassium: White to brown dead spots occur between the veins of the old leaves, similar to lesions such as downy mildew, and care should be taken.
Calcium deficiency: A wide, irregular, white, dead spot occurs on the top or middle of a new leaf. Heart rot occurs in the middle of the bulb.
Boron deficiency: The growth and development of the new leaves are blocked, and the leaves are deformed and shed green. Sulfur deficiency: The leaves of new leaves are pale.
Magnesium deficiency: Light green to yellow between veins.
4 Onion Fertilization Technology
Onion nursery bed should be selected loose fertile, strong water retention of the soil, apply enough base fertilizer, generally 11 m2 nursery pods in the application of decomposed organic fertilizer 25 ~ 30kg, plus phosphorus pentoxide 0.08 ~ 0.15kg; seedling stage can be combined with pouring Decomposition of water, human fecal urine 17 ~ 20kg, or nitrogen topdressing 0.09 ~ 0.12kg, in order to promote seedling growth. The seedlings are planted in the field 15-18 cm before colonization to form an advantageous environment for onion suction. The amount of organic fertilizer used is about 20-40 tons per hectare, 450-600 kg of plant ash can be applied to acidic soils, and 55-90 kg of phosphorus pentoxide can be added to fields with insufficient phosphorus fertilizer. After the onion is slowly growing, it enters the growth of stems and leaves. In order to promote the formation of a good vegetative organ, it is necessary to pay close attention to the first application of fertilizer, and apply 15 to 19 tons of excrement per hectare, or topdressing 30 to 45 kg of nitrogen. The expansion of the bulb should be followed by 2 to 3 times of "pushing head fertilizer", applying 45 to 60 kg of nitrogen per hectare. Following the method of applying inorganic fertilizer, the seedlings can be applied for an hour, and then watered immediately. No delay should occur. After the plants grow up, they can be combined with water and fertilize. 30 to 50 days after planting, that is, bulbs began to rapidly expand, as the focus of fertilizer period, the effect of onion production was significant. When topdressing, it is necessary to pay attention to quantity and quality, and pay attention to the suitable period for topdressing. If the time for key fertilizers is too late, the bulbs will lack adequate nutrition when they are rapidly expanded. The mature period will be delayed and it will not be able to be put into dormancy in time, which will affect the yield of onion and it will not be conducive to storage. If the top dressing is too early, the leaves of the shoots will be greedy for growth. It is not conducive to bulb enlargement.
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