Selected questions and answers on pollution-free and high-yield cultivation techniques of onion!

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1. What kinds of onions are there?

According to the characteristics of bulb formation, it can be divided into common onion, tillering onion and top bulb onion; according to the requirements of bulb formation on sunshine length, it can be divided into three ecological types: long sunshine, short sunshine and short sunshine. Most of the early-maturing varieties were short-day type and the late-maturing varieties were long-day type. Common onions are divided into red onions, yellow onions, white onions and so on. At present, the varieties of onions exported are: Dabao, Earth, Red Leaf Light, Beijing Yellow Peel, Tianjin Dashui Peach, Quanzhou Middle High Yellow, Golden Jade Onion and so on.

2. When will onions be sown? How should the seeds be treated before sowing? How to cultivate strong seedlings?

It is generally appropriate to sow seeds between the first and middle of September, early sowing is easy to bolting, sowing is too late, small seedlings are weak before overwintering, it is difficult to overwintering, and the yield is low. Because if the onion seedling has 5 leaves and the diameter of the pseudostem is more than 0.6cm, after a low temperature of 2 ℃-5 ℃, it can pass the vernalization stage in 50-60 days, and early bolting will occur after turning green in spring, which will affect the yield. The requirements for strong seedlings of appropriate age are as follows: when planting (late October to early November) or before overwintering, the seedlings have 3-5 leaves, plant height 2-15 cm, pseudostem diameter not more than 0.6 cm, and bolting rate in the next spring is controlled at 1% Mel 5%, which is suitable for seedling age.

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Soak seeds with special soaking and mixing agent before sowing, add onion seeds in 50 ℃ warm water 2.5kg, add onion seeds (suitable amount of diluent is suitable for soaking seeds), soak for 3-5 hours, remove and dry before sowing. Don't snuff out the seeds and sprout.

In order to cultivate strong seedlings, the seedling ground should be turned 25 cm deep, and 3000 kg of high-quality rotten ring fertilizer and 30 kg of potassium sulfate compound fertilizer should be applied every 667m2. Rake fine rake evenly, make a flat border, 100-120 cm wide, 20 m long, the border surface must be flat, evenly sow seeds after irrigation, 4-5 kg of seeds for every 667 square meters, and cover fine soil 1-1.5 cm thick. The seedlings are watered after coming out, and the grass is pulled carefully. After that, according to the soil moisture of the seedbed and the growth of the seedlings, properly irrigate the small water for 2-3 times, combined with watering, apply a small amount of Jiamei potash to lift the seedlings. If the seedling growth is too prosperous, it is necessary to control fertilizer and water to prevent the seedling from being too large and cause early bolting.

3. How to prevent onion frost damage?

(1) the suitable planting period: the western Shandong and the inland areas of the peninsula were planted from the end of October to the beginning of November, which could slow down the seedlings and restore the root growth before overwintering, sending out 3-4 new roots and forming strong seedlings. The coastal areas of Qingdao, Weihai and Yantai in eastern Shandong can also be planted in spring and can be planted before and after the Spring Equinox.

(2) spraying Jiameijin point: after onion seedlings were planted, 800 times liquid Jiamei gold point was sprayed twice every 10-15 days, to promote rooting, improve plant cold resistance, disease resistance and adaptability, and prevent frost injury.

(3) strengthen the management before winter: water the seedlings slowly after planting, and after 2-3 days, carefully plow and hoe the soil to promote the recovery of root growth. Before freezing, it is necessary to irrigate the overwintering water again, after carefully paddling the soil, using hoe board to push the topsoil to improve the ground temperature and preserve soil moisture, and to protect the ground with soil dung or wheat bran, crushed grass or plastic film to ensure safe overwintering.

4. How to manage fertilizer and water when planting onions?

Onion is a two-year-old vegetable crop with shallow root system, poor absorptive capacity, long growth period of more than 200 days and high yield. According to research, for every 1000 kg bulb, about 2.4kg of nitrogen, 0.9kg of phosphorus and 4.1kg of potassium are needed.

To plant onions, you should choose fertile loam or sandy soil with high organic matter content, turn about 30 cm deep after stubble, and sunburn for 30-45 days. Combined with deep ploughing, 5000 kg of high-quality ring fertilizer, 15 kg of potassium sulfate, 50 kg of superphosphate and 30 kg of ammonia bicarbonate are applied every 667m2. Note that the above chemical fertilizers should be added to organic fertilizers in advance and retted evenly for 10-15 days. After turning deeply, rake the ground repeatedly after sunny days, rake the ground at least 3-5 times, rake fine rakes evenly, and then prepare the ground carefully. Before planting, the bed is 120-150 cm wide and 20-30 m long. Combined with the whole bed, 100 kg of organic biological fertilizer was sprinkled every 667 square meters, then carefully raked and planted.

After overwintering, when the temperature begins to rise, it is necessary to remove the grass cover and increase the ground temperature. Green onion seedlings began to turn green, combined with watering for topdressing, every 667 square meters topdressing Jiamei potash de 10-12 kg. When the dry soil is exposed on the surface, immediately draw a hoe, combined with a hoe to clean the rhizosphere soil, so that the rhizome is exposed to facilitate the growth of onions. Before and after the Qingming Festival, the leaves entered the vigorous growth period, watering and fertilizing again, topdressing Jiamei with a profit of 10-15 kg per 667 square meters. Note that the amount of fertilizer and water should not be too large, and squat seedlings for about 10 days later, so as not to affect the growth of onion leaves.

Grain Rain after the festival, the temperature reached 20 ℃ or so, onions began to expand, need to be combined with watering again topdressing, every 667 square meters topdressing Jiamei potash 10-12 kg. After the Beginning of Summer, the bulb enters the rapid expansion period, can be combined with watering again, every 667m2 Jiamei profit to 10-15kg, plus a bag of dividend, to help loosen the soil, and increase the watering times, once every 3-5 days, until 7 days before harvest.

At the same time, foliar nutrition should be sprayed at the right time, once every semimonthly, the first two times spraying Jiameijin 800x liquid, the Qingming Festival spraying Jiameinao platinum 800x liquid, and Grain Rain spraying Jiamei dividend liquid after the festival, which can increase production by more than 30%.

5. What are the common diseases of onions? How to prevent and cure?

The common diseases of onion are downy mildew, purple spot, gray mold, anthracnose and so on.