Large-scale production technology of white onions for export in Chongming area

1 Variety selection

Changbao, Changyue, Chunwei and other varieties were selected according to export specifications and time requirements. Such as long Yue, late bolting, heat resistance and cold resistance, can be planted closely, planted in March to May, harvested from November to January of the following year.

2 Nursery

2.1 Preparation of seedbeds

Seedbed preparation procedure: field preparation (deep ploughing 350m, frozen sowing) → basal fertilizer application → ploughing twice (25cm) → bed preparation (bed surface specification 1.5 m ×30m).

Basic fertilizer application: 20 days before sowing, 1500kg biological organic fertilizer and 15kg diammonium phosphate were applied per 667 square meters.

2.2 sowing

The seeds are sown in the protected field from late February to early March, and the seedlings are raised in the open field from mid-March to early April.

Seed belt sowing technique was used, 82~100 seeds/m, row spacing 7cm, covering depth 0. 5 cm. Cover soil layer should be loose, cover plastic film after sowing. After soil covering, it is forbidden to water the surface directly for many times to avoid soil hardening. The watering should be carried out by means of infiltration irrigation in the ditch. The water surface should not exceed the ridge surface during infiltration irrigation.

2.3 seedbed management

① Fertilizer is mainly base fertilizer, topdressing can be carried out after 15 days of seedling age, mainly slow effect fertilizer, quick effect fertilizer should not be excessive.

(2) Humidity: After sowing and mulching, the seedbed should be humidified by furrow irrigation and infiltration, and the humidity of the seedbed should be verified, but the humidity is too high, which may lead to uneven emergence. Furrow irrigation standard: water level should reach 2/3 of ditch depth, and it is forbidden to exceed the surface of furrow. Early spring irrigation should be carried out in the morning, afternoon drainage, irrigation time to 4~6h is appropriate. In the future, once a week, special weather should change the watering cycle appropriately.

(3) Mulch management: When seedlings reach film, and 60% of seedlings are removed in time, and shade nets are covered according to weather to prevent heavy rain from washing seedbeds. Early February seedlings should be carried out in protected areas to prevent night temperatures from being too low. In late April seedlings should be timely uncovered film, in case the temperature is too high seedlings burn.

Sunshade net management should be strictly in accordance with the use of norms, before transplanting must be carried out seedling training. At the beginning of mulching, the seedlings were covered all day, at the middle stage, from 9:00 a.m. to 4:00 p.m., and at the later stage, the seedlings were not covered.

4. The control of diseases, insect pests and weeds is mainly non-infectious diseases in seedling stage, mainly salt damage, lack of nutrients and other physiological diseases, which are controlled by soil improvement methods.

The main pests in seedling stage were onion fly, cutworm, etc., which were controlled by Sukai and Miman.

After the seedling height is 8cm, artificial weeding can be carried out. Weeding should be prevented with large pieces of soil, in case of injury to onion roots.

3 Colonization

When the seedlings reach the required seedling age (45 days) or 3~4 leaves and 1 heart, they should be transplanted in time.

3.1 field preparation

Field preparation (including deep ploughing 35cm, frozen soil) → basal fertilizer application (decomposed organic fertilizer 1000kg/667 square meters) → ploughing and furrow making (furrow spacing 1.1 m, depth 25cm) → basal fertilizer application (calcium superphosphate 25kg/667 square meters, vegetable fertilizer 50kg/667 square meters).

3.2 colonization

Healthy and orderly seedlings were selected and planted according to the plant spacing of 3.3cm and row spacing of 1.1m. Planting should be close to one side, and strictly control the quality of planting onions.

4 Field management

4.1 fertilizer

Apply enough base fertilizer, topdressing with quick-acting and slow-acting fertilizer combined principle. Topdressing should be applied less frequently, especially after white onion enters the rapid growth period, topdressing should be applied within 15cm on both sides of the root. Topdressing was started one month after planting, with 20kg of ammonium phosphate and 100kg of decomposed organic fertilizer applied to 667 square meters.

4.2 humidity

In the growth period should be strictly controlled moisture, a large amount of accumulated water easy to lead to the emergence of diseases such as root rot; too little will inhibit the growth of white onion. Clear ditches and drain water in time after rainstorm. Artificial water supply should be strengthened in spring and summer, and the humidity of 3cm below the surface should be taken as the standard.

4.3 weed pest control

According to the specific conditions of the field, herbicides such as glyphosate can be injected at one time in spring, and appropriate artificial weeding can be carried out in the early field, and weeding can be carried out in the late stage by using cultivated soil.

4.4 pest control

① Onion rust begins to occur in late spring and early summer, and is most severe in autumn. It belongs to fungus harm, suitable temperature 9~18℃, germination rate decreases obviously above 24℃. Control should apply enough organic fertilizer, increase phosphorus and potassium fertilizer, irrigate frequently with small water, remove sick leaves in time; spray 20% triadimefon 2000 times solution at the initial stage to control.

② Brown spot disease, also known as leaf tip verticillium wilt, mainly damages leaves. Control can choose heat-resistant varieties; strengthen management, prevent onion field too wet, improve root activity; use methyl thiophane 1000 times solution, chlorothalonil 800 times solution spray control.

(3) Leaf miner infects larvae, mostly from August to October. Adults were most active at 8:00~11:00 a.m. and 3:00~5:00 p.m., and most of them inhabit the tip of leaves. Remove leaf residues, control with 2500 times solution of Qianke or 10ml/667 square meters of insect light.

④ Noctuid leaf-eating pests mostly occur in high temperature weather from June to September. The damage speed is particularly fast, and it is easy to form a certain drug resistance. It is mainly controlled by chemical agents such as rice, rice and rice.

4.5 with earth

The position of soil cultivation should be at the bifurcation of 4 leaves, mainly large soil cultivation, and 3~4 times of soil cultivation should be carried out in the whole cycle. Green length (soil surface from the four-leaf bifurcation) should be controlled within 12cm for soil cultivation, and its length should be reduced (about 6 cm) in typhoon season, and soil cultivation should be in place every time.

5 Harvest

Avoid breaking and damaging onion leaves during harvesting; avoid scratching onion white with tools for digging onions; packaging should not be too tight, and the length should be about 80cm.