Key Technical Points for Summer Sowing of Broccoli and Solutions to Common Problems

Preparatory Work

(1) Variety. Choose early-maturing F1 hybrid varieties with strong stress resistance and the highest yield. The main varieties are Yuguan, Teji Yuguan, Wanlü, etc.

(2) Plot. A sandy loam or clay loam rich in organic matter with good drainage and moderate water-holding capacity, with moderate pH, and where cruciferous crops have not been grown in the previous season, is required.

(3) Land preparation and fertilization. Clear the previous crop early and remove weeds, then plow and prepare the land so that the soil is loose, the field is level and fertility is uniform. Apply 6000-8000 kg of high-quality farmyard manure and 35 kg of compound fertilizer per mu, and form ridges 80 cm wide.

Sowing and Seedling Raising

(1) Seedbed. Choose a field with higher terrain, good water source conditions and high organic matter content. Before sowing, plow repeatedly and then apply 300-400 kg of high-quality farmyard manure.

(2) Sowing. Summer sowing can be carried out in June. Before sowing, water the seedbed thoroughly, and after the water has drained, spread a thin layer of sieved fine soil, then broadcast the seeds at a rate of 3-5 grams per square meter, and cover with culture soil.

(3) Seedling raising method and seedbed management. Shade facilities such as shade nets should be provided: cover at 9 a.m. on sunny days and uncover at 5 p.m., and do not cover on cloudy days. After emergence, water with a watering can according to whether the seedbed soil is dry or wet, cover with 0.5 cm of culture soil to protect the sprouts, and after the seedlings grow true leaves, water once with a 500-fold solution of monopotassium phosphate.

Planting and Field Management

(1) Planting. Summer-sown seedlings are transplanted with soil when they are 30-35 days old and have 5-6 leaves, at a spacing of 50 cm × 60 cm. After planting, water to settle the seedlings and help them recover.

(2) Topdressing.

① Before budding, mainly use quick-acting fertilizers. 7-10 days after planting, use a 200-fold compound fertilizer solution or a 10-fold decomposed human urine solution to promote seedling growth, and at the same time apply 2 kg of urea per mu; 14 days later, apply 15 kg of urea per mu.

② At the beginning of budding, apply 10-15 kg of urea per mu in holes around the plants, and together with pest and disease control, alternately spray a 200-fold urea solution and a 1000-fold Shibao solution at 14-day intervals.

③ After the main head is harvested, apply 10 kg of urea and 3 kg of potash fertilizer per mu, and combine with irrigation to promote the development of side heads.

(3) Cultivation and irrigation. During high temperature and drought, irrigate in time to maintain soil moisture, and carry out irrigation together with fertilization. During continuous rainy weather, drain in time so that the plants are not waterlogged. Cultivation is generally carried out after rain or irrigation together with weeding, fertilization and earthing up. Carry out the first topdressing, cultivation and weeding once, and earth up at the same time; stop cultivation in the later growth stage.

(4) Pest and disease control. Downy mildew mainly occurs at the seedling stage and can be sprayed with a 600-fold 70% mancozeb solution or a 600-fold 75% chlorothalonil solution. For aphids, use 25% pymetrozine water-dispersible granules at 20 g per mu or a 2000-fold 32% insecticide emulsion spray. For cabbage caterpillars and diamondback moths, use a 2000-fold solution of 2.5% deltamethrin or 2.5% cyhalothrin.

Harvesting

The harvest period for summer sowing is from late August to early September. Harvest when the flower buds have fully grown but the individual small buds have not yet opened. Harvest in the early morning on sunny days and bring to market promptly.

Common Problems and Control Measures

1) Bolting

Premature bolting occurs when the plant has not grown large enough; it appears as small heads accompanied by coarse flower granules. The main cause is low-temperature damage at the seedling stage, and bolting is more likely to occur if stress factors such as weak roots and lack of fertilizer are also present at the seedling stage.

Solutions:

① Choose a suitable sowing time; ② Choose seedlings with good roots for planting; ③ Cover with plastic film to maintain soil temperature; ④ Do a good job of water and fertilizer management.

2) Head Formation

After head formation begins, excessively high or sharply fluctuating temperatures can produce abnormal heads, which show different characteristics according to the different growth stages and temperature conditions. Too much fertilizer or excessive humidity during the head formation stage can also cause these symptoms.

3) Cat's Eye

The flower granules of the head are uneven in size, generally occurring when the day-night temperature changes sharply.

Solutions:

① Choose a suitable sowing period for each variety; ② Avoid applying too much fertilizer from budding to the head enlargement stage; ③ Maintain good soil moisture conditions throughout the growing season, since head damage is likely to occur under drought and sharply fluctuating moisture conditions.

4) Purple Flower Granules

Purple heads mainly occur under low-temperature conditions, and can also occur with lack of fertilizer, drought and excessive moisture.

Solutions:

① Avoid late-summer sowing; ② Apply an appropriate amount of fertilizer in the later growth stage, not excessively; ③ Keep the roots healthy.

5) Brown-Yellow Flower Granules

The plant does not have enough energy to keep all the flower granules green, causing the flower granules at the top of the head to die and turn yellow. High temperature, root damage and lack of fertilizer can all cause flower granules to turn brown-yellow.

Solutions:

① Avoid high temperature; ② Keep the roots healthy; ③ Maintain an appropriate fertilizer supply; ④ Harvest under cool conditions.

6) Waterlogging Impact

Solutions:

① Crush hard clods in the soil to make the soil looser; ② Apply organic fertilizer to improve soil conditions; ③ Dig drainage ditches deep for good drainage; ④ Use high-ridge cultivation.

7) Boron Deficiency

Symptoms are: damage to the flower stem forming scabs.

Causes and solutions:

① Boron deficiency in the soil: apply boron fertilizer to the soil; ② Excessive nitrogen fertilizer: improve the amount and ratio of fertilizer applied; ③ Root damage caused by drought, too much water or too low temperature: keep the roots healthy

8) Hollow Stem

Boron deficiency causes holes in the stem that enlarge with rapid growth and finally turn brown.

Causes:

① Low-density planting; ② High temperature and high soil moisture; ③ Application of excessive nitrogen fertilizer; ④ Boron deficiency.

9) Magnesium Deficiency

Causes:

① Insufficient magnesium; ② Soil pH too high; ③ Too much phosphoric acid or accumulation of manganese, copper and salts; ④ Drought.

10) White Flower Stems

Since this is caused by whiteflies, it occurs in large numbers under warm conditions.

11) Clubroot

The fungus is a soil-borne disease that infects the root hairs of cruciferous plants; high temperature, high soil moisture and acidic soil contribute to the occurrence and increase of this disease.

Solutions:

① Isolate plots where clubroot occurs; ② Use fungicides; ③ Crop rotation or use disease-resistant varieties; ④ Adjust pH; ⑤ Improve drainage; ⑥ Increase beneficial microorganisms.

12) Rot Spots on the Head

Symptoms: ring spots occur on the leaves, and black spots appear on the surface of the head

Solutions:

So far there is no more effective fungicide; the following methods can be used to solve the problem.

① Good drainage and good ventilation to control the disease; ② Keep plants healthy (plants should not be too large) ③ Avoid applying too much nitrogen fertilizer and supplement trace elements.

13) Rot at the Top of the Head

Symptoms: the head turns yellow and then rots.

Solutions:

So far there is no more effective fungicide; the same solutions as for rot spots on the head can be used.

14) Black Rot

Symptoms: "V"-shaped lesions occur at the leaf margins, and the area around the lesions turns yellow or black.

15) Black Heart

Symptoms: the stem turns black, and when people eat these parts there is a bitter taste. This disease is often seen at winter harvest, and it prefers humid and cool environments.

Solutions:

① Spray fungicides at the appropriate time; ② Improve air circulation and drainage; ③ Reduce the amount of nitrogen fertilizer used and increase the use of trace elements.