What are the key points for summer cultivation and management of broccoli?
Broccoli is an annual or biennial herbaceous plant, native to the eastern Mediterranean coastal region. It is cultivated in small quantities in China, mainly for Western cuisine. Broccoli is rich in nutrients, containing protein, sugar, fat, vitamins and carotene, and ranks first among vegetables of its kind in nutritional content, and is known as the “crown of vegetables”.
Broccoli is a type of vegetable, belonging to a variety of cabbage. Broccoli is a cruciferous plant, an annual or biennial herbaceous plant with broad leaves, a blunt base, wavy edges, smooth and hairless, and yellow-white flowers. Leaves grow from the roots, the main stem and branch stems grow from the leaves, and the stems are covered with small granules that form a flower-like shape. The flower is fleshy and block-shaped, resembling a large flower overall, white in color and attractive. Broccoli is tender in texture, sweet and delicious, and easily digested and absorbed after eating.
Broccoli has a well-developed root system and strong regeneration capacity, making it suitable for seedling raising and transplanting. It is susceptible to freezing damage below 0°C, and it is difficult to form flower heads above 25°C. Leaf cluster growth and bolting and flowering require warmth, with an optimum temperature of 20-25°C. Flower head formation must go through a low-temperature vernalization stage. Cauliflower does not have strict requirements for light conditions, but has relatively strict requirements for moisture, being neither tolerant of waterlogging nor drought. It has strong adaptability to soil, but sandy loam soil with high organic matter and deep soil layers is best. The suitable soil pH is 5.5-6.6. It has strong salt tolerance and can still grow normally in soil with a salt content of 0.3%-0.5%.
Key points for summer cultivation and management of broccoli
1. Select good varieties and sow at the right time
The suitable temperature for broccoli growth is between 16°C and 22°C. During the vegetative growth period, the suitable temperature range is wide. The flowering and budding stage generally requires an average daily temperature below 25°C. If the flower bud development period encounters high temperatures (above 30°C), it will cause overly rapid bolting, low yield, and poor flower head quality. Therefore, selecting disease-resistant and heat-tolerant varieties and scientifically arranging sowing time are the keys to the success of summer sowing cultivation. In our county, early-maturing and heat-tolerant excellent varieties imported from Japan such as Gaosheng, Balv, and Zhulv are generally selected, with 55-65 days from transplanting to harvest; areas at an altitude of 1000-1200 m sow from late June to mid-July, and areas at an altitude of 800-1000 m sow from mid-July to early August. To facilitate harvesting and sales, it is best to sow in stages, with 1 stage every 5-7 days. Harvest from late September to mid-November, striving to finish harvesting before coastal products are massively marketed, which helps increase product prices and create better economic benefits.
2. Cultivate strong seedlings and transplant at the appropriate age
For summer cultivation of broccoli, which is in a high-temperature and rainy season, cultivating strong seedlings is key. The method of raising seedlings in nutrient bags or nutrient soil balls should be selected. Nutrient bags (or soil balls) are calculated at 3300-3500 per 667 sq m of field. The formula is 600-700 kg of fertile and loose paddy soil, 30-40 kg of rice husk ash, 80-100 kg of decomposed and fermented pig and cattle pen manure, 0.5-1.0 kg of imported compound fertilizer (preferably a compound fertilizer containing potassium sulfate with N:P:K=21:6:13), 3 kg of calcium magnesium phosphate, 2 kg of lime powder, and 450 times dilution of 15% hymexazol (or quintozene) for soil disinfection. After mixing evenly, cover and seal with plastic film and pile for about 10 days. Before sowing, fill 8 cm × 10 cm seedling bags with nutrient soil (or print into nutrient soil balls), then sow 1 seed per soil bag (or soil ball), cover the seeds with sifted burned soil and miscellaneous fertilizer, and build a greenhouse covered with a shade net with 65% shading rate. Strengthen fertilizer and water management during the seedling stage, and transplant when the seedling age is 25-30 days (4 leaves and 1 heart to 5 leaves and 1 heart).
3. Select land, plow deeply, and apply sufficient base fertilizer
According to the growth characteristics of broccoli and its requirements for environmental conditions, the planting site should be selected as paddy soil at an altitude above 800 m, with deep soil layers, relatively high organic matter content, good drainage and irrigation conditions, strong water and fertilizer retention capacity, and moderate sand-clay ratio. Fields where cabbage crops were previously planted must absolutely not be selected. Most soils in southern mountainous areas are strongly acidic. About 1 month before planting, apply 100-1200 kg of lime powder per mu, combined with deep plowing and sun-whitening, with a deep plowing thickness of 30-35 cm. Base fertilizer should be applied throughout the layer 10-15 days before transplanting, using 1000-13000 kg of fermented pig and cattle pen manure and 120-200 kg of plant ash per mu; or 500-600 kg of imported ternary compound fertilizer containing potassium sulfate and 200-300 kg of calcium magnesium phosphate. Broccoli has a relatively high demand for the trace element boron. Therefore, regardless of whether chemical fertilizer or organic fertilizer is used as base fertilizer, 2 kg of borax must be applied per mu to meet its growth and development needs.
4. High-ridge cultivation and rational close planting
Broccoli is a crop that likes warm light but fears intense heat, and likes moisture but fears waterlogging. To improve light energy utilization, increase soil permeability, and improve the field microclimate, high-ridge cultivation and rational close planting should be emphasized. Especially in southern mountainous areas with annual rainfall of 1800-2000 mm, deep-ditch and high-ridge cultivation is of special significance. Generally, the ridge with ditch width is 1.1-1.2 m, the ridge height is 25-30 cm, and the surrounding drainage ditches and field middle waist ditches are required to be 50-60 cm deep, so that all ditches are connected and easy to irrigate and drain. Gaosheng, Balv, Zhulv and others all belong to early-maturing broccoli varieties, which are conducive to close planting, generally with a plant spacing of 50-60 cm and a row spacing of 35-40 cm, planting 2800-3200 plants per mu. When transplanting seedlings raised in nutrient bags, carefully tear off the nutrient bags and use the shallow-hole transplanting method, with a hole depth of 5-8 cm. If planted too deep, the ventilation at the stem base is poor, which easily induces damping-off disease.
5. Strengthen field management
1. Rational topdressing Broccoli generally requires 4 topdressings. After transplanting and surviving, apply a plant-development fertilizer, which can be applied with 10%-15% dilute human urine; the 2nd and 3rd times are carried out 15-18 days and 25-28 days after transplanting respectively, using 5-6 kg of urea and 4 kg of potassium chloride per mu; the 4th time is carried out 37-40 days after transplanting, when it has entered the rosette stage and is about to bud. This is a period requiring large amounts of water and fertilizer, so the budding fertilizer should be heavily applied in time to promote rapid growth of flower buds, using 20 kg of compound fertilizer containing potassium sulfate per mu, applied deeply in holes 15-20 cm away from the stem base (application by watering is inconvenient after the rows have closed), and immediately cover with soil after application, and irrigate to moisten the soil so that the fertilizer dissolves and is absorbed. To promote robust plant growth and increase the finished product rate of flower heads, foliar fertilizers such as Shuangxiao micro-fertilizer, Penshibao, and Plant Power 2003 can be selected and sprayed once each at the seedling stage, vigorous growth stage, and budding stage.
2. Scientific irrigation After transplanting broccoli, water should be applied to protect the seedlings. If conditions permit, cover with shading materials to increase the survival rate. After survival, appropriately control water to favor deep rooting. Water demand is large in the middle and late growth stages, and water evaporates quickly in summer. In drought, water every evening, or irrigate once about every 3 days with a running-water irrigation, keeping the soil moist. Cover the ridge surface with rice straw or weeds to reduce water evaporation. At the same time, typhoons and rainstorms are frequent from July to September, so timely ditch clearing and drainage should be carried out to meet the requirement that ridge ditches do not accumulate water after the rain stops.
3. Intertillage and earthing up Broccoli should be intertilled and earthed up 1-2 times before the rows close. After the rows close, no more intertillage should be carried out, but weeds should be pulled by hand. After typhoons and rainstorms, loosen the soil in time to prevent soil compaction, increase soil permeability, and promote root growth. Soil loosening should mainly be shallow hoeing, taking care not to injure the root system.
6. Timely prevention and control of pests and diseases
1. Damping-off and Rhizoctonia rot These are the main diseases at the seedling stage. For damping-off, 500 times dilution of 58% metalaxyl-mancozeb or 500 times dilution of 64% oxadixyl can be used for spray control. For Rhizoctonia rot, 1200 times dilution of 20% tolclofos-methyl EC or 450 times dilution of 15% hymexazol aqueous solution, or 1000 times dilution of 70% dexon can be used, sprayed when diseased seedlings first appear.
2. Bacterial soft rot, black rot, and black spot These 3 diseases are bacterial diseases and are also the main diseases in off-season cultivation, and should be controlled in time. Flower buds begin to differentiate as the susceptible stage. In the early stage of disease, spray with 1000 times dilution of 75% agricultural streptomycin, or 800 times dilution of 70% Kechade. When the disease is severe, alternate the above drugs, spraying once every 5-7 days, continuously for 2-3 times, which can effectively control the disease.
3. Pest control Mainly aphids, diamondback moths, cabbage caterpillars, beet armyworms, etc. Biological pesticide Bt at 500-800 times dilution (when pest density is high, a small amount of pyrethroid pesticide can be added, but it cannot be mixed with fungicides), or 40% Lorsban at 1000 times dilution, 2.5% Kung Fu cypermethrin EC at 2000 times dilution, 21% Mieshabi at 3000 times dilution and other drugs can be used for spray control.