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 only in small amounts in China, mainly for Western cuisine. Broccoli is rich in nutrients, containing protein, sugar, fat, vitamins and carotene. Its nutritional content ranks first among vegetables of its kind, and it is known as the crown of vegetables.
Broccoli is a type of vegetable, belonging to a variety of cabbage. Broccoli is a cruciferous plant, a kind of 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 lump-shaped, resembling a large flower overall, white and beautiful. Broccoli has tender flesh and a sweet, delicious taste, and is easily digested and absorbed after eating.
Broccoli has a well-developed root system and strong regeneration ability, making it suitable for seedling raising and transplanting. It is susceptible to frost 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. Broccoli 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 vegetative growth, the suitable temperature range is wide. During the flowering and budding stage, the average daily temperature is generally required to be below 25°C. If the bud development stage encounters high temperatures (above 30°C), it will cause excessively 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 such as Japanese-imported Takamori, Balü and Zhulü are generally selected, with 55-65 days from transplanting to harvest; areas at an altitude of 1000-1200 m are sown from late June to mid-July, and areas at an altitude of 800-1000 m are sown 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. Harvesting is carried out 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 right age
For summer cultivation of broccoli, which occurs in a hot and rainy season, cultivating strong seedlings is key. A seedling-raising method using nutrition bags or nutrition soil balls should be adopted. Nutrition 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 compound fertilizer containing potassium sulfate with N:P:K=21:6:13), 3 kg of calcium magnesium phosphate, and 2 kg of lime powder. Use 450-fold dilution of 15% hymexazol (or quintozene) for soil disinfection, stir evenly, cover with plastic film and pile tightly for about 10 days. Before sowing, fill 8 cm × 10 cm seedling bags with nutrition soil (or press into nutrition soil balls), then sow 1 seed per soil bag (or soil ball), cover the seeds with sifted burnt 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 seedlings are 25-30 days old (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 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 brassica crops were previously planted must absolutely not be selected. Most mountain soils in the south are relatively 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 depth of 30-35 cm. Base fertilizer is applied throughout the whole 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 large demand for the trace element boron. Therefore, whether chemical fertilizer or organic fertilizer is used as base fertilizer, 2 kg of borax per mu must be applied 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. In particular, the southern mountain areas have annual rainfall of 1800-2000 mm, so deep-ditch and high-ridge cultivation is of special significance. Generally, the ridge width including the ditch is 1.1-1.2 m, the ridge height is 25-30 cm, and the surrounding drainage ditches and field waist ditches are required to be 50-60 cm deep, so that all ditches are connected and irrigation and drainage are easy. Takamori, Balü, Zhulü 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 nutrition bags, carefully tear off the nutrition bags and use shallow-hole transplanting, with a hole depth of 5-8 cm. If planted too deep, the air permeability at the stem base is poor, which easily induces damping-off.
5. Strengthen field management
1. Rational topdressing Broccoli generally requires 4 topdressings. After transplanting and survival, apply a plant-development fertilizer, which can be applied as a drench with 10%-15% dilute human urine; the 2nd and 3rd applications 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 application is carried out 37-40 days after transplanting. At this time, it has entered the rosette stage and is about to bud, which is a period requiring large amounts of water and fertilizer. The budding fertilizer should be applied heavily 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 (drenching is inconvenient after the rows have closed). After application, promptly cover with soil and irrigate to moisten the soil so that the fertilizer dissolves and is absorbed. To promote robust plant growth and improve the marketable 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, and where conditions permit, shade materials should be used to increase the survival rate. After survival, appropriately control water to help roots grow deep. Water demand is large in the middle and late growth stages, and water evaporates quickly in summer. During drought, water should be applied every evening, or a running-water irrigation should be given about every 3 days to keep the soil moist. The ridge surface should be covered with rice straw or weeds to reduce water evaporation. At the same time, typhoons and rainstorms are frequent from July to September, so ditches should be cleared and drainage carried out in time to meet the requirement that ridge ditches do not accumulate water after 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 damage the roots.
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-fold dilution of 58% metalaxyl mancozeb or 500-fold dilution of 64% Sandofan can be used for spray control. For Rhizoctonia rot, 1200-fold dilution of 20% tolclofos-methyl EC, or 450-fold dilution of 15% hymexazol aqueous solution, or 1000-fold dilution of 70% dexon can be used, sprayed for control when diseased seedlings first appear.
2. Bacterial soft rot, black rot and black spot These 3 diseases belong to bacterial diseases and are also the main diseases in off-season cultivation, and should be controlled in time. Flower bud differentiation begins as the susceptible period. In the early stage of disease, use 1000-fold dilution of 75% agricultural streptomycin, or 800-fold dilution of 70% Kocide for spray control. When the disease is severe, use the above drugs alternately, spraying once every 5-7 days for 2-3 consecutive applications, which can effectively control the disease.
3. Pest control The main pests include aphids, diamondback moths, cabbage caterpillars and beet armyworms. Biological pesticide Bt 500-800-fold dilution can be used (when pest density is high, a small amount of pyrethroid pesticide can be added, but it must not be mixed with fungicides), or 40% Lorsban 1000-fold dilution, 2.5% Kung Fu cypermethrin EC 2000-fold dilution, 21% Mieshabi 3000-fold dilution and other drugs for spray control.