Detailed Guide to Broccoli (Calabrese) Seedling Cultivation
How to grow broccoli (calabrese) seedlings? Please explain. Broccoli is a major vegetable export crop of Zhejiang Province, with a stable annual planting area of around 10,000 hectares across the province. However, because the broccoli sowing season falls during the high-temperature and typhoon-active period from July to September, how to make full use of the limited growing season to cultivate strong seedlings has become the key to broc...
How to grow broccoli (calabrese) seedlings? Please explain
Broccoli is a major vegetable export crop of Zhejiang Province, with a stable annual planting area of around 10,000 hectares across the province. However, because the broccoli sowing season falls during the high-temperature and typhoon-active period from July to September, how to make full use of the limited growing season to cultivate strong seedlings has become the key to broccoli production, processing and export trade. The Xiangshan County Modern Agriculture Experimental Farm, guided by the purpose of carrying out technical research and services around leading industries, successfully cultivated broccoli seedlings for 140 hectares in 2001-2002, effectively solving the seedling supply problem for production. The details are as follows:
I. Environmental Requirements for Broccoli Seedling Growth and Development
Broccoli seedling growth and development includes three stages: the germination stage, the basic vegetative growth stage, and the rapid seedling growth stage.
Broccoli prefers cool conditions and is a semi-cold-tolerant vegetable. Its minimum germination temperature is 3°C, the optimum is 20-25°C, and the maximum is 35°C. The optimum temperature for plant growth is 20-22°C, and the curd will suffer cold damage at low temperatures of -5 to -3°C. Flower bud differentiation does not have strict low-temperature requirements; early-maturing varieties can complete flower bud differentiation as long as the average temperature is below 20°C. However, exposure to low temperatures during the seedling stage will cause the formation of small curds, resulting in loss of marketability and reduced yield. Growth is slow when the temperature is below 8°C. Mid- and late-maturing varieties require lower temperatures for flower bud differentiation, so they cannot be cultivated in high-temperature seasons; otherwise they will form leafy curds, hairy curds and scorched buds. Therefore, broccoli has strict requirements for the sowing period.
Broccoli requires sufficient light, but does not have strict requirements for day length. It prefers moist conditions but is not drought-tolerant or waterlogging-tolerant, and has relatively strict water requirements. Especially during the seedling stage, drought prevention and waterlogging prevention are the focus of seedling management. The seedbed soil is required to be loose, fertile, and have good water retention and drainage performance.
II. Seedling Raising Methods
The seedling raising method for broccoli is related to its varietal characteristics and crop rotation arrangements. The eastern coastal area of Zhejiang Province generally adopts the method of open-field sowing plus shading net coverage for cooling plus agricultural film coverage for rain protection.
III. Standards for Strong Seedlings
Seedling age 30-35d, leaf age 5-6 true leaves, robust growth, free from pests and diseases, thick stems, relatively short internodes, larger and thicker leaves, normal leaf color, well-developed root system with abundant fibrous roots, and uniform plant growth.
IV. Seedbed Preparation
1. Seedbed selection. For broccoli seedling cultivation, select a field with high and dry terrain, good drainage, good ventilation and light transmission, loose soil rich in organic matter, and where cruciferous vegetables have not been planted in the past two years, as the seedbed. For seedling cultivation, reserve sufficient seedbed at a ratio of 1:20. Plow the soil 1 week before sowing, apply 25kg of high-efficiency compound fertilizer per 667 sq m, deeply incorporated throughout the layer; seedbed width including furrow 2m, furrow width 40-50cm, height 15-20cm, deep furrows with high beds; seedbed preparation requires coarse bottom and loose top, with the bed surface fine, flat and smooth.
2. Seedbed disinfection. For export broccoli seedling cultivation, the national operating regulations for pollution-free vegetable production should be strictly implemented. For seedbed disinfection, use 25% Ridomil 500x solution plus 40.7% Lorsban 800-1000x solution sprayed on the seedbed before sowing for disinfection and sterilization and to kill underground pests.
3. Pre-sowing chemical weed control. To reduce weed damage during seedling cultivation and lower seedling production costs, use the upland herbicide Dual, which has good safety and a broad herbicidal spectrum. The dosage is 70% Dual EC 20mL added to 15kg of water, sprayed on the bed surface before sowing, and water thoroughly to moisten the seedbed.
4. Pre-sowing soil moisture regulation. While completing the above tasks for broccoli seedling cultivation, the seedbed soil moisture must be properly adjusted. Too little soil moisture affects seed imbibition and germination; too high humidity causes soil air blockage and seed rot. Therefore, the principle of pre-sowing moisture regulation for broccoli is that the bed surface is thoroughly wet and water seeps into the furrows. This not only reduces soil porosity and prevents broccoli seeds from sinking too deep and affecting emergence, but practice has also proven that the degree of soil dryness and wetness is directly related to emergence quality.
V. Sowing
1. Determine a reasonable sowing period. The main basis for determining the sowing period is varietal characteristics, weather conditions and cultivation purpose. For cultivation in the eastern coastal area of Zhejiang: extra-early-maturing varieties such as Lufeng and Qingfeng have a sowing period from mid-July to mid-August; early-maturing varieties such as Youxiu have a sowing period in early to mid-August; mid-maturing varieties such as Ludaiizi and Malasong have a sowing period from late August to early September; late-maturing varieties such as Meilü 90 and Fuxing have a sowing period from mid-September to early October.
2. Determine a reasonable seeding rate. Broccoli seeds are small. To ensure a sufficient number of seedlings for the field and give the seedlings adequate growing space, the field seed quantity must be scientifically calculated. The formula is: seed quantity (g/667 sq m) = [number of seedlings/667 sq m x (1 + safety factor)] x 1000-grain weight ÷ germination rate. The germination rate of qualified seeds is above 85%, and the safety factor for raised seedlings is 80%. At present, the 1000-grain weights of the main varieties are: Youxiu 3.17g, Ludaiizi 3.6g, Meilü 90 5.56g, Chaoli 2.96g, Fuxing 3.94g. Calculated, the seed quantity per 667 sq m of field is: Youxiu 12g, Ludaiizi 15g, Meilü 90 20g, Chaoli 12g, Fuxing 15g.
3. Sowing. Sowing must be uniform. For seedling cultivation, the method of mixing seeds with fine sand or mud and direct sowing of dry seeds is often used, evenly sowing broccoli seeds on the prepared seedbed. The sowing time should preferably be on a clear evening or a cloudy day. Generally, after sowing broccoli seeds, fine soil is not used to cover the seeds; instead, after sowing, water is sprayed with a fine nozzle so that the seeds and bed surface are in close contact, and then 2-3 layers of shading net are covered on the bed surface for shading, cooling and moisture retention.
VI. Seedbed Management
1. Management during the germination and emergence stage. Broccoli takes 2-3 days and nights from sowing to emergence. The time is short, but management requirements are high. The focus should be on strengthening observation. Proceeding from the overall environmental conditions of the seedling stage, attention should be paid to regulating the two main factors of temperature and moisture. Throughout the germination stage, field observation must be carried out 3 times a day: in the morning, in the afternoon and in the evening, observing seed sprouting, the dryness and wetness of the bed surface soil, and the intensity of sunlight or field drainage in rainy weather. Under clear and high-temperature conditions from July to September, during the germination and emergence stage, watering is mainly relied upon to regulate soil temperature, keeping the soil temperature at a suitable 25-30°C to facilitate normal emergence. Watering can be done before noon and in the evening, and try to avoid encountering cloudy and rainy weather after watering. During this period, cover the bed surface with 2-3 days and nights of shading net for cooling and rain protection. After emergence, when the two cotyledons unfold and turn green, remove the shading net in time.
2. Management during the basic vegetative stage of seedlings. From cotyledon greening to the 2-leaf 1-heart stage is the basic vegetative stage of broccoli seedlings. After the broccoli cotyledons unfold and turn green, they enter an independent autotrophic stage. During this period, if root growth and absorption are poor, or the temperature in the seedbed is too high, the seedlings are prone to poor growth and development. With the growth and unfolding of true leaves and the expansion of leaf area, the role of the cotyledons gradually disappears after the 2-leaf 1-heart stage. Management during this period is the key to cultivating strong seedlings. Management mainly focuses on the following aspects: First, promptly set up a small arch shed and cover it with a shading net. Cover with shading net from 8 a.m. to 4 p.m. on clear days for cooling, remove the shading net at other times, do not cover on cloudy days and light rain, and the intermittent net covering lasts for 1 week. Second, strengthen water management. After rain, clear the furrows and drain in time to ensure no water accumulation in the field; on clear days, water timely after the soil surface becomes dry to preserve moisture. Third, prevent typhoons and rainstorms. Closely monitor forecasts of severe weather such as typhoons and rainstorms, and take various disaster prevention measures before typhoons and rainstorms arrive. Agricultural film can be covered on the small arch shed, and along the bed edge every 2m use an arch rod to roll up the agricultural film into a ventilation opening to ventilate and reduce humidity. Between every two arch rods, use a stake to secure the film, cover the top of the agricultural film with a shading net, and tighten and fix it to the stakes with nylon rope or film-pressing wire. After typhoons and rainstorms, promptly remove facilities such as the agricultural film and shading net to prevent seedling spindling. Fourth, strengthen pest and disease prevention. After emergence to the 1-leaf 1-heart stage, promptly use 40.7% Lorsban 800x solution plus 3% Jinggangmycin 500x solution to prevent damage by the striped flea beetle and to prevent damping-off and seedling blight. At the 2-leaf 1-heart stage, use 75% chlorothalonil 1000x solution plus 3% Jinggangmycin 500x solution to prevent damping-off and seedling blight.
3. Management during the rapid growth stage of seedlings. After the 2-leaf 1-heart stage, seedlings enter the rapid growth stage, during which 90% of seedling growth occurs. At this time the temperature is still relatively high, and the root system forms and grows very quickly. To cultivate strong seedlings, management during this period should focus on control. Management mainly focuses on the following aspects: First, continue to do a good job in preventing typhoons and rainstorms, with methods referring to the basic vegetative growth stage of seedlings. Second, continue to do a good job in water management with alternating dry and wet conditions, preferring dry over wet. Third, do a good job in thinning at the 2-leaf 1-heart stage so that the seedling growing space in the seedbed reaches a uniform level of 10 sq cm per plant, ensuring 50,000 seedlings per 667 sq m. Fourth, control fertilization throughout the seedling growth period, but apply a small amount of urea to weak and small seedlings to promote uniformity. Fifth, strengthen pest control. During the pest occurrence period, use 5% fipronil 1500x solution to control diamondback moth, cabbage caterpillar and cabbage webworm; use 20% Mimic 1000x solution plus 10% beta-cypermethrin 1500x solution to control beet armyworm and tobacco cutworm; use 10% imidacloprid 3000x solution to control aphids.
VII. Seedling Delivery from Nursery and Management
After management through the above series of measures, seedlings must be delivered from the nursery and transplanted into the field in time at 5-6 leaves. Apply a small amount of urea 2d before transplanting as a starting fertilizer, inspect and control pests and diseases well, and achieve transplanting of strong seedlings with medicine, fertilizer and soil blocks. When lifting seedlings, water the nursery thoroughly to prevent root damage, and select large seedlings with uniform growth for delivery from the nursery. After pulling the seedlings, water timely to facilitate the growth and development of the remaining small seedlings; after 1 week of cultivation, the small seedlings become strong seedlings for delivery from the nursery.
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