Key technical points of sowing and seedling raising in broccoli cultivation

At present, the seeds of broccoli cultivars for export are all imported from abroad, the price is relatively high, sowing is extensive, the emergence rate is low, the amount of seed used is large, and seeds are wasted. Precise sowing should be advocated to improve sowing quality. The main measures are: ① Sow and raise seedlings under protected environmental conditions (plastic tunnels or small arched sheds). For summer sowing, provide shade to lower temperature and prevent heavy rain; for winter and spring sowing and seedling raising, electric heating or plastic tunnels should be used for insulation, and after sowing, 20-25°C should be maintained to ensure uniform emergence. ② Before sowing, prepare nutrient soil or seedling substrate. ③ For sowing density, 10 grams of seeds require about 3 sq m of sowing bed or 4 seedling trays; it should not be too dense, to prevent the production of leggy seedlings. ④ For seed treatment, seeds without seed coating can be dressed with 50% thiram at 0.4% of seed weight or 2.5% at 0.8% of seed weight at the appropriate time.

(1) Seedling raising methods: At present, broccoli seedling raising generally uses open-field seedling raising, plug trays or plastic pots, and nutrient solution seedling raising.

① Open-field seedling raising: The broccoli seedling stage is relatively short. The seedbed should be selected in a field with high terrain, convenient drainage and irrigation, soil rich in organic matter, and where cruciferous vegetables have not been planted within two years or the previous crop was rice. The seedbed should preferably run north-south. Deep plow 15-20 days before sowing. 7-10 days before sowing, apply 15 kg of ternary compound fertilizer plus 5 kg of superphosphate per mu, or splash 2500 kg of decomposed human manure, to ensure sufficient nutrient supply during the seedling stage. Turn and rake the soil thoroughly, and make a sowing bed about 1.2 m wide, with a seedling field ratio of 1:20-30. Before sowing, water the seedbed thoroughly once, and apply 1000-fold phoxim and other pesticides to prevent underground pests. When sowing, mix the treated seeds evenly with an appropriate amount of sand and spread them evenly in the seedbed. After sowing, press with a shovel, then spread a layer of medicinal soil mixed with 0.1% carbendazim and dexon. In summer, after laying a layer of shade net flat on the seedbed, set up a small arched shed, then cover with another layer of shade net, for double-layer shading, moisture retention, and cooling seedling raising; in winter and spring, use one layer of plastic film and one layer of shed film for double-film coverage and heat-preserving seedling raising.

② Plug tray or nutrient pot seedling raising: The plug trays currently used (each tray 24 cm × 60 cm) mainly have 3 types: 72-cell, 100-cell, and 128-cell. Nutrient pots have two calibers: 5.0 cm and 6.5 cm. The nutrient soil can be prepared from 70% sieved garden soil that has not grown cruciferous vegetables within two years, 30% decomposed organic fertilizer, and then adding 2%-3% superphosphate (or 1/3 rice husk ash, 1/3 decomposed organic fertilizer, 1/3 sieved garden soil, plus 4 kg/cubic meter of compound fertilizer). Before sowing, pour through with an appropriate amount of carbendazim or dexon, phoxim, and other pesticide solutions and set aside. When sowing, sow the treated seeds one by one into plug trays or nutrient pots, or broadcast them into seedling trays, then cover with a shade net or shed film, with the same method as open-field seedling raising.

③ Nutrient solution seedling raising: Nutrient solution seedling raising is currently a relatively good seedling raising method. It has the characteristics of low cost, convenient management, high seedling survival rate, and centralized seedling supply, and is welcomed by production and processing enterprises. ① Substrate: 25% vermiculite, 65% peat, 10% perlite. ② Substrate stacking and disinfection: After fully and evenly mixing all raw materials, evenly spray 50-100 times formalin (40% formaldehyde) onto the substrate, then cover tightly with plastic film, keep sealed for 4-5 days, uncover the film for ventilation, and turn the nutrient soil so that formaldehyde volatilizes out; it can be used after 2 weeks. Also, the pH of the substrate needs to be adjusted to 6.5-7. If too acidic, adjust with lime; if too alkaline, neutralize with dilute hydrochloric acid. ③ Sowing: Fill the plug trays with substrate, water thoroughly, then use a special hole-punching machine to make sowing holes, use a seeder to sow the seeds into the sowing holes, and cover with substrate. The rest is the same as plug tray or nutrient pot seedling raising.