1. For sowing eggplant seedlings, early or mid-maturing varieties are recommended. Seedlings grown in Yangshuo can be sown from late November to early December, with a minimum seedling age of 90 days. If electric hotbeds or winter greenhouses are used, the seedling age can be reduced to 70–80 days, allowing sowing to be delayed until mid-December. The ideal seedlings should show signs of budding. For detailed planting techniques, refer to Chapter 5.
2. The optimal temperature for transplanting eggplants is when the soil temperature at 10 cm depth stabilizes between 12–15°C. In all regions of Shandong, arched circular greenhouses covered with a single layer of plastic film are typically planted in late March. Greenhouses with multiple layers or single-slope spring-use structures can be planted as early as late February to early March. Before planting, it's essential to cover the greenhouse in advance to raise the internal temperature. Greenhouses previously used for crops should be emptied quickly, and old structures must be fumigated and disinfected.
After clearing the greenhouse, deep plowing should be carried out, combined with base fertilizer application, and ridges should be formed. Land preparation, base fertilizer application, and ridge-making methods are similar to those used for overwintering cultivation.
3. Post-planting management
(1) Seedling stage management: Low ground temperature after planting is a major factor affecting eggplant growth. Within 10–15 days after planting, greenhouse temperatures should be increased. During the day, the temperature inside the shed can reach 30°C or higher. At this time, short-term ventilation through the top vents is allowed, but door or end vents should not be opened. Soil loosening should be strengthened to increase soil temperature and promote root development. Single-slope and multi-layer greenhouses should ensure early removal of opaque covers, proper insulation, and full light exposure.
(2) Fruit set management: After fruit set, attention should be given to preserving fruits and promoting leaf growth to establish a strong production structure. Temperature regulation is crucial during this period. Greenhouse temperatures should be maintained at 28–30°C for more than 5 hours daily. Ventilation should start when the temperature reaches 32°C in the morning, and vents should be closed when the temperature drops below 25°C in the afternoon. It's also important to balance plant growth and fruiting by removing all lateral branches below the first branch, such as double pruning, and promptly removing excess buds. After fruit set, the soil should be lightly hilled to about 10 cm to promote root development and prevent lodging. Early water management should focus on controlled irrigation and frequent soil loosening. Soil moisture during the flowering stage should not be too high, as excessive moisture may lead to flower and fruit drop. When the fruit reaches walnut size, topdressing and irrigation should be done. Apply 20 kg of urea per acre or 1,000 kg of manure. Watering should be done in the morning on sunny days to avoid temperature drops, using furrow irrigation if needed. To protect flowers, use 2,4-D at a concentration of 20 mg/l (20 ppm).
(3) Fruit development management: As the fruiting period begins, greenhouse temperatures rise significantly. To avoid heat stress, ventilation should be increased. Roll up the film under the eaves. When nighttime temperatures remain above 17°C, the skylight can be left open overnight for ventilation. To enhance photosynthesis and fruit coloring, remove the top film after June. During the fruiting stage, large amounts of nutrients are required to support fruit development. Water every 5–6 days and apply fertilizer after every two waterings. It's best to alternate between chemical and organic fertilizers. As the fruiting period progresses, remove old and yellow leaves from the base to improve air circulation and light penetration, concentrating nutrients on fruit development.
4. Disease and pest prevention is crucial. In the middle and late stages of greenhouse growth, rising temperatures and humidity create favorable conditions for pests and diseases. Common diseases include Bacillus subtilis and brown vein disease, while pests like aphids, tea yellowing, and whiteflies are prevalent. Prompt control measures are necessary. Disease prevention starts with managing temperature and humidity, particularly temperature control. These diseases are not directly caused by high humidity, but maintaining good ventilation and dehumidification, especially after watering, is key to reducing their occurrence.
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