Sowing seedlings should be done using early or mid-season varieties. In Yangshuo, seedlings 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 seedling stage is when buds begin to appear. For detailed techniques, refer to Chapter 5.
The optimal temperature for transplanting eggplants is when the soil temperature at 10 cm depth stabilizes between 12–15°C. In Shandong, arched greenhouses covered with a single layer of plastic film are typically planted in late March. Greenhouses with multiple layers or single-slope spring structures allow planting to start as early as late February or early March.
Before transplanting, it’s essential to cover the greenhouse in advance to raise the internal temperature. If previous crops were grown, they must be removed promptly. Old greenhouses need fumigation and sterilization to prevent disease.
After clearing the greenhouse, deep plowing is required, along with mixing in base fertilizer and forming ridges. Land preparation, fertilization, and ridge formation follow the same procedures as those used for overwintering cultivation.
Post-planting management includes several key stages:
(1) Seedling care: Low ground temperatures after planting can limit growth. Within 10–15 days, greenhouse temperatures should be increased. During the day, temperatures can reach 30°C or higher. Morning ventilation through the top vents is recommended, but avoid opening doors or side vents. Soil should be loosened regularly to promote root development. Single-slope and multi-layer greenhouses should ensure early removal of opaque covers and maintain good insulation and light exposure.
(2) Flowering and fruiting stage: After fruit set, focus on preserving fruits and promoting leaf growth to build a strong production structure. Maintain daytime greenhouse temperatures between 28–30°C for more than 5 hours. Ventilate when temperatures exceed 32°C in the morning and close vents when temperatures drop below 25°C in the afternoon. Control plant growth by pruning lateral branches below the first fruit cluster and removing excess buds. After fruit set, hill up the soil to about 10 cm to encourage root growth and prevent lodging. Water management should be controlled, with less irrigation and more soil aeration. Avoid high soil moisture during flowering to prevent flower and fruit drop. When fruits reach walnut size, apply a top dressing of 20 kg urea per acre or 1000 kg of compost. Water in the morning on sunny days to avoid temperature drops. To protect flowers, use 2,4-D at 20 mg/L (20 ppm).
(3) Fruit development stage: As the greenhouse enters high-temperature periods, increase ventilation. Roll up the plastic film under the eaves. When nighttime temperatures remain above 17°C, close the skylights and ventilate overnight. Remove the top film after June to improve photosynthesis and fruit coloring. Apply large amounts of fertilizer to support fruit development, watering every 5–6 days and applying fertilizer every two waterings. Alternate between chemical and organic fertilizers for balanced nutrition. During full fruiting, remove old and yellow leaves to improve air circulation and light penetration, directing nutrients toward fruit development.
Disease and pest control is crucial. High humidity and temperature in greenhouses during mid-to-late growth stages create favorable conditions for pests and diseases such as Bacillus subtilis and brown vein disease, as well as aphids, thrips, and whiteflies. Proper temperature and humidity management is the first line of defense. While humidity plays a role, the main control method is effective ventilation and dehumidification, especially after irrigation. Regular monitoring and timely intervention are essential for healthy crop growth.
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