Overwintering eggplant seedlings in greenhouse
Overwintering eggplant cultivation in solar greenhouses typically begins with planting seeds in early September. Seedlings are then transplanted into the greenhouse in late October, and the first harvest occurs around early December. The plants are usually pulled up between June and July of the following year. This method plays a crucial role in meeting the demand for fresh eggplants during the harsh winter and early spring seasons. Average yields range from 4,000 to 6,000 kilograms per mu.
Selecting the right varieties is essential for successful overwintering eggplant cultivation. Local taste preferences are considered, along with the need for early-maturing, cold-tolerant, and disease-resistant varieties. Ideal choices include those that have strong resistance to low light, Verticillium wilt, bacterial wilt, and root-knot nematodes. Varieties like Fast Round Eggplant, Fengyan No. 2, Round Hybrid No. 2, and Solanza No. 8 are commonly recommended due to their thick skin, good storage qualities, and resistance to diseases such as Brown Spot and M. elegans.
Grafting is widely used to enhance the plant's resilience against various soil-borne diseases. Common rootstocks include Torurubam, C. oleifera (CRP), or red eggplant. Among these, Torurubam is preferred due to its strong grafting compatibility and improved growth potential. The rootstock should be about 10–15 grams, while the scion should weigh 30–40 grams. Grafting is usually done when both the rootstock and scion have 5–7 true leaves, typically in mid-to-late September.
On the day of grafting, it’s important to spray the seedlings with an antibiotic solution, such as 800,000 units of streptomycin in 15 kg of water, or use chlorothalonil diluted 800–1000 times to prevent infection. The rootstock should be slightly controlled before grafting to avoid brittle stems. A small incision is made on the stem, and the scion is cut at a similar size and inserted into the rootstock. The graft is secured with a clip and placed in a shaded area.
After grafting, the seedlings are kept in a nursery bed with proper moisture and temperature control. For the first five days, the daytime temperature should be maintained at 24–26°C, and nighttime at 18–20°C, with humidity above 90%. Gradually reduce humidity to 80% after five days, allowing limited light exposure. By day 10, the shed can be removed, and the graft clip is taken off. Regular monitoring is required to remove any shoots growing below the graft union, which could drain nutrients from the plant.
If growing your own rootstock, it’s best to use plug seedlings to protect the roots. If transplanting, seedlings should be raised in open fields before being moved to the greenhouse. In colder regions, especially high latitudes or high-altitude areas, seedlings must be grown in greenhouses or under protected conditions. Nighttime insulation is particularly important to ensure healthy growth.
Soil preparation is critical for long-term cultivation. Two weeks before planting, fumigation with sulfur powder or dichlorvos mixed with sawdust is recommended to eliminate pathogens. Alternatively, the greenhouse can be sealed and heated for a week to kill pests and eggs. Plastic mulch should be laid in advance, and cold-proof soil should be prepared outside the walls before planting. In northern colder regions, this step is vital for protecting the crop from freezing temperatures.
Fertilization involves applying 10,000 kg of well-rotted manure, along with decomposed chicken manure and diammonium phosphate. After leveling the field, rows are set at 90 cm wide and 70 cm narrow, with trenches dug 40–50 cm wide and 30 cm deep. Fertilizer is mixed thoroughly into the soil, and water is added to the trench. Once the water is absorbed, the trench is filled to a height of 20 cm and width of 60 cm. A 30 cm walkway is left in the wide row, and a 10 cm water ditch is created in the narrow row. All these preparations should be completed 7–10 days before planting.
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