Planting Seedlings
It is currently winter, and seedling cultivation can only be done in a nursery. Eggplant germination requires higher temperatures, and the growth of seedlings is relatively slow. Under the current low-temperature conditions, it's essential to raise the seedlings in a controlled environment like a nursery. Compared to tomatoes, eggplant seedlings take longer to grow—approximately 70 days. Therefore, transplanting is usually done in late March, and sowing should ideally begin in early January. Eggplant seedlings are prone to bacterial wilt and damping-off, so it's crucial to disinfect the seedbed soil thoroughly before planting. Due to their slow growth, it's efficient to spread out the seedlings initially and perform 1-2 transplantations later. Typically, the first transplantation occurs when the seedlings have 3 or 4 true leaves, and the second one when they have about 6 leaves. The final spacing between plants should be around 10–13 cm. After germination, eggplants should be soaked before sowing to ensure uniform and quick emergence. The temperature during the nursery period should be slightly higher than that for tomatoes and peppers. In a greenhouse, the temperature should be maintained at about 25°C after sowing, 15–20°C on cloudy days, and 25–20°C on sunny days. At night, it should be kept around 10°C. Fertilization in the seedbed should also be more generous than for tomatoes. In addition to organic manure, some phosphorus fertilizer should be added to support strong root development and healthy seedling growth.
In the early stages of seedling growth, it's common to transplant them 1–2 times. Seedlings that are too dense or weak should be transplanted around 30–50 days after sowing, as mentioned earlier. When the seedlings have 3–4 true leaves, the first transplant is done, and a second one is carried out about a month later. This helps ensure robust and healthy growth.
Transplanting (Daejeon)
Next spring, the seedlings will be transplanted. It’s important not to plant eggplants together with other solanaceous crops like tomatoes or peppers to prevent diseases such as bacterial blight and bacterial wilt. A crop rotation of 3–4 years is recommended. Eggplants require fertile, well-drained soil with good water retention. Deep plowing, about 30 cm, promotes microbial activity, increases nutrient availability, improves water retention, and encourages strong root development. This leads to stronger plants, fewer lodging issues, and higher yields. Using slag fertilizer as a base is beneficial for better results.
Proper planting density is key to increasing yield. A reasonable close planting allows the leaf area coefficient to reach its peak earlier, which supports early fruiting and higher total output. For example, in Chengdu, a spacing of 66 cm between rows and 50 cm within the row is suitable. Wide and narrow row planting can improve air circulation and light penetration. However, if the spacing becomes too tight, it may lead to issues like brown spot disease and poor fruit coloration. Therefore, it's important to maintain an optimal balance.
Field Management
Fertilization: Since eggplants have a long growing season, proper top-dressing is essential for high yields. After transplanting, apply thick manure or chemical fertilizers, mainly nitrogen-based, such as urea at 10–15 kg per acre. Top-dressing should be applied multiple times throughout the season. There should be 2–3 heavy fertilizer applications, with the first one applied before soil cultivation at a concentration of 60–70%, and the later ones placed in the furrow. Eggplant fruiting follows a cyclical pattern, with periods of lower fruit production between harvests. Experiments show that more frequent fertilization leads to higher yields and less fluctuation in production. Insufficient fertilization, on the other hand, can cause irregular fruiting and reduced yield.
Eggplants need consistent moisture. Irrigation should be provided when the soil is dry. Poor drainage can increase the risk of disease, so it's important to manage both irrigation and drainage, especially during the rainy season.
Cultivation: Mid-season cultivation involves loosening the soil and controlling weeds. In the early stages, it should be done about 5–7 cm deep, and shallower (3–4 cm) in later stages. After heavy rain, cultivate the soil when it's semi-dry to prevent compaction. When the plants reach about 30 cm in height, combine cultivation with soil mounding around the roots. Before cultivating, apply top-dressing to avoid exposing the roots and reduce wind damage. As eggplants grow taller, staking is necessary to prevent lodging.
Pruning and Leaf Removal: Eggplants have lush foliage, which can lead to poor ventilation and light transmission, causing flower drop and fruit loss. Removing the lower lateral branches near the root can help improve air circulation and reduce these issues.
Timely Harvesting
Eggplants are typically harvested in mid-June. The harvesting process usually involves several cycles. If fruits are picked on time, there will be more fruits and the cycle will be less noticeable. Delayed harvesting affects both fruit quality and yield, as the seeds inside consume a lot of nutrients. The standard for harvesting is to look for the white or light green ring at the junction of the fruit and the calyx, known as the "eggplant eye." A wide ring indicates rapid growth, while a fading ring suggests slower growth and the need for timely harvesting.
Seed Retention
High bamboo shoots and eggplants are two varieties that can be retained for seed. Each year, it's important to purify and rejuvenate the plants to maintain a high-quality eggplant brand. Select healthy seedlings without pests or diseases. Add phosphorus and potassium fertilizers to the retained plants, while limiting nitrogen to promote better seed development. The preserved eggplants should be fully matured on the plant, with yellow and soft skin, before being harvested for seed. Usually, the second layer of fruit is selected, while the first or last fruits are not used.
After the fruit is mature, it can be picked and left to ripen indoors for 7–10 days. Once ripe, the seeds are separated from the pulp, cut into pieces, and the ends removed. The middle part is then crushed in water, allowing the seeds to sink and be washed out. After drying, cover the seeds with a cloth to protect them from direct sunlight. The number of seeds varies by variety; for example, Chengdu Moke eggplants can yield about 0.6 kg of seeds per 100 kg of fruit. Different eggplant varieties may crossbreed, but as long as they are planted more than 50 meters apart, cross-pollination is unlikely.
Author: Agronomist from the Chengdu Agricultural Quality Monitoring Center
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