At present, greenhouse tomatoes are entering their fruiting stage during autumn and winter. The climatic conditions at this time are generally favorable for the growth of solanaceous crops. However, as the season progresses, external temperatures gradually drop, daylight hours shorten, and if field management is not properly carried out, it can directly affect crop quality and yield. Therefore, effective field management is essential. Below are some key technical measures to improve greenhouse tomato cultivation:
First, managing the growing environment is crucial. This includes:
1. **Temperature Control**: During the early growth phase in autumn and winter, when outside temperatures are relatively high, the focus should be on preventing leggy growth. When the minimum outside temperature is above 12°C, the greenhouse roof and vents should remain open at night (except during rain) to increase the day-night temperature difference. When temperatures fall below 12°C, vents should be closed at night. If the minimum temperature drops below 6°C, insulation covering should be applied promptly. In cold periods, warming and frost protection measures are necessary. Ideal temperatures are: 23–30°C during the day, 15–18°C at night, with a minimum night temperature of no less than 10°C. The soil temperature should be maintained at 20–22°C. On sunny days, the temperature may rise to 32°C, so ventilation should be done to prevent overheating.
2. **Light Management**: Tomatoes require high light levels. Use high-transmittance plastic films or anti-drip films, and clean them regularly. During winter, remove the shade cloth as soon as possible to extend light exposure. On cloudy or snowy days, if the greenhouse temperature stays above 12°C, the shade cloth can be removed before and after noon to allow plants to receive scattered light. In prolonged overcast weather, cover the shade cloth gradually to avoid sunburn. Installing reflective film on the back wall in November helps maximize light intensity.
3. **Humidity Regulation**: The ideal relative humidity varies by growth stage: 80–90% during seedling, 60–70% during flowering, and 50–60% during fruiting. Reducing indoor humidity after temperature drops is critical to prevent disease. Methods include using drip irrigation under the film, short-term morning ventilation, and adjusting temperature.
4. **Carbon Dioxide Enrichment**: Winter ventilation is limited, and organic fertilizer application may be insufficient, leading to low CO₂ levels. Applying CO₂ fertilization after short-term ventilation, when the greenhouse temperature reaches 20°C or higher, can significantly enhance growth. Maintain CO₂ concentration at 1000–1500 mg/kg, especially during fruit enlargement.
Second, **vine training and pruning** is essential. Replace bamboo scaffolding with silver-gray plastic ropes to support the plants. Remove lateral shoots, old, and yellow leaves. Leave 4–6 fruits per plant, and when the plant reaches the top, prune the tip and leave 2–3 leaves above the upper cluster. For long-season cultivation, continuous topping and pruning can be used. When fruits are nearly ready for harvest, cut the main vine and allow a new lateral branch to grow for continued fruiting.
Third, **flower spraying and fruit thinning** should be done carefully. When two-thirds of the flowers have opened, spray “Shen Nong No. 2†to protect the fruit, adjusting the concentration based on temperature. Add “Pythium†pesticides to prevent gray mold. After fruiting, remove excess and malformed fruits. For single-fruit harvesting, keep 4 per cluster; for bunch harvesting, 5–6 per cluster.
Fourth, **watering should be moderate**. Use drip irrigation under the film or dark irrigation. Water when planting and after seedlings establish. Start watering when the first ear reaches 2 cm. Later, water sparingly to avoid lowering ground temperature. Avoid flooding and ensure proper soil moisture to promote growth and prevent cracking. Maintain soil moisture at 60–80% during fruiting.
Fifth, **fertilization should be balanced**. Avoid excessive nitrogen and apply small amounts frequently. Ensure sufficient potassium. Begin top-dressing when the first ear reaches 2–3 cm. Apply 5 kg of potassium nitrate and 15 kg of compound fertilizer per acre. Later, use 10 kg of NPK and 4 kg of water per acre. Alternatively, apply 20 kg of compound fertilizer (with ≥30% NPK) by digging holes. Stop top-dressing 30 days before harvest. During mid-to-late growth, spray foliar fertilizer 4–5 times with 0.3% potassium dihydrogen phosphate and 0.5% urea, focusing on the underside of leaves.
Sixth, **pest control** should prioritize prevention and biological methods. Avoid using medium- or high-toxicity pesticides. For example:
- **Late blight** thrives in low temperatures and high humidity (15–23°C, >75% RH). Ventilate and adjust conditions. Use fungicides like Ank-manganese zinc or Previcur.
- **Leaf mold** occurs in hot, humid, and poorly ventilated areas. Prevent by controlling humidity and use chlorothalonil or other sprays.
- **Virus diseases** spread through pests and wounds. Install insect nets, disinfect tools, and spray antiviral agents early.
- **Aphids and whiteflies** can be controlled with yellow sticky traps, silver mulch, and insecticides like acetamiprid, imidacloprid, or azadirachtin. Spray in the early morning and fumigate with dichlorvos in the evening.
By implementing these practices, growers can ensure healthy, high-yield tomato production in greenhouses throughout the cold season.
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