With the onset of autumn and winter, greenhouse-grown tomatoes are entering their fruiting stage. The current climatic conditions are generally favorable for the growth of solanaceous crops. However, as temperatures gradually drop and daylight hours shorten, effective field management becomes crucial to maintain both crop quality and yield. Proper management not only ensures better productivity but also helps prevent disease outbreaks and other adverse effects.
To optimize tomato production during this period, the following key management practices should be implemented:
**1. Environmental Control**
- **Temperature**: During the early growth phase, when outside temperatures remain above 12°C, it's advisable to keep greenhouse vents open at night (except in rainy weather) to increase the day-night temperature difference. When temperatures fall below 12°C, close vents at night. If temperatures drop below 6°C, apply additional insulation. In colder months, maintain daytime temperatures between 23–30°C, nighttime temperatures between 15–18°C, and ensure that nighttime temperatures do not fall below 10°C. Ground temperature should be kept around 20–22°C. On sunny days, when temperatures reach up to 32°C, ventilate the greenhouse briefly to avoid overheating.
- **Light**: Tomatoes require high light intensity. Use high-transmittance plastic films and clean them regularly to maximize light penetration. During winter, remove shade cloths during sunny periods to extend light exposure. In cloudy or snowy weather, allow plants to receive scattered light by uncovering cloths before and after noon, provided the greenhouse stays above 12°C. Avoid direct sunlight on overcast days to prevent plant damage. Install reflective films on the back walls in November to enhance light efficiency.
- **Humidity**: Maintain relative humidity at 80–90% during seedling stages, 60–70% during flowering, and 50–60% during fruiting. Reduce indoor humidity after temperature drops to prevent disease spread. Techniques include covering the soil with mulch, using drip irrigation, short-term morning ventilation, and adjusting temperature levels.
- **Carbon Dioxide Enrichment**: Limited ventilation and insufficient organic fertilizer can lead to low CO₂ levels. Apply CO₂ fertilization after short-term ventilation when temperatures exceed 20°C, aiming for a concentration of 1000–1500 mg/kg. This is especially important during fruit development.
**2. Pruning and Vine Management**
Replace traditional trellises with silver-gray plastic ropes to support vine growth. Remove lateral shoots, old, and yellow leaves regularly. Keep 4–6 fruits per plant, and pinch off the top when the plant reaches the desired height, leaving 2–3 leaves above the upper cluster. For long-season cultivation, use continuous pruning techniques, allowing new lateral branches to continue fruiting while the main vine is redirected downward.
**3. Flower Spraying and Fruit Thinning**
Spray "Shen Nong No. 2" when two-thirds of the flowers have opened to protect against fruit rot. Adjust the spray concentration based on greenhouse temperature and add fungicides like "Pythium" to control gray mold. After fruit set, remove excess, malformed, or damaged fruits. For single-fruit harvesting, aim for 4 per cluster; for bunch harvesting, 5–6 per cluster.
**4. Watering Practices**
Use drip irrigation under mulch to maintain consistent moisture without waterlogging. Water when the first ear reaches 2 cm in size, and then apply small amounts of water periodically. Minimize watering in cold seasons to avoid lowering soil temperature. Ensure proper soil moisture to promote healthy growth and prevent cracking. Maintain soil moisture at 60–80% of maximum holding capacity during fruiting.
**5. Fertilization Strategies**
Apply balanced fertilizers in small, frequent doses. Avoid excessive nitrogen and instead ensure adequate potassium supply. Begin top-dressing when the first ear is 2–3 cm in size. Apply 5 kg of potassium nitrate and 15 kg of compound fertilizer per acre, followed by 10 kg of NPK and 4 kg of water per acre for each subsequent application. Stop fertilizing 30 days before harvest. Apply foliar sprays of 0.3% potassium dihydrogen phosphate and 0.5% urea 4–5 times during the growing season, focusing on the underside of leaves for better absorption.
**6. Pest and Disease Control**
Focus on integrated pest management, combining physical and biological methods. Avoid high-toxicity pesticides and follow safe intervals to ensure pesticide-free produce.
- **Late Blight**: Thrives in cool, humid conditions (15–23°C, >75% humidity). Improve ventilation and manage humidity levels. Treat with mancozeb or chlorothalonil.
- **Leaf Mold**: Occurs in high humidity and poor ventilation. Prevent by controlling moisture and use chlorothalonil or other suitable sprays.
- **Virus Diseases**: Spread through pests and human contact. Install insect nets, disinfect tools with potassium permanganate, and spray antiviral agents early.
- **Whiteflies and Aphids**: Use yellow sticky traps and silver reflective strips. Spray with imidacloprid, azadirachtin, or dichlorvos during early morning or evening.
By implementing these comprehensive management strategies, growers can significantly improve the health, yield, and quality of their greenhouse tomatoes throughout the autumn and winter seasons.
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