Watermelon cultivation requires careful attention to its reproductive characteristics and proper agricultural techniques. Watermelons thrive in warm, dry, and sunny conditions with optimal temperatures of 20-25°C during the seedling stage, 25°C during pollination, and 30°C during fruit development. Nighttime temperatures should not drop below 22°C. Watermelons are sensitive to frost and do not grow well in low temperatures. They also have poor root tolerance in both very dry and waterlogged conditions, and cloudy or rainy weather can negatively affect pollination. Therefore, it's best to avoid planting during cold, cloudy, or rainy seasons. The ideal soil for watermelons is loose, well-drained sandy loam with a pH between 5.0 and 7.0, and rich in organic matter.
In terms of cultivation techniques:
1. **Planting Period**: In southern China, sowing typically occurs from December to early February in spring, and July to early September in autumn. For other regions, adjust according to local climate conditions.
2. **Seed Soaking and Germination**: Soak seeds for 6–8 hours, depending on temperature. After soaking, wash the seeds thoroughly and remove any sticky residue. Dry them slightly, ensuring no sticking between seeds. Wrap them in a damp cloth and keep at a constant temperature of 28–30°C for 24–30 hours until germination.
3. **Sowing**: To ensure a high germination rate and ease of management, use seedling trays filled with nutrient-rich, loose soil. Soak the trays in water for 1–2 hours before sowing. Plant the seeds with the sprout facing down, about 0.4 cm deep, once the sprout reaches 0.2 cm.
4. **Seedling Management**: Once the seedlings emerge, carefully remove the seed coat to prevent it from restricting the cotyledons. Maintain an optimal temperature of 20–25°C. Avoid excessive humidity, improve ventilation, and increase light exposure to prevent diseases.
5. **Land Preparation**:
- Choose a flat area with good drainage and access to irrigation.
- In hot and rainy southern regions, use a deep trench system (3–4 meters wide) with plant spacing of 0.7–1.2 meters.
- Apply base fertilizer such as 50 kg of phosphate per mu and 50 kg of compound fertilizer. Use two trenches: one near the seedlings and another closer to the mature plants.
- Apply lime if the soil is acidic and borax if there’s a boron deficiency.
- Cover the field with silver-black plastic mulch to suppress weeds, retain moisture, and reduce pests.
6. **Fertilizer Management**:
- About 10 days after planting, apply a 0.3–0.5% urea solution to promote growth.
- Use a small amount of ternary compound fertilizer with irrigation to support vine growth, but avoid overuse of nitrogen to prevent leggy growth.
- During flowering, control water and apply high-phosphorus and high-potassium foliar fertilizer to encourage female flower development.
- When fruits begin to enlarge, increase phosphorus and potassium application and ensure adequate irrigation.
7. **Pruning and Fruit Thinning**:
- Prune based on variety, climate, and plant spacing. A common method is to leave one main vine and two strong side vines.
- For smaller varieties, allow fruit to develop after the second female flower, but avoid over-thinning to prevent deformation.
8. **Pest and Disease Control**:
- **Seedling Blight**: Prevent by improving ventilation and using fungicides like Ridomil or Kocide.
- **Anthracnose**: Treat with copper-based sprays when temperatures are high and rain is frequent.
- **Downy Mildew**: Apply fungicides like Rifampin or Mancozeb when humidity is high.
- **Fusarium Wilt**: Rotate crops, adjust soil pH with lime, and use copper or potassium permanganate solutions.
- **Broom Disease**: Treat affected areas with copper preparations or thiophanate-methyl.
- **Deformed Fruits**: Improve soil quality, ensure proper pollination, and provide sufficient sunlight.
**Harvesting**:
- Small watermelons are ready for harvest around 35 days after pollination, with timing adjusted based on season.
- Tap the middle of the melon; a mature one will sound hollow.
- Check the stripes and color—mature watermelons have clear, spaced stripes and bright skin.
- Look for yellow curly hairs on the stem end, which indicate ripeness.
If you have any questions or need further assistance, feel free to contact us. Happy farming!
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