In early spring, the use of plastic greenhouses for growing bitter gourd can advance planting by more than 20 days compared to open-field cultivation. This method not only brings high economic returns but also provides significant social benefits. The semi-intensive cultivation techniques are outlined below:
1. **Soil Preparation**
The greenhouse was constructed in mid-January, followed by deep tilling of the soil. A mix of 6 parts fresh garden soil and 4 parts well-decomposed organic fertilizer was used. Additionally, 0.1-0.2% superphosphate and 0.3% wood ash were added and thoroughly mixed. To prevent soil-borne diseases, 200-300 ml of formalin was diluted 100 times per 1000 kg of soil, mixed well, covered with a plastic sheet for 2-3 days, and left open for 5-7 days before use. Alternatively, 8 grams each of 70% pentachloronitrobenzene powder and 65% zineb were mixed into 15 kg of culture soil for sowing and covering.
2. **Container Seedling Production**
Bitter gourd seedlings are best grown in containers. The containers are placed flat on the seedbed, filled with prepared soil, and the top is leveled while filling gaps. For germination, select strong, heat-resistant seeds. Soak them in warm water (around 55°C) for over 12 hours, then rinse and carefully crack the seed coat using a damp cloth. Wrap the seeds in a cloth and place them at about 30°C to germinate. Sow when the sprouts are about 3 mm long, typically 5-6 days before planting. Sow 250-300 g per 100 m², placing 1-2 seeds per container. After sowing, cover with 1 cm of sifted soil and close the bed with mulch and the greenhouse. Remove the mulch once the seedlings start to emerge.
3. **Seedling Care**
Maintain daytime temperatures around 25°C and nighttime temperatures between 19-20°C until emergence. After seedlings appear, lower the temperature to 23-25°C during the day and 15-18°C at night. Ensure proper ventilation, especially on cloudy or rainy days, and increase it during sunny afternoons. Seedlings should be transplanted one week before transplanting, when they have one leaf and one heart.
Water management should keep the soil loose and moist, while reducing humidity. Water sufficiently before planting, and apply seedling water after emergence. Dry soil should be sprinkled over the leaves after drying. Avoid frequent watering unless necessary. Top-dressing with 0.2% potassium dihydrogen phosphate and 0.3% urea solution can be applied 1-2 times before transplanting.
Use new mulch and cover with straw to enhance light exposure. During the seedling stage, spray 75% chlorothalonil (600x) or 50% carbendazim (500x) to control damping-off disease.
4. **Transplanting**
By mid-March, when seedlings are 25-30 days old with 3-4 leaves, they can be transplanted. Choose fertile loamy fields with deep soil, rich in organic matter, and well-drained. In autumn, till deeply and add 3000-4000 kg of decomposed manure, 50 kg of superphosphate, and 100 kg of wood ash. After fertilizing, perform shallow plowing and hoeing. Plant in clear, windless conditions, ensuring cotyledons are above ground. Cover the planting hole with fine soil and water immediately.
5. **Field Management**
After transplanting, gradually reduce greenhouse temperatures. Maintain 20-30°C during the day and 15°C at night. If temperatures drop, reinforce insulation; if too high, ventilate. Ventilate when temperatures exceed 30°C. Gradually remove the "skirt film" to balance internal temperatures, aiming for around 25°C. After 30 days, expose plants to outdoor conditions, removing the skirt during the day and replacing it at night. By summer, remove all plastic films except the roof if needed.
Topdressing: Combine decomposed human and animal urine (10%) with watering to strengthen seedlings. Apply 0.3-0.5% quick-acting liquid fertilizer to promote vine growth. When the first female flowers appear, apply 20% decomposed manure to support fruit development. During flowering, spray 0.5% rare-earth micro-fertilizer on the upper and lower leaf surfaces. After harvesting the first batch, apply 25 kg of peanut bran and 20 kg of compound fertilizer per mu. After 2-3 harvests, spray 0.5% vegetable hormone every 10 days. Continue applying 30% decomposed manure every 7-10 days. At the end of the season, apply 20-25 kg of calcium phosphate and 10 kg of potassium chloride per ditch. Spray 0.2% urea and 0.3% potassium dihydrogen phosphate in the evening to promote late flowering.
Watering: Water roots after transplanting, then control moisture to reduce greenhouse humidity. Water every 2-3 days from flowering to harvest, keeping the soil moist. Drainage is crucial in spring and summer, with increased irrigation during fruiting, especially before and after autumn. Irrigate in the early morning or late afternoon, using ditch irrigation.
Cultivation and weeding: Loosen the soil early and remove weeds later. First cultivation occurs 4-5 days after root water, loosening the top 7-10 cm. Second cultivation two weeks later, 3-5 cm deep. Remove weeds during each session. Mulching eliminates this task.
Vine training: Guide vines after 9 AM, tying every 30 cm, and then every 4-5 knots. Ensure growth points face the same direction. Prune side vines 5-7 days after tying, removing 1-2 at the base. Select one main vine and one side vine for flowering. Once vines reach the trellis, prune lower yellow leaves.
6. **Disease and Pest Control**
Common diseases include anthracnose, controlled with 50% thiophanate (800x) or 75% chlorothalonil (600x). For wilt disease, use 50% carbendazim (500x) or 36% thiophanate-methyl (400x). For infected plants, apply 5% Jinggangmycin (1000-1600x) or 90% Diocesone (500x), 400-500g per plant. For powdery mildew, spray 15% triadimefon (1500x) or 30% Teflon (1500-2000x). Stop chemical use 15 days before harvest.
7. **Harvesting**
Bitter gourd fruits develop slowly under low temperatures. Harvest as soon as fruits are full, shiny, and the color fades. Early harvest ensures better quality and marketability.
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