Before a rainstorm, proper vegetable management is essential to protect crops and ensure efficient drainage. First, it's important to thoroughly clean and maintain the drainage channels. The main ditch should be at least 80 cm deep, secondary ditches over 50 cm, the back ditch more than 30 cm, and the small ditches around 20 cm. The slope from high to low must be designed so that rainwater can drain quickly. In regions like southern China, where spring rains are common, each planting block should have deep trenches—more than 20 cm in depth, narrow (less than 90 cm wide), and with tall sorghum planted for better water flow. For large fields longer than 50 meters, a central waist ditch should be created, along with a 50 cm deep and 40 cm wide trench around the perimeter.
In addition, the greenhouse structure needs to be inspected and reinforced before the storm. Wind often accompanies heavy rain, so check the plastic film on the shed for damage and repair any holes. Ensure the binding lines are secure to prevent the film from being torn by strong winds. It’s also important to properly cover the mulch film. Seal the edges with fine soil to prevent wind from lifting it or tearing through the planting holes. The sides of the beds should also be sealed with mud. Before covering, shape the surface into a slight mound and flatten it slightly to ensure the film fits tightly, reducing the risk of wind damage.
Pre-rain prevention measures should also be taken. High humidity and temperature after rain can lead to disease outbreaks. Apply a preventive spray of streptomycin sulfate, thiophanate-methyl, or chlorpyrifos zinc (Kreis) to reduce the risk of infection.
After the rain, immediate action is needed. Check the field for blocked ditches and clear them promptly to allow water to drain. Soil compaction often occurs after heavy rain, so loosen the soil to improve aeration and root health. If plants have been washed out or their roots exposed, they should be repositioned and replanted as needed. Once the plants start growing again, apply diluted human waste water or urea to help them recover.
Pest and disease control should also be addressed. Use insecticides such as phoxim, trichlorfon, or chlorpyrifos to manage pests, and fungicides like procymidone, oxalin, chlorpyrifos, streptomycin, or neomycin to control diseases like gray mold and scab.
Finally, manage the greenhouse environment carefully. After heavy rain, high humidity can create favorable conditions for diseases. Adjust the opening and closing of the greenhouse based on temperature—ideally 28°C in the morning and 25°C after planting. Open vents and doors in the morning and close them in the afternoon to maintain optimal conditions for plant growth.
Proper preparation and post-rain care are crucial for maintaining healthy crops and minimizing losses due to weather-related issues.
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