In recent years, the development of greenhouse vegetable cultivation has accelerated rapidly, playing a vital role in promoting efficient agriculture. However, due to the high temperature and humidity inside greenhouses, ventilation and light transmission are often inadequate. Improper fertilizer application can lead to various issues, including fertilizer burn, which negatively affects plant growth and yield.
**Causes of Fertilizer Damage**
1. **Excessive Fertilizer Application**: Greenhouse vegetables are often over-fertilized, especially with quick-acting organic fertilizers like manure or cake fertilizer. When applied in excess, these can cause direct damage to plants. Symptoms include root difficulty in absorbing water, stunted seedlings, deformed leaves, and eventual wilting or even death of the plants.
2. **Improper Fertilization Techniques**: Applying fertilizer too close to the root zone or using large amounts of organic manure as base fertilizer can cause reverse osmosis in crops. This leads to leaf edges being burned, resembling scalding from boiling water, and eventually turning brown.
3. **Toxic Gas Injury**: Ammonium nitrogen fertilizers or fresh organic materials can release large amounts of ammonia in high-temperature greenhouses, especially if not properly covered. Sensitive crops like cucumbers and tomatoes may show water-soaked spots on their leaves, followed by brown lesions. In severe cases, extensive browning between the veins can occur.
4. **Salt Accumulation**: Excessive fertilizer use causes soluble salts to rise to the soil surface, leading to salt buildup. This can cause physiological problems such as short plants, dark green leaves, poor growth, and leaf margins curling or drying out.
5. **Nutrient Imbalance**: Over-application of one nutrient can interfere with the absorption of others. For example, excessive phosphorus reduces zinc availability, while too much potassium can limit calcium, magnesium, and boron uptake, resulting in deficiency symptoms.
**Prevention and Control Measures**
1. **Use Organic Fertilizers**: Adding organic matter improves soil structure and enhances its buffering capacity. It also helps reduce chemical fertilizer use and prevents salt damage. Fresh organic fertilizers should be fully composted before application.
2. **Implement Balanced Fertilization**: Overuse of fertilizers is the main cause of damage. It's essential to control the quantity, reduce nitrogen and phosphate inputs, increase potassium, and supplement trace elements like boron, zinc, and molybdenum instead of blindly pursuing high yields.
3. **Choose Suitable Fertilizers**: Use low-chlorine and low-nitrogen compound fertilizers where possible. Avoid excessive use of chlorine-containing fertilizers to prevent additional stress on plants.
4. **Apply Fertilizers in Small Amounts**: Deep application of fertilizers into the soil layer can protect them from volatilization and reduce direct injury. Avoid spreading fertilizers on the soil surface. It’s recommended to apply 70–80% of total fertilizer as base fertilizer, and top-dress in small, controlled amounts.
5. **Ensure Proper Ventilation**: During midday when temperatures are high, open vents to allow air circulation. After fertilizing, proper ventilation is crucial to reduce toxic gas buildup and minimize damage.
6. **Desalinate During Downtime**: During periods when the greenhouse is not in use, take measures to reduce salt accumulation. For instance, during summer, irrigation can help flush salts deeper into the soil, reducing surface salinity and its harmful effects.
By following these practices, farmers can effectively manage fertilizer-related issues and ensure healthier, more productive greenhouse vegetable cultivation.
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