How Can Greenhouse Cultivation Prevent the Harm of Toxic Gases?
Plastic greenhouses are widely used for growing vegetables, but improper fertilization and lack of proper ventilation often lead to the accumulation of toxic gases inside. These harmful substances can damage crops and are frequently mistaken for diseases, resulting in reduced yields or even total losses.
1. Hazards Caused by Excess Nitrogen:
Excessive use of urea or other soluble fertilizers, as well as improper application methods—such as applying un-decomposed organic fertilizer—can release greenhouse gases under high temperatures. This can cause water-soaked spots on the leaf edges and severe wilting. These symptoms are often misdiagnosed as frost damage or other plant diseases. Cucumbers, tomatoes, and zucchini are especially sensitive to ammonia.
2. Nitrous Acid Gas:
Overuse of ammonium nitrogen fertilizers can reduce the activity of certain bacteria in the soil, leading to partial acidification. When the pH drops below 5, nitrous acid gas may form. This causes white spots on leaves, which can eventually turn completely white and die. It is often mistaken for powdery mildew. Vegetables such as eggplants, cucumbers, zucchini, celery, and peppers are particularly vulnerable.
3. Ethylene and Chlorine Gases:
If low-quality agricultural films or plastic sheets are used, or if leftover plastic remains in the soil, exposure to sunlight and high temperatures can cause the release of volatile gases like ethylene and chlorine. At high concentrations, these gases can cause yellowing between leaf veins or edges, turning them white and causing the entire plant to wither. This is often mistaken for bacterial infections, and cucumbers are especially affected.
4. Carbon Monoxide from Heating:
During winter heating, if fuel is not fully burned, toxic gases like carbon monoxide can be released. Poor ventilation can lead to excessive carbon dioxide buildup, which negatively affects crop growth and development.
2. Prevention Measures:
1. Proper Fertilization: All organic fertilizers used in greenhouses must be fully composted. The most effective method is to use fermented fertilizers. Chemical fertilizers should be of high quality, and urea should be mixed with superphosphate. Apply basal fertilizer at least 20 cm deep, and top-dress chemical fertilizers at a depth of about 12 cm.
2. Good Ventilation: On sunny days, ventilate to regulate temperature. In rainy or snowy weather, ensure proper air exchange to prevent gas buildup.
3. Use Safe Agricultural Films: Choose non-toxic and safe plastic films, and remove any residual plastics or waste from the greenhouse regularly.
4. Enhance Plant Resistance: Throughout the growing season, you can use plant growth regulators to improve disease resistance, increase yield, and improve product quality.
By implementing these strategies, greenhouse farmers can significantly reduce the risk of toxic gas damage, ensuring healthier crops and better economic returns.
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