Plastic greenhouses to cultivate vegetables, often due to improper fertilization methods, neglect of ventilation, so that excessive toxic gas inside the shed, endanger the vegetables, but often misdiagnosed as a disease, resulting in deficit or even no income.
First, the harm
1. Nitrogen: Due to the application of excessive amounts of urea, ammonium sulfate and other available fertilizers, or improper fertilization methods, such as the application of organic fertilizer without decomposition, ammonia gas decomposition in the greenhouse under high temperature conditions, it will damage the vegetables, so that the edge of the tissue Water spotted spots appeared, and the whole leaf wilted and died when severe. Often misdiagnosed as frost or other diseases, cucumbers, tomatoes, zucchini, etc. are sensitive to ammonia.
2. Nitrous gas: The excessive application of ammonium nitrogen fertilizer once will reduce the effect of certain bacteria and cause local acidity of the soil. When the pH is less than 5, it will produce nitrous acid gas, which can cause white spots on the leaves of vegetables. In severe cases, the whole leaf turns to white withers and is often misdiagnosed as powdery mildew. Vegetables sensitive to nitrous acid are eggplant, cucumber and zucchini. Celery, pepper and so on.
3. Ethylene and chlorine: If the quality of the agricultural film or plastic film is poor, or there is residual plastic film in the ground, and it is exposed to sunlight, the harmful gases such as ethylene and chlorine gas will be easily generated in the greenhouse under high temperature conditions. When the concentration reaches a certain level, yellowing between the leaf edges or veins of the vegetables can occur, which in turn turns white. In severe cases, the entire plant withers. Often misdiagnosed as bacterial keratoses, the damage to cucumber is particularly severe.
Second, prevention
1. Reasonable fertilization. The organic fertilizer applied in the greenhouse must be decomposed by fermentation, and the chemical fertilizer should be of high quality. Urea should be mixed with phosphorus and calcium. Basal fertilizer should be applied 20 centimeters deep, and the depth of topdressing chemical fertilizer should reach about 12 centimeters.
2. Ventilation. In sunny and warm weather, ventilation should be performed in conjunction with adjusting the temperature, and ventilation and air exchange should be performed in rain and snow.
3. Use safe and non-toxic agricultural film and plastic film to timely remove waste plastics and residues from the shed.
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