In recent years, greenhouse vegetables have developed rapidly and have played an important role in the development of efficient agriculture. However, due to the special microclimate of the greenhouse, the conditions for ventilation and light transmission are poor, and the temperature inside the greenhouse is high and the humidity is high. If the fertilization is slightly improper, it is easy to produce fertilizer. First, the main types and causes of fertilizer damage 1, the concentration is too high direct damage: greenhouse vegetables often have high levels of fertilizer, especially chemical fertilizers or fast-acting organic fertilizer (human waste, cake fertilizer, etc.) once the amount is too high, can easily cause fertilizer damage, The performance of the crop is root water absorption difficulties, no stiff seedlings, and deformed leaves. In severe cases, the crop gradually wilts and dies. Improper fertilization methods also cause injuries, such as high-concentration compound fertilizers, application or application of leaves from the root system, causing reverse osmosis of the crops. The edges of the crop leaves are burnt like boiling water, and are scorched after a few days. 2. Ammonia Volatilization Injury: When ammonium nitrogen fertilizer or fresh organic fertilizer is applied in a greenhouse, the temperature in the greenhouse is high and it will decompose a large amount of ammonia in a short period of time and volatilize it into the greenhouse air, especially when the fertilizer is applied to the soil. In the case of failure to cover the table, the damage was particularly serious. When some sensitive vegetables such as cucumber and tomato are damaged, water stains appear, and the cells lose water and form brown spots. In severe cases, there are massive brown spots between veins. 3, nitrogen dioxide poisoning: due to the application of large amounts of nitrogen fertilizer, ammonium in the role of nitrous acid bacteria into nitrous acid, when the accumulation of nitrite gasification, the production of toxic gases, NO2 harm crops. When sensitive vegetables such as beans, cucumbers, eggplants, tomatoes, peppers, and crucifers were injured, irregular water-stained lesions first appeared on the leaves, and then expanded to the whole leaves, resulting in irregular white to yellow spots. 4. Salt accumulation accumulates poison: There are many fertilizers in greenhouse vegetables. Under the condition of uncovered soil surface, the soluble salt in soil rises with groundwater to the soil surface, causing salt accumulation in the topsoil. Due to the high salt content in the surface layer, the vegetables have physiological obstacles, such as short stature, dark green leaves, poor growth, serious dead or browning inward from the leaf margin, and even the inability to continue farming. 5. Decrease in the effectiveness of nutrients: When an excessive amount of nutrients is used, it will lead to a decrease in the effectiveness of other elements, or produce antagonistic effects, and the crops will show symptoms of nutrient deficiency. Excessive nitrogen, for example, causes calcium deficiency, causing dry heartburn in Chinese cabbage. The high concentration of salt accumulation in soil inhibits the absorption of calcium from strawberry roots, resulting in physiological calcium deficiency in strawberry. Too much potassium reduces the effectiveness of calcium, magnesium, and boron. Too much phosphorus reduces the effectiveness of calcium, zinc, and boron. 6. Surplus ammonia poisoning in plants: Due to the large amount of nitrogen applied, when there is excess nitrogen in the plant and free nitrogen appears, the crop can be poisoned. 7. Human and livestock poisoning by nitrogen and oxygen compounds: When there is a large amount of nitrous acid in the soil, it can easily cause the accumulation of toxic nitrogen and oxygen compounds such as nitrogen dioxide and nitric oxide in the plant. After humans and animals eat it, poisoning will occur. Second, prevention and control measures 1, promote balanced fertilization. Excess fertilizer is the root cause of fertilizer damage. It is necessary to start with controlling the total amount of fertilizer to reduce or avoid fertilizer damage. The amount of nitrogen and phosphorus fertilizers should be appropriately reduced, potassium should be supplemented, and boron, zinc, molybdenum and other trace elements should be used. Before the scientific means for fertilizing vegetables in greenhouses has not been perfected, it is advisable to control the amount of fertilizers at the mid-range level, instead of unilaterally pursuing high yields and blind fertilization. 2, pay attention to increase organic fertilizer. Fresh organic fertilizer can be applied only after it has been thoroughly cooked. The application of organic fertilizer can improve the soil structure, improve the buffering properties of the soil, reduce the amount of chemical fertilizers, and reduce salt damage. 3, select the appropriate fertilizer varieties. It is best to use less fertilizers. Less use of nitrogen-containing fertilizer, promote the application of low-nitrogen high-concentration compound fertilizer. 4. Master the principle of applying thin fertilizers. The amount of fertilizer should not be too much, ammonium bicarbonate is less than 25kg/mu, ammonium sulfate is less than 15kg/mu, urea is less than 10kg/mu, and superphosphate is less than 25kg/mu. 5, to promote the full depth of chemical fertilizer or ditch applied to cover the soil, you can play to protect fertilizer, reduce volatile losses, reduce the role of direct injury, do not spread fertilizer on the surface. At present, the more feasible approach is to use 70-80% of the total amount of fertilizer as a full-scale application of basal fertilizer. 6, the implementation of flood and drought rotation, the advantages and disadvantages, complementary advantages. Simple greenhouse, winter and spring vegetables, rice in summer and autumn. 7. Within one week after fertilization of greenhouse vegetables, moderate ventilation and ventilation should be taken to reduce the toxic gas concentration in the shed. 8. Other measures may be taken to reduce the accumulation of salt in vegetable bases and permanent facilities. Such as summer and autumn combination of drought irrigation or washing with salt; can also take measures to deepen the soil; cover mulch or straw is a more feasible approach to reduce evaporation of soil moisture and reduce salt damage.
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