The continuous cropping hazards in greenhouses refer to the long-term use of physiological acidic fertilizers in vegetable greenhouses, excessive nitrogen fertilizer application, large accumulation of nitrate nitrogen, low organic fertilizer application, poor soil buffering, and soil acidification, and severe crop failure. Seedlings, growth point necrosis and other phenomena.
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One, greenhouse soil continuous hazards
1. Soil salinization: Vegetable greenhouses have a high soil temperature throughout the year. Combined with high humidity, soil microbial activity is strong, accelerating the transformation of soil nutrients and the decomposition of organic matter. At the same time, due to unreasonable excessive fertilization all year round, it is also lacking. The leaching of rainwater causes the various fertilizer salts remaining in the soil to accumulate with the irrigation water to the tillage layer to form secondary salting. When the local soil salt concentration is 0.3%~0.5%, the crop water absorption is difficult because of higher concentration than that of the plant cell solution, and withering is easy to occur; when the soil alkalinizing nitrogen, available phosphorus, available potassium, etc. exceed the critical concentration of salt damage At the time, greenhouse vegetables are prone to salt toxicity and affect root growth.
2. Nitric oxide and ammonia excess poisoning: vegetable farmers in greenhouse fertilizers are often placed on the application of nitrogen fertilizer, nitrogen fertilizer that quick, easy to increase production, but ignored the case of excessive nitrogen fertilizer, ammonium nitrogen easily converted to nitrite dioxide Nitrogen, when nitrogen dioxide reaches a certain concentration, will poison the leaves of vegetables, and the appearance of white spots and yellow spots on the back of the leaves, and at the same time there is too much free ammonia in the plants, and pests and diseases are prone to occur and intensify.
3. Soil nutrient imbalance: Under continuous cropping, the same or similar fertilizers are continuously applied in large quantities, and specific crops have a certain selectivity for the absorption of nutrients, which will lead to an overabsence of certain elements, and some elements will form too much accumulation. , causing imbalance in soil nutrients. Many chemical fertilizers and organic fertilizers affect the natural quality of vegetables. Excessive nitrogenous fertilizers and lack of potash fertilizers will reduce the nitrogen fertilizer utilization rate and increase fertilizer damage. A large number of elemental fertilizers will often reduce the effectiveness of medium and trace element fertilizers such as nitrogen. Too much phosphorus will reduce the effectiveness of calcium, boron, zinc and other nutrients. Continuous cropping of vegetables is prone to calcium deficiency caused by Chinese cabbage dry heart, tomato, sweet pepper umbilical rot, etc., boron deficiency causes radish, celery stem crack disease and the leaves twist thickening, brittle and other symptoms.
4. Alienation of soil microbial population: The alienation of soil microbial population in greenhouses will produce some biological toxic substances. The same crop root exudates are the same, resulting in a large number of soil microbial reproduction, some soil microorganisms are inhibited, so that the microbial population will be alienated, which is not conducive to the maturity of the soil and decomposition of fertilizer nutrition, resulting in deterioration of soil properties. In addition, the continuous change of the microbial population in the soil can cause the disease to accumulate year by year, the number of soil pathogenic fungi increases rapidly, and the inhibition of antagonistic bacteria and actinomycetes can cause serious diseases such as wilt disease and bacterial wilt.
Second, prevention and control measures
1. Application of straw bioreactor technology: straw is transformed into carbon dioxide required for plant growth under the action of microbial strain scavenger, heat-resistant disease spores, enzymes, organic and inorganic nutrients, in the reactor planting layer, 20 cm farming Layer soil porosity increased by more than 1 time, beneficial microbial population increased, water, fertilizer, gas, and heat were moderate, and there was a permanent cure for continuous cropping of soil in greenhouses.
2. Increase the application of organic fertilizer: organic fertilizer has a full range of nutrients, which can regulate the pH, salt, plough, and buffering properties of the soil.
3. Balanced fertilization: The unreasonable application of chemical fertilizers, especially the excessive use of nitrogen fertilizers, is the dominant factor in soil hazards in continuous cropping greenhouses. Therefore, balanced fertilization is a key measure for the high yield, quality, and efficiency of greenhouse vegetables.
4. Rational rotation and dumping: The use of different vegetable crops for differences in nutrient requirements and pest resistance, and reasonable rotation and intercropping, mixed cropping and nesting, can also reduce the incidence of disease.
5. Deep-disinfection: Deep-turning can increase soil tillage layer, break soil compaction, improve soil permeability, improve soil physical and chemical properties, and eliminate continuous soil hazards. Combining deep-displacement soil preparation with cotton granules for chemical disinfection can also effectively reduce the risk of continuous cropping.