Soil acid damage
In continuous cropping vegetable greenhouses, due to the long-term use of physiological acid fertilizers, excessive application of nitrogenous fertilizers causes a large accumulation of nitrate nitrogen, less organic fertilizers, and poor soil buffering, which results in acidification of the soil. Severe crops may show dead seedlings, growth point necrosis, etc. phenomenon.
2. Soil salinization
The greenhouse soil in vegetable greenhouses has a high soil temperature throughout the year. In combination with high humidity, soil microbial activity is strong, accelerating the conversion of soil nutrients and the decomposition of organic matter. At the same time, due to unreasonable excessive fertilization all year round and lack of rainwater leaching, residual Various fertilizer salts in the soil accumulate with the irrigation water to the tillage layer to form secondary salt. According to the determination, when the soil salt concentration reaches 0.3~0.5%, the crop water absorption is difficult because of the higher concentration of the solution in the plant cells, and withering is more likely to occur. When the soil alkalinizing nitrogen, available phosphorus, and available potassium exceed the critical concentration of salt damage , Vegetables in greenhouses are prone to salt toxicity and affect root growth.
3. Nitric oxide and ammonia excess poisoning
Vegetable growers tend to focus on applying nitrogenous fertilizers in greenhouse vegetables. They think that nitrogen fertilizers are quick and easy to increase production. However, neglecting the excessive nitrogen fertilizers, ammonium nitrogen is easily converted into nitrous acid NO2-gasification when the concentration of NO2- reaches 210. -6 o'clock, it will poison the leaves of vegetables, the back of the leaves produce white spots and yellow spots and other fertilizer harm, while the plant free ammonia is too much, pests and diseases are prone to occur and intensify.
4. Soil nutrient imbalance causes physiological deficiency
Under continuous cropping, the same or similar fertilizers are continuously applied in large quantities, and certain crops have a certain selectivity for the absorption of nutrients. This will lead to the overabsence of certain elements, and excessive accumulation of some elements, resulting in the loss of soil nutrients. balanced. (1) There are many chemical fertilizers and less organic fertilizer, which affects the natural quality of vegetables. (2) Too much nitrogen fertilizer and lack of potassium fertilizer will reduce the nitrogen fertilizer utilization rate and increase fertilizer damage. (3) Numerous elements and more fertilizers tend to reduce the effectiveness of medium and trace element fertilizers. For example, excessive nitrogen and phosphorus will reduce the effectiveness of calcium, boron, zinc, and other nutrients. Continuous use as a vegetable is prone to calcium deficiency caused by Chinese cabbage dry heartburn. , Tomatoes, sweet pepper umbilical rot, etc., boron deficiency caused radish, celery stem crack disease, leaves thickened and fragile and other symptoms.
5. Alienation of soil microbial populations, resulting in some biotoxic substances
The same crop root exudates are the same, resulting in the proliferation of some soil microorganisms, and some soil microorganisms are inhibited, so that the microbial population will be alienated, which is not conducive to the maturity of soil and decomposition of fertilizer nutrition, resulting in deterioration of soil properties. In addition, the continuous change of microbial populations in the soil can cause the accumulation of diseased bodies year by year. The number of soil pathogenic fungi increases rapidly, and antagonistic bacteria and actinomycetes are inhibited, causing blight, bacterial wilt and root-knot nematodes and other soil-borne diseases. Seriously happened.
Measures for Preventing Continuous Crop Damage in Vegetable Greenhouses
1. Application of straw bioreactor technology
Straws are transformed into carbon dioxide required for plant growth under the action of microbial strain scavenger, heat-resistant disease spores, enzymes, organic and inorganic nutrients, soil porosity in 20 cm plowing layer is more than doubled in the reactor planting layer. The increase of beneficial microbial populations, moderate water, fertilizer, gas, and heat have a permanent effect on continuous cropping of soil in greenhouses.
2. Increase organic fertilizer
The organic fertilizer has a comprehensive nutrient content and regulates pH, salinity, ploughability, and buffering properties of the soil. (1) It is advisable to apply 30 m3/mu of high-quality farmyard fertilizer every quarter in greenhouse vegetable land. (2) The use of straw to cover the field, return fertilizer to the field technology, can play a role in improving the soil, moisturizing, and protecting the earthworms. (3) Apply 150~200kg/mu of commercial bio-organic compound fertilizer containing more than 30% organic matter. Because of its reasonable ratio of nutrition and nutrition, it also contains more organic components, which can meet the nutrient demand for vegetable growth. Then topdressing nitrogen and potassium can be fertilized.
3. Balanced fertilization
The unreasonable application of chemical fertilizers, especially the excessive use of nitrogen fertilizers, is the dominant factor in the continuous development of soil barriers in vegetable greenhouses. Therefore, balanced fertilization is a key measure for greenhouse vegetable production, high yield, high quality, and high efficiency. (1) Reasonable application of nitrogen, phosphorus and potassium, the general principle is to control nitrogen, stabilize phosphorus and increase potassium. In general, root and tuber vegetables are dominated by phosphorus and potassium fertilizers, with nitrogenous fertilizer; leafy vegetables are dominated by nitrogen fertilizers, suitable for phosphorus and potash fertilizers; fruits and vegetables are dominated by nitrogen and potassium fertilizers, with phosphate fertilizers. Application of nitrogen fertilizer, potassium fertilizer 50% as base fertilizer, phosphate fertilizer 100% as base fertilizer. The basal fertilizer should be fully mixed with the soil and the top dressing should be combined with irrigation for flushing. (2) The high-efficiency instant microelement fertilizer and biofertilizer can be applied in an appropriate amount to prevent the occurrence of a deficiency syndrome. (3) According to the law of nutrient demand at different stages of crop growth, the corresponding irrigation and fertilization should be combined with irrigation.
4. Reasonable rotation
The use of different vegetable crops for differences in nutrient requirements and resistance to diseases and pests, and reasonable rotations, intercropping, and intercropping can also reduce the occurrence of soil and soil-borne diseases.
5. Deep-disinfection
Deep plowing can increase soil tillage layer, break soil compaction, improve soil permeability, improve soil physical and chemical properties, and eliminate continuous cropping obstacles. Combining deep-displacement soil preparation with cotton granules for chemical disinfection can also effectively reduce the occurrence of continuous cropping obstacles.
6. Adjust soil pH
Soil acidification caused by continuous cropping of vegetables is a common phenomenon. Every year, the soil in the shed is subject to a PH value test. When PH≤5.50, 50~100 kg of lime can be applied per acre when it is turned to the ground to fully mix with the soil. Can increase the PH value, but also have a killing effect on the soil bacteria.
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