The hazards encountered in continuous cropping of greenhouse vegetables are as follows:
1. Continuous cropping of soils and vegetables Due to long-term application of physiological acid fertilizers, excessive application of nitrogenous fertilizers causes a large accumulation of nitrate nitrogen. At the same time, organic fertilizers are applied infrequently and the soil has poor buffering properties. As a result, the soil becomes acidified, and crops will appear dead when severe. , growth point necrosis and other phenomena.
2. Soil salinization Vegetable greenhouses have 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, it lacks rainwater. Leaching, so that the various fertilizer residues in the soil with the water poured into the plow layer accumulation, the formation of secondary salt. It was determined that when the soil salt concentration reached 0.3% to 0.5%, due to the higher concentration of plant cell solution, the crop water absorption was difficult, and withering was easy to occur. When the soil alkalinized nitrogen, available phosphorus, and available potassium, exceeded the critical concentration of salt damage At the time, greenhouse vegetables are prone to salt toxicity and affect root growth.
3. Nitric oxide and excess ammonia poisoning vegetable growers tend to place more emphasis on applying nitrogenous fertilizers in greenhouse vegetables. They think that nitrogen fertilizers are quick and easy to increase production, but neglecting the excessive nitrogen fertilizers, ammonium nitrogen is easily converted to nitrous acid dioxide. Nitrogen gasification, when the concentration of nitrogen dioxide reaches 210-6, will damage the leaves of the vegetables, causing white spots and yellow spots on the back of the leaves. At the same time, there is too much free ammonia in the plants, and diseases and pests are prone to occur and intensify.
4. Soil nutrient imbalance caused by physiological deficiency In the continuous cropping situation, continuous application of the same or similar fertilizer, and specific crops on the absorption of nutrients have a certain degree of selectivity, this will lead to excessive lack of certain elements, and some elements Too much surplus builds up, causing imbalance in soil nutrients. If too much nitrogen and phosphorus will reduce the effectiveness of calcium, boron, zinc and other nutrients, continuous use of vegetables for calcium deficiency caused by Chinese cabbage dry heart, tomato, sweet pepper rot, etc., boron deficiency caused by radish, celery stem crack Disease, the blades are thickened and become brittle, and the symptoms are cramped.
The alienation of the soil microbial population produces some biological toxic 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 after year, the number of soil pathogenic fungi increases rapidly, and the inhibition of antagonistic bacteria and actinomycetes can cause soil-borne diseases such as wilt disease, bacterial wilt and root knot nematodes. Seriously happened.
Measures to Prevent Continuous Crop Damage in Vegetable Greenhouses:
1. Application of Straw Bioreactor Technology Straw, under the action of microbial strain scavenger, etc., is directed into the carbon dioxide needed for plant growth, heat-resistant disease spores, enzymes, organic and inorganic nutrients, in the reactor planting layer, 20 cm tillage layer Soil porosity more than doubled, beneficial microbial populations increased, water, fertilizer, gas and heat were moderate, and there was a permanent effect on continuous cropping of soil in greenhouses.
2. Increase organic fertilizer organic fertilizer nutrient comprehensive, regulating the soil pH, salt, plough, buffering.
3. The use of balanced fertilization of chemical fertilizers is unreasonable, especially the excessive use of nitrogen fertilizers, is the dominant factor in continuous crop failure of vegetable greenhouses. Therefore, balanced fertilization is a key measure for greenhouse vegetable production, high yield, high quality, and high efficiency.
4. Rational rotation and utilization of different vegetable crops on the differences in nutrient requirements and pest resistance, a reasonable rotation and intercropping, mixed, interplanting, can also reduce the incidence of soil and soil-borne diseases.
5. Deep-dip disinfecting and deep-turning can increase soil tillage layer, break soil compaction, improve soil permeability, improve soil physical and chemical properties, and eliminate soil 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. Adjusting soil pH It is a common phenomenon that vegetable continuous cropping causes soil acidification. A pH value should be measured every year in the shed soil. When the pH value is 5.5, 50 to 100 kg lime can be applied per acre when plowing the soil. Mix well, this will not only increase the pH, but also kill the soil bacteria.
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