In fact, excessive application of nitrogen fertilizer in vegetables poses a serious threat to people's health. The nitrate content of vegetables with excessive nitrogen application is 20-40 times that of normal conditions. Nitrate is converted into nitrite during transport or storage in the human body or in vegetables. Nitrite combines with various amines in the human body to form a strong carcinogen, nitrite.
Excessive application of nitrogen fertilizer also causes serious pollution to soil and water. Long-term application of large amounts of nitrogen fertilizer, especially ammonium sulfate, chlorination, etc., will gradually acidify the soil. The toxic substances such as sulfate, chloride and biuret remaining in the soil gradually reduce the microorganisms and cockroaches in the soil. The acidification of the soil also accelerates the leaching of nutrients in the soil, eventually causing the soil to be compacted and losing the value of cultivation.
Vegetables should pay attention to the application of nitrogen fertilizer. When applying nitrogen fertilizer, it is necessary to measure the amount to prevent excessive. Non-polluted cultivated vegetables should be banned from nitrate-nitrogen fertilizer and compound fertilizer produced from nitrate-nitrogen fertilizer. Adopt scientific fertilization method: the base fertilizer is mainly composed of decomposed organic fertilizer, and combined with phosphorus and potassium fertilizer. Topdressing should be based on the amount of fertilizer needed in different growth stages of vegetables. Note that the base fertilizer should be applied layer by layer, deep application or ditch application. Foliar spray or combination with watering and top dressing. Vigorously promote organic fertilizer and reduce the amount of nitrogen fertilizer. It is necessary to use more fully-fertilized high-quality livestock and poultry manure and other manure, and rational use of human excrement. Manure must be treated by accumulation, full fermentation, etc., and can be fermented by biogas at high temperature. Human excrement should be stored in a septic tank for fermentation, and add 3-5% superphosphate and gypsum powder to reduce the volatilization and loss of ammonia.
Screws are threaded fasteners that create permanent or temporary assemblies. They are inserted and removed by turning in one direction or another. Wood screws, floor screws, and sheet metal screws have flat heads that sit flush when holding material together. Machine screws fasten metal to metal and are inserted into a prethreaded hole or mated with a nut. Thread-cutting screws are self-tapping screws that cut away and remove the surrounding material to create a tapped hole. Deck screws resist rust and corrosion to hold outdoor decking materials together. Drywall screws have fine tips, coarse threads, and tapered bugle heads to penetrate drywall and grip wood without damaging material. Hex-head bolts, cap screws, and lag screws are driven with wrenches rather than screwdrivers or drill bits. Captive panel screws and thumb screws can be tightened and loosened without tools on parts that are frequently removed such as access panels. Screw caps can help to cover screw heads for both safety and aesthetic purp
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