With the improvement of people's living standards, people's health awareness and environmental awareness have been further enhanced. Unpolluted vegetables have become an urgent need for people. Non-environmental pollution vegetables refer to vegetables whose residual levels of harmful substances in vegetable products meet the national health and safety standards. First, pesticide residues do not exceed the standard. Non-polluted vegetables do not contain banned high-toxicity, high-residue pesticides. Other pesticide residues do not exceed the national maximum. Permissible limit; Second, the nitrate and nitrite content does not exceed the standard; Third, the "three wastes", heavy metals and pathogenic microorganisms pollution does not exceed the standard. Among them, the problem of heavy metal, nitrate and nitrite content is closely related to the rational use of fertilizers. There are many factors that restrict the production of pollution-free vegetables, and how to correctly select and apply fertilizers is one of the key measures for the production of pollution-free vegetables. First, the choice of fertilizers should be selected to use fertilizer types and types that do not have adverse effects on the environment and vegetable nutrition and quality. The types and types of fertilizers that can be applied in the production of pollution-free vegetables include the following: (1) Organic fertilizers include farmyard fertilizers and commodity organic fertilizers. Farmhouse fertilizers also include compost, mud, cake, manure, biogas, green manure, and crops. Straw and so on. The compost should meet the ny/t394-2000 "Hygienic standards for high-temperature composting." Commodity organic fertilizers shall comply with ny/t5018 "Standard for Permissible Contaminant Content in Organic Fertilizers". (b) Microbial fertilizers include humic acid fertilizers, rhizobia fertilizers, potassium bacterial fertilizers, phosphorus bacterial fertilizers, and composite microbial fertilizers. The number of viable microbial organisms must meet the requirements of 4.1 in the “Microbial Fertilizer” ny227, and the hygienic indicators must meet the requirements of 4.2, “Innocuity of finished products” in ny227. (3) Inorganic mineral fertilizers include inorganic nitrogen fertilizers, mineral potassium fertilizers, and mineral phosphate fertilizers. Inorganic nitrogen fertilizer should be applied with ammonium nitrogen fertilizer or urea. Phosphorus and potassium fertilizers should meet ny/t394-2000 health standards. Phosphate fertilizer should promote the use of calcined phosphate. The impurity control index is: 1% phosphorus pentoxide, as≤0.004. %, cd ≤ 0.01%, pb ≤ 0.002%; potassium fertilizer promotes the use of potassium sulphate, impurity control indicators are: each containing 1% kalium oxide, as ≤ 0.004%, cl ≤ 3%, sulfuric acid ≤ 0.5%. (4) Fertilizers prepared from trace elements such as calcium, magnesium, copper, iron, boron, zinc, molybdenum, manganese, etc. in small and medium-sized non-elementary fertilizers. Second, the rational use of fertilizer (a) increase the application of high-quality organic fertilizer a large number of organic fertilizer is the basic principle of fertilizer production of pollution-free vegetables. In order to ensure the high quality and high yield of vegetables and reduce pollution, it is necessary to abandon the fertilization method of reusing fertilizer light organic fertilizer. Increase the use of organic fertilizers, reduce the amount of chemical fertilizers, and produce high-quality vegetables with low nitrate content under the premise of achieving high yields. Organic fertilizers have strong enzyme activity, can increase beneficial microbial communities, and provide energy and nutrition for microbial activity. The application of organic fertilizers can induce crop resistance to diseases and can also directly inhibit the activity of harmful bacteria. Practice has proved that the application of organic fertilizer is the most effective method for difficult-to-control soil-borne diseases caused by continuous cropping obstacles for many years of vegetables, especially in protected areas. To apply completely decomposed organic fertilizer. (2) Balanced fertilization If no organic pollutants are used in the production of pollution-free vegetables, it is difficult to meet the needs of the crops in terms of comprehensive and sufficient nutrients, and it is difficult to achieve continuous high-quality and high-yield production. Therefore, we must promote the use of balanced fertilization, which is dominated by controlled nitrogen, in production so that nitrogen, phosphorus, potassium and calcium, magnesium, and various trace nutrient-free fertilizers can be properly matched to maintain a proper ratio between nutrients and nutrients. Full price nutrition to avoid excessive accumulation of nitrates in vegetable products. Fertilizers must be used in conjunction with inorganic fertilizers. The ratio of organic nitrogen to inorganic nitrogen is not less than 1:1. (3) Promoting biological fertilizers and applying organic, inorganic, and biological fertilizers in conjunction with application of biological fertilizers have the effect of increasing the utilization rate of fertilizers, reducing the nitrate and nitrite content in vegetable crops, inhibiting the occurrence of soil-borne diseases and enhancing disease resistance. At the same time, there are still many problems with biological fertilizers. Except for a small amount of microorganisms such as nitrogen-fixing bacteria, the vast majority of microorganisms can not bring people exogenous nutrients into the soil. For example, phosphorus-solubilizing bacteria and potassium-solubilizing bacteria can only absorb and transform the soil itself to a very limited extent. Phosphorus and potassium. Therefore, only the combined application of organic, inorganic and biological fertilizers can give full play to the efficacy of biological fertilizers. In soils with high soil fertility, the application amount of biological fertilizers can be appropriately increased, and the application amount of inorganic fertilizers, especially chemical nitrogen fertilizers, can be reduced. (D) Adopt scientific fertilization methods Organic fertilizers must be detoxified before application (if fully decomposed at high temperatures), and phosphate fertilizers can be blended with organic fertilizers for more than 20 days prior to application. When using chemical fertilizers as base fertilizers, apply full-thickness deep treatments, and do small quantities several times when doing top dressings. Fertilizers should be applied deeply and early, and deep application can reduce nitrogen volatilization, extend fertilizer supply time, and increase utilization rate. Early application will help plants to grow quickly and prolong, extend fertilizer efficiency, and reduce nitrate accumulation. The general ammonium nitrogen fertilizer is applied to the soil layer below 6cm, and urea is applied to the soil layer below 10cm. When deep nitrogen fertilizer is applied, nitrogenous fertilizer inhibitors must be used in combination. The application of nitrogen fertilizers should follow the principle of “pre-light weight and light weight”, and do the interval between the safe and reasonable use of nitrogen fertilizer. Potash fertilizer should be changed to one-time basic application as the basis for topdressing and paying attention to topdressing phosphorus and potassium fertilizers during the picking period.