1, the control of nitrogen fertilizer: nitrogen fertilizer reasonable, in addition to increase production of vegetables, but on the quality of vegetables have improved to some extent, because of this rational application of nitrogen fertilizer is one of the main measures of pollution-free vegetable production. The amount of nitrogen fertilizer should be properly controlled in the type of nitrogen fertilizer. The ratio of suitable inorganic nitrogen to organic nitrogen is 1 : 1 . Low-nitrogen nitrogen fertilizer ammonium chloride should be used in the variety to reduce the nitrate content in vegetables. Nitrogen fertilizer should be assigned on a "first-tapping, control tail" Nitrogen technology, not late growth facilities available nitrogen, 70% of short-term food as basal nitrogen. In the application method, deep application of base fertilizer, application of fertilizer, bottom application, or application of acupoints.
　　 2 , the application of phosphorus and potassium fertilizer: phosphate fertilizer, can provide phosphorus nutrients for vegetables, but also inhibit the activity of heavy metals such as cadmium, lead, zinc, arsenic, reduce toxicity and reduce harm. Potash, can reduce the accumulation of nitrate in vegetables, vegetable products to improve quality. After applying potassium fertilizer to vegetables, the content of vitamin C and sugar in the fruit is obviously increased, and the storage durability is also improved. The application of potassium fertilizer on the basis of nitrogen and phosphorus fertilizer can reduce the nitrate content of spinach by 12.9% ~ 237.2% . The salt decreased by 28.2% , and the nitrate of lettuce decreased by 12.0~217.4% . The nitrate reduction of celery increased with the increase of potassium application. The proportion of the three elements together with the nitrogen, phosphorus and potassium is generally short courses of 1: 0.2: 0.5, to 1 long vegetables: preferably 0.6: 0.5.
　　 3 , the application of organic fertilizer: organic fertilizer, can increase the soil organic matter content and soil adsorption capacity of pollutants, which can effectively curb cadmium, mirror poisoning of vegetable crops; at the same time can also reduce the nitrate content of vegetables. It is determined that the application of organic fertilizer is about 45% than that of the chemical fertilizer nitrate nitrate catalyst . For example , the organic fertilizer nitrate content of celery is 744 mg / kg, and the application of organic fertilizer is 49.7% lower than that of chemical fertilizer . Therefore, the application of organic fertilizer can reduce the pollution of vegetables and soil.
　　 4 , interplanting green manure: interplanting legume green manure such as medlar, medlar, etc., obtain more abundant nitrogen resources, improve soil organic matter content; at the same time, through microbial activities and decomposition, the traits of soil granule structure can reach sustainable soil fertility An effective way to use it.
　　 5 , balanced fertilization: according to soil fertility and vegetable yield, as well as the characteristics of different vegetables, the rational use of chemical fertilizers, the use of special fertilizers, the use of root dressing technology. For example, spraying molybdenum fertilizer can reduce the nitrate content in lettuce by 14.8%~228.1% , and the nitrate content in Chinese cabbage and spinach can be reduced by more than 50% .
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