Pollution-free cultivation has become a trend how to control nitrogen by fertilizing vegetables

At present, pollution-free cultivation is the trend of the times. The use of low-toxic pesticides in vegetables has become a consensus, but vegetable farmers seldom associate fertilization with the hygienic quality of vegetables.

In fact, excessive application of nitrogen fertilizer to vegetables has posed a serious threat to people's health. The content of nitrate in vegetables with excessive nitrogen fertilizer is 20-40 times higher than that in normal condition. Nitrate will be transformed into nitrite in the human body or in the process of transportation, storage and processing of vegetables. Nitrite combines with all kinds of amines in human body to form strong carcinogen-nitrite amine.

Excessive application of nitrogen fertilizer also causes serious pollution to soil and water. Long-term application of a large amount of nitrogen fertilizer, especially ammonium sulfate and chlorination, will gradually acidify the soil. Toxic substances such as sulfate, chloride ion and biuret in urea will gradually reduce the number of microorganisms and earthworms in the soil. Soil acidification also accelerates the leaching of nutrient elements in the soil, resulting in soil consolidation and loss of farming value.

Vegetables should pay attention to the controlled application of nitrogen fertilizer. When applying nitrogen fertilizer, it should be measured as input to prevent excess. Nitrate nitrogen fertilizer and compound fertilizer produced with nitrate nitrogen fertilizer as raw materials should be prohibited in pollution-free vegetables. The scientific fertilization method is adopted: the base fertilizer is mainly rotten organic fertilizer, combined with the application of phosphorus and potassium fertilizer. Topdressing should be divided into several times according to the timely fertilizer requirements of vegetables at different growth stages. Pay attention to the layered application of base fertilizer, deep application or ditch application. Foliar spraying or combined with watering and topdressing. Vigorously promote organic fertilizer and reduce the amount of nitrogen fertilizer. It is necessary to use more barnyard manure such as fully mature high-quality livestock and poultry manure, and rational use of human feces and urine. Barnyard manure must be treated by accumulation and full fermentation, which can be accumulated at high temperature or fermented with biogas. Human feces and urine should be stored and fermented in septic tanks, and 3-5% calcium superphosphate and gypsum powder should be added to reduce ammonia volatilization and loss.