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Strictly control the time of topdressing nitrogen fertilizer.
Strictly control the time of topdressing nitrogen fertilizer. The nitrate content of vegetable crops is constantly changing. The nitrogen that enters the vegetable body is further transformed into protein during the metabolic process. According to research, with the passage of time of nitrogen fertilizer topdressing, the nitrate content in vegetables tends to gradually decrease. After 18 days of topdressing, the nitrate content in vegetables has met the recommended standards for green food. Therefore, the top dressing time for green vegetables should be 15-20 days before harvest.
To control the amount of nitrogen fertilizer to ensure higher yields and economic benefits for green vegetables, proper application of nitrogen fertilizer is necessary on the basis of applying organic fertilizers, but the amount must be controlled to resolve the contradiction between quality and yield, yield and benefits . At the same time, pay attention to the selection of nitrogen fertilizer varieties. The accumulation of nitrate in vegetables is reduced by the influence of sodium nitrate, ammonium nitrate, urea, and ammonium chloride.
Balanced fertilization combined with various fertilizers is easier to reduce the content of nitrate in vegetables than a single application of nitrogen fertilizer. Combination of nitrogen and phosphorus and spraying of micro-fertilizers can reduce the content of nitrate in vegetables. Especially, the combination of potassium fertilizer can promote protein synthesis and reduce the content of nitrate in the body.