Deep application of soil and deep application of nitrogen fertilizer can reduce its direct contact with air and sunlight, so as to avoid volatile loss and pollution of vegetables. Generally, the nitrogen fertilizer should be applied to the soil layer of 10-15 cm deep. For the plots of the roots of the solanaceous, yam and root vegetables, the nitrogen fertilizer should be applied to the root layer below 15 cm.
Early application of leafy vegetables and vegetables with short growth period should be applied with nitrogen fertilizer at an early stage. Generally, it should be applied at the seedling stage, and no excessive application of nitrogen fertilizer should be applied in the middle and late stages of vegetable growth. For vegetables that do not readily absorb nitrate, the application of nitrogen fertilizer should be stopped 30 days before harvest.
Controlled dosage The accumulation of nitrate in vegetables will increase with the increase of nitrogen fertilizer application. Therefore, the application rate and application frequency of nitrogen fertilizer should be minimized. Generally, the amount of nitrogen fertilizer per mu should be controlled below 20 kg of standard nitrogen, and the vegetable land with higher fertility should be controlled below 10 kg or no nitrogen fertilizer. If nitrogen fertilizer is needed, 70-80% of the nitrogen fertilizer should be applied as the base fertilizer, and the rest should be used for deep application in the seedling stage.
Avoid foliar application Leafy vegetables should not be sprayed with nitrogen on the foliage. Because the ammonium ions in the nitrogen fertilizer are easily converted into nitrate ions after contact with air, they are absorbed by the leaves, and the leafy vegetables have a short growth period, so that the nitrates are easily accumulated in the leaves. Therefore, leafy vegetables should not be sprayed with nitrogen fertilizer, especially in the 28 days before harvest, foliar spray can not be carried out to prevent contamination of vegetables.
Four points of nitrogen in the vegetable field
Nitrogen application in vegetable gardens is one of the effective measures to increase vegetable yield. However, if it is used improperly, it will cause pollution to vegetables and reduce the quality of vegetables. To reduce the pollution of vegetables by nitrogen fertilizers, the following four points must be noted:
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