Chemical fertilizer should not be applied frequently in vegetable fields.

Many vegetable farmers think that the more fertilizer in the field, the better, but in fact, the frequent application of chemical fertilizer in vegetable land has many disadvantages, often affecting the quality of vegetables and causing damage to the soil. Therefore, the amount of chemical fertilizer should be reduced as far as possible, so that it can be applied in conjunction with organic fertilizer.

The edible parts such as stems and leaves of vegetables with long-term application of chemical fertilizer, especially the "nitrogen fertilizer vegetables" produced by excessive nitrogen fertilizer, are seriously polluted by nitrate, which will double the content of nitrate in vegetables. Nitrate is easy to be reduced to nitrite in the human body. Nitrite is a highly toxic substance that can cause hypoxia in human cells. If children eat this vegetable for a long time, it will cause mental decline and can cause cancer, which is extremely harmful. Therefore, in some developed countries, nitrogen fertilizer vegetables have been banned from listing in order to effectively protect the interests of consumers.

Fresh and tender vegetables produced entirely by chemical fertilizers look like tender stems and leaves, but those who do not know the truth think they are of high quality. in fact, the nitrate content of this vegetable exceeds the standard, and it is easy to mildew and deteriorate in the process of stacking and storage, increasing the content of toxic substances. It is determined that in the process of storage in winter and spring, the decay damage rate of cabbage with nitrogen fertilizer is more than 20% higher than that of cabbage with farm manure, and the content of nitrate will double.

Long-term application of ammonium sulfate, potassium sulfate and nitrogen-containing chemical fertilizer in vegetable soil will destroy soil structure, make soil solidify, lose flexibility and elasticity, and reduce water permeability. With the long-term application of chemical fertilizer, the calcium ions on the soil colloid were constantly exchanged. Under the leaching of Rain Water and irrigation water, ammonium sulfate and calcium chloride were leached to the lower layer of the soil, resulting in calcium deficiency in the tillage layer, destruction of soil structure, and soil consolidation. Fertility decreased, vegetables grew poorly, and yield was reduced. Because of the good soil structure, except for a large amount of organic matter, it is generally rich in calcium. No matter how good the soil structure of lack of calcium is, it is not fixed and easy to be destroyed. Only the soil containing certain calcium, its calcareous water-stable aggregate structure, is the most ideal soil, which can produce high-yield and high-quality vegetables.

Frequent application of chemical fertilizer will cause soil acidification harm. Ammonium sulfate, ammonium chloride, potassium chloride, calcium superphosphate and other acidic chemical fertilizers will make a large number of acid substances remain in the soil and make the neutral soil sour. Acidic soil is more acidified, which not only destroys the soil microbial flora, but also is not conducive to the normal growth of most vegetables. Long-term application of chemical fertilizer, especially ammonium sulfate, potassium sulfate and potassium chloride, can only increase the content of sulfate ion and chloride ion in soil, and these two ions are harmful ions to soil, which are not only harmful to the growth of vegetables, but also cause soil secondary salinization, destroy soil structure and affect the absorption of other nutrient elements by vegetables. Long-term excessive application of chemical fertilizer in vegetable land will not only cause harm to vegetables, but also hinder the absorption of other nutrient elements by vegetables, resulting in element deficiency. For example, excessive application of nitrogenous fertilizer will cause calcium deficiency in vegetables; excessive nitrate will lead to molybdenum deficiency; excessive potassium will reduce the effectiveness of calcium, magnesium and boron; excessive phosphorus will reduce the effectiveness of calcium, zinc, boron and so on.

Therefore, the vegetable field should maximize the application of organic fertilizer or other non-chemical nitrogen fertilizer to replace chemical nitrogen fertilizer, and try to replace chemical nitrogen fertilizer with organic fertilizer such as ring fertilizer, chicken manure and all kinds of cake fertilizer without affecting the normal growth and development of vegetables. in order to prevent vegetable pollution and reduce the residue of chemical fertilizer and the pollution and damage to the soil.