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The main disadvantages of the seedbed with overgrown seedlings are as follows: when the amount of one-time fertilization is too large, it is easy to cause the growth of vegetables or the disease of excessive nutrition. When the amount of fertilization is further increased or the fertilization is too concentrated, it is also easy to cause the solution concentration of local soil to be too high, causing damage to the root system of vegetables, that is, the so-called "root burning" phenomenon occurs; The fertilizer effect period is relatively short, and when the fertilization work cannot keep up with it, vegetables are easy to be de fertilized and premature aging occurs.

Microelements refer to the nutrients that require less iron, boron, zinc, manganese, molybdenum and other vegetables and require less fertilizer. After partial application of nitrogen fertilizer, the absorption of phosphorus in the soil by vegetables will be hindered, and phosphorus deficiency will easily occur; The partial application of potassium fertilizer will reduce the utilization rate of potassium and easily lead to soil alkalization. At the same time, excessive application of potassium can also hinder the absorption of calcium, magnesium and other nutrients, and indirectly lead to calcium deficiency and magnesium deficiency.

However, in the high-efficiency cultivation of vegetables in protected areas, because vegetables are cultivated all the year round, with high yield, the consumption of soil is much greater than that of conventional cultivation, and the continuous cultivation is relatively serious, after a period of cultivation, the content of some trace elements in the soil will be insufficient, which will affect the normal absorption and utilization of large elements, reduce the fertilizer efficiency of large elements, and cause a certain trace element deficiency.

Therefore, according to the demand of vegetables for trace elements, greenhouse and greenhouse vegetables should be fertilized with the combination of macro elements and trace elements. Generally, coarse fertilizer and fine fertilizer are used together. Coarse fertilizer mainly refers to some conventional farm fertilizers with low content of effective nutrients such as crop straw fertilizer, ring fertilizer and green fertilizer, and slow fertilizer effect. In order to ensure fertilizer efficiency, the amount of this kind of fertilizer is relatively large, and the amount of fertilizer per hectare is generally more than 60m3.

Long term coarse fertilizer is the most widely used organic fertilizer because of its large amount of fertilizer, obvious effect on improving soil, and no harm to vegetables. Fine fertilizer refers to a kind of organic fertilizer with high content of effective components such as cake fertilizer, oil residue, grain powder, human feces and urine, livestock feces and urine, fast fertilizer effect, high utilization rate after fertilization, and less fertilization. Generally, the amount of fine fertilizer is relatively small, and most of them adopt the centralized fertilization method for hole application and ditch application.

In addition to the above two formulas, there is also a simpler nutrient solution formula. This formula uses nitrogen phosphorus potassium ternary compound fertilizer (nitrogen phosphorus potassium content is 15-15-15) as raw material. Each nutrient component should be fertilized in combination. The main purpose of fertilizing each nutrient component is to maintain the balance of soil solution and avoid destroying the balance relationship between the nutrient concentrations in the soil after single fertilization, resulting in nutrient deficiency or excess.