The nutrient water bought in the market can be used as foliar fertilizer.

For the purpose of foliar absorption, the nutrients needed by crops are directly applied to foliar fertilizer, which is called foliar fertilizer.

Foliage fertilizer is a kind of fertilizer that applies nutrients to the surface of crop leaves and exerts its basic functions through the absorption of leaves. The leaves of plants have two layers of epidermis, which are composed of fine epidermis. The cells on the epidermis have cuticle and wax outside, which can protect mesophyll cells under the epidermis from adverse external conditions. There are many tiny stomata on the leaves to exercise the function of gas replacement. Studies have shown that the stratum corneum is composed of a long-chain fatty acid polymer with hydroxyl and carboxyl groups. The molecular gaps and hydrophilic groups of hydroxyl and carboxyl groups on this polymer can allow aqueous solution to penetrate into leaves. Of course, the pores on the surface of the leaves are more convenient channels for foliar fertilizer to enter the leaves. Urea in chemical fertilizer can soften the cuticle of epidermal cells and accelerate the penetration of other nutrients, so urea can soften the cuticle of epidermal cells and accelerate the penetration of other nutrients, so urea becomes an important component of foliar fertilizer.

Fertilizers used as foliar fertilizers mainly include urea, potassium dihydrogen phosphate and borax.

Leafy vegetables can be mainly nitrogen fertilizer, or they can be sprayed with a small amount of mixed solution of urea and potassium dihydrogen phosphate, for example, 3 parts of urea 1 part of potassium dihydrogen phosphate and water are prepared according to 0.2% solution.

To clarify the principle of foliar fertilizer, we must first clarify the leaf structure. The basic structure of leaves is leaves, petioles and stipules. Leaves include epidermis, mesophyll and veins. Mesophyll is generally divided into palisade tissue and sponge tissue (c3 plants are different from c4 plants).

Characteristics of angiosperm leaves: epidermis is divided into upper epidermis and lower epidermis, which is generally composed of a layer of cells. There are pores on the epidermis, which are generally composed of two kidney-shaped guard cells. The leaf structure of monocotyledonous Gramineae is basically the same as that of common angiosperms. But the epidermis has two kinds of cells, rectangular and square. Stomatal guard cells are dumbbell-shaped, and there are subsidiary guard cells outside the guard cells.

Generally speaking, stomata are open during the day and closed at night. When foliar fertilizer is sprayed, the fertilizer enters from stomata and is absorbed by plants.

According to their functions, foliar fertilizers can be classified into the following four categories. The first kind of compound foliar fertilizers, such as Tianda 2 1 16, chitosan oligosaccharide, etc., contain marine active components and also contain various trace element fertilizers necessary for plant growth. It can activate the expression of plant resistance genes and strengthen plant nutrition.

The second category: nutrient foliar fertilizer. This foliar fertilizer is rich in nutrients such as nitrogen, phosphorus, potassium and trace elements. Its main function is to provide various nutrients for crops and improve the nutritional status of crops, and it is especially suitable for supplementing various nutrients in the later period of crop growth. The third category: regulated foliar fertilizer. This foliar fertilizer contains substances that regulate plant growth, such as auxin and hormone, and its main function is to regulate the growth and development of crops. Suitable for the prophase and metaphase of plant growth. The fourth category: biological foliar fertilizer, which contains microorganisms and metabolites, such as amino acids, nucleotides, nucleic acids and so on. Its main function is to stimulate crop growth, promote crop metabolism, and reduce and prevent the occurrence of pests and diseases.

Generally, it can be divided into macro-element foliar fertilizer, micro-element foliar fertilizer, humic acid foliar fertilizer and amino acid foliar fertilizer. Their characteristics are: rapid direct absorption by leaves, high nutrient utilization rate, and rapid improvement of crop nutrient supply. Humic acid and amino acid foliar fertilizer can also enhance crop stress resistance and obviously improve product quality. However, foliar topdressing cannot replace soil fertilization. Because foliar fertilizer is sprayed on the surface of leaves during crop growth, it can only temporarily supplement nutrients. For fertilizers with large elements such as nitrogen, phosphorus and potassium, crops need a lot, and simple foliar fertilizer is not enough. Soil fertilization is also needed.