Extra-root nutrition and foliar fertilizer

"those with long mouths need to eat, and those with long roots need to be fat." Since ancient times, people have linked fertilizers, fertilizers and plant roots. The root system growing in the ground does not have safflower and green leaves, so it is not so eye-catching, but it plays a particularly important role in the process of plant life. Well-developed roots can penetrate into the soil and bond with the soil, so that the aboveground parts of plants, that is, stems, leaves, flowers and fruits, can settle on the soil. How can plants without roots grow on the soil and how can they be connected with the soil? However, the main function of the root system is not to fix and support plants, but to absorb water and nutrients. Developed roots and huge root surfaces, like open mouths, constantly capture nutrients and water from the soil from everywhere. Once nutrients reach the surface of the root system, they pass through the water membrane around the root system, into the cell wall, through the membrane in the cell wall, the protoplast membrane, to the inside of the cell, and then through cell-to-cell transmission, extending in all directions to all parts of the plant. The root system can not only absorb ready-made food and use nutrients, but also "set up fertilizer factories" to process food for itself. The solution is to secrete acidic organic matter into the soil all the time, liberating nutrients sleeping in the soil and turning them into something that crops can use when they dissolve. Because the nutrients needed by plants growing on land are mainly absorbed by the root system, the root system has always been regarded as an absorbing organ. Fertilization is generally applied to the soil and nourishes the plant through root absorption. Although the root system is the main organ for plants to absorb nutrients, it is not the only organ. In addition to the root system, the leaves of the aboveground part of the plant also have the function of absorbing nutrients. Leaves are outside the root system, so the process of absorbing and utilizing nutrients by leaves is called extra-root nutrition, and the process of spraying fertilizer to leaves is called extra-root fertilization or foliar fertilization. The stomata in the leaves are the door through which nutrients enter. Gas nutrients such as carbon dioxide, sulfur dioxide and oxygen and water vapor in the air can enter leaf cells through stomata, and inorganic nutrients such as nitrogen, phosphorus, potassium and trace elements can also enter through stomata. The process of entering the leaf cell is the same as entering the root cell. Compared with root fertilization, the remarkable characteristic of extra-root fertilization is that fertilizer is sprayed directly on leaves and does not deal with soil. Spray on the leaf can be directly absorbed by the leaf, without having to go through the root system to take a long and tortuous road, and then reach the leaf. Therefore, the effect is quick, and the obvious results can be seen in one or two days after spraying. In some experiments, after applying phosphate fertilizer outside the root for 5 minutes, the effect of phosphorus content in each organ was similar to that after 15 days of root fertilization. Spraying on the leaves can also avoid the trouble caused by the fixation or transformation of nutrients in the soil. In the fertilizers we use, there are many nutrients, such as phosphorus, manganese, iron, zinc and so on, which can interact with the soil into forms that crops can not use, and lose their effect. If extra-root fertilization does not come into contact with the soil, these problems will not arise. Although extra-root fertilization is applied to leaves, it can be transported to all parts of the plant through the leaves, and the role is not limited to leaves. Extra-root fertilization can improve photosynthesis and form more organic nutrients. After the organic nutrients are transferred to the roots, they will promote the root growth and enhance the ability of the roots to absorb water and nutrients; when transferred to the stems and leaves, they will make the branches and leaves flourish, increase the "green factory" and form more organic matter. Extra-root fertilization can also more effectively regulate the activity of enzymes in plants. Enzyme is the catalyst to promote all chemical changes in plants, and all chemical reactions in plants can only be completed with its help. In fact, enzymes and proteins are a family, because they play a role in promoting chemical reactions, so they have another name. Extra-root fertilization can effectively regulate the activity of enzymes, so it can effectively regulate a series of important physiological processes in plants. For example, spraying urea in the early stage of growth can enhance the synthesis process caused by enzymes in crops and make crops grow vigorously; spraying phosphorus and potassium fertilizers in the middle stage can enhance the decomposition process caused by enzymes in crops, which is conducive to the transfer of organic matter in leaves to reproductive organs; spraying boron fertilizer during flowering can promote seed formation, and so on. Extra-root fertilization saves fertilizer: the amount of phosphorus, potassium and trace element fertilizer is only a fraction to a tenth of the amount applied by the soil; although the amount of nitrogen fertilizer is higher, it is still less than soil fertilization. Saving fertilizer is both an advantage and a disadvantage: if you use less fertilizer, it will not last long. Therefore, it often needs to be sprayed several times in order to achieve the desired results.