What is the difference between foliar nutrition and foliar fertilizer?
Fertilizer is the "food" of vegetables. Except for carbon, hydrogen and oxygen, the other 13 nutrient elements are all supplied by the soil, and applying base fertilizer is an important measure for replenishing soil nutrients. At present, the types of fertilizer used on vegetables are broadly divided into three categories: organic fertilizer (farmyard manure), inorganic fertilizer (chemical fertilizer) and microbial fertilizer (biological bacterial fertilizer)...
"Creatures with mouths must eat, plants with roots must be fed." Since ancient times, people have linked fertilizer, fertilization and plant roots.The root system growing underground has no red flowers or green leaves and is not so eye-catching, but it plays a particularly important role in the life of the plant. A well-developed root system can penetrate the soil and bind with it, so that the aboveground parts of the plant, namely the stems, leaves, flowers and fruits, can settle on the soil. How could a plant without a root system grow on the soil, and how could it establish contact with the soil? However, the main role of the root system is not to fix and support the plant, but to absorb water and nutrients. The well-developed root system and its huge surface are like an open mouth, constantly capturing nutrients and water from the soil everywhere. Once nutrients reach the root surface, they pass through the water film around the root, enter the cell wall, pass through the membrane inside the cell wall - the plasma membrane - and reach the interior of the cell, then travel in all directions through transfer between cells and arrive at every part of the plant. While the root system absorbs ready-made food, that is, available nutrients, it can also "open a fertilizer factory" to process food for itself. The method is to secrete acidic organic substances into the soil at all times, liberating the nutrient elements sleeping in the soil and, after dissolving them, turning them into things the crops can use. Because the nutrients needed by plants growing on land are mainly taken up by the root system, people have always regarded the root system as an absorbing organ. Fertilization is generally applied to the soil, and plants are nourished through root absorption.
Although the root system is the main organ for plants to absorb nutrients, it is not the only organ. Besides the root system, the leaves of the aboveground parts of the plant also have the function of absorbing nutrients. Leaves are the parts outside the root system, so the process by which leaves absorb and use nutrients is called foliar nutrition, and the process of spraying fertilizer onto leaves is called foliar fertilization or leaf fertilization.
The stomata on the leaves are the gateway for nutrients to enter. Gaseous nutrients such as carbon dioxide, sulfur dioxide, oxygen and water vapor in the air can enter the leaf cells through the stomata; inorganic nutrients such as nitrogen, phosphorus, potassium and trace elements can also enter through them. The process of entering leaf cells is the same as the process of entering root cells.
Compared with root fertilization, the notable feature of foliar fertilization is that the fertilizer is sprayed directly onto the leaves and does not deal with the soil. Once sprayed onto the leaves, it can be directly absorbed and used by the leaves, without having to travel the long and winding road through the root system and then reach the leaves. Therefore, it takes effect quickly, and generally obvious results can be seen one or two days after spraying. Some people have tested that 5 minutes after foliar application of phosphorus fertilizer, the phosphorus content in various organs was equivalent to the effect 15 days after root fertilization. Spraying onto the leaves can also avoid the trouble caused by soil fixation or transformation of nutrient elements. Many nutrients in the fertilizers we use, such as phosphorus, manganese, iron and zinc, can react with the soil and become forms that crops cannot use, thus losing their effect. Foliar fertilization does not contact the soil, so these problems will not arise.
Although foliar fertilization is applied to the leaves, it can be transported through the leaves to every part of the plant, and its role is by no means limited to the leaves. Foliar fertilization can increase photosynthesis and form more organic nutrients. After organic nutrients are transported to the roots, they will promote root growth and enhance the root system's ability to absorb water and nutrients; when transported to the stems and leaves, they will make the branches and leaves luxuriant, enlarge the "green factory" and form more organic matter.
Foliar fertilization can also more effectively regulate the activity of enzymes in the plant body! Enzymes are catalysts that promote all chemical changes in the plant body, and all chemical reactions in the plant body depend on their help to be completed. In fact, enzymes and proteins are one family; because they serve the role of promoting chemical reactions, they have another name. Foliar fertilization can effectively regulate enzyme activity, and therefore can effectively regulate a series of important physiological processes in the plant body. For example, spraying urea in the early growth stage can enhance the synthesis process caused by enzyme action in the crop body, making the crop grow vigorously; spraying phosphorus and potassium fertilizers in the middle stage can enhance the decomposition process caused by enzyme action in the crop body, which is beneficial for the transfer of organic matter in the leaves to the reproductive organs; spraying boron fertilizer at flowering can promote seed formation, and so on.
Foliar fertilization saves fertilizer: the amount of phosphorus, potassium and trace element fertilizers used is only one-several to one-plus-ten-several of the amount applied to the soil; although the amount of nitrogen fertilizer used is somewhat higher, it is still very little compared with soil fertilization. Saving fertilizer is an advantage, but it is also a disadvantage: with less fertilizer used, the duration of effect is not long. Therefore, spraying several times is often needed to achieve the expected effect.