In addition to the nutrients absorbed by the roots, the leaves can also absorb nutrients. Foliar fertilization is also called top dressing or foliar spray. This kind of fertilization is a fertilization method often used in production. Its outstanding features are strong pertinence, fast absorption of nutrients, avoiding the fixation of soil to certain nutrients, improving nutrient utilization, and less fertilization. It is suitable for the application of micro-fertilizers, and the yield increase effect is remarkable, especially the soil environment. Poor, excessive water or drought and low humidity conditions, soil peracid and alkali and other factors cause root absorption is blocked or crop deficiency is urgently needed to supplement nutrition and root absorption capacity declines in the late stage of crop growth, foliar topdressing can make up for root infertility. Can achieve better yield increase effect.
First, the type of foliar fertilizer There are many kinds of foliar fertilizers, and there are hundreds of species and even thousands of species in the country. According to its function and function, foliar fertilizer can be summarized into the following four categories.
The first category: nutritious foliar fertilizer: such foliar fertilizers have higher nutrient contents such as nitrogen, phosphorus, potassium and trace elements. The main function is to provide various nutrients for crops and improve the nutritional status of crops, especially suitable. Supplementation of various nutrients in the late stage of crop growth.
The second category: regulated foliar fertilizer: This type of foliar fertilizer contains substances that regulate plant growth, such as auxin, hormones and other components, the main function is to regulate the growth and development of crops. Suitable for pre- and post-plant growth.
The third category: bio-foliar fertilizer: This type of fertilizer contains microorganisms and metabolites, such as amino acids, nucleotides, nucleic acids. The main function is to stimulate crop growth, promote crop metabolism, reduce and prevent the occurrence of pests and diseases.
The fourth category: composite foliar fertilizer: This type of foliar fertilizer has a wide variety of compounds and mixed forms. Its functions are various, a foliar fertilizer can provide nutrition, and can stimulate growth regulation and development.
Second, foliar fertilization technology Foliar fertilization effect is often restricted and affected by a variety of factors, in order to improve the effect of foliar fertilization should adopt scientific fertilization methods and correct fertilization techniques.
(1) Choosing the appropriate fertilizer variety: Select the appropriate foliar fertilizer variety according to the growth and nutrition of the crop. In the early stage of crop growth, in order to promote the growth and development of the selected type of foliar fertilizer, if the crop is lack of nutrients or the root absorption capacity declines in the late growth stage, nutritive foliar fertilizer should be used. The fertilizers commonly used in foliar application in production are mainly urea, potassium dihydrogen phosphate, superphosphate, potassium sulfate and various trace element fertilizers. The appropriate fertilizer varieties can be selected according to the specific conditions.
(2) The concentration of spraying should be appropriate: within a certain concentration range, the speed and quantity of nutrients entering the leaves increase with the increase of the concentration of the solution, but the concentration is too high and the fertilizer is easy to occur, especially the trace element fertilizer, and the crop nutrition is lacking. The critical range between the excess is very narrow, and should be strictly controlled. Foliar fertilizers containing growth regulators should also be sprayed strictly according to the concentration requirements to prevent improper control. Different crops have different concentration requirements for different fertilizers. Taking urea as an example, the suitable concentration on grass, wheat and other grass crops is 1.5%-2.0%, 1%-1.5% on radish, cabbage, cabbage and cucumber, and 0.5% on potato, watermelon and eggplant. 0.8%, the concentration of apple, pear, grape and tea is 0.5%, and the concentration of onion, tomato and greenhouse cucumber is 0.2%-0..3%.
(3) The spraying time should be suitable: the amount of nutrients absorbed by the leaves during leaf fertilization is related to the length of time of the wet leaves of the solution. The longer the wetting time, the more nutrients are absorbed by the leaves, and the better the effect. Under normal circumstances, it is advisable to keep the leaf wet time in 30-60 minutes. Therefore, foliar fertilization is best carried out in the windless weather in the evening; spraying fertilizer in the morning with dew will reduce the concentration of the solution and affect the effect of fertilization. Foliar topdressing can not be carried out on rainy days or before rain, because nutrients are easily leached and cannot function as they should. If it rains 3 hours after spraying, it should be refilled once on sunny days, but the concentration should be appropriately reduced.
(4) Spraying should be uniform, meticulous and thoughtful: foliar fertilization requires fine droplets and uniform spraying, especially pay attention to spraying the upper leaves and the back of the leaves, because the new leaves are more absorbed than the old leaves and the back of the leaves. Nutrients are fast and have strong absorption capacity. Especially for peaches, pears, persimmons, apples and other fruit trees, the front of the stratum corneum is 3-4 times thicker than the back, and more attention should be paid to spraying the back of the leaves for absorption. Therefore, when fertilizing the leaves, the front and back sides of the leaves should be sprayed as carefully as possible.
(5) The number of spraying should not be too small, there should be an interval: the concentration of crop topdressing is generally low, and the amount of absorption per time is very small, which is much lower than the demand of crops. Therefore, the number of foliar application should not be less than 2-3 times. As for nutrients (such as iron, boron, calcium, phosphorus, etc.) that have little or no movement in the crop, it is necessary to pay attention to the appropriate increase in the number of sprays. When spraying foliar fertilizer containing conditioner, it should be noted that there should be intervals between spraying, the interval should be at least one week, and the number of spraying should not be too much to prevent improper regulation and damage.
(6) Foliar fertilizer should be used properly: when foliar topdressing, two or more foliar fertilizers can be mixed reasonably, which can save spraying time and labor, and the yield increasing effect will be more significant. However, after the fertilizer is mixed, there must be no adverse reactions or no reduction in fertilizer efficiency, otherwise the purpose of mixing will not be achieved. In addition, the concentration of the solution and the pH should be paid attention to when the fertilizer is mixed. Under normal circumstances, the pH value of the solution is about 7 and the neutral condition is favorable for the absorption of the leaves.
(7) Adding a wetting agent to the fertilizer solution: There is a layer of thick and thin stratum corneum on the leaves of the crop. It is difficult to infiltrate the solution. For this reason, an appropriate amount of a wetting agent, such as a neutral soap, may be added to the foliar fertilizer solution. A good quality detergent, etc., to reduce the surface tension of the solution, increase the contact area with the blade, and improve the effect of foliar topdressing.
When purchasing foliar fertilizer, attention should be paid to the type and function of the foliar fertilizer indicated in the package, so that the purpose of foliar fertilization is consistent with the function of foliar fertilizer; it should also be noted whether the product has a foliar fertilizer registration certificate issued by the Ministry of Agriculture. No. and product standard certificate number to ensure the quality and application effect of foliar fertilizer.
Huaxian County Agricultural Products Inspection and Testing Center Chang Bili
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