New fertilizer foliar fertilization technology
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In order to maintain a normal life movement, crops need to absorb energy and nutrients from the outside world. Therefore, only when cultivated under appropriate environmental conditions, provide sufficient energy (such as sunlight) and various nutrients, the crop can grow, develop and reproduce.
The nutrients absorbed by the crops are mainly carried out through the root system, but the leaves (including the surface of some stems) can also absorb some nutrients through the method of osmotic diffusion. For example, spraying urea, potassium dihydrogen phosphate and trace elements into the foliage can also be used. The crop is absorbed into nutrients such as nitrogen, phosphorus, potassium, boron, molybdenum and zinc. This type of fertilization is often referred to as extra-root fertilization or foliar fertilization. It is mainly used as an important fertilization measure to strengthen the nutrition of crops and prevent certain elements of crops. At the same time, it is also an important way to improve the utilization rate of fertilizers. This is a new technology for fertilization that has developed rapidly in recent years.
First, the important significance of foliar fertilization
(1) Rapid supplementation of nutrients
In the late stage of crop growth, the roots are declining, the ability to absorb fertilizers is reduced, or some nutrient deficiencies are exhibited during crop growth, or when soil environmental conditions are hindered by the absorption of nutrients in crop roots, crops need to be quickly restored. Growth, at this time, the root application method can not meet the nutrient needs of the crop in time, only the foliar spray can quickly supplement the nutrients to meet the needs of crop growth and development.
(2) Give full play to fertilizer efficiency
Some fertilizers such as phosphorus, iron, manganese, copper, zinc fertilizer, etc., if root application is applied, are easily fixed by the soil, reducing the fertilizer utilization rate and affecting the fertilization effect, while the foliar application is not limited by the soil conditions. For example, some fruit trees and other deep root crops can not fully exert the fertilization effect in time if the traditional root application method is difficult to apply to the root absorption site in time, and the foliar spray can overcome the above-mentioned deficiencies and achieve better results. For example, Ningbo Cixi Yangmei Spray Boron, Ninghai and Xiangshan Sea-coated citrus sprayed iron and zinc tests have achieved good yield-increasing effects.
(3) Economical cost
Various trace elements are essential nutrients in the process of crop growth and development, but the application amount is very small, such as molybdenum fertilizer, the application rate per acre is only 10-15 grams. If the root application method is adopted, it is difficult to apply evenly. Foliar spray can be cost effective. According to the experimental research, the general crop sprays boron fertilizer on the foliar surface, and the utilization rate of boron is 8.18 times that of the base application. From the economical point of view, the foliar spray is much more cost-effective than the root application.
(4) Reducing pollution to the soil
As we all know, the accumulation of nitrate in groundwater and vegetables is harmful to humans. About 75% of the nitrates absorbed by humans come from vegetables. If foliar fertilization is used, the amount of fertilizer applied to the soil can be appropriately reduced. Reduce the nitrate content in plants. According to our measurements on 105 samples of 19 vegetable plants in several major vegetable bases in Ningbo, it is shown. The nitrate content in vegetables exceeded 64.7%, and the rate of nitrite exceeded 29.0%. The reason for the analysis was related to the amount of chemical nitrogen fertilizer. For example, in Jixian County of Ningbo City, the celery pH was as high as 30 kg per mu, in celery. The nitrate content is 4930.8 mg/kg, while the celery in Jiangbei District is 20 kg of nitrogen and 1000 kg of organic fertilizer. The nitrate content of celery is only 1387.0 mg/kg, which is much lower than that of celery grown in Jixian. content. According to relevant tests, in the cultivation of cabbage, each tomato cabbage reduced the amount of nitrogen fertilizer by 0.5 g, which can be compensated by spraying 0.1 g of nitrogen on the foliar surface. The yield level of 0.5 g of nitrogen can also be obtained. It can be seen that the planting crop adopts the foliar fertilization method, which not only saves the fertilizer amount, but also reduces the pollution to the soil and water source, and is an effective fertilization technology with two advantages.
All in all, foliar fertilization is a new technology for rational fertilization that is both economical and effective. In particular, some trace elements are used for foliar application, and they have unique merits. Although foliar fertilization has many advantages, on the other hand, foliar fertilization is troublesome and requires a lot of man-hours, and is also limited by climatic conditions. Because of different crop types and fertility, the effects of foliar fertilization vary greatly, especially for some large elements such as nitrogen, phosphorus, potassium and other fertilizers. According to experiments, foliar application of more than 10 times can reach the total absorption of nutrients in the roots. the amount. Therefore, foliar fertilization can only be carried out on the basis of root application. It absorbs energy as a supplement to rhizosphere nutrition and does not completely replace rhizosphere fertilization.
Second, the main features of foliar fertilization
(1) Fast absorption
The various nutrients sprayed through the foliage can enter the crop directly from the leaves, participate in the metabolism and synthesis of organic matter, and the speed and effect are faster than the soil fertilization, especially suitable for making up for crop defects caused by severe weather. Injury, such as drought and water shortage, soil fertility is difficult to dissolve and release, when using foliar spray, the plant will quickly resume growth. The effect is better. For example, on August 7, 1997, the city of Lone wave was hit by a strong typhoon in the 1911. Large farmland was impregnated with seawater and rainwater. The roots of rice, cotton and other crops were severely punished and the fertilizer was blocked. At that time, we used a large area to spray foliar fertilizer. Remedy. Rice and cotton were restored to growth in a relatively short period of time. According to statistics, the yield of rice and cotton sprayed with foliar fertilizer is close to that of the surrounding undamaged farmland.
In addition, some experiments have shown that corn is sprayed with zinc fertilizer at the 4-leaf stage. After 3 and a half hours, the absorption of zinc by the upper leaves has reached 11.3%, the central leaves have reached 8.3%, and the lower leaves have 7.2%. After 48 hours, The upper leaf absorption has reached 51.36%. Spraying fertilized foliar fertilizer on the leaves of lentils, after 24 hours, the absorption rate of most elements in the sprayed nutrients can reach more than 50%.
Since the soil is fertilized, various nutrients are first adsorbed by the soil. Some fertilizers must undergo a transformation process in the soil, and then be absorbed by the crop roots by ion exchange or diffusion, through the vascular bundles of roots and stems, and then to the leaves. Therefore, the transportation distance is long and the speed is slow. For example, when applying nitrogen fertilizer such as urea or ammonium sulfate in the soil, the fastest speed from the root to the blade must be 72 to 94 hours, so the foliar application is carried out, and the rate of leaf fertilizer is higher than that of the root. The speed is about 1 time faster.
(2) Good effect
A special function of green plants is to synthesize various organic substances by means of photosynthesis of various nutrients absorbed from the outside world. It has been determined that the photosynthesis products generally account for 90% to 95% of the total dry weight of the dry matter forming the crop yield. Photosynthesis is strong, and there are many kinds of nutrients in the plant, so there are more organic substances produced. When foliar fertilization is carried out on crops, the leaves absorb a large amount of nutrients, which better complements the progress of various physiological processes of crops. Main performances: First, the intensity of photosynthesis is significantly improved. Studies have shown that after foliar fertilization on tea trees, the new shoot leaves, the old leaves below the leaves and the old leaves on the canopy can significantly enhance photosynthesis. The intensity of photosynthesis and photosynthesis intensity increased by 31.1% on average. The photosynthesis rate of new shoot functional leaves increased the fastest, and the photosynthesis rate of new shoots decreased by 46.8%. According to the results of several measurements on the photosynthesis intensity of soybean in Hunan Province, the photosynthesis intensity of foliar fertilization was 22.69 mg/dm/h, which was 19.5% higher than the control. Secondly, the enzyme was significantly promoted. Activity. The strength of the enzyme activity depends on many factors, mainly the effects of nutrient conditions, because the nutrients required by many crops are part of the enzyme or a catalyst for the enzyme. For example, both catalase and cytochrome enzymes contain elements such as iron, nitrogen, phosphorus and sulfur, carbonic anhydrase contains zinc, arginase contains manganese, and calcium and magnesium are enzyme activators. Wait. It can be seen that if these nutrients are absent, the enzyme cannot be formed. According to the research, after foliar fertilization on garlic, the activity of enzymes in roots, stems and leaves increased by 15% to 31% compared with the control; on the beet, the activity of catalase was compared with that of the control. The increase of 14.5%; peanut fertilization in the pod stage, nitrate reductase activity increased by 17% compared with the control, peanut, soybean and other legume crops after foliar fertilization, the activity of nitrogenase can be increased by 5.1% to 24.7%. Since the enzyme participates in the process of synthesis, decomposition and transformation of various organic substances in the crop, the activity of the enzyme is directly related to various physiological activities of the crop, and the activity of the enzyme is enhanced, which is beneficial to the process of various physiological activities of the crop, which is beneficial to the process. Promote plant growth and development.
In addition, according to experiments, after spraying nutrients such as boron, manganese and phosphorus in the flower bud stage, it can promote flowering and pod formation and reduce the pod rate. Because in the flowering of rapeseed, the high content of boron and manganese in the flower (especially in the torus) is beneficial to the germination of the pollen grains and the elongation of the pollen tube, and promote the fertilization, which can improve the seed setting rate. Boron, manganese, phosphorus and other elements can also participate in the synthesis and conversion of carbohydrates, which is conducive to the accumulation of fat, can improve yield and improve quality.
(3) Consumption province
Foliar fertilization is a cost-effective new fertilization technique compared with soil fertilization. A large number of experimental materials show that the fertilizer is directly applied to the soil, and its utilization rate is generally only 20% to 40%. There are four reasons for the low utilization rate: 1. Volatilization loss, especially ammonium bicarbonate, etc., other chemical fertilizers applied on the surface of the soil, exposed to sunlight, and volatilized too much; 2. Loss and leakage, such as Shi After the rain, it will be lost, or it will leak into the deep layer of the soil with the infiltration of water in the soil; 3. It will be fixed by the soil due to the physical and chemical action of the soil, or it will become a poorly soluble substance. For example, phosphate fertilizer is easy to chemically change with iron and aluminum ions in acidic soil to reduce the effectiveness of phosphorus; 4. It is absorbed by field weeds. If foliar spray is applied, the above drawbacks can basically be avoided. Generally, the application rate of the soil is several times to several tens of times larger than the dosage. According to the relevant test materials, the leaves are sprayed with a dilution of 0.05% boron fertilizer 1 to 3 weeks after the falling of the apple. . It has the same effect as fertilizing 0.02-0.04 kg per apple tree every 3 years; in the onion growth period, it is sprayed with 0.25 kg of manganese sulfate and water for 200-300 times per acre for foliar application, and soil application is 3.5 to 3.75 kg. The effect of manganese sulfate is similar; when the pea seedling height is 10 cm, foliar spraying is carried out with 3.7 g of ammonium perchlorate and 50-60 kg of water per acre. The effect is better than applying 60 grams of ammonium phosphate per acre of soil. In addition, it has been proved by isotope tracking test that after phosphorus application on the surface of sugar beet, the amount of phosphorus absorbed by plants is higher than that of soil phosphorus application by more than 40%.
In summary, foliar fertilization is indeed an economical and effective fertilization technique, especially for nutrients such as boron, zinc and iron, which are less necessary for crops but are essential trace elements. For the elements such as manganese, copper wall, and molybdenum, the effect of foliar spraying is more significant. In addition, if some soil lacks certain nutrient elements, and crops are urgently needed, if soil fertilization can not meet the needs in time, or when the crops need a large amount of certain nutrients during the growth period, the roots absorb for a while. If it is not met, the need for crops can be replenished in time by foliar application. The shortage of soil fertilization is better overcome.
Third, the mechanism of foliar fertilization
(1) Basic functions of the blade
The leaves are the main place for photosynthesis and respiration in the autotrophic life of plants, and can enter the body through epidermal cells and stomata. In the process of photosynthesis, the leaves can directly synthesize simple inorganic substances absorbed in the external environment into various complex organic substances through various biochemical changes, forming them as their own components and converting solar energy into Chemical energy, stored in organic matter, releases energy for life activities.
In addition to photosynthesis, the leaf has an important function, that is, transpiration. A large amount of water can continuously evaporate from the stomata of the leaf to the atmosphere, which helps to regulate the balance of energy in the crop, and at the same time promotes root absorption. Transport of moisture, nutrients and nutrients in the body.
(two) the absorption mechanism of the leaf surface
The foliage (including the surface of a part of the stem) absorbs nutrients, mainly through the diffusion of pores and the penetration of the stratum corneum, allowing nutrients to enter the plant. For example, through the pores, plant leaves can absorb carbon dioxide, water vapor and sulfur dioxide, etc., especially the absorption of sulfur dioxide by the leaves plays a large role in the sulfur nutrition of plants.
1. The absorption of carbon dioxide. Carbon dioxide in the air is the main carbon source for crop photosynthesis. Carbon dioxide enters the interior of the blade mainly through the pores of the blade. The way the leaves absorb carbon dioxide from the air is called “air nutritionâ€. The amount of carbon dioxide absorbed by the leaves through the leaves accounts for about 75% to 80% of the total carbon absorbed by the crops. The roots absorb carbon dioxide, carbonic acid and carbonates from the soil. 20% to 25%.
2. Absorption of mineral elements. In the process of crop growth, it is undoubted that crops extract various mineral elements from the soil from the roots. The question of whether plant foliage can absorb mineral elements has not been widely recognized by farmers. In fact, this problem has long been confirmed. According to relevant information, as early as the 1940s, it was discovered that plant foliage can also absorb mineral nutrients. By the 1930s, advanced fertilizer countries in the world had listed foliar fertilization as an important promotion project. In recent years, China has also applied foliar fertilization as an important technical measure to increase production and improve quality and to correct various deficiency diseases. For example, in some areas where there are some areas, the fertilized leaves of rapeseed and peanuts are sprayed with boron fertilizer to prevent and control the "flowers and not real" disease; spraying molybdenum fertilizer on legumes to promote growth and increase yield; in fruit trees such as citrus In the spraying of iron, zinc, molybdenum, magnesium and other elements, the lack of symptoms of these elements is eliminated, the yield is improved, and the quality is improved. The above situation indicates that the crop not only absorbs mineral nutrients from the roots and enters the body to directly participate in metabolic activities, but also absorbs faster than the roots, and the effect is also remarkable. From the structure of the leaf epidermal cells, the pathway and possible mechanism of mineral permeation can be understood. The outer surface of the epidermis on the surface of the leaf is the stratum corneum and the waxy layer. In the past, it was considered that the stratum corneum and the waxy layer were difficult to pass through foreign substances. However, according to the scientific research department, the thin layer culture experiment was carried out, and the culture medium was sprayed on the surface of the thin layer cells for culture. As a result, it was found that the cells sprayed with the culture liquid can quickly undergo cell division, and the cells also contain a large amount of elements and trace elements. Various hormones and other substances. It is thus proved that the stratum corneum and waxy layer on the surface of the leaf can also pass through foreign substances to achieve the purpose of absorbing mineral nutrients.
Plant cells are mainly composed of four parts: cell wall, cytoplasm, nucleus and vacuole. The main constituent material of the cell wall is cellulose. Cellulose is a kind of crystal which is arranged in a chain. The long chain of crystals is first assembled into micelles, and microfibers are formed by a number of different cells. The interstitial space is generally about 1 mm, and the microfiber gap is about 10 nm. These gaps are cell wall micropores, which constitute a passage for substances to enter and exit, and water and nutrients can enter the inside of the cells. However, the particle size or ionic particle size of many nutrients can only pass smoothly when the distance between the cell gap and the microfiber gap is smaller.
Plants absorb external nutrients, whether through root absorption in the lower part or through the leaves in the upper part of the ground, the absorption pathway is basically the same, nutrients from the medium solution → cell wall water film → cell wall → protoplasmic membrane → cell interior, Participate in metabolic activities. According to the isotope measurement, the nutrients absorbed by the foliar surface are mainly transferred to the growth center, and during the reproductive growth period, the main solid organs are transferred. Therefore, the nutrients absorbed by the foliage are more effective in the plant than in the roots.