The fruit tree mainly absorbs various nutrients from the soil solution by root system, but its branches, leaves and fruits also have certain nutrient absorption capacity. Therefore, there are two main methods for fertilizing fruit trees in production: soil fertilization and foliar fertilization. According to the dynamic balance between the upper and lower parts of the fruit trees, scientific and rational fertilization techniques can be selected to achieve high yield, stable yield and high quality of fruit trees, and increase the utilization rate of fertilizers by fruit trees. Generally, the fertilization of fruit trees is mainly divided into base fertilizer and top dressing, and top dressing can be divided into soil topdressing and leaf surface topdressing. Because foliar fertilization has the characteristics of simple and easy operation, low fertilizer consumption, fast fertilizer efficiency, high nutrient utilization rate and obvious effect, it can also avoid the fixation and loss of soil fertilization, and also supplement the water requirement of the tree body. Combined with the prevention and control of pests and diseases, and the mixing of certain pesticides, it is more than one way, saving labor and time. Therefore, foliar fertilization is a kind of fertilization measure that can not be ignored in fruit tree production. However, foliar fertilization is only an auxiliary measure for soil fertilization, so as to achieve timely and rapid replenishment of plant body nutrition; and generally foliar spray fertilizer is only effective for 12 to 15 days, and needs to be sprayed continuously for 2 to 3 times or more. Spraying affects root growth and weakens the physiological function of the root system. Therefore, on the basis of soil fertilization, foliar fertilization should be carried out in a timely and appropriate amount.
First, the role and effectiveness of foliar fertilization of fruit trees
Foliar fertilization in the growing season of fruit trees is an effective measure to supplement the soil fertility deficiency, especially in the seasons of high yield, drought and water shortage. Because the fruit is competitive to the photosynthetic compound, the root growth is not good, and soil fertilization is not easy to play. Foliar fertilization can effectively improve the nutritional status of the tree and create conditions for fruit tree growth and development. Therefore, in the absence of irrigation conditions and root damage and intercropping orchards, reasonable foliar fertilization can effectively increase fruit set rate, promote fruit hypertrophy, enhance quality, and enhance resistance. For example, fruit trees such as apples, pears, hawthorns, etc., can improve fruit setting rate by foliar fertilization at flowering stage; foliar fertilization in leaves and fruit growth period can promote fruit enlargement, increase chlorophyll content, increase fruit yield and improve fruit quality.
By fertilizing the leaves of the results, the demand for nitrogen, phosphorus and other trace elements in the tree can be satisfied and supplied, and the fruit setting rate and fruit yield of the fruit trees can be improved. The spraying time and dosage of nitrogen, phosphorus and potassium fertilizers can effectively promote the growth of new shoots, increase fruit yield and promote flower bud differentiation. For example, spraying nitrogen fertilizer during the full flowering period can increase the fruit setting rate. Spraying nitrogen fertilizer at the young fruit stage can promote the expansion of young fruit. Spraying nitrogen fertilizer from May to June , and adding phosphorus fertilizer and potassium fertilizer can effectively promote flower bud differentiation. Practice has proved that spraying phosphate fertilizer and potassium fertilizer in the late growth season of fruit trees can increase the sugar content of fruits, accelerate the coloration of fruit, improve the quality of fruit and enhance disease resistance. When trace elements are lacking or potentially lacking, timely and appropriate application of trace elements can timely and effectively prevent trace element deficiency, improve yield and improve fruit quality.
Foliar fertilization can also effectively prevent cracking of fruit trees. Cracking fruit is a physiological disease of fruit trees. Some varieties such as citrus, peach, pear, jujube and medlar have fruit cracking. After cracking the fruit, it can cause pathogens and dust pollution, fruit drop, rot, reduce yield and quality, and seriously affect the value of the commodity. The fruit tree cracking fruit generally begins in the middle and late stages of fruit enlargement. In addition to the characteristics of the variety itself, it also causes the imbalance of water, nutrients and endogenous hormones due to climate change. In general, after a high temperature and drought, there will be severe rain and cracking will occur. Therefore, the fundamental measure to prevent cracking is to solve the coordination relationship between water, nutrients and hormones of fruit trees. In addition to selecting varieties with strong crack resistance and corresponding scientific cultivation management techniques, foliar fertilization is also an effective prevention and control measure. For example, foliar application of 0.2% to 0.5% urea plus 150 mg/kg gibberellin solution, or 2 % to 3% straw ash leaching solution plus 2% lime water mixture, or 0.2% to 0.3% potassium dihydrogen phosphate The solution can effectively reduce and prevent citrus cracking.
Second, the factors that influence the effect of foliar fertilization of fruit trees
1. The time and amount of spray liquid remaining on the surface of the fruit leaves. Only when a sufficient amount of nutrient solution is retained on the foliage, branches or fruits for a long time can it be fully absorbed to achieve the desired spraying effect. This is mainly related to the following two aspects: ( 1 ) the structural characteristics of the blade surface: the leaf characteristics of the fruit tree affect the retention time and quantity of the spray liquid on the leaf surface, such as the uprightness, smoothness and bulge of the stomata Or the depression, the number of hairy bodies, the thickness of the stratum corneum, etc., will affect the retention time of the fertilizer on the leaf surface and the absorption of nutrients. If the blade is a surface with many trichomes, the liquid droplets are often supported by the hairy body and cannot directly contact the surface of the leaf, so that the nutrients therein are difficult to be absorbed by the leaves. Generally, the back of the leaf has more stomata than the surface of the leaf, and the horny layer is thin. It has loose sponge tissue and large cell gap, which is good for nutrient penetration and absorption. Because the physiological function of the young leaves is strong, the proportion of leaf stomata is large, so its The absorption intensity is larger than that of the old leaves, which is beneficial to the foliar absorption of nutrients. ( 2 ) The amount of spray liquid on the leaf surface: due to the presence of the waxy layer of the foliar and the surface of the skin, it is hydrophobic, which is not conducive to the wetting and adhesion of the spray liquid on the leaf surface, but in the spray liquid Adding a certain amount of surfactants (such as washing powder or soap) can increase the wetting of the foliage by the spray solution and prolong the residence time. Under normal circumstances, the spraying liquid is within a certain range, the amount of retention on the tree is proportional to the amount of spraying, but after a certain limit, the spraying liquid will slide down a lot and cause nutrient loss. Usually, the amount of liquid sprayed is to be discharged from the blade without flowing down (to be dripped but not dripped) Time is the best.
2. Characteristics and use of fertilizers. ( 1 ) Type and concentration of fertilizer: There is a significant difference in the speed at which different nutrients enter the leaves. The speed at which nutrients enter the leaves is one of the important conditions that determine whether they can be used as foliar fertilization. At the same time, the concentration of the nutrient solution is related to the rate at which nutrients are absorbed. According to research, most fertilizers generally have higher concentration and faster absorption, but the absorption of magnesium chloride has nothing to do with concentration. ( 2 ) The pH of the spray solution: alkaline solution, which is beneficial to the absorption of cationic nutrients (such as K+ , Mg2+ , Ca2+, etc.), and the acidic medium contributes to the absorption of anion nutrients.
3. Climatic conditions. Temperature is one of the climatic conditions that have a great influence on foliar fertilization. It is usually within a certain allowable range. When the temperature is high, the foliar application effect is better, but after a certain limit, the high temperature will inhibit the foliar absorption of nutrients. This is because high temperature can promote the concentration and drying of the sprayed liquid on the one hand, and on the other hand, it is easy to cause the pores of the blade to close and is not conducive to nutrient absorption. Therefore, when the temperature is high, the droplets should not be too small when the foliage is sprayed, so as to prevent the water from rapidly evaporating and causing damage. Under normal circumstances, the suitable temperature range for foliar fertilization is 18 to 25 °C. Therefore, the foliar application should avoid the noon of strong sunlight, and the best effect is best in the semi-yin and windless days. It is advisable to do it before 10 am (after dew) or after 4 pm.
Third, the fruit leaf surface fertilization technology points
1. Determine the appropriate spray concentration. The concentration of the spray solution depends on the species, climate, phenological period, and type of fertilizer. Under the premise of no fat damage, you can use high concentration to maximize the demand for nutrients in fruit trees. However, a small test must be done before spraying to determine if it can cause fat damage and then spray it over a large area. Generally, when the temperature is low, the humidity is high, and the leaves are old, the fertilizer has weak damage to the leaves, and the spraying concentration can be appropriately increased. Otherwise, the spraying concentration should be appropriately reduced.
2. Spray at the right time and in the right amount. In theory, foliar fertilization can be carried out from the beginning of the leaf spreading of the fruit tree until the leaves stop growing. However, especially when the fruit tree is in urgent need of a certain nutrient element and exhibits some symptoms of deficiency, spraying the nutrient element is the best. For example, in general, fruit trees need a large amount of boron during flowering, and spraying borax or boric acid at this time can increase the fruit setting rate. Spraying is best when the leaf area is long enough. For example, the young leaves are sensitive to the reaction of the fertilizer, but the leaf surface is too small and the contact probability is smaller, so the spraying effect will be worse. Spraying at the right time can exert the effect of foliar spraying to a greater extent. The spraying of phosphate fertilizer during the flowering period can increase the fruit setting rate; the potassium fertilizer is mostly used in the growth of fruit trees, and the spraying of potassium fertilizer in the young fruit stage can promote the expansion of young fruit, and the later spraying Potassium fertilizer (appropriate application of phosphate fertilizer) can increase the sugar content of the fruit and promote coloration; while trace elements can be sprayed before and after flowering. Autumn foliar spray fertilizer can prolong the function of leaves, use nutrient elements to absorb nutrients, accumulate nutrients, provide nutrients for flower bud differentiation and growth of fruit trees in the following year, ensure the harvest of fruit trees in the next year, and avoid excessive concentration of fertilizers in tree nutrition. The center caused the phenomenon of fruit trees.
3. Determine the best spray site. When the foliage is sprayed, the back of the leaf is generally focused on, because the surface of the leaf has less horniness and more pores, and the nutrients are easily absorbed. However, because the mobility and re-utilization of different nutrient elements in the fruit tree are different, the spraying parts are also different. Trace elements are poorly mobile in the tree and are best sprayed directly onto the most needed organs, such as young leaves, young shoots or flowers. For example, boron should be sprayed on the flowers to better improve the fruit setting rate. Calcium sprayed on the surface of the fruit can effectively prevent the physiological calcium deficiency or improve the storability of the fruit.
4. Choose the right fertilizer variety. Different tree species react differently to the same fertilizer. For example, apples spray urea significantly, while citrus and grapes perform poorly. Therefore, according to the characteristics of fertilizers and tree species and other factors, select the appropriate fertilizer varieties, formulate suitable fertilizer concentrations and select the appropriate number of spraying to avoid fertilizer damage. In addition, the specific choice of the type of fertilizer to be sprayed depends on the nutritional status of the tree and the amount of the fruit. For example, for fruit trees with more fruits and more nutrients, it can be sprayed with nitrogen fertilizer to supplement nutrition, which can significantly enhance the next year. The amount of flowers will increase the yield and quality of the fruit; for the trees, young trees, fruit trees with low or no yield in the current year, phosphorus and potassium fertilizers should be sprayed to promote the formation of flower buds, thereby achieving the early results and the purpose of early yielding.
Fourth, the fruit leaf surface fertilization fertilizer type and suitable concentration
1. Nitrogen fertilizer. Generally, nitrogen fertilizer should be used in the early and late stages of fruit growth. Spraying the concentration and dosage can effectively promote the growth of new shoots, increase the yield of fruit, and facilitate flower bud differentiation. Nitrogen fertilizers commonly used for foliar application include: urea [CO(NH 2 ) 2 ] , ammonium sulfate [ ( NH 4 ) 2 S ) O 4 ] , ammonium nitrate ( NH 4 NO 3 ), ammonium chloride ( NH 4 ) Cl ), etc., wherein urea is preferred. Although urea has a high nitrogen content ( 46% ), it is generally not toxic to fruit trees after spraying. Because urea is a neutral organic nitrogen-containing compound, it has small molecules and strong diffusibility. It is easy to penetrate into the cell through the cell membrane and has strong hygroscopicity. The leaves remain moist after spraying and the absorption speed is fast. Therefore, whether it is old leaves or young leaves, soft leaves or hard leaves can absorb well. While ammonium sulfate and sodium sulfate are selectively absorbed by causal trees, SO 4 2- and Na + are easily accumulated in the tree, and excessive spraying will be harmful to the growth of fruit trees.
      However, the spraying concentration of nitrogen fertilizer is different in the early and late growth seasons. If urea is used as nitrogen fertilizer, the initial spraying concentration is 0.2% to 0.3% , and the later period is 0.3% to 0.5% . If the manure is used, the concentration is applied in the early stage. It is 5% , and it is 10% in the middle and late. Spraying nitrogen fertilizer can be combined with phosphorus and potassium fertilizer.
2. Phosphate fertilizer. It is generally believed that after spraying, the phosphate fertilizer can be absorbed by the leaves and transported to the new shoots, stems and roots. Experiments have shown that foliar application of phosphate fertilizer can promote the growth of new shoots and roots and the effects of flower bud differentiation. The amount of phosphate fertilizer should be mastered in the principle of “less in the early stage and more in the middle and late stagesâ€. Phosphate fertilizers commonly used for foliar application are: Ammonium phosphate [(NH 4 ) 2 HPO 4 , NH 4 H 2 PO 4 ] , calcium superphosphate [Ca(H 2 PO 4 ) 2 · H 2 O+CaSO 4 ] , potassium monohydrogen phosphate [K 2 HPO 4 ] Potassium dihydrogen phosphate [KH 2 PO 4 ], etc., among which ammonium phosphate has the best effect. The type of phosphate fertilizer used is different, and the spraying concentration is also different. Generally, the ammonium phosphate spraying concentration is 0.5% to 1.0% ; the potassium dihydrogen phosphate is used in the concentration of 0.1% to 0.5% ; and the superphosphate calcium leaching solution is used in the concentration of 1% to 3%. .
3. Potassium fertilizer. Potassium can promote the growth of new shoots and roots of fruit trees; it can effectively promote fruit coloration and improve fruit quality; it can enhance disease resistance and reduce the occurrence of citrus wrinkles and floating fruit and other physiological diseases. Potassium can also be absorbed from the leaves and rotated to various parts of the tree. In the production, potassium fertilizer is mostly applied in the middle and late stages. Commonly used potassium fertilizers for foliar application are: potassium chloride ( KCl 2 ), potassium sulfate ( K 2 SO 4 ), potassium nitrate ( KNO 3 ), potassium monohydrogen phosphate [K 2 HPO 4 ], and potassium dihydrogen phosphate [KH] 2 PO 4 ] and so on. Among them, potassium dihydrogen phosphate has the best effect. Generally, the concentration of potassium dihydrogen phosphate is 0.1% to 0.5% ; the concentration of potassium sulfate and potassium nitrate is 0.3% to 0.5% ; the amount of plant ash can be 5 to 15kg with 0.5kg of water, soaked for 24 hours, and the slag can be filtered to carry out the leaf surface. Spray.
4. Trace elements. Spraying trace elements is mainly used for prevention and correction of nutrient deficiency syndrome. The trace element fertilizers commonly used for foliar application are: ferrous sulfate ( FeSO 4 ), zinc sulfate ( ZnSO 4 ), copper sulfate ( CuSO 4 ), manganese sulfate ( MnSO 4 ), and boric acid ( H 3 BO 3 ) or borax. ( Na 2 B 4 O 7 · 10H 2 O ) and the like. They are generally applied at a concentration of 0.1% to 0.5%, but with different concentrations of different periods of spraying using, e.g., a year before the fruit was found lobular disease, spraying may be 1 month 3% to 5% sulfuric acid the following year before fruit bud Zinc solution; in the growth period, 0.1% to 0.2% zinc sulfate solution should be sprayed. If found in fruit growing leaf chlorosis, yellowish white, can be sprayed of 0.3% to 0.5% ferrous sulfate solution once every half; reduced when the fruit malformation found, there is the appearance of dry spots can be the following year before flowering Then spray 0.3% to 0.5% borax solution.
5. Nitrogen, phosphorus and potassium are combined with other nutrients for spraying. According to the test, the combined effects of nitrogen, phosphorus and potassium are better. For example, at the same time, 18- year-old grapes were sprayed with calcium phosphate 3.0% , potassium salt 0.50% , Chilean saltpeter ( NaNO 3 ) 20.1% , boric acid 0.05% , manganese sulfate 0.02% , before flowering, after berry ripening and during berry growth. Spraying 3 times (single spray and mixed spray), the results show that the combination of nitrogen, phosphorus and potassium with trace elements is more effective in increasing the yield of grapes; while the three-component mixed spray area is similar to the control area, only berries The sugar content has increased. Therefore, higher soil fertility in orchard, or micronutrient deficiencies orchard, three elements must be administered with an appropriate amount of trace elements, in order to further improve the application of results.
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