The nature of the fertilizer is different, and the transformation after application to the soil varies, and the nutritional effects and aftereffects of the growth stages of the fruit tree are different. Therefore, understanding and mastering the characteristics of various fertilizers is essential for balancing tree nutrients and improving fertilizer efficiency.

Organic fertilizers There are many types of organic fertilizers, mainly animal urine, manure, compost, green manure, cake fertilizer, soil fertilizer, bad residue fertilizer, decay fertilizer, domestic garbage, pollution and so on. Organic fertilizer is a kind of complete fertilizer. It is rich in organic matter and various nutrients needed by crops. The use of organic fertilizer is an indispensable part of energy and material circulation in agricultural production, and it is also one of the important measures to produce pollution-free fruits. . In addition to nutritional effects, increased fruit yield, and improved fruit quality, organic fertilizers have unique effects in improving soil and fertility.

Since the organic fertilizer is applied to the soil and then re-synthesized into humus by microbial decomposition, and the inorganic nutrients are released for absorption by the roots of the fruit trees, the fertilizer is slow and long-lasting, and is suitable for base fertilizer application. The combination of organic fertilizer and quick-acting fertilizer can improve fertilizer efficiency, help each other, and complement each other, and give full play to various yield increasing potentials and land-raising effects.

According to the nutrient types and forms of fertilizers, chemical fertilizers can be divided into chemical nitrogen fertilizer, phosphate fertilizer, potassium fertilizer, calcium, magnesium, sulfur fertilizer, trace element fertilizer and compound fertilizer. Fertilizer has the characteristics of high nutrient content, fast fertilizer efficiency and easy to be absorbed by roots, but it is volatile, lost, rinsed, fixed, low in utilization rate and easy to pollute the environment. Therefore, the fertilizer is easy to be used as a top dressing or a foliar spray, and the fertilizer effect is remarkable. The types, properties and application techniques of fertilizers commonly used in the fertilization of fruit trees are recommended for application.

Root fertilization (leaf spray)

The top dressing is a fertilization method in which the fertilizer is formulated into a certain concentration of solution and sprayed on the crown. It is simple and easy to use, with less fertilizer, quicker fertilizer, and can be mixed with certain pesticides, saving labor and trouble, and also can supplement the water needs of the tree. Especially in the season of high yield and drought, due to the strong competitiveness of the fruit on the photosynthetic composition, the root growth is not good, and the effect of top dressing is better. In the absence of irrigation conditions and damage to roots and intercropping orchards, reasonable root dressing can improve fruit yield, promote fruit hypertrophy, enhance quality, enrich branches, and enhance resistance.

(1) Factors affecting the effect of topdressing

1. The time and amount of fertilizer solution remaining on the surface of the fruit leaf can only be fully absorbed by the sufficient amount of nutrient solution to remain on the leaf surface branches for a long time.

1 Spraying amount: When the fertilizer liquid is within a certain concentration range, the retention amount on the tree body is proportional to the spraying amount, but if it exceeds a certain limit, the fertilizer liquid will be lost a lot. Generally, the optimum amount of spray is optimal when the liquid will flow from the blade without flowing down.

2 Structural features of the surface of the tree: the uprightness and smoothness of the fruit leaves and the bulges or depressions of the stomata, the number of trichomes, and the thickness of the stratum corneum all affect the absorption and retention time of the fertilizer. For example, the surface of the trichome is often supported by the liquid bead and cannot directly contact the surface of the leaf, making it difficult to absorb.

2. Fertilizer characteristics and use

1 Types and concentrations of fertilizers: There are significant differences in the speed at which different fertilizers enter the leaves. The speed at which the fertilizer enters the blade is one of the important conditions that determine whether it can be pursued as a root. At the same time, the concentration of the fertilizer solution is related to the entry speed. Most fertilizers generally have a higher concentration and faster entry, but magnesium chloride has nothing to do with concentration.

2 The pH of the fertilizer solution: It is beneficial to the absorption of cations (such as K+, Mg2+, Ca2+, etc.) in an alkaline solution, and the absorption of anions in an acidic medium.

3. Tree growth status and leaf structure

1 The physiological function of young leaves is strong, the absorption intensity is large, and the proportion of stomata is large, which is beneficial to nutrient absorption.

2 leaves have many stomata on the back, thin horny layer, and loose sponge tissue and large cell gap, which is beneficial to the absorption of fertilizer solution.

4, climatic conditions High temperature can promote the concentration and drying of the fertilizer, easy to cause the pores closed and not conducive to absorption. The suitable temperature for top dressing is 18~25°C. Therefore, if summer is best done before 10 am and after 4 pm. When the temperature is high, the spraying effect is better. Spraying the mist at a high temperature should not be too small to prevent the water from rapidly evaporating and causing damage.

(2) Precautions for top dressing

1. Master the proper concentration of fertilizer solution. Under the premise of no fertilizer damage, use high concentration to meet the nutrient demand of fruit trees. However, a small test must be done first to determine if it can cause fat damage and then spray it over a large area. The concentration is closely related to tree species, climate, phenological period, and fertilizer type. Generally, when the temperature is low, the temperature is high, and the leaves are old and mature, the fertilizer can be used to lightly damage the leaves, and on the contrary, it must be smaller.

2, when spraying in a timely manner when the fruit tree is in urgent need of a certain nutrient element and exhibits symptoms of deficiency, spraying the element is the best. In general, fruit trees need a large amount of boron during flowering. At this time, spraying borax or boric acid can increase the fruit setting rate. When the leaf area is long enough to be applied to a certain size. The young leaves are sensitive to the reaction of the fertilizer, but the leaf surface is too small and the contact probability is also small.

3. Determine the optimal spraying site. The mobility and re-utilization of different nutrients in the tree are different, so 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. If boron should be sprayed onto the flower, the fruit setting rate can be increased, and the calcium sprayed onto the fruit can prevent physiological calcium deficiency or improve the storability of the fruit.

4, choose the appropriate fertilizer varieties to prevent the occurrence of fertilizer damage, different tree species react differently to the same fertilizer. The effect of spraying urea on apples is obvious, followed by citrus and grapes. At the same time, according to the characteristics of fertilizers and tree species, the appropriate concentration and number of applications should be formulated to avoid the occurrence of fertilizer damage.

(3) Commonly used materials and appropriate concentration of top dressing

The types and concentrations of fertilizers suitable for roots are related to tree species, tree age, phenological period, etc. The following table shows the types and concentrations of commonly used root dressings in China's main tree species, which can be used as reference.

1. Nitrogen foliar spray applied to the foliar application of nitrogen fertilizers are urea, ammonium sulfate, ammonium nitrate, ammonium chloride, etc., of which urea is better. Because urea is a neutral organic nitrogen-containing compound, its molecular volume is very small, its diffusivity is strong, it is easy to penetrate into the cell through the cell membrane, and it 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. Although the nitrogen content is high (46%), it is generally not toxic to fruit trees after spraying. On the other hand, ammonium sulfate and sodium sulfate, etc., are selectively absorbed by causal trees, and SO2-4 and Na+ are easily accumulated in the tree body, such as excessive spraying is harmful to the growth of fruit trees.

2. Foliar spray of phosphorus is commonly used in foliar application of phosphorus fertilizer, such as ammonium phosphate, superphosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate, etc. Among them, ammonium phosphate has the best effect, spraying The concentration is 0.5% to 1.0%. Experiments have shown that ammonium foliar application of phosphorus can promote the growth of new shoots and roots and the effect of flower buds. It is believed that the phosphate fertilizer is absorbed by the leaves and transported to the new shoots, stems and roots.

3. The potassium salts sprayed on the foliar surface of potassium are potassium chloride, potassium sulfate, potassium nitrate, monopotassium hydrogen phosphate and potassium dihydrogen phosphate. Among them, potassium dihydrogen phosphate has the best effect. Potassium can promote the growth of new shoots and roots of fruit trees, and can reduce the wrinkles of citrus and the occurrence of physiological diseases such as floating skin. Potassium can also be absorbed from the leaves and rotated to various parts of the tree.

4. Nitrogen, phosphorus and potassium are combined with other nutrient elements to test the results. The combination of NPK three-component spraying is better. At the same time, the 18-year-old grape was sprayed with calcium phosphate 3.0%, potassium salt 0.50%, Chilean saltpeter (NaNO3) 20.1%, boric acid 0.05%, manganese sulfate 0.02%, and sprayed 3 times before flowering, after berry ripening and during berry growth period. (Single spray or mixed spray), Bordeaux mixture is added to the mixture at the time of spraying, and the roots and top dressings combined with the three elements and trace elements have a significant effect on the yield increase of the grapes. However, the three-element spray zone is in line with the yield of the control zone, and only the sugar content of the berries is increased. It can be seen that in orchards with high soil fertility or orchards lacking trace elements, the three elements must be combined with the application of trace elements, and the effect is better.

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