In recent years, the symptoms of calcium deficiency in apples have gradually increased. The main manifestations are as follows: First, the brown spots on the surface of the fruit appearing on the surface of the fruit, and the pulp tissue under the epidermis becomes soft and brown. After the bag was picked, the spots were first seen on the top of the fruit and the fruit surface. As the color of the fruit gradually increased, the spots became red around the surface, shrinking into acne spots, and a sponge-like, brown, bitter bitter plaque with a diameter of 5 mm appeared. Second, after harvesting, the symptoms of the fruit are aggravated with the prolonged storage period, and red and black spots, bitter pox disease, spot disease and water heart disease appear. Third, the root system is damaged, the growth point of the root tip is obviously inhibited, the new shoot stops growing prematurely, the young leaves are curled, the edge of the leaves is yellow, the veins are necrotic, and the tree is weak.
First, the cause of calcium deficiency in apples
1. Climate factors. The apples were dry in the early stage of growth and had little rainfall. Drought leads to a decrease in soil water content, mineral nutrients cannot be absorbed by roots; due to soil compaction, root activity of fruit trees is limited, new root formation is rare, and nutrient uptake is not normal, and calcium nutrition can only be absorbed by the root tip. It is said that absorption is more difficult, and the calcium deficiency of trees and fruits is particularly serious. In the later stage of fruit growth, there is more precipitation. Excessive rainfall increases soil mineral nutrient leaching. On continuous cloudy days, the transpiration of fruit trees is reduced, while calcium is mainly absorbed by the root tip of plants, and transported with transpiration water, so the rain absorbs calcium. Not good.
2. Fruit bagging. Fruit bagging is an important technical measure for the production of green fruits. However, after bagging, it changes the wet, warm and light microclimate of the fruit, which in turn affects the absorption of calcium during fruit growth and development. After bagging, the humidity in the bag is significantly higher than that outside the bag, and the transpiration is reduced, while the concentration of auxin in the fruit is increased under dark conditions, and the fruit is correspondingly increased, further reducing the calcium concentration of the fruit.
3. Reasons for fertilization. In the use of chemical fertilizers, attention is paid to nitrogen, phosphorus and potassium fertilizers, and the application of micro-fertilizers is common. For example, trace elements such as calcium, boron, iron and zinc, amino acids and humic acid foliar fertilizers are applied less on apples. The application of a large number of chemical fertilizers increases the concentration of soil solution, reduces the soil water potential, and reduces the concentration of soil calcium solution. At the same time, due to the large amount of nitrogen and potassium ions, the calcium ion is antagonized, which not only inhibits the absorption of calcium by apples, but also reduces the transfer of calcium to fruits, resulting in physiological diseases of the fruit (pox, bitter, sickness, etc.) ).
4. Reason for trimming. The amount of pruning is too large, which weakens the total growth of the whole tree, especially the growth inhibition of roots, and it is difficult to form new roots, which affects the absorption of calcium and other nutrients by the roots of fruit trees. At the same time, due to the excessive weakening of the aboveground part, it affects the balance between the ground and the ground, causing some branches to grow up, consuming too much nutrients, reducing the nutrients in the tree, competing for calcium in the leaves and fruits, and causing calcium deficiency in the fruits. symptom.
Second, preventive measures
1. Deeply turn the soil and improve the structure. Deep turning can improve soil permeability, improve soil water retention and fertilizer retention capacity, and regulate soil nutrient environment. It has obvious effects on enhancing drought resistance and stress resistance of plants, and reduces the incidence of physiological diseases such as calcium deficiency. At the same time, combined with winter fertilization, it has a significant effect on improving the yield and quality of fruit and reducing the incidence of trace elements such as calcium deficiency. Deeply turning between the rows of fruit trees, digging a trench of 30-40 cm wide and 50 cm deep, laying a layer of crop straw at the bottom of the ditch, covering the soil, mixing some compound fertilizers, and using 70% of the total amount of phosphate fertilizer for the whole year, nitrogen fertilizer 60%, 50% of potassium fertilizer and various micro-fertilizers are mixed and applied.
2. Add organic fertilizer to enhance the tree potential. Organic fertilizer can promote the formation of roots of fruit trees, which can not only strengthen the root system, but also ensure that the fruit trees can fully absorb and utilize various mineral nutrients in the soil, and improve the soil nutrient environment. Therefore, the application of organic fertilizer is an important measure to balance the nutrient status of orchard soil, increase fruit yield and improve quality. Generally, 4,000 to 5,000 kilograms of organic fertilizer is applied in acre, combined with quick-acting fertilizer, and applied once in spring.
3. Scientific calcium supplementation. There are two key periods for the absorption of calcium in fruit trees: one is that within 50 days after flowering, more than 80% of the amount of calcium required for fruit accumulates in the young fruit stage. In this period, calcium should be supplemented 3 to 4 times, 7 to 10 days apart. Second, 30 to 40 days before fruit harvest, calcium should be supplemented 1 or 2 times. When supplementing calcium, try to spray calcium on the surface of the fruit or on the back of the leaf.
Calcium fertilizer types should be selected for high calcium ion concentration, strong activity, high absorption rate, such as Merrill's high-efficiency calcium, CA2000 calcium treasure, gold calcium and so on. In the later stage of fruit tree growth, emphasis should be placed on “controlling nitrogen, increasing potassium, stabilizing phosphorus and supplementing microâ€, increasing the application of trace elements to reduce the concentration of soil solution, optimize soil nutrient environment, and improve the resistance of fruit trees.
4. Reasonable load, bagging at the right time. Reasonable flower thinning and fruit reduction, reducing nutrient consumption. Red Fuji apple should leave one flower every 20 to 25 cm, and leave 40 leaves for one fruit. After Xie Hua, first combine the spray, add calcium twice, and then carry out the bagging. The bagging is too early and the fruit grows slowly, affecting the absorption of calcium.
5. Scientific irrigation to keep the soil moist. 4 to 7 weeks after Xiehua is the peak of calcium absorption. At this time, water shortage, affecting the occurrence of new roots, calcium is fixed by the soil, which is not conducive to absorption. During the harvest period of the fruit, keep the soil moist, and it is strictly forbidden to fill the water before harvesting.
6. Reasonable trimming to make the tree body ventilate and transmit light. Close planting, try to thin, to achieve ventilation and light, try to use winter heavy shear instead of thinning. Paying attention to the growing season pruning can not only regulate the tree structure, but also adjust the growth balance under the tree and under the tree, which is conducive to root growth, so that the fruit tree can absorb enough calcium and other trace elements to ensure the fruit yield and quality.
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