Blueberry leaves are curly, the tips are withered, and the leaves are light green and thin. Why?

(1) Common nutrient deficiency \x0d\ ① Iron deficiency chlorosis: it is a common nutritional disorder of blueberry. The main symptom is green veins, even green veins in severe cases, and the symptoms of upper leaves of new shoots are more serious. The main causes of iron deficiency chlorosis are high soil pH value, calcareous soil and insufficient organic matter content. The most effective method is to apply acid fertilizer ammonium sulfate, and if acid peat is mixed with soil, the improvement effect will be better. Spraying 0. 1% ~ 0.3% comprehensive iron on the leaves is better. \x0d\ ② Magnesium deficiency: When berries are ripe, the leaf edges and veins lose their green color, which mainly appears on the old leaves with fast growth of new shoots, then the green part turns yellow and finally turns red. Magnesium deficiency can be corrected by applying magnesium oxide in soil. \x0d\ ③ Boron deficiency: Its symptom is abnormal bud opening, the terminal bud withers and turns dark brown several weeks after germination, and finally the top end dies. The main reason for boron deficiency is insufficient soil moisture. Adequate irrigation and foliar spraying with 0.3% ~ 0.5% borax solution can be corrected. \x0d\ (2) Fertilization \x0d\ ① Nutritional characteristics and fertilization reaction: Blueberry is a typical calcium-intolerant plant. When cultivated in calcareous soil, it often loses its green due to excessive calcium. Blueberries are nutrient-poor plants. Compared with other fruit trees, the contents of nitrogen, phosphorus, potassium, calcium and magnesium in trees are very low. Because of this feature, blueberries should be specially protected against excessive fertilization to avoid fertilizer damage. Another characteristic of blueberry is that it belongs to the fruit tree that likes ammonium nitrogen, and its absorption ability of ammonium nitrogen in soil is stronger than nitrate nitrogen. When blueberry is planted, the soil has been mixed with organic matter or covered with organic matter, so blueberry fertilization mainly refers to topdressing. Farmhouse manure is rarely used in blueberry cultivation. The main components of blueberry orchard are nitrogen, phosphorus and potassium fertilizer. \x0d\ nitrogen fertilizer: Due to the different soil types and fertility, the response of blueberry to nitrogen fertilizer is very inconsistent. Fertilization experiment of new blueberry cultivated on dark brown soil in Changbai Mountain area showed that with the increase of nitrogen fertilizer application, the yield decreased, the fruit became smaller, the fruit maturity was delayed, and the overwintering was serious. Therefore, the dark brown forest soil type has high nitrogen content, and applying nitrogen fertilizer is not only ineffective, but also harmful. According to foreign research, it is effective to increase the application of nitrogen fertilizer to blueberries under the following conditions. Blueberries have been planted in sandy soil and mineral soil with low soil fertility and organic matter content for many years, and the soil fertility has decreased or the soil pH value has been higher (greater than 5.5). \x0d\ phosphate fertilizer: The soil type of water wetland latent soil in Changbai Mountain area is often short of phosphorus, and the effect of increasing phosphate fertilizer is remarkable. However, when the phosphorus content in the soil is high, increasing the application of phosphorus fertilizer will not only not increase the yield, but will delay the fruit ripening. Generally, when the phosphorus level in soil is lower than 6mg/kg, phosphorus pentoxide 15 ~ 45 kg/ha should be applied. \x0d\ Potassium fertilizer: Potassium fertilizer can significantly increase blueberry yield, early maturity, improve quality and enhance stress resistance. However, excessive consumption did not increase the yield, but made the fruit smaller, severely damaged during the winter and lacked magnesium. In most soil types, the suitable potassium application rate of blueberry is 40 kg/ha potassium chloride. \x0d\ ② Fertilization type, method, period and application amount \x0d\ Type: The yield of whole fertilizer is increased by 40% compared with that of single fertilizer. Therefore, blueberry fertilization advocates the ratio of nitrogen, phosphorus and potassium. The proportion of fertilizer tends to 1: 1: 1. In the soil with high organic matter content, the amount of nitrogen fertilizer decreases, and the suitable ratio of nitrogen, phosphorus and potassium is 1∶2∶3. The content of phosphorus and potassium in mineral soil is high, and the ratio of nitrogen, phosphorus and potassium is 1: 1 or 2: 1: 1. Blueberries are not only difficult to absorb nitrate nitrogen, but also cause harm such as poor growth of blueberries. Therefore, it is best to apply ammonium nitrogen fertilizer such as ammonium sulfate to blueberry. Ammonium sulfate can also reduce the pH value of soil, especially in sandy and calcareous soil with high pH value. In addition, blueberries are sensitive to chlorine, which easily leads to excessive poisoning. Therefore, when choosing fertilizer types, do not choose chlorine-containing fertilizers, such as ammonium chloride and potassium chloride. \x0d\ Method and period: Vaccinium vitis-idaea and Vaccinium vitis-idaea can be furrowed, and the suitable depth is 10 ~ 15 cm. When shrubs and blueberries grow into a garden, they are connected together, mainly by spreading. Generally, the period of soil fertilization is before germination in early spring, which can be applied twice, and then applied 1 time when berries are mature. \x0d\ Fertilization amount: blueberry excessive fertilization is easy to cause tree damage or even the whole plant death. Therefore, the determination of fertilization amount should be cautious, depending on soil fertility and tree nutrition. In American blueberry producing areas, leaf analysis technology and soil analysis technology are widely used in production. According to the production test and years of research results, the standard values of leaf analysis of high cluster blueberry and rabbit eye blueberry were established, which avoided the blindness of fertilization.