Letters from official texts:
How is the bark cracking of young jujube trees? Does it have a big impact? How to deal with it? thank you
Reply:
Expert reply June 2009 19.
This jujube farmer friend:
Hello! What is the reason for the cracking of young jujube bark? Wang Yu, a senior engineer of the National Forestry Science and Technology Extension Center, answered the following questions:
One of the main reasons for jujube tree cracking is freezing injury and excessive growth in winter, that is, excessive fertilizer and water lead to jujube tree cracking.
If your fruit tree is peeling now, it should be because there is too much fertilizer and water and too much nutrient growth, which leads to the peeling of jujube trees. For young jujube trees, the impact is not great. At present, normal water quantity of trees can be ensured, fertilization can be reduced or stopped, and attention should be paid to fertilizer control until winter irrigation in June 5438+ 10, which can not only slow down the vegetative growth of jujube trees, but also prevent the jujube trees from freezing injury caused by excessive growth in winter.
At the same time, the performance and prevention methods of jujube after freezing injury are also introduced here, hoping to help your jujube planting!
First, the symptoms of jujube after freezing injury
Many years' practice shows that mature jujube trees in Xinjiang may suffer from freezing injury when the temperature is below-24℃ for more than 7 days or below-26℃ for more than 24 hours in winter. When the temperature is below -23℃ for more than 2-3 days, young trees planted for one year may be frostbitten.
1. Trunk freezing injury: The temperature is low in winter and changes sharply. The phloem (bark) of jujube trunk is vulnerable to freezing injury. When the frost damage is serious, longitudinal cracks can be formed, and the bark often leaves the xylem along the cracks, and it will roll out when it is serious. Mild frost crack can heal with the increase of temperature, and the whole plant will die when it is severely frostbitten. Frost cracking of phloem (bark) mostly occurs at the position 10-20cm above the root neck. Young trees planted in 1-3 years have weak cold resistance, trunk phloem is easy to freeze and crack, and big trees have strong cold resistance.
2. Freezing injury of branches: Due to the variety difference, or the lack of nutrition accumulation in branches after stopping growing in late autumn or bearing too many fruits, branches at all levels will be frozen to varying degrees after severe cold in winter. In mature branches, the cold resistance of cambium is the strongest, followed by cortex, and the cold resistance of xylem and pith is the weakest. Therefore, after mild freezing injury, the pith changes color first, and with the aggravation of freezing injury, the xylem changes color. Only when severe freezing injury occurs, the phloem is frostbitten, and the branches lose their recovery ability when the cambium changes color.
The flower bud differentiation of jujube began in May, and it bloomed at the same time, and differentiated and flowered many times. In winter, flower buds have not yet formed, so there is no problem of flower buds freezing.
3. Root neck freeze injury: The root neck is the part of the aboveground part that enters dormancy at the latest and ends dormancy at the earliest, with low cold resistance. In addition, the root neck is close to the surface, and the temperature changes sharply, which is most vulnerable to low temperature or temperature change. After the root neck is frozen, the bark first changes color and becomes a local or annular epidermis. The root neck freezing injury is very harmful to jujube trees, which can lead to the weakness of the tree and the death of the whole plant.
4. Root freeze injury: the cold tolerance of jujube root system is worse than that of aboveground part. The roots turn brown after freezing, and the bark is easily separated from the xylem. Generally, thick roots have stronger cold resistance than fine roots, but thick roots near the ground are prone to freezing. Newly planted jujube trees have small and shallow roots, which are vulnerable to freezing injury, while big roots are more cold-resistant. After freezing injury, the roots germinate late and grow weakly, and the new roots can grow normally only after they are sent out.
Second, preventive measures.
1. Jujube trees should be planted on sunny slopes after ditching, so as to reduce root neck temperature deficit and reduce the impact of freezing injury.
2. In summer, we should strengthen the management of fertilizer and water in jujube orchard, strictly control the application of nitrogen fertilizer from July to September, increase the application of phosphorus and potassium fertilizer, and timely pick and germinate jujube trees; In mid-August, water was strictly controlled. 10 Stop the irrigation of jujube trees before the middle of June, so that the trees will be further enriched and the roots will extend underground.
3. Turnover jujube trees in autumn is aimed at blocking soil capillaries and preventing groundwater from rising, just like covering the ground with a quilt to kill overwintering pests and reduce the occurrence of pests and diseases.
4. Deep application of base fertilizer to jujube trees in autumn, the depth of fertilization is below 50 cm, guiding the root system of jujube trees to extend downwards, and improving the cold resistance and drought resistance of jujube trees.
5. Young trees 1-2 years after planting should be covered with soil or grass, and the trunk and branches of big trees should be painted white (mixed by 5 kg lime, 0.5 kg lime, 20 kg sulfur mixture with water and100g salt) to prevent the injury of phloem (bark) caused by sunlight during the day and low temperature at night. After the trunk is painted white, it can be properly wrapped with cloth strips, sacks, cotton felt, reeds or other thermal insulation materials.
6. Root neck soil is beneficial to the safe overwintering of roots. Cultivate soil to protect the root neck and prevent the injury caused by freezing injury and alternating freezing and thawing after the root neck is released from hibernation in early spring.
Thank you for your attention to Bazhou Rural Economic Information Network. I hope you can constantly improve your technical level and get better income!