Young walnuts have a large pith core, high water content, and weak cold tolerance. In cold and arid northern regions, the branch bark often becomes shriveled and dry during winter, a phenomenon commonly referred to as "drawing." This condition affects the development of the sapling canopy and can lead to plant death, especially in early varieties where drawing is more prevalent. After five years of observation and experimentation, we have identified effective strategies that fruit farmers can apply based on the underlying causes of walnut sapling drawing.
**Causes of Drawing**
1. **Improper Fertilization and Irrigation Management**: Many trees that experience drawing have been over-fertilized with nitrogen in the later stages of growth, or they’ve received excessive irrigation or rainfall without proper drainage. This leads to overly vigorous growth, long and late shoots, and poor nutrient accumulation. As a result, the shoots are underdeveloped, reducing the tree’s ability to withstand cold. Additionally, some orchards are overwatered early in spring, which lowers soil temperature and hinders root water absorption, leading to increased water loss from the shoots and higher chances of drawing.
2. **Climate Factors**: Early winter brings sudden drops in temperature, preventing trees from acclimating properly. Abnormal temperature fluctuations—hot and cold spells—can stress the trees. In early spring, dry and windy conditions increase transpiration from branches, delay warming, and affect root moisture uptake, further contributing to drawing.
3. **Inadequate Preventive Measures**: Some orchards attempt to protect against drawing by covering the soil around the trunk, but if this is done too early, it delays the warming of the ground and increases the imbalance between water supply and demand in the tree. Also, tying the trunk with grass for protection is often ineffective and fails to prevent drawing.
**Preventive Measures**
1. **Scientific Fertilizer Management**: In late autumn, deep plowing and organic fertilizer application should be done. Afterward, adequate watering for winter is essential. In early spring, top-dressing combined with watering helps improve soil moisture and root absorption. During the growing season, foliar fertilization should be increased. Before July, nitrogen-based fertilizers should dominate, while after July, phosphorus and potassium should be applied to enhance photosynthesis, promote nutrient accumulation, and strengthen shoot development. From July onward, watering should be reduced until leaves fall, and drainage must be ensured. Nitrogen fertilization should stop by August.
2. **Summer Pruning**: It's important to control the second flush of growth in early walnut varieties. These shoots grow vigorously but are not fully developed, so they should be pruned promptly to prevent excessive growth.
3. **Chemical Growth Control**: For vigorously growing varieties, applying 300–500 times diluted paclobutrazol or PBO once or twice during summer and autumn can help regulate growth and promote full maturation of branches.
4. **Pest and Disease Control**: Throughout the growing season, attention should be paid to managing pests like the Cloudy Hornbill, moths, Helicoverpa armigera, and diseases such as Ulcer and Branch Blight.
5. **Winter Protection Measures**: For one- to two-year-old saplings that cannot survive outdoors, bending and covering them with soil is the most effective method. In early winter, wrapping branches with 10 cm wide plastic cloth helps protect them. Before the soil freezes, a half-moon-shaped earth mound (0.5 m long, 0.3 m high) should be built 0.3 m away from the tree on the northwest side to shield it from strong winds. The trunk should also be coated with a mixture of whitewash, petrolatum, and polyvinyl alcohol (prepared by dissolving industrial polyvinyl alcohol in warm water at a ratio of 1:15, then stirring for 20–30 minutes and applying once cooled).
Neck Brace,Cervical Collar,Neck Collar Brace,Cervical Brace
Hebei Dingli Medical Equipment Co., Ltd. , https://www.dinglimed.com