Causes of freezing damage of walnut in Tianshui, Gansu and antifreeze remedies
Tianshui City is located in the southeastern part of Gansu Province. It has a temperate monsoon climate with an annual average temperature of 11 °C, a frost-free period of 185 days, an average temperature of 22.8 °C, an annual average precipitation of 491.7 mm, and an extreme winter minimum temperature of -17.4 °C. It is suitable for cultivation of various deciduous fruit trees. . In recent years, the Tianshui walnut industry has become a new growth point in the rural economy. However, due to several low-temperature freezing damage and late frost damage, the yield of walnuts has decreased, especially in 2006 and 2010, which caused the walnuts to be harvested. Therefore, in order to solve this problem, the area After investigation and research in 2013-2016, we finally found out the causes of freezing damage and effective preventive and remedial measures in time.
1 The main causes and characteristics of freezing damage
1. 1 Rainy (or high temperature) in autumn and too low in early autumn
Autumn is the season when the walnut tree transitions from growth to dormancy. At this time, the weather is at a high temperature and rainfall. It will affect the walnut tree into dormancy, which will make the walnut branches long and greedy. If it suddenly cools down, it will cause serious damage. Branches are frostbitten, and some still cause the whole plant to die.
1. 2 The absolute low temperature and low temperature duration in winter is too long
Absolute low temperature in winter will cause the intercellular water to freeze. When the cells are destroyed, it will cause freezing damage. The main manifestations are the cracking of the trunk skin, the drying of the new shoots, and the blackening of the medulla and xylem.
1. 3 spring cold and drought
The cold resistance of walnut trees decreases with the rise of temperature. Therefore, in the spring, the cold and drought are easy to cause damage to walnut trees. At the same time, the freezing damage of walnut trees is closely related to tree species, tree age, tree parts, topography and management.
1. 4 low temperature lasts for a long time
The long duration of the low temperature causes the walnut branches, the formation layer, the xylem and the pith to be frozen by the tissue.
1. 5 Snowfall is large, snow is accumulated for a long time
The temperature difference between day and night under the snow layer is 6 ~ 8 °C larger than the ground. When the ice and snow coexist, the skin, the phloem and the formation layer of the trunk will absorb the heat of the contact surface, which will cause the walnut to freeze.
1. 6 Autumn is prosperous, not picking up in time
The control of nitrogen and water control is not in place, the moisture content of branches is high, the sugar content is low, and the frost resistance is poor, which leads to the freezing of the strips and branches.
1. 7 Summer trimming is too heavy, germination is not timely
The thick, thin and weak twigs are shrunk, and the quality of leaves and flower buds is poor, so that the branches and flower buds are frozen.
1. 8 high output, strong and strong
Many trees, diseased trees, injured trees, weak trees, and trees that have been dried up for years have serious frost damage due to insufficient accumulation of nutrients in the branches.
1.9 Winter protection measures are not in place
The height and thickness of the branches and soils are not enough, and they are not strictly buried with dry soil.
2 main measures for antifreeze
2. 1 Walnut tree freeze damage remedy
(1) Protective measures
Before germination in early spring, the whole tree should be sprayed with stone sulphur mixture to remove surface adhesion and various wintering pathogens that are lurking on the surface.
(2) Watering in time
After the occurrence of the freezing damage, water was sprayed in time in April of the second year to promote the germination of the tree.
(3) Cutting anvil for freezing
The young saplings of walnuts that have not sprouted after watering are cut and germinated; for the big trees, the bark with severe rot is to be scraped to prevent the spread of rot.
(4) Surgical treatment of diseased spots in a timely manner to prevent rot and continue to infect and spread
Scrape the rotten tissue and scrape the healthy tissue around the lesion. Finally, apply 843 remediation agent stock solution, or Guoconkang original solution, or 70% methyl thiophanate WP 50 times to prevent infection. The rot disease can occur multiple times during the growth period, so Xiaqiu should promptly check for treatment.
2. 2 Main measures to prevent freezing damage
(1) Strengthening soil and fertilizer management
More organic fertilizer, less nitrogen fertilizer, the proportion of nitrogen, phosphorus and potassium fertilizer should be appropriate; 3-4 months irrigation 1 germination water, late growth stop fertilizer, control irrigation; after dormancy, before irrigation, irrigation once perfusion.
(2) Creating a sound shelter forest system
New or existing walnut trees should be built or supplemented with protective forests; use shelter forests to reduce wind speed and weaken the direct impact of cold air on walnut trees, thus improving the orchard microclimate.
(3) Strengthen pest management
If the diseases and insect pests of walnut trees are serious, it is necessary to prevent and control in time to ensure the health of the tree and improve the ability of the walnut tree to prevent its own damage.
(4) Winter protection
In the autumn, the walnut branches are dryly coated with white ash, and the roots and necks are soiled and protected against cold in the future; before the deciduous and cold currents are coming, the high-fat film or fruit tree antifreeze can be sprayed to improve the cold resistance; after the winter snowfall, the tree tray should be removed in time. Snow on the surrounding, trunks and branches; the evening of heavy snow should be in the park, and 6 piles of smoke per mu of orchard will heat up.
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