Detailed Explanation of Key Points for Cold-Resistant Cultivation Techniques of Jujube Trees

Jujube cultivation in Liaoning Province is mainly concentrated in the Chaoyang, Huludao and Jinzhou areas. In recent years, the high price of jujube, especially the high returns from superior new varieties, has driven many growers in many areas to successively introduce and plant on a large scale, but most failed due to freeze damage. New development areas are limited to Dalian and Yingkou, and the varieties are only Pear Jujube, Jinling Round Jujube and the like. Other areas still have scattered courtyard plantings, and mostly with old varieties. To enable better development of jujube production in Liaoning Province, the author believes that attention should be paid to cold-resistant cultivation of jujube.

1 Selection of cold-resistant varieties

There are nearly a hundred main cultivated varieties of jujube in China. Different varieties have different adaptability to different environments, so blindness must be avoided in variety selection. On the premise of paying attention to marketability, the climate difference between the variety's place of origin and the introduction site, as well as the variety's range of adaptation, should first be considered, and then a small-scale trial planting should be carried out.

1.1 Pay attention to marketability

The variety should have the characteristics of good quality and high market price, and within a certain period (within 5-10 years) its returns should be higher than those of other fruit trees such as apple and pear. For example, Pear Jujube is large; Winter Jujube has thin skin, crisp flesh and extremely strong sweetness; Zanhuang Large Jujube has a sweet-sour taste and uniform fruit size. The price of Pear Jujube was 30 yuan/kg in 1998 and 5 yuan/kg in 2004, 1-1.5 times higher than that of apple and pear.

1.2 The premise is adaptability

When selecting a variety, in addition to examining its marketability, its adaptability must also be examined, especially its cold resistance. It is also necessary to understand whether the variety has already been planted in the local area and how it has performed. In particular, consider whether the local climate conditions are consistent with those of the place of origin, whether the frost-free period is sufficient, and whether it can meet the demands for temperature, light, water, etc. at different phenological stages.

1.3 Trial planting must be carried out

For the selected variety, first choose representative plots for small-scale trial planting, investigate its adaptability and the economic performance of the fruit, and only after successful trial planting carry out large-scale extension.

2 Planting

The level of planting technology directly affects the quality of orchard establishment, affects tree growth and development, and further affects the cold resistance of the tree. When planting, start with the planting time, seedling quality and planting method, strictly control each step, and ensure rapid recovery from transplanting, a high survival rate, and uniform, robust growth and development.

2.1 Planting time

Generally carried out before bud break, and not too early. In Liaoning, it is usually carried out from late April to early May.

Jujube trees bud late. When the spring temperature reaches 13-14°C, the buds begin to swell. Only under the condition that root activity begins to strengthen before bud break can the tree obtain sufficient nutrients and water to meet the needs of its growth and development. If planted too early, root activity is poor, and prolonged drought can cause branch dieback, slow recovery from transplanting, and even the appearance of false death or actual death.

2.2 Seedling quality

2.2.1 No freeze damage

When selecting seedlings, first check whether the seedlings have freeze damage. Check whether the cortex within 20 cm of the root crown has split, and whether the cambium has turned yellow, brown or black. If so, they cannot be used to establish an orchard. Generally, lightly frozen seedlings should be left in place to reduce damage to the root system from lifting, allow them to recover naturally and heal the injured parts, and then be used the following year.

2.2.2 High maturity

When selecting seedlings, choose seedlings with a plant height of 80-120 cm and a plump bud zone at a height of 40-60 cm. This type of seedling has more nutrient accumulation and stronger cold resistance, and after trunk heading it buds quickly and grows vigorously. Seedlings that are too tall mostly stop growing relatively late, have a low level of stored nutrients, relatively poor cold resistance, and the plump buds are located high; below the trunk heading height they are mostly shriveled buds, budding is late, branching ability is poor, tree vigor is weak, and false death often occurs, with no budding or branching in the current year. Seedlings that grow too weakly have few nutrients; although they can bud and grow normally, the amount of growth is small, branch growth and development are not substantial, and dieback easily occurs in winter.

2.2.3 No pests or diseases

Strictly carry out quarantine and prohibit the planting of diseased seedlings, such as those with crown gall disease or jujube witches' broom. Do not introduce varieties from epidemic areas, so as to prevent the spread and expansion of pathogens, which can cause tree weakness or death and harm jujube production in the whole orchard and even an entire region.

2.2.4 No severe water loss

Jujube roots lose water very easily under conditions without water-retention measures. Planting seedlings with severe water loss results in slow recovery from transplanting, delayed growth and development, and poorly developed branches. During storage and transport of seedlings, carefully do a good job of moisturizing the seedlings and adopt various moisture-retention measures, such as burying and planting in wet sand in trenches, and packaging and transporting with wet sawdust.

2.3 Planting method

2.3.1 Digging planting holes

Dig planting holes according to different varieties and different densities. The most suitable row spacing and plant spacing is 2 m x 3 m. The planting holes should not be too large or too small; a width and depth of 50 cm each is appropriate. Place topsoil and subsoil separately. First mix the topsoil with organic fertilizer and backfill it into the hole, then backfill the subsoil.

2.3.2 Root soaking and quick planting

To ensure rapid recovery from transplanting and a high survival rate after planting, the roots should be soaked for 12-24 h before planting. Because spring in Liaoning is dry and soil moisture is poor, dig holes quickly, plant quickly, and firm the soil so that the roots are in close contact with the soil. Immediately after planting, irrigate thoroughly, and after the water infiltrates, seal the planting hole tightly in time. In areas with better irrigation conditions, irrigate once more within 1 week after planting, and then cover the planting hole with black plastic film to conserve moisture, raise soil temperature and suppress weed growth. When covering with film, make the center of the hole lower than the surroundings, so as to help the root system collect rainwater and allow water droplets condensed on the inner surface of the film to flow toward the roots.

2.3.3 Trunk heading