A, jujube seedlings freeze injury symptoms

The jujube seedlings freeze damage position mainly occurs in the jujube seedling rhizome or grafted joints, and the severity of the freeze injury is relatively large due to variety and topography. In the case of light freeze injury, the rhizome phloem was cut open with a knife. The cortex and formation layer were yellow in color; the weight was yellowish-brown or brown; in severe cases, the root phloem and xylem were separated, and the longitudinal opening or peeling of the trunk was tubular.

Second, jujube seedlings freeze damage characteristics

1, jujube seedlings breeding methods are different, there are differences in the severity of freezing injury

Through investigation and comparison of jujube grafted seedlings and returning seedling rooted seedlings, jujube seedlings exhibited freezing and damage, and grafted seedlings suffered heavy damage. 1 year old and 2 years old Jingtai jujube seedlings in Jingtai County, Gansu Province did not suffer from freezing injury. The freezing damage rate of Zhongning Ningyuan jujube returning seedlings was about 12% in Jiaozishan Forest Farm in Zhongning County, while the 1-year-old Zhongning jujube grafted seedlings suffered freezing injury. The rate has reached about 40%. The annual freeze-injury rates of Zaohuang jujube and jujube in the two counties of Shaanxi and Qingde were 64% and 68% respectively.

2, varieties, topography is different, there are differences in frost

By investigating the breeding conditions of the grafted seedlings of our region, such as Concentric Circle Date, Zhongning Jujube, and Lingwu Long Jujube, the results showed that the concentric circular jujube and the Zhongning jujube were cold and light, and the Lingwu long jujube was freezing and injuring. Located in Yongning County on the 52nd acre of the Yellow River, the frost damage rate of the Ningyuanzao jujube grafted seedlings is almost zero, while the frozen injury rate of the 8 mu grafted seedlings of the neighboring plots is about 8%.

The same variety and different soils showed different performances. The two red jujube nurseries with the cooling buffer of the Yellow River water body, and the 1-year-old Zhongning jujube grafted jujube seedlings in the Yongning Yellow River sand land had zero freezing damage rate, while the Zhongning Mozu Forest Farm The annual frost-free rate of one-year-old Ningyuanzao grafted seedlings grown in clay land reached 84%.

3, different ages, there are differences in freezing injury

In the same variety, the performance of the jujube seedlings was light and cold, and the young jujube seedlings suffered heavy damage. Lingwu horticultural team is located 3 years old Wuling jujube grafted seedlings cryoprotection rate is zero, and 1 year life Ling Wu long jujube frost damage rate of about 70%.

4. Microclimate can significantly reduce jujube seedlings freezing injury

The investigation found that the 1-year-old Ningyuan jujube grafted nursery without freezing injury was under two microclimate conditions: first, the nursery was located in the buffer zone for cooling water in the Yellow River; second, the nursery was located in the protected area of ​​the village; therefore, the warming microclimate could be significant. Reduce jujube seedlings freezing injury.

Third, some suggestions

1. The jujube development seedlings must be based on the three local breeds in the area. To adjust the seedlings, we must carefully check the roots and the grafting interface. As the temperature rises, the symptoms of frost damage will become more and more obvious.

2. For the jujube nursery, which is seriously affected by freezing, it is recommended that jujube seedlings be leveled in place to prevent the decline in planting survival rate due to seedling movement.

3, to strengthen the management of planting 1-2 raw jujube garden, the occurrence of cracked trunk of the saplings with plastic film winding (about 40 cm in height), spraying water retaining agent on the tree and other measures.

4. Take effective measures to prevent wild rabbits from eating jujube seedlings and trunks of young jujube trees to avoid causing new losses.

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