Take active measures to prevent and control the freezing injury of tea trees

Freezing injury is the main weather disaster suffered by tea trees. After the tea tree suffered from frost injury, it would affect the yield and quality of tea, and seriously cause serious defoliation and even death of the whole plant. According to the growing season, tea freezing injury can be divided into overwintering freezing injury and budding freezing injury, and the latter has the greatest influence on the yield and quality of spring tea in that year.

Prevention of freezing injury in overwintering period

In the growing season, we should strengthen the management of fertilizer cultivation, pay attention to the prevention of diseases and insect pests, and implement the combination of collection and cultivation to promote the healthy growth of tea trees, so as to accumulate more organic matter and improve the resistance to low temperature. In autumn and winter, base fertilizer, especially organic fertilizer, should be re-applied to improve soil temperature.

During the tea interval, the raw soil on the surrounding barren hills was cultivated in the tea garden, and the tea rhizosphere was raked flat to promote the tea tree to take root downward. This helps to preserve fertilizer, water and heat preservation, not only promote the growth of tea trees, but also enhance the ability of cold resistance.

The leaf retention period of alpine tea garden is closely related to the frost injury of tea trees. the leaves in the late autumn tea are easy to suffer frost injury because of the tender leaves during the winter. The leaf retention period should be at the end of spring tea or the beginning of summer tea, when the leaves are mature and have a strong ability to resist low temperature, which is conducive to the safety of tea trees in winter.

Spreading grass between rows of tea gardens can resist both drought and freezing. The low temperature of grass-laying tea garden in winter can increase by 1 / 2 ℃ than that of non-grass-laying tea garden, which can reduce the degree and depth of permafrost and maintain soil moisture.

Interplanting overwintering green manure between rows of tea garden in autumn, covering the ground, can increase soil temperature and reduce frost injury, and these green manure can be used as fertilizer in spring. The green manure suitable for interplanting are pea, vetch, alfalfa and so on.

The establishment of protective forest in tea garden can reduce the wind speed, adjust the temperature, reduce evaporation and improve the microclimate of tea garden obviously. The alpine tea garden planting shelterbelt in the windward mouth can effectively resist the attack of cold wave.

Prevention of late Frost

Late frost has a great impact on the production of famous and high-quality tea, so it is very important to actively prevent late frost. For the prevention of late frost, in addition to the preventive measures of frost injury during the overwintering period, the following measures can also be taken:

Smoke to ward off frost. The function of smoking is to form smoke in the air of the tea garden, to prevent the radiation diffusion of heat, and to use "Greenhouse Effect" to prevent late frost. The method is to set up a pile according to the wind direction, terrain and area before the frost comes that night, and the temperature drops to about 2 ℃ to light the fire, which can not only prevent the late frost and accumulate fertilizer, but also kill two birds with one stone.

Spray water to wash the cream. Tea gardens with water sources and sprinkler irrigation equipment can make use of these equipment to spray water when frost is harmful that night to wash away the frost on the tea buds.

Cover with frost protection. Before the advent of low temperature and cold wave, cover the surface with straw, weeds and sunshade nets to protect tea trees from frost.

The methods of preventing late frost in foreign tea gardens include air supply method (installing fans in the field), spray freezing method (keeping the temperature of bud leaves about 0 ℃), heating method (increasing the temperature of tea canopy) and so on.

Remedial measures for freezing injury

Pruning. For the tea trees that are severely frozen (branches and leaves freeze to death, freeze-dried), the frozen branches and leaves should be pruned immediately after the temperature is warmed up to prevent the germination of frozen buds and leaves. The pruning height should be mastered to cut off the frozen branches and leaves and cut lightly with slight frost damage. Too heavy pruning will delay the growth and germination of spring shoots, delay the mining time, and affect the yield. However, for the tea garden with no symptoms of frost injury on the canopy, the period of light pruning can be changed to the middle of May after spring tea instead of pruning before spring tea. In this way, spring tea can germinate early and pick famous and high-quality tea early.

Shallow tillage and fertilization. Freezing injury brings certain trauma to tea trees, so shallow ploughing and fertilization should be carried out as soon as possible. After the occurrence of frost injury in overwintering period, spring bud fertilizer should be re-applied, and the amount of fertilizer should be increased by about 20%, and a certain amount of phosphorus and potassium fertilizer should be applied at the same time. After the occurrence of freezing injury in the sprouting stage, spraying foliar fertilizer when the spring bud fish leaf unfolds to the first leaf can promote the restoration of tea plant vitality, tea bud germination and new shoot growth.

Cultivate the crown. For the tea trees that have been lightly repaired after being frozen, spring tea should be picked with a large leaf, while summer and autumn tea should be picked routinely, which is not only beneficial to maintain the crown, but also can pick some high-grade high-quality tea to reduce the loss caused by freezing injury. The frozen tea trees after re-pruning or table-cutting should be mainly cultivated, and the specific requirements should be referred to the cultivation and management of heavy-pruning and Taiwan-cut tea gardens.

Clear ditches and drain water. For the tea garden land with poor drainage and waterlogging, the clear ditch drainage should be grasped as soon as possible, so that the groundwater level can be lowered below the tillage layer.