Cultivation techniques of tea plant

Temperature is the basic condition for the life activity of tea trees. It not only affects the geographical distribution of tea, but also restricts the growth rate of tea. The effect of temperature on tea tree is mainly manifested in two aspects: air temperature and soil temperature.

Air temperature mainly affects the growth of aboveground parts, while ground temperature mainly affects the growth of roots. But air temperature and ground temperature are interrelated. As far as temperature is concerned, tea trees from the tropics to temperate zones can adapt widely. But as far as fertility is concerned, there are three basic points of temperature, namely, the starting temperature of tea tree growth, the suitable temperature and the low limit temperature.

(1) growth threshold temperature

The average temperature that causes tea sprouting is called the threshold temperature of growth, and biologically it is called the lowest temperature. The daily average temperature of most tea varieties needs to be stable above 10 ℃, and the tea buds begin to sprout. However, a few tea varieties began to sprout in less than 10 ℃ because of their different ecological environment, such as Zhejiang Biyun, Longjing 43, Jiangxi Wuyuan early bud germination threshold temperature is ≥ 6 ℃, this kind of early bud varieties, the mining period can be earlier than other varieties.

(2) the optimum temperature

After the tea bud germinated, when the temperature continued to rise to 14-16 ℃, the tea bud gradually expanded its tender leaves. The optimum temperature for tea plant growth is between 20-30 ℃. If it is within this range, the growth of tea shoots will be accelerated, and the average daily growth can be more than 1-2 cm. From Qingming Festival (early April) to Frosts Descent (late October), the daily average temperature in most tea areas in China is between 20-30 ℃, which is the most suitable period for tea growth and tea harvest season.

The cumulative value of biological effective temperature (daily average temperature more than 10 ℃) in tea growing season is called effective accumulated temperature. The effective accumulated temperature for tea plant growth is above 4000 ℃. The annual effective accumulated temperature of tea areas in China is generally between 4000 and 8000 ℃. The more the effective accumulated temperature is, the longer the annual growth period is. Due to the difference of climatic conditions in the north and south of China, the growth period of tea trees is also different. The annual growth period of tea trees in most tea areas is about 8-9 months, while the exploitable period is 7-8 months.

(3) low limit temperature

In most mountainous areas of China, when the average temperature is lower than 10 ℃ from December to February of the following year, tea buds stop germinating and are in a state of overwintering dormancy, and sometimes severe low temperature frost occurs, which will cause frost damage to tea seedlings, young trees or varieties with poor cold resistance. The absolute lowest temperature that tea plant can endure varies with variety, tree age, organ, cultivation management level and growing season. When the temperature drops to-2 ℃, most of the camellias fall off and die; when the temperature drops to 1-2 ℃, the germinated tea buds also wither and scorch, while the shoots of tea trees have a strong ability to endure low temperature, and tree-type large leaf species can endure about-5 ℃. Shrub middle and small leaf species have a stronger ability to endure low temperature, which is generally about-10 ℃. If they are covered with heavy snow, they can endure a low temperature of about 15 ℃ below zero. For another example, the cold resistance of different tea varieties is different, but the performance of the same variety is also different under different ecological conditions. Ruzheng and Dabai tea can tolerate the low temperature of-7 ℃ in Fujian, but can endure the low temperature of-8 to ℃-10 ℃ in the tea area of southern Anhui. Generally speaking, freezing damage will occur when it is lower than the low temperature limit of "tolerance" of tea trees. The degree of freezing injury of tea trees is not only directly related to the temperature, but also closely related to the duration of low temperature, wind speed and freezing time. According to the investigation of Zhejiang Meteorological Bureau in Shengxian County, Zhejiang Province, during the overwintering period, when the temperature drops to about-6 ℃ and freezes continuously for 6 days, when the wind speed from the northwest is every 6-8 meters, the young shoots of local tea varieties will suffer varying degrees of frost injury; when the lowest temperature drops to-8 ℃ for more than 12 days, it will cause serious freezing injury, which will cause tea shoots to freeze to death and old leaves to turn yellow. Generally speaking, under certain low temperature conditions, the longer the low temperature and soil freezing time, coupled with the dry northwest wind or the sudden drop of temperature after the climate warming in early spring, will aggravate the degree of freezing damage.

It is true that too low temperature will cause tea trees to suffer frost damage, and too high temperature will also cause heat damage to tea trees, but there are not many opportunities to encounter. If the average temperature of the day is more than 35 ℃, the growth will be inhibited, and the daily extreme maximum temperature reaches 39 ℃. Under the condition of less rainfall, some tea trees appear burnt and scorched leaves and young shoots wilt. This phenomenon is the heat damage of tea trees. It is usually new shoots and young leaves that are more vulnerable to such adversity than aging branches.