Litchi seedlings have main roots, high-pressure seedlings have no main roots, and lateral roots are densely connected to form root discs, fibrous roots are reticulate and mycorrhizal. The root system has no natural dormancy period all year round, and its ability and range of absorbing nutrients are large. Root system has three growth peaks in the annual growth cycle, and its growth is closely related to soil depth, groundwater level, temperature and soil fertility.

The growth and development of litchi roots need high temperature and high humidity. Suitable for mountain red soil, yellow loam, flat sandy loam, alluvial soil and even clay. However, the acid sandy loam with pH5~6 is characterized by deep soil layer, rich alluvium and organic matter, loose soil, good drainage and irrigation performance, good fertilizer conservation performance and promotion of mycorrhizal reproduction.

2. Vegetative growth characteristics of new shoots

Litchi replaces fruiting branches by growing new buds. New shoots germinate many times a year. Generally, young trees germinate 3~5 times a year, 10~20-year-old fruit trees germinate 2~3 times a year, and decades-old trees germinate only 1~2 times a year. The early and late sprouting, frequency and length of the same tree age are related to the nutritional status of the tree. Healthy trees with adequate nutrition produce bamboo shoots early, frequently and for a long time.

3. Vegetative growth characteristics of leaves

The leaves are pinnately compound, and 2~4 pairs of leaflets are alternate or opposite. The life span of leaves is 1~2 years, and the old leaves fall off one after another at the germination stage of new shoots. The replacement of new leaves and old leaves makes litchi consume more nutrition.

4. Fruit growth and development characteristics

Litchi is a panicle. In the process of fruit development, fruit dropping may occur at various stages. Fruit drop is the most serious in the young fruit period, also known as physiological fruit drop. According to Zhong Yangwei's observation (1983), the nutritional status of glutinous rice paste is poor, and the fruit drop rate at the end of the first stage of fruit development is as high as 90%. When entering the seed development stage, lack of nutrition will lead to embryo death and fruit drop in the second stage; According to relevant investigation data, malnutrition occurs in young fruit stage, and the mortality rate in mid-embryo is 54%~76%. 32P tracer test showed that fruit drop was related to phosphorus deficiency. When phosphorus is insufficient, the temperature is too high during the day and the water loss is too fast, even if the young fruit with normal pollination and fertilization will drop fruit; In the later stage of fruit development, nutrients are transferred and accumulated in the fruit. If there is insufficient nutrients in the middle stage, the fruit will drop in the third stage and then pick it. From this point of view, ensuring adequate nutrition supply at this stage is an important measure to obtain high yield and high quality litchi.