What is the reason for the low fruit hanging rate of longan?

The low fruit setting rate of longan may be related to climatic conditions, water and fertilizer management, etc. Now the cultivation techniques of longan are provided for your reference. 1. Seedlings should be planted in September 9- 10/0 in autumn or March-May in spring and summer. Select the first-class seedlings of excellent varieties with complete "three certificates" and complete mud blocks, and plant them according to the spacing of 4×6m. Before planting, cut off the injured big roots and immature branch tips, leave 60 cm short sections for non-branched seedlings and 50 cm short sections for branched main branches. When planting, the planting should be straight and the depth should be appropriate (bare roots should be covered with soil), then a planting pier with high outside (30cm above the ground) and low inside should be built, and finally root water should be poured and covered with straw and weeds. Second, soil management: intertillage the fruits immediately after picking, and shallow plow the soil in the dish in time after the rain in summer and autumn to ensure that the soil is loose and breathable. 3. Fertilized longan is a fruit tree with high potassium requirement. The ratio of nitrogen, phosphorus and potassium in the annual fertilization should be 1.0: 0.5: 1.2. 1. Fertilization of young trees: adhere to the principle of "two fertilizers at one tip and thin application", that is, in the middle and late March, early May, mid-June, early August and early September, apply 0.5 kg 1-4 plants of urea per decomposed human and animal manure, and spray 0.3% urea +0.5 on the leaves every time when the new leaves are close to maturity. When the first batch of new buds are mature after planting, the first batch of fertilizer for planting seedlings is applied. Apply human and animal manure once in winter as heat preservation fertilizer. 2. Fertilization of fruiting trees: ① Fertilization before flowering: In the middle and late March, decomposed human and animal manure should be combined with compound fertilizer (chlorine-containing compound fertilizer cannot be used). Fertilization accounts for 30% of the whole year. ② Strong fruit fertilizer; From late June to early July, nitrogen, phosphorus and potassium fertilizer were applied at one time to make summer shoots strong. The quality of this fertilization has a great influence on the current year and next year's output. Fertilization accounts for 50% of the whole year. (3) Fruit picking fertilizer: after fruit picking, apply available nitrogen fertilizer in time to promote early autumn shoots and restore tree vigor. Late-acting fertilizer should not be used in this fertilization to avoid late autumn or winter shoots, and the application amount accounts for 20% of the whole year. 3. Fertilization method: Young trees and fruiting young trees alternately furrow and fertilize outside the crown drip line to accelerate the growth of horizontal roots. Adult trees should be furrowed radially in the crown, and each tree should be fertilized with 6-8 furrows to improve the utilization rate of fertilizer. Four, the main pest control 1, downy mildew: adult tree diseases, which have a great impact on yield. (1) Remove dead trees and leaves in winter, cut off fallen branches in summer and burn them centrally. (2) Spraying metalaxyl and ethyl phosphate on the crown before and after flowering in early and middle July respectively. 2. Bemisia tabaci: At the early stage of leaf spreading of each new shoot, that is, in the middle and late April, early July and late September-10/early October, trichlorfon or chlorpyrifos are sprayed continuously for 2-3 times respectively, once every 7 days. 3. Integrated control of other pests: Other pests in longan mainly include Lepidoptera, Spinibarburidae, Curculicidae, Scarabaeidae, stinkbug and so on. Field inspection should be strengthened. According to the insect situation, timely drug control should focus on the insect situation in the field before flowering, after flowering, in the middle and late June, from the end of July to the beginning of August, and before fruit picking. Trichlorfon and mirex can be used interchangeably. 5. Shaping and pruning 1, young tree shaping, mostly adopting natural round head shape, the stem height is 50-60 cm, each plant selects 3-4 main branches with uniform distribution direction, each main branch starts to select 2-3 auxiliary branches with uniform distribution direction at about 40 cm from its branches, and each auxiliary main branch starts to select 2-3 tertiary branches at 30 cm from its branches, and so on. Young trees grow vigorously in summer shoots, so they should leave 30-40 cm for topping in time. In order to prevent the crown from drooping, the oblique drooping side branches should be cut off, so that the whole crown can form a compact natural round head shape that is dwarfed without drooping. At the end of 10, all immature late autumn branches should be removed. 2. Pruning of fruiting trees: usually carried out in March after frost breaking and before germination in spring, mainly pruning dense weak branches, clustered branches, short cut branches of pests and diseases, drooping branches, knocking out moldy piles, and paying attention to keeping some strong riding branches and branches with normal growth in the inner cavity to form a three-dimensional fruiting crown. The fruiting young trees with short crown and easy operation should be combined with summer and autumn pruning, short cutting of flowers and blurring of summer shoots.