The first is to adjust the balance between growth and results. In the life cycle of fruit trees, the relationship between growth and fruiting is constantly changing. Both exist at the same time, restrict each other and can be transformed into each other under certain conditions. Young fruit trees mainly grow in nutrition. If they are allowed to grow naturally without pruning, the total growth is often large, but the tree shape is disordered, the total branch quantity is large, and it is easy to rot, the tree body ages quickly, the fruit quality is poor, and the economic benefit is low. However, through pruning and adjustment, such as increasing the opening angle of main branches, pulling branches, twisting tips, removing stones, etc., the vegetative growth of trees can be slowed down, the formation of flower buds can be promoted, and the simple vegetative growth can be quickly turned to reproductive growth-flowering and fruiting. The adjustment function of pruning is to transform young trees in time according to the growth and fruiting habits of different fruit trees and varieties, and often adjust and maintain the growth and fruiting balance of mature trees.

The second is to adjust the light intensity and enhance photosynthesis. The results of scientific research show that 90% ~ 95% of organic matter in fruit tree products is the product of photosynthesis. Therefore, in order to obtain high yield, we must try to increase the number of leaves and leaf area coefficient, prolong the photosynthesis time and improve the photosynthetic efficiency of leaves. Plastic trimming can directly or indirectly affect the above factors. For example, for peach trees that like light, they are like trees, cups or disks; For moderately light-loving tree species, such as apples and pears, adopt evacuation layered shape or delayed open heart shape; Reasonable opening angle of main branches, properly reducing the number of big branches, reducing the height of crown, increasing the distance between layers, changing the extension direction of branches and adjusting the density of branches can all improve the lighting conditions of the whole tree or part, so that each branch can see the light, thus prolonging the lighting time, enhancing photosynthesis, increasing the nutrient accumulation of trees, promoting the formation of flower buds and improving the early yield.

The third is to adjust the tree nutrition and improve the fruit yield. Pruning will affect the growth and development of fruit trees. The fundamental reason is that pruning can change the production, transportation, distribution and utilization of nutrients in trees. If the fruit trees are pruned again, the water content in the branches can be increased; Girdling and tip twisting can increase the sugar content above girdling site, increase the ratio of carbon to nitrogen, and help to form flower buds.

The fourth is to adjust the leaf-fruit ratio and the flower-leaf-bud ratio. Whether the fruit tree can steadily increase its yield and prolong its full-fruiting period after entering the fruiting period depends on the comprehensive management of soil, fertilizer and water. The leaf-fruit ratio and the flower-leaf-bud ratio must be appropriate, neither too high nor too low. Using pruning technology to adjust, the effect of high and stable yield in successive years is obvious, which overcomes the phenomenon of bearing fruit in big and small years and improves the fruit setting rate and fruit quality.

The fifth is to adjust the fruit load. Fruit load refers to the number of fruits produced by a fruit tree or 667 square meters (1 mu). The more fruits, the greater the fruit load, and the less fruits, the smaller the fruit load. However, due to different kinds and varieties of fruit trees, different age and crown size, different tree vigor and different suitable fruit load. Generally, the load of strong trees can be appropriately larger, the load of weak trees and old trees can be appropriately smaller, and the load of medium trees is in the middle. If the number of fruits per unit area is calculated, the fruit reserves per hectare in high-yield apple orchards should be 225,000 ~ 300,000 large fruits such as Red Fuji, Golden Crown and Starkrimson, and 450,000 ~ 600,000 small fruits. Too many achievements, small scale, poor quality, low economic benefits, and easy to cause the number of years of achievements, shorten the life of achievements. Therefore, according to the variety and variety characteristics, age, tree potential, management level and site conditions of fruit trees. , through pruning adjustment, keep the appropriate load.