(1) keep in balance
The balance system directly related to fruit tree pruning technology mainly includes the following three aspects:
(1) Maintain the balance between crown and root system. Because the crown and the root system above the ground are in a mutual supply and demand relationship, they always keep a certain relative balance. However, the life of fruit trees is sometimes forced to be tested by some unfavorable environments in nature, and any damage to the crown or root system will weaken the normal growth of the other. Therefore, it is necessary to maintain a certain root-shoot ratio balance by pruning. Pay special attention not to disturb this balance artificially when pruning. This is why trees that have not been pruned for many years are easy to peel off if they are pruned too much at one time, and it is more difficult to bear fruit.
(2) Keep the balance between growth and fruit. The growth and fruiting of fruit trees are in the relationship of unity of opposites, which are mutually utilized and influenced. When fruit trees are allowed to develop naturally, there will often be some uncoordinated contradictions in the formation and development of branches, leaves, flowers and fruits, which is the imbalance between tree growth and fruit. Fruit trees with this phenomenon will not grow and produce good fruit. For example, young trees grow too much and it is difficult to blossom and bear fruit; There are too many flowers and fruits in a big tree, which is easy to cause tree weakness and "big and small years" and so on. Therefore, during the development of fruit trees in a year or a lifetime, pruning measures such as adjusting branch angles and thinning flowers and fruits are often needed to maintain the balance between vegetative growth and reproductive growth.
(3) Balance between tree potential and branch potential. Tree potential and branch potential refer to the growth momentum of crown and branches respectively. The growth of trees that meet the requirements in production should be moderately balanced. The key to achieve this requirement is to maintain a balanced growth relationship among all kinds of main branches, especially the growth intensity of reactions between main branches at the same level should be similar in branch length and thickness. Therefore, pruning often uses the polar advantage, heterogeneity and damage effect of branch buds to "restrain the strong and help the weak, and promote the control reasonably" in order to maintain the basic balance between tree potential and branch potential.
(2) improve the relationship
In a year and life, with the growth and development of branches, internal and external conditions often change, leading to the constant transformation of various contradictions and new problems. Therefore, timely pruning is needed to improve the relationship between internal and external conditions of fruit trees.
① Improve the relationship between fruit trees and the environment As the saying goes, "Fruit trees will not grow without fertilizer, and branches and buds will not bear fruit without light", "The branches and leaves are luxuriant, and the flowers and fruits are fragrant." Light, water and air in the environment of fruit trees are all necessary raw materials for leaf photosynthesis to produce organic nutrients, which in turn affects the formation of flower buds and the development and coloring of fruits. Therefore, it is very important to improve the ventilation and light transmission conditions of the crown by frequent pruning.
(2) Improve the relationship between nutrient distribution and utilization in trees. Whether it is inorganic nutrients and water absorbed by roots from soil or organic nutrients produced by photosynthesis of leaves, it is impossible for fruit trees to meet the growth and development needs of branches, leaves, fruits and other organs at the same time, but the supply of current growth and development centers should be ensured first. However, there are often unfavorable factors, which lead to interference and competition from non-growth and development centers. In this case, it is necessary to make local adjustment through pruning to ensure the punctuality, sequence, rhythm and quality of the growth and development of various organs.
(3) Renewal and revival
The optimal growth and development of various organs of fruit trees and the ability to blossom and bear fruit have certain age stages. Beyond this age limit, physiological function will decline. Especially the fruiting ability of fruiting branches is very obvious. Too young and aging branches are not conducive to flowering and fruiting. Young branches are difficult to blossom and bear fruit; Although the old branches can grow into flowers, it is difficult to bear fruit, which is often manifested as more flowers and less fruits and poor quality. Therefore, attention should be paid to the timely renewal and rejuvenation of aging and weak branches when pruning.