(1) Young trees bear fruit early and yield early.
The important goal of fruit tree cultivation is to make fruit trees bear fruit early, yield early and prolong the full fruit period. Therefore, in fruit tree pruning, peach trees and other trees and varieties with the characteristics of early maturity and multi-bud growth can quickly expand their crowns, form early and bear early fruits by coring for many times; For vigorous and upright tree species and varieties, the opening angle and young trees should be gently cut and slowly released, and axillary buds or autumn cuttings should be used to blossom and bear fruit early. The purpose of these measures is to make fruit trees enter the full fruit stage ahead of schedule. By pruning, adjusting the reasonable subordinate relationship, cultivating a strong skeleton, enhancing the bearing capacity of trees, rejuvenating old trees in time and prolonging the economic cultivation life of fruit trees.
(2) Improve the lighting conditions of trees.
The length and intensity of light have great influence on fruit yield. Among deciduous fruit trees, peaches and apples like light the most, followed by grapes, pears and chestnuts, and persimmon trees are more tolerant to shade. Plastic pruning can improve the light conditions of trees and improve the efficiency of photosynthesis of fruit trees. If you choose a suitable tree shape, open the angle of main branches, reduce the number of main branches, reduce the height of the tree and the thickness of the leaf curtain, you can improve the lighting conditions and increase the effective leaf area. By reasonably increasing fertilization, improving leaf quality and photosynthetic efficiency and prolonging photosynthetic time, the accumulation of photosynthetic products can be increased, which is beneficial to flowering and fruiting. For young trees and flourishing trees, taking measures such as light pruning, long planting and multi-branching, changing the extension direction of branches and adjusting the density of branches can effectively improve the light conditions of trees, enhance the photosynthetic efficiency of leaves, reduce ineffective consumption, increase the nutrient accumulation of trees, and be conducive to flowering and fruiting and increase early yield. However, if a few young people cut it long, there will inevitably be bad phenomena such as horizontal branches, thick leaf curtains and poor lighting conditions, which will affect fruit yield, quality and economic benefits. On the other hand, although a large number of pruning in successive years can improve the light conditions of trees, the yield is often low because of the overall weakness, excessive nutrient growth, too long branches, insufficient nutrient accumulation in trees, difficulty in flowering and fruiting.
(3) improve tree nutrition
Plastic pruning can improve the metabolic capacity of trees and improve their nutrition. The storage nutrients in fruit trees are basically carbohydrates and nitrogen-containing substances, and their content and proportion have great influence on the growth and fruit of trees. The research results of Fruit Research Institute of China Academy of Agricultural Sciences showed that five-year-old Redjade apple trees were pruned in early April. Two weeks later, it was found that the contents of nitrogen and water in pruned tissues were much higher than those in untrimmed tissues, while the contents of starch and sugar in pruned branches were lower than those in the control. This shows that pruning changes the nutritional composition of fruit tree branches, which is beneficial to the formation of flower buds and the improvement of early yield.
Correct application of pruning technology, especially for big trees in full fruit period, can obviously improve their light conditions, increase the photosynthetic efficiency of leaves, especially improve the nutritional status of leaves in canopy; For trees with many flowers and weak vigor, cutting off some flower buds can reduce nutrient consumption, increase nutrient accumulation of the whole tree, increase the area of the whole leaf and the total number of branches, and promote the growth and development of the whole tree. Pruning of fruit trees in summer also has obvious influence on the nutrient content of branches. The summer pruning experiment of Jin Shuai 10 apple tree by Hebei Fruit Research Institute showed that girdling and twisting the top can increase the accumulation of organic nutrients in the branches, promote the conversion of carbon-nitrogen ratio in the trees to the direction favorable for flower bud formation, and thus promote the flowering and fruiting of summer pruning branches.
(4) It affects the distribution and transportation of tree nutrients.
The research results at home and abroad show that the growth of fruit trees is directly related to the content, species, distribution, transportation and hormones of nutrients in trees. Reasonable pruning can regulate the distribution and utilization of nutrients, thus regulating the growth of fruit trees, so that they can not only promote the robust growth of trees, but also blossom and bear fruit normally. Trimming measures such as changing the head of the back branch, bending and girdling the trunk, girdling and twisting the tip. The original transport direction of nutrients and water was changed by destroying the transport organization of branches, thus improving the local nutritional status, slowing down the vegetative growth of trees, promoting the germination and formation of short branches, and being conducive to early fruiting and high yield. In terms of endogenous hormones, there are more hormones at the top of natural new buds, which can inhibit the germination of lateral buds. However, if the branches are cut off or girdled above the buds, the downward transport channel of endogenous hormones at the top of the branches will be interrupted, which can also stimulate the germination of the lower lateral buds. In addition, the opening of branches such as branches and curved branches will also affect the distribution and transmission of endogenous hormones. Therefore, these pruning measures can also promote the germination of lateral buds and increase the number of short branches, which is beneficial to flowering and fruiting.
(five) affect the growth of fruit trees.
The growth and fruit of fruit trees are mutually restricted and promoted, and can be transformed into each other under certain conditions. Fruits need to be planted on branches with a certain leaf area and a certain number of branches and leaves, so as to make enough nutrients for the growth and development of fruits and form flower buds for the next year to continue to blossom and bear fruit. Therefore, growth is the foundation of fruit, and fruit is the goal of culture. However, if the pruning is too heavy, the nutrition grows too vigorously, the number of strips is too much, and the consumption of nutrition is greater than the accumulation, it will affect the formation of flower buds or the growth and development of young fruits due to insufficient nutrition. For example, after the fruit tree enters the fruiting period, if there are too many fruits and too much nutrition consumption, it will inhibit the vegetative growth of the tree, lead to the loss of nutrients in the tree, weaken the growth of the tree or appear the phenomenon of fruiting in different years. Pruning can effectively adjust the appropriate proportion of flowers and leaf buds and maintain the relative balance between growth and fruiting; Improve ventilation and light transmission conditions; Increase the nutrient accumulation of trees and prolong the fruiting period. In actual production, pruning measures are often used to adjust the size of a year, that is, for large-flowered trees, too many thin and short fruit branches are removed and some medium and long fruit branches are cut short to improve the ratio of leaves to fruits, so as to maintain high quality and high yield year after year.
Enhance the ability to resist natural disasters
According to the local climatic conditions, taking corresponding pruning measures can enhance the ability of fruit trees to resist natural disasters. For example, in windy areas, use low stems and short crowns, or use column or shed pruning to enhance wind resistance; In cold areas such as Northeast China and Xinjiang, in order to facilitate burying in the ground to prevent cold, apples and grapes are cultivated by creeping, fan-shaped pruning, with small crowns and many main vines. In the north with high light intensity, the big branches are easy to get sunburned, so it is necessary to keep the back branches on the main branches; The cold current in early spring often freezes the flowering period of early-flowering tree species such as cherry blossoms and apricot trees, so more flower buds in autumn shoots should be reserved during pruning to reduce the losses caused by adverse weather.
(7) increase fruit yield
Reasonable pruning can adjust the growth potential of all fruit trees in the whole garden to make it balanced, so as to give full play to the overall production capacity of fruit trees in the whole garden. If combined with other agricultural comprehensive technical measures, the growth and development of each fruit tree in the whole garden will be uniform, so that the production potential of each individual can be fully exerted and the output per unit area can be reliably guaranteed. Through shaping and pruning, a certain number of branches per unit area are maintained, and a proper proportion of developing branches and fruiting branches are maintained, so that their configuration is reasonable, their distribution is even and their growth is balanced. At the same time, attention should be paid to fertilizer and water management and pest control, and attention should be paid to thinning flowers and fruits, which has obvious effects on overcoming the phenomenon of fruit bearing in different years, improving fruit yield and maintaining high quality and high yield year after year.
(8) Improve fruit quality and increase commodity value.
Reasonable pruning can make trees and dwarf rootstocks with different ages, different growth and different crown widths bear corresponding fruit yields. For the branches of each tree, the reasonable amount of fruit can be determined according to its planting position, extension direction, opening angle, thickness, occupied space and results over the years, so that all trees and main branches of the same tree can get reasonable load. In this way, fruit trees can grow and develop evenly, with the same size and high commodity quality. If the number of branches is appropriate, and good ventilation and light transmission conditions can be maintained, the fruits inside and outside the crown can get sufficient light, the red varieties can be fully colored, and the yellow or green varieties have smooth fruit surfaces without watermarks and rust spots. In this kind of orchard, the first-class fruit rate can reach more than 80%, while the external fruits such as pests, deformed fruits and small fruits can be reduced to less than 5%, or even lower or none. This orchard is not only convenient for harvesting, but also conducive to post-harvest grading packaging, storage and transportation. The appearance quality of fruit is good, and the commodity value and economic benefit will also be improved.