1. Appropriate stem height: The height of the trunk should be considered and determined according to the purpose of cultivation and production. Generally speaking, walnut orchards that mainly produce fruit should adopt low-stem shaping, and the height of the fixed stem is 1.2 ~ 1.5 meters. Gao Qian should be used to shape the walnut forest which mainly produces wood, and the suitable dry height is 2.5 ~ 3.0m If the fruit is the main material and other crops are intercropped under the tree, the middle dry shaping should be adopted, and the fixed dry height is1.5 ~ 2.5m.. From the point of view of fruit production, when the trunk is low, the crown is large, growing vigorously, branching quickly, bearing fruit early and yielding high. The fixed stem is too high, the crown is small, the growth is weak, the growth is slow, the fruit is late and the yield is low.
2. The tree structure should be enlarged: no matter what tree shape is used for shaping, the crown volume and the spacing between main branches and lateral branches should be about twice as high as the tree structure standard mentioned in the first section of the second part of chapter 2 according to the specific variety characteristics and plant spacing. Otherwise, the branches and leaves of peach trees in five years will be seriously crowded with the acceleration of growth, which will affect ventilation and light transmission. Especially for common late-maturing varieties, the distance between the first lateral branch and the central trunk should be more than 70 cm to prevent the formation of "door side". The width of the shaping belt of the lower first layer of main branches should be kept at 50 ~ 70cm, and adjacent arrangement must be avoided to prevent the growth force of the central trunk from weakening and forming the phenomenon of "neck sticking".
3. The cultivation of backbone branches should be flexible: young walnut trees have few branches, which makes it difficult to shape the crown. Therefore, the target tree can be selected flexibly according to the position and tree, and the cultivation of the central trunk and main lateral branches cannot be mechanically copied. We should make good use of technical methods such as "taking the main branch as the side", "taking the side as the main branch" and "changing the head with strong branches" as appropriate, and handle the dialectical complementary relationship between the two pruning principles of "pruning by shape" and "shaping by branches".
4. Young trees should be branched as much as possible during the plastic period: young walnut trees have straight branches, low germination rate, weak branching ability, mostly uniaxial elongation and few branches, which is not conducive to the selection, retention and cultivation of backbone branches. Therefore, pruning should promote branching as much as possible and accelerate crown formation. The method of promoting branching should be determined according to the growth potential of branching. Generally, in summer, the vigorous new shoots can be peeled or shortened by 60 ~ 80 cm, or the buds in proper positions but not germinated can be carved to promote them to germinate into branches. Don't cut the weak branches short, but use the full buds at the top to germinate long branches to increase the number of branches. Because the central pulp of the weak branch is large and the tissue is not full, the wound on the cut branch heals slowly and is easy to lose water and dry up. The inappropriate position of strong upright branches should be controlled by pulling branches and removing cores, so as to promote the germination of middle and lower parts and the culture of fruiting branches from middle and short branches.
5. Control the competition of back branches as soon as possible: Compared with other fruit trees, walnut trees have an obvious difference in growth and development, that is, in the state of natural growth, the back branches on the main branches, side branches and auxiliary branches are easy to flourish, thus weakening or even exceeding the growth ability of the original head. If it is not controlled early, it is easy to form the phenomenon of "backward pulling", which will disturb the normal cultivation of tree structure and affect the balanced development of crown and light transmission. Therefore, attention should be paid to the early control of the upper and lower branches of walnut trees in the process of young tree shaping to prevent them from competing for the first place and maintain the orderly and balanced development of the backbone branches.