The pruning period of walnut tree is different from other tree species. If the period is not appropriate, there will be "bleeding" phenomenon, which will make the tree lose nutrients and lead to tree weakness. Generally, pruning can be divided into dormant period and non-bleeding period. According to the experiment, we can also divide it into four pruning periods: spring, summer, autumn and winter. Pruning in different pruning periods has different problems and different pruning effects.

Spring pruning Spring pruning refers to the pruning of walnut trees from germination to leaf spreading. As the temperature rises, after the trees germinate, the nutrients stored in the roots are continuously transported upwards, and the nutrients begin to transform. At this time, the tree needs more nutrients, so pruning will cause bleeding, a large part of nutrients will be lost, which will weaken the tree potential, reduce the fruit setting rate, affect the yield and quality, and thus reduce the income. If it is a barren tree or a overgrown tree, pruning at this time can control the growth well, weaken the tree potential and bear fruit early. Therefore, when walnut trees enter the early fruiting period (early fruiting varieties), they should not be pruned, but should be pruned for trees that have grown excessively and have no fruit, which is suitable for use before the early fruiting period of late fruiting varieties and should promote their early fruiting.

Summer pruning summer pruning must master the pruning period. If the temperature reaches about 30℃ after pruning, the walnut fruit will be exposed, which will easily cause burns and reduce the nutritional quality, thus reducing the benefits. After observation, it is best to finish it from late May to the end of June. At this time, pruning is combined with cutting, mainly short cuttings, with branches up to 3 cm in length, external buds or lateral buds and spacing between layers; Loosen the branches that are too dense and recover the drooping branches. Management of fertilizer and water must be strengthened after cutting. Specific practice: from the end of June to the defoliation stage, spray 300 times of potassium dihydrogen phosphate every 10 day. Stop applying nitrogen fertilizer after July and increase the application of phosphorus and potassium fertilizer; Don't water the leaves before August; Spraying paclobutrazol in mid-September to control growth and enhance pruning effect.

Pruning in autumn will be carried out after harvesting walnuts and before the leaves turn yellow (from mid-September to165438+1early October). At this time, the leaves have not fallen and there is no bleeding. Too dense branches and shaded branches are easy to see, so they should be thinned out to facilitate ventilation and light transmission. But at this time, the nutrients did not completely flow back, and the cut leaves and branches contained a lot of nutrients that did not flow back. Moreover, if the temperature is unstable in autumn and winter, there will still be bleeding, and the branches with a diameter less than 1.5 cm are slightly heavier (about 2 cm). Therefore, autumn pruning is suitable for pruning weak trees, old trees and walnut trees on the hillside. At this time, it can move the big branches smoothly without injury, and promote the tree force.

Theoretically, the best time for pruning in winter is from the great cold to the Spring Festival. The bleeding of walnut trees generally begins after defoliation and stops after germination in the following spring. However, not all dormancy periods have bleeding. When the temperature fluctuates around 0℃, sometimes bleeding does not occur, and when the temperature is stable above or below 0℃ for a long time, bleeding appears slight or does not occur. In addition, the size of bleeding has a great relationship with tree potential, environment and soil moisture, and the bleeding of trees decreases with the increase of branch order. It can be seen that it is feasible to take advantage of the favorable opportunity to prune in winter every year according to the actual situation of temperature and climate, but the middle branches should be pruned at a critical period. Pruning at this time can alleviate the time conflict between spring and autumn and busy farming.

In a word, the pruning of walnut trees should follow the following points: intensify the pruning in summer and do a good job in post-pruning management. Pruning in autumn and winter, big branches in autumn and small branches in winter. Growers can choose the suitable pruning period according to their actual situation.