Analysis of Common Problems and Countermeasures in Nanguo Pear Production

I. Planting Density Issues

In old Nanguo pear orchards, the spacing between trees is large, the number of trees per unit area is small, the tree canopy is tall, management is extremely inconvenient, production costs are high, early yields per unit area are low, and the trees take a long time to reach full bearing age. Based on current advanced management methods and techniques, rational close planting is advocated. Given that Nanguo pear trees exist both as standard-rootstock trees and as dwarfing interstock trees, we believe that the suitable planting density for standard-rootstock Nanguo pear trees is a tree spacing of 3-4 m and a row spacing of 4-5 m, with 33-35 trees planted per mu of orchard. With this tree and row spacing, through the comprehensive application of various pruning measures, the trees can enter the high-yield period earlier, and the canopy spread can be controlled at 3-4 m. If water and fertilizer conditions are good and the canopy cannot be controlled, in the later stage the method of removing every other tree and removing every other row can be adopted to gradually increase the tree and row spacing. However, when establishing the orchard, permanent trees and temporary trees must be designated. Permanent trees should use a large-canopy tree form, while temporary trees should use a small-canopy tree form that bears fruit early. As the canopy of the permanent trees continuously expands, the canopy of the temporary trees should be gradually reduced to ensure the tree form and yield of the permanent trees. For dwarfing interstock Nanguo pear trees, the suitable planting density is generally a tree spacing of 1.5-2 m and a row spacing of 3 m, with a planting density of 111-148 trees per mu. On mountainous land with high elevation and steep slopes, the soil layer is often thin, management is inconvenient, and the canopy does not grow large, so under the condition of not affecting orchard operations, the planting density can be appropriately denser. On flat land with fertile soil, the canopy generally grows tall, so the planting density can be appropriately sparser.

II. Training and Pruning Issues at Different Stages

1. For orchards of newly planted young trees where the selected target tree form does not match the planting density, the suitable target tree form should be re-determined according to the planting density, and transformation should be carried out according to the conditions of each tree. For fruit trees that have been allowed to grow freely, because pruning was neglected, the leader and branches within the canopy are not differentiated, and some trees show two or three co-dominant trunks growing together, seriously affecting the growth and fruiting of the pear trees. When pruning and renovating, first select a suitable target tree form according to the planting density. Second, according to the tree form structure, select and retain the central leader and the main and lateral branches, remove excess strong vigorous branches and water sprouts, and bend flat and lightly release the remaining branches. For the retained branches, open the angles promptly if the angles are small. For fruit trees with two or three co-dominant trunks, select and retain the best one and remove the other excess co-dominant trunks, then select main and lateral branches as required and cultivate them year by year.

2. From the initial fruiting stage to the early full fruiting stage in pear orchards Although the training stage of the trees during this period is about to be completed, those with unreasonable tree form structures still need to be renovated to form a reasonable framework, so that full fruiting branch groups can be cultivated and a good tree form foundation can be laid for future production. Therefore, renovating and improving the tree form and cultivating fruiting branch groups are equally important. For trees with trunks that are too low, plan to remove the excessively low large branches to raise the trunk height. After the trunk height is raised, the angles of the main branches can be opened wider, which both improves light conditions and facilitates operations under the tree. For trees with small main branch angles and excessively long branch axes, the pruning focus should be on widening the main branch angles. The best time for opening the angles is during the growing season. At the same time, moderately retract the main branches, and the branching vigor at the retraction site should be comparable. Through branch bending and retraction, a certain amount of space should be left under the tree and between rows to facilitate orchard operations. During branch bending and retraction, note that the amount of pruning within one year should not be too large and should be controlled at 20%-30%. After winter pruning and before spring budbreak, remove excess buds to avoid the sprouting of large numbers of ineffective "shoots" that consume tree nutrients and worsen ventilation and light penetration conditions.

3. Old orchards Old orchards refer to those with a tree age of more than 40 years. Due to a poor foundation of training and pruning, the tree vigor is weak, the fruiting area has moved outward, the branch tips droop, the central leader is not obvious, the number of main branches is large, the main branch angles are small, the canopy is closed, and light conditions are poor. The pruning focus for fruit trees in this period is the renewal and rejuvenation of branch groups, maintaining tree vigor, adjusting the relationship between growth and fruiting, improving ventilation and light penetration conditions, stabilizing yield, and prolonging the economic fruiting life.

For trees whose fruiting area has moved outward, whose tips droop, and whose vigor is weak, and whose outer branches are abundant and form an "umbrella" canopy, the middle should be headed down and the top opened, and the outer drooping branches should be retracted to promote branching in the inner canopy and gradually lower the canopy height. For trees with few outer branches and several main branches forming a "ladle" shape, appropriately retract the drooping tip branches, and the degree of retraction should be slightly greater to stimulate new branches to sprout from the lower part and lower the canopy height. After new branches are stimulated, adopt the method of combining heading and light release, cultivate branch groups downward, make the canopy full again, form three-dimensional fruiting, keep the branch groups young, and maintain moderate and robust tree vigor.

For trees with an inconspicuous central leader, many main branches, small angles, and a closed canopy, the number of fruiting branch groups is insufficient and there are few fruiting sites. The pruning focus is to systematically remove excess large branches and reduce "sticks." At the same time, according to the amount of space, cultivate suitable fruiting branch groups. By reducing large branches and rationally arranging large, medium, and small branch groups, solve the ventilation and light penetration problems and keep the leaf canopy layer thickness no more than 2 m. After winter pruning, the spacing between the upper and lower layers of main branches should reach more than 1 m.

For trees with many "shoots" in the inner canopy, the pruning focus is to remove excess "shoots" and solve the ventilation and light penetration problems. During winter pruning, remove excess water sprouts and thin weak branches in the inner canopy, and lightly release plump branches. After spring budbreak, use various summer pruning methods to control the re-sprouting of "shoots." At budbreak, promptly remove excess buds sprouting on the central leader and trunk. Bend flat and lightly release the branches retained during winter pruning, retract them after flower formation and fruiting, and cultivate them into branch groups. Never use a single winter pruning approach to renovate the tree body.