1.1 Principles of pruning
1.2 Objectives of pruning
1.4 Kinds of pruning
1.5 Special pruning practices
1.6 Chemical pruning
1.7 Amount of pruning related to bearing habits
2. Population adjustment
High planting density is considered one of the modern management systems in new fruit orchards. Pruning and population adjustment are some of the main way to approach high productivity and good fruit quality under the modern management systems.
Pruning is defined as the management of plant structure and fruiting wood and it is considered one of the main factors affecting fruit trees production. There are many objectives for pruning i.e. controlling the direction of growth, developing a strong framework, controlling the amount of growth, improved productiveness, improving quality product, utilizing space efficiently and increasing the usefulness of plant. There are three main systems of fruit trees training (i) Central leader system, (ii) Modified leader system, (iii) Open center or vase system. Also there are several kinds of pruning i.e. heading back and thinning out, fine and coarse pruning and root pruning. However, it is important to select the suitable training system and kind of pruning according to the target of the pruning to reach optimum vegetative growth and maximum yield with high fruit quality.
On the other hand, population adjustment (plant distribution or planting density) is very important factor affecting fruit trees production. We can reach the optimum usefulness of the planted area by using best population adjustment of trees in the plantation. Trees can be planted using different systems:- triangle, rectangle, square system…..etc. On the other side, presence of pollinator trees through the orchard is very important for many fruit trees. Pollinator can be planted either in (1) Complete along rows, as one row of pollinator per two or four rows of the main cultivar. (2) The second tree in the second row. (3) The third tree in the third row. (4) Across rows through the orchard. On the other hand, good plant distribution is very helpful for mechanical serves in the plantation,
We can say that the key objective in planning a new orchard should be to maximize yield in the early years and still effectively produce larger yield of high quality fruits in the next years. This may be happened by utilizing space efficiently and increasing the usefulness of plant using the suitable training system, kind of pruning, also good population adjustment of the trees in the orchard beside the importance of the other factors affecting production process.
There are many factors affecting fruit trees production, some of these factors are related to the environment conditions and the others are related to the plant it self.
Pruning of fruit trees and population adjustment play an important limiting role on fruit trees productivity.
Pruning is considered the main factor affecting some fruit trees production such as grapevine; also it is an essential factor for the productivity of either deciduous or evergreen fruit trees.
Population adjustment of fruit trees plays very important role as a one of the first steps of plant arrangement in the plantation, since plant distribution or planting density (the same meaning of population adjustment) are generally affecting fruit trees production, and had a great effect in a special case such as banana or trees which need a pollinator.
However, it is clear that there is a correlation between both pruning and population adjustment and both are considered limiting factors affecting fruit trees productivity. In this respect, Zimmerman and Steffens (1995) reported that tree size was inversely related to planting density.
So, we will try to make a focus on the role and the effect of both pruning and population adjustment on fruit trees through the following items.
The management of plant structure and fruiting wood is called pruning. It involves removing parts of a plant’s top or root system to increase its usefulness. Limbs, branches, twig, shoot, or roots can be removed. Pruning also includes the training of plants, or shaping them to forms that function more efficiently. Pruning is important for the successful production of both deciduous or evergreen fruit trees. Horticulturists look at yield, size, colour, shape, or quality of fruits in terms of potential profit, while for amateurs factors like size, beauty, or quality are ends in themselves. Pruning helps both to achieve their goals more effectively.
1.1 Principles of pruning
Some important principles of pruning are summarized, following Malik,(2000):-
1.1.1. Modification of apical dominance:-
Apical dominance occurs when hormones produced in the stem apices travel down the stem and inhibit or reduce branching and growth of lateral buds. When the terminal growing point is removed, the production and flow of these hormones to lateral buds is stopped and the initiation rate of lateral growth of branches is increased.
1.1.2 Balance of roots and top:-
Plant growth, development, and reproduction are influenced by the ratio of roots to top. Reduction of leaf area in the growing season or reduction of the number of buds in the dormant season has little effect on root area, but a reduced number of growing points results in stronger shoots with larger leaves. Increase leaf area increases transpiration and photosynthesis, and puts more demands on the roots. However, root pruning reduces the absorbing area, slowing top growth. Stored food is utilized to replace roots, and top growth dose not resume immediately after root replacement since manufactured food must first be stored in the stem. Proper pruning affects a balance of top and roots.
1.1.3. Altering growth phases:-
Regular annual pruning of a growing tree stimulates shoot growth. Heavy annual pruning of young fruit trees delays early fruit production, therefore pruning should be minimal from the juvenile to the productive stage. For maximum flower and fruit production, however, a plant should show good annual shoot growth. If annual shoot growth decreases, as happens with older trees, pruning will stimulate growth and production is usually increased. However, excessive pruning can cause the plant to a vegetative state.
1.1.4. Environmental factors:-
Desirable pruning and training practices are influenced by several environmental factors:-
- Trees grown in heavy shade are pale coloured, have fewer flowers, and are usually smaller. Frequent pruning to maintain good form allows light to strike the leaves and produces dense foliage in hedges.
- Pruning can also influence air movement. In spreading foliage, air movement is increased. Open structures allow better spray penetration for controlling insect pests and diseases.
- Excess moisture tends to produce water sprouts on trunks and primary branches. If excess moisture is preceded or accompanied by severe pruning, the increased water sprout production wastes plant growth.
- Since pruning reduce transpiration, it is useful during drought periods.
- Temperature should be considered when deciding whether to prune. Soft, succulent growth resulting from over- pruning or late summer pruning is more susceptible to winter injury, because there is less time for hardening and storing food before the cold weather.
- Crown and crotch injuries due to cold are more likely on trees, which have not been trained or pruned to desirable branching angles.
- The trunks of trees trained to a low-headed shape receive less intense light, and the bark may be protected from sunscald.
1.2 Objectives of pruning
Major objectives of pruning are summarized below as Malik, (2000):-
1.2.1. Controlling the direction of growth:-
The natural form of a plant can be modified to induce it to branch and spread more profusely. Low-branching types can be trained to branch higher. Branches can also be trained to grow away from utility wires or buildings.
1.2.2. Developing a strong framework:-
Some trees have naturally narrow crotch angles (40o or less from the vertical). Narrow crotches result in a greater loss of limbs from windstorms and heavy loads of fruit than crotches with larger angles. The strongest crotches are those in which branches grow up from the trunk at angles ranging from 40 - 90o. Scaffold branches should be evenly spaced around the tree, with each branch at least 90o from the next one.
1.2.3 Controlling the amount of growth:-
Pruning can either dwarf or invigorate a tree. The type, manner, and time of pruning is determined by the objective. A combination of dormant and summer pruning promotes dwarfness. It is the frequency of pruning rather than its severity that is critical in promoting dwarfness. Increased in vigour is produced by dormant pruning of older wood.
- Quote paper
- Mohamed Saleh (Author), 2002, Pruning and Population Adjustment in Relation to Fruit Trees Productivity, Munich, GRIN Verlag, https://www.grin.com/document/176054