ROLE OF PRUNING IN CITRUS, TIMING AND ITS IMPACT ON TREE AND FRUIT

*Muhammad Shafique Khalid, *Muhammad. Amin, *Omer Hafeez, **Muhammad Umar and **Faheem Haider

* PhD Scholar, Institute of Horticultural Sciences, University of Agriculture Faisalabad

** M.Sc Scholar Institute of Horticultural Sciences, University of Agriculture Faisalabad

Pruning fruit trees is a technique that is employed by gardeners to control growth, remove dead or diseased wood or stimulate the formation of flowers and fruit buds. Pruning of tree fruits and vines is a horticultural practice handed down from ancient time. It has in common the objectives of manipulating various aspects of vegetative and fruiting behaviour. Some of the benefits traditionally attributed to pruning and girdling in the practical culture of citrus have been called into question by field research in the past few decades.

Citrus is a perennial crop. As long as the trees remain healthy, they can flower and fruit for years on end, some times for as long as twenty or thirty years (Mazhar and Nawaz, 2006). However, if the trees are not maintained at a proper size, the height and canopy shape of mature trees in a citrus orchard will not be uniform and the branches will be too crowded. In a crowded orchard, disease and pests can spread quickly. Fruit quality tends to be poor, and trees may not bear fruit every year. A proper training and pruning program is essential for the maintenance of a healthy and productive orchard.

Benefits of pruning in citrus

The major benifits of pruning in citrus include:

1. The total effective leaf area is increased resulting in increased photosynthesis by exposing the leaves to light and air.
2. The water use efficiency and the conversion of available plant nutrients is increased.
3. By removing diseased or infested branches and exposing leaves to light and air, a good training and pruning program helps control pests and diseases in citrus orchard.
4. Proper pruning of the tree keeps it in the right size.
5. It also increases the vigor of the tree, enhances its tolerance of various stresses, and helps maintain the most efficient balance between vegetative growth and fruiting.

Pruning and skirting (removal of low-hanging limbs) affects on canopy temperature, relative humidity (RH), and fruit yield and quality of Orlando' tangelo trees (Citrus paradisi Macf. x Citrus reticulata Blanco). Pruning increased the percentage of large fruit and reduced the percentage of small fruit. (Morales et al., 2000).

The alternate tendency exists across all varieties of the citrus. To attenuate alternate bearing, pruning and fertilization are processes the only options which growers can exploit. For pruning to be effective, it must be done after the end of an “off” or light crop year, i.e., prior to the season of anticipated high production. It should not matter whether the pruning is conducted before or after the bloom, as the results should be about the same, reduction in production during the season following pruning (Mazhar and Nawaz, 2006).

Eissenstat and Duncan (1992) reported that total reducing and ketone sugars (free fructose, sucrose and fructans) in the fine roots were less in pruned than unpruned trees 20 days after pruning, but not thereafter. By 30 days after pruning, at least 20% of the roots of the pruned trees at a soil depth of 9 to 35 cm apparently died. By 63 days after pruning, root length density had recovered to that of the unpruned trees, although starch reserves were 18% less in the fine roots of pruned than unpruned trees at this time.

Growers should select the correct time for the pruning. Since citrus trees are evergreen, they do not have a period of true dormancy. However, the metabolism of the tree is less active in the period after fruit harvesting. This period of reduced metabolism activity is the time to prune. Light pruning can also be conducted at other seasons to remove unwanted and overcrowded shoots.

Tree age is another important factor that should be taken into account, because the tree’s response to pruning varies according to age (Mazhar and Nawaz, 2006). Therefore citrus growers have to recognize the characteristics of the different cultivars they are growing in order to select the best training and pruning system for their orchards.

References:

Eissenstat D.M and L.W Duncan.1992. Root growth and carbohydrate responses in bearing citrus trees following partial canopy removal. Tree Physiol. 10(3): 245-57.

Mazhar, M.S. and M.A. Nawaz. 2006. Pruning as a tool to improve yields in citrus. Pakistan Horticulture. 4(1): 23-25.

Morales, P., F.S. Davies and R.C Littell. 2000. Pruning and skirting affect canopy microclimate, yields, and fruit quality of 'Orlando' tangelo. Hort Science. 35: 30-35.

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