THE citrus fruit ranks at the top in production and trade among all fruits produced the world over. It is highly prized and remunerative fruit, cultivated almost all over the world.

Citrus comprises about 40 per cent of all fruits that grow in Pakistan. It is cultivated over an area of 185,400 hectares with an average annual production of about 1.67 million tons.

More than 95 per cent of citrus fruit is produced in Punjab and 70 per cent of it is under kinnow. In fact kinnow has monopolised the citrus farming in the country.

As compared to other countries, production of citrus in Pakistan is very low. The reasons are many.

One among them is the population explosion which puts pressure on agricultural land leaving little of it for fruit cultivation.

Improving the yield of citrus in terms of quantity as well as quality, with the ever-limiting resource of cultivated land, is very important to meet the needs of the increasing population as well as export.

With that objective in mind, a lot of studies are being carried out on various aspects of kinnow cultivation, including effect of planting space on quantity and quality of the fruit.

It has been found that citrus yield could be enhanced by optimising tree to tree space in orchards.

In most of the orchards, the trees are set with standard planting space, at the corners of square or rectangles of such size to accommodate the trees when fully grown. Whereas, the full distance allowed from tree to tree is not normally required for early 10-15 years. In the meantime, inter plantings is also more often done to take the advantage from the fallow land.

However, in Pakistan, citrus tree is planted at 22 X 22 ft or 20 X 22 ft for giving 90 and 99 citrus plants per acre, respectively; but the tendency since 1990 has been towards closer planting distances.

The results of earlier work on density have indicated that close spacing produces more fruit per acre, if a number of grooves have been planted as “hedgerow” plantings on 11 X 22 ft spacing.

In many countries, higher yields are obtained from high-density citrus orchard as compared to low-density orchards. To date, these higher yields have been more evident during the initial 4-10 years period after establishment.

The current interest in closely-spaced, higher density orchards has been stimulated by a number of factors. These include the irreversible reduction in the availability for prime citrus land through urbanisation; the energy costs involved in the use of farm machinery for pest control and harvesting operations etc. Greater difficulties are faced at those orchards where availability of water is scarce and suitable labour force for hand harvesting not available.

Thus shortage of land, energy, water and skilled harvesting labour, together with higher fixed costs, which require a more rapid return on capital, have contributed to the trend of higher planting densities.

The major advantage of close plantation is higher convenience and efficiency of tree care, plant protection operations, harvesting and early production of commercial yields.

Early productivity shortens investment period and enables quick supply of market demands for newly developed fruits. Furthermore tree spacing has become an increasingly important consideration in citrus rootstock management, because of the benefits of higher tree density on early production and financial returns.

Due to changes in labour wages, government regulations and tree loss rates require continual evaluation of citrus plantings, to establish optimum system.

The citrus plantings should be planned so that the biological and management aspects are interrelated to maximise economic return.

The citrus production in future must make more efficient use of limited area of good land provision, for more rapid recovery of investment capital, in order to provide maximum average net return. The tree spacing has become an increasingly important consideration in citrus rootstock management also because of the benefits of higher tree density on early production and financial returns.

The grower can get earlier return on investment; better spray coverage at less cost, easy harvesting and return to fulfill production sooner after tree damage or removal by high-density plantation.

In case of kinnow, the plants grow taller than its normal pattern of spreading canopy at closer plant spacing, which is due to competition among plants for light interception, owing to which plants gain more height. In closer spacing, plants also compete for nutrients which may cause lower and inferior quality fruits. Canopy volume reflects the efficient use of nutrients, light and water. At wider spacing, the plants have spherical type canopy, because they have enough space for canopy spread. At wider spacing, the plants received more light around the canopy and lateral buds proliferate effectively leading to the lateral branch development.

As a response to more light interception at higher branches, the pattern of growth in kinnow mandarin changed to upright as against spreading. This is very particular behavior of canopy development in relevance to plant height needs regular pruning for canopy management.

While at wider spacing, the number of trees per hectare is less due to which cumulative yield is low.

These are some of the very clear examples to understand the importance of optimum planting space in citrus.

However, it has been achieved as a result of many experiments that the moderate planting space between trees, along with the canopy management, is required for early and better return.

Therefore, the growers are advised to take this aspect into consideration and try to maintain optimum planting space for increasing citrus yields.