Introduction:

Orange (Citrus sinensis L) is grown under both subtropical and tropical conditions. It is grown in almost all the sates of India.

Climate and soils:

Dry and arid conditions, coupled with distinct summer and winter having low rainfall, are most favourable to the growth of the sweet orange. Atmospheric humidity exerts a great influence.
The sweet orange can be grown on a wide range of soils, from heavy clays to very light sands, with pH ranging from 6.0-8.0. The tree is sensitive to high concentrations of salts and cannot stand water logging.

Varieties::

Propagation

Usually propagated by budding. The most suitable rootstock is Jamberi or jatti khatti. For Pineapple, Hamlin, Jaffa and Valencia Late varieties, kharna khatta also provide a suitable root stock. The trees are planted 6-7.5 metres apart each way in January or August-September in the north and in July-August in the south. The bud union should kept at least 15 cm above the ground while planting.

Pruning

All branches that start within a few centimeters of the union are removed, leaving about half a metre of clean straight stem with a few well placed branches. All unwanted branches are removed once a month during the first yea r after planting, and once in two to three months in subsequent years. The bearing trees require little or no pruning.

Fertilizer :

Farmyard manure, 20-25 kg per tree, is applied at planting, together with about half a kilo of ammonium sulphate. A mixture supplying 0.09 kg each of nitrogen, phosphorus and potash per tree may be applied in the first year after planting, and the dose is gradually increased to 0.45 kg of each nitrogen and phosphorus and to 0.90 kg of potash per tree in the seventh year and kept constant thereafter. The dose of farmyard manure is increased to 50 kg per tree.

Irrigation:

After the first heavy irrigation given soon after planting a second light watering follows in four to five days Under well irrigation, water is given after every eight days in hot months and about 12-15 days in cold months. Where irrigation is from canals, the usual interval is about 14 days. A light soil requires irrigation more often than a heavy soil. When the trees are young, irrigation water is applied in basins of about one-metre radius. The basins are enlarged as the trees advance in age.

Root exposure:

Root exposure is given to the trees to bring them into flowering at a particular time of the year. Water is withheld for about two months in advance of the normal flowering season, and after about a month, the roots are exposed by removing about 10cm of the soil in the case of light soils and about 20cm in the case of heavy soils. After about 10 days, the soil is returned mixed with manure and a light irrigation is given. After four of five days, a more copious watering is given, followed by 10 days later by the full dose of water. In the case of light soils, the withholding of water without root exposure is sufficient to check vegetative growth and force blossoming.

Plant protection:

Pests

Lemon butterfly
Feeds on leaves and defoliate trees; serious in nurseries.
Controls
Hand pick caterpillars and pupae, remove alternative host plants; spray 0.04% Monocrotophos or Phosphamidon

Citrus feaf miner
Caterpillars feed inside the leaf tissues, forming zigzag shining streak like galleries on leaves; the infested leaves dry up
Control
Prune heavily affected parts during winter and burn them; spray with neem cake suspension (300 g in 5 litres of water) or 0.04% Phosphamidon or Monocroptophos.

Fruit sucking moth
Puncture the fruits and suck the juice fruits rot and ultimately fall down
Control
Destroy wild plants on which moths breed; bag individual fruits; poison-baiting with 20g Malathion 50% W.P. or 50ml Diazinon+200g gur or molasses in 2 litres of water.

Disease

Brown rot or gummosis
The bark is invaded and ruptured lengthwise, and large quantities of gum are exuded; the bark is ultimately killed.
Control
Apply Bordeaux paint to the trunk; dust the pits at the planting time with a mixture of zinc sulphate, copper sulphate and lime (5:1:4); scrape the affected bark and apply a wash of zinc copper lime mixture.

Damping off
Seedlings rot at the soil level, topple over and die
Control
Adopt rotation

Fruit fall
Fruits turn yellow prematurely and fall
Control
Spray 1-% Bordeaux mixture; apply nitrogenous manures.

Harvesting and Storage:

Trees begin to bear fruits from the fourth year onwards, but normal crops are borne from the seventh year. The main harvesting season in the north is December to February, whereas in the south, it is October to March. Picking may be done any time during the day, taking care that the stem is cut close to the fruit without damaging the rind. The fruits are washed, dried and graded for size and packed into wooden cases for disposal.