Oranges: nutrition, benefits and a profitable orchard

As soon as winter sets in, heaps of oranges appear on handcarts everywhere, from the pavements of Dhaka to village markets. Pick one up and the scent of the peel alone lifts the mood. We take oranges to people who are ill, put them in children's lunch boxes and set them out for guests. Yet a large share of the oranges Bangladesh eats comes from abroad. Meanwhile, orchards on the hillocks of Sylhet, the slopes of the Chattogram Hill Tracts and the soil of Panchagarh in the far north are quietly proving that the fruit grows well here, and that farmers can make money from it.

The orange is a nutritious and delicious fruit that is becoming known as a profitable crop in Bangladeshi farming. It is not only good to eat; it plays an important part in keeping people healthy. Because its nutritional value, demand and market price are all high, growing oranges opens a path to profit. With proper care and management, an orange orchard gives high yields and a steady income for many years, and through it farmers can become financially self-reliant.

This report looks at what oranges offer nutritionally, why they are worth growing, and how feeding, irrigation, weed control and picking should be handled for a good harvest.

The orange belongs to the citrus family, which also includes lemons, limes, malta and pomelo. The oranges grown in Bangladesh are mainly mandarins, with thin, loose skins that peel by hand and segments that come apart neatly. Sylhet, Moulvibazar, Panchagarh and the hill districts of the Chattogram Hill Tracts are known as the areas best suited to them. In recent years many new orchards have also been planted in the northern border districts.

A leading centre for orange research is the Citrus Research Station of the Bangladesh Agricultural Research Institute (BARI) at Jaintapur in Sylhet. Founded in 1960 to 1961 as a fruit development station, it works on new citrus varieties and on better growing methods. Among BARI's orange varieties, BARI Komola-1 is a familiar name. Anyone planting a new orchard is safest buying grafted saplings of approved varieties from a government horticulture centre or a reliable nursery.

The orange is rich in vitamins and minerals, and above all it is known for vitamin C. According to the United States Department of Agriculture's food composition database, 100 grams of raw orange contains about 53 milligrams of vitamin C, a large part of an adult's daily need. Vitamin C strengthens the body's defences and keeps skin healthy. Oranges also contain:

• Vitamin A, which is good for the eyes.
• Antioxidants, which remove harmful free radicals from the body. Free radicals are unstable molecules that can damage cells.
• Fibre, which aids digestion and relieves constipation.
• Potassium, which helps control blood pressure.
• Few calories, which suits a weight-control diet.

For comparison, the Office of Dietary Supplements at the United States National Institutes of Health recommends 90 milligrams of vitamin C a day for an adult man and 75 milligrams for an adult woman. One or two medium oranges can therefore cover a large part of the daily need. The body does not store vitamin C, so it has to come from food every day, which is why nutritionists recommend eating seasonal fruit such as oranges regularly. Vitamin C is also destroyed by heat and by long exposure after cutting, so an orange is best eaten soon after it is peeled.

• Calories: 47
• Carbohydrate: 11.8 grams
• Protein: 0.9 grams
• Fat: 0.1 grams
• Fibre: 2.4 grams

The figures show that an orange is mostly water, natural sugar and fibre, with almost no fat. A medium orange fills the stomach well while adding very few calories. Eating the whole fruit is better than drinking packaged juice, because the fruit keeps all its fibre and carries no added sugar.

Nutritionists describe the orange as a fruit of many virtues, and eating it regularly helps keep a range of problems at bay. First, it strengthens immunity. Its vitamin C and antioxidants help protect the body against colds, coughs and other infections. It is worth noticing that the orange season falls in winter, exactly when colds and coughs are most common.

Second, oranges lower the risk of heart disease. Their potassium and antioxidants keep the heart healthy and help control blood pressure. Third, they keep the skin bright. Vitamin C helps the body make collagen, a protein that keeps skin firm and healthy.

Fourth, being low in calories and high in fibre, oranges curb hunger and help with weight loss. Fifth, their fibre improves digestion and relieves constipation. Sixth, nutritionists believe the antioxidants and phytochemicals in oranges, the beneficial chemical compounds plants make for themselves, help hold back the growth of cancer cells. No single fruit cures disease on its own, however; the orange gives its full benefit as part of a balanced diet.

For a farmer, the first attraction of oranges is their price. Demand runs all year, so the fruit sells well and brings a good income. The home market is huge, and oranges are among the most widely traded fruits in the world. More production at home would also mean less dependence on imports, a gain for the country as a whole.

The second advantage is that orange growing involves few complications and comparatively little labour. Unlike rice or vegetables, there is no need to plough, sow or transplant afresh every season. A tree planted once bears fruit for many years; that is the heart of the long-term income. Once an orchard is established, it keeps yielding year after year.

Third, with proper care and feeding, a hectare of orchard can produce a large crop. Fourth, Bangladesh's climate and soils, especially hill slopes and the higher land of the north, suit the orange. On slopes where rice cannot grow, an orchard turns unused land into a source of income.

Fifth, the costs of orange growing are relatively low and the returns high. Income need not come from fresh fruit alone: juice, jam and marmalade turn small or less attractive fruit into products that sell at a good price. This is a promising field for women entrepreneurs in rural areas.

A good orchard begins with good planting material. Specialists advise planting grafted saplings of a good variety. A grafted sapling keeps the qualities of its mother tree exactly and bears fruit much sooner than a seedling. Trees grown from seed take longer to fruit, and their fruit may not match the parent's quality.

It helps to know what a graft is. A grafted sapling has two parts joined together. The lower part, the rootstock, is usually a hardy, disease-tolerant citrus seedling whose roots draw water and food well from the soil. The upper part, the scion, is a shoot taken from a mother tree known for good fruit. The two grow together into one tree, combining strong roots with good fruit. When buying, check that the graft union is smooth and firmly joined and that the leaves are fresh and unspotted. Any shoots that sprout below the union should be cut off, or the branches of the rootstock will grow up and weaken the true tree.

The land must be free of standing water. Orange roots cannot tolerate waterlogging at all; a few days of water around the trunk weakens the tree and rots the roots. That is why oranges do well on hill slopes and high ground. Regular pruning lets light and air into the tree: cutting out diseased, dead and crowded inner branches lets sunlight reach inside the canopy and improves the fruit.

Correct feeding is essential for a good orange harvest. Fertiliser should be applied according to the soil and the tree's stage of growth. A young sapling and a mature, bearing tree have different needs, so it is best to settle the doses after a soil test and on the advice of the upazila agriculture office.

Organic manure is the foundation of an orange orchard. Every year, cow dung, compost or vermicompost should be applied around the base of the tree. Vermicompost is organic manure made with earthworms, and it leaves the soil loose and fertile. Each tree needs 10 to 15 kilograms of organic manure a year. Organic matter improves the soil's ability to hold water and makes chemical fertiliser work better.

Three main nutrients are needed from chemical fertiliser. Nitrogen drives the growth of leaves and branches; urea is its main source. Phosphorus helps the roots grow; it comes from TSP. Potash, or potassium, enlarges the fruit and makes it sweeter; its source is MoP. Whether an orange turns out sour or sweet depends a good deal on whether the tree gets enough potash.

Timing matters too. Fertiliser is usually applied before the monsoon and again when the flower buds appear. Applied before the rains, it is washed into the soil and reaches the roots. It should go on a little away from the trunk, in the ring beneath the spread of the branches, because that is where most of the feeding roots lie. Overuse must be avoided. Too much fertiliser brings no benefit; it can harm the tree, burn the roots and raise costs for nothing.

Good irrigation can raise orange yields considerably. In the dry season, water every 7 to 10 days. In summer, when it is hot, the trees need more water at the base. In the monsoon, by contrast, there must be a way to drain surplus water quickly. Channels cut through the orchard stop heavy rain from pooling around the trunks.

Drip irrigation is the most effective method for oranges. In a drip system, water passes drop by drop through small holes in narrow pipes straight to the base of the tree, so little is wasted and fewer weeds grow. Without drip equipment it is still better to water the base of each tree directly rather than flood the whole field. Standing water in the orchard is harmful, and that point cannot be repeated too often.

When water is scarce, mulching helps. Mulching means covering the soil around the tree with straw, dry leaves or some other layer. The sun then cannot dry the soil out so quickly, and moisture lasts longer. In hill areas, where water is hard to find in the dry season, many orchards depend on it.

Weeds compete with the trees for nutrients and water. They take a share of the fertiliser and water meant for the orchard, and yields fall. The damage is greater in young orchards, where the saplings' roots have not yet gone deep.

• Hand weeding: pull weeds from around the base of each tree by hand. In a small orchard this is the safest method.
• Mulching: covering the base of the tree with organic mulch such as straw, leaves or compost keeps weeds down and holds moisture at the same time.
• Machinery: in larger orchards, the ground between rows can be cleared with farm machinery.
• Selective herbicide: where weeds are very heavy, a low dose of herbicide can be used.
• Caution: when using herbicide, make sure it does not touch the leaves or trunk of the orange trees.

Feeding, water and weeds are only part of orchard care; a successful grower also needs to recognise disease and pests. Citrus trees have several well-known problems that also appear in Bangladeshi orchards. The most feared is citrus greening, also called huanglongbing or yellow shoot disease. It is a bacterial disease carried from tree to tree by a tiny insect, the citrus psyllid. The leaves of an infected tree turn yellow in blotchy patterns, the fruit is small, lopsided and sour, and the tree slowly dies. There is no cure, so the main defences are buying saplings from disease-free nurseries, controlling the psyllid and removing infected trees.

Another familiar disease is citrus canker, which leaves rough, raised brown spots with yellow halos on leaves, twigs and fruit. Spotted fruit sells for less. The disease spreads with splashing rain in the monsoon. The usual control is to prune and burn infected branches and, on the advice of an agriculture officer, to spray an approved copper-based fungicide.

Among insects, the citrus leaf miner tunnels in winding trails inside young leaves, which then curl; it does most harm to saplings and young trees. The caterpillars of the lemon butterfly eat tender leaves, and fruit flies lay eggs in ripening fruit, which then rots and drops. Walking through the orchard regularly, burying fallen and rotten fruit, picking off and destroying infested parts, and using pesticide only when needed and on the advice of the upazila agriculture office make up the most effective and least costly approach.

Oranges picked at the right time and in the right way keep their quality and store better. The fruit matures 7 to 8 months after flowering. When its colour begins to turn from light green to yellow or orange, it is ready to pick. In Bangladesh oranges usually ripen in winter, which is also the peak season for local oranges in the markets. Unlike mangoes or bananas, an orange does not go on ripening or sweetening once it is picked, so fruit taken too early stays sour. Letting it mature fully on the tree is the condition for good fruit.

Pick by hand or cut the stalk with sharp clippers. Pulling the fruit off tears the skin near the stalk and lets rot in. Take care that the fruit is not bruised; it should never be thrown into a basket or allowed to fall to the ground. After picking, clean the fruit and let it dry in the shade so that any water or dew on the skin evaporates.

Store the fruit in a cool, dry place. In modern cold storage oranges keep well for a long time. With good storage, a farmer does not have to sell the whole crop at once at the low prices of early season, and can sell gradually as prices rise. Grading the fruit by size and quality also brings a better price.

Orange growing is a profitable venture, but it is also a crop of patience. For the first few years after planting, the trees grow and the harvest builds slowly. During this time many farmers earn extra money by growing vegetables or spices in the gaps between the young trees. Once the orchard comes into bearing, it pays year after year.

Sound feeding, timely irrigation, weed control and careful picking are the few tasks that make an orchard succeed. With demand rising at home and export prospects in view, the orange can become a financially rewarding crop for Bangladeshi farmers. A farmer who plans today and plants an orchard of good grafted saplings may, a few years from now, find the best reward for the work on a winter morning, in trees heavy with bright fruit. And the more local oranges stand beside the imported ones in the markets, the stronger the country's farm economy will be.

Photo: A mandarin orange tree at the National Tree Fair, Dhaka / Salim_Khandoker / Wikimedia Commons (CC BY-SA 3.0)