The orange has got its origin in China and largely Asia. The first oranges were introduced in Uganda in 1900. From that time until today, the orange one of the leading commercial fruits grown in Uganda. Oranges can be grown on a wide range of soils. However, light, well-drained soils (sandy) are best. In Uganda, oranges are mainly grown in Teso, Busoga, parts of West Nile, Mityana and Mubende.
There are mainly four main varieties grown in Uganda. These include Washington navel, which is seedless, sweet orange, mainly suitable for eating. There is the Valencia, which is smaller than the Washington navel. It has a rough skin and a lot of juice. It is best used for juice. Then the Hamlin, which is small, with a smooth shiny skin. It too has got a lot of juice.
There are two ways of propagating oranges. You can grow them from seeds directly, however, for commercial farmers, grafted or budded seedlings are appropriate. Trees grown directly from seeds are not as productive and take close to eight years before bearing fruits, while grafted seedlings take three to four years to fruit. As a result, most farmers either graft their own seedlings or buy from other farmers. The average cost of a seedling is sh3,000.
For effective grafting, you need to visit a farmer who does it to get the skills. However, grafting involves the joining of two orange parts, one of which comprises the roots and the other the leaves. Seedlings take as many as four to six months to mature and by this time, the farm must be ready. These commercial varieties are budded/ grafted onto seedlings of species known to give good results when used as rootstock. It is highly important to use rootstocks known to grow and are adapted to the soil conditions on which the trees are to be grown. Budding is by far the most generally used method of propagation.
Grafting apparently gives just as good results, but it is slower and requires more scions as compared to budding.
Raising citrus rootstock
Seed for rootstock is obtained from fresh fruit, which is picked from the tree. Select mature lemon fruits from healthy plants.
The easiest way to extract seed is to cut shallowly through the rind, all the way around the fruit and then twist the fruit apart. The pulp is then squeezed through a sieve and the seeds washed. Seeds are sown immediately after washing. If seeds are to be stored, the surface of the seeds should be rapidly dried after washing to prevent drying of the inside. Seeds can then be treated with a seed fungicide such as thiram.
Seeds are then placed in plastic bags, sealed off and kept at temperatures between 6ºC and 10ºC. Seeds stored under these conditions will survive up to six or eight months.
Seeds are planted in containers or more commonly in seedbeds.
The soil should be at least 30cm deep, light in texture, uniform and well-drained. If only a few seedlings are to be grown, the seeds may be planted in boxes of convenient sizes. The boxes should be put in a warm, partly shaded place and the soil should be kept moist, but not wet. If large numbers of seedlings are to be grown, seedbeds must be prepared. It is desirable to use virgin soil, which has not for several years been used for growing citrus seedlings or vegetables.
Select a site at some distance away from other citrus seedlings in order to reduce the danger of infestation from pests.
Care in the bed Before and after seedling emergence, the soil should be given frequent light watering to keep the surface moist. When the plants are 10cm high, the frequency of watering is decreased to once a day, but the quantity increased. Keep seedlings weed free. This promotes quick growth.
Pest and disease control
Damping off is the most serious disease. Wet soil, dense shading and humid environment and overcrowding are conditions favourable for damping off and hence should be avoided. Pests include aphids and leaf miners. These are treated by spraying using recommended pesticides. For fruit flies, there are now fruit fly traps on the market that you can set up in the farm at a rate of one for every 200 trees.
It is important that trees are planted in straight rows. To do this, you are advised to use a wire or string. Dig holes of 60cmx60cmx60cm with spacing of 10x10ft. For each hole, top soil should be separated from red sub-soil. Make sure you plant at the beginning of the rainy seasons so that the seedlings have enough water to start up.
During the dry seasons, oranges need to be watered, so arrange to do it manually if you do not have an irrigation system. You can use DAP fertilisers at a rate of 25 grammes per hole before planting. NPK fertilisers should be applied at the rate of half a kilogramme per tree per year of growth, split into three applications. A 50kg of DAP or NPK costs sh150,000-sh180,000.
Farm yard manure, for example, animal droppings, can be added at a rate of 10kg tins per tree per year. You can intercrop with beans or groundnuts to increase nitrogen in the soils.
Budded or grafted oranges start fruiting three years after planting. However, peak productivity is only reached after six to 10 years. Oranges stay on the trees for six to nine months and maturity is seen with a change in colour to yellowish.
Harvest the ripe fruits by clipping or pulling from the tree. The average yield per acre is nine to10 tonnes in a year. One tree can produce as many as 100kg per season. There is market for oranges right from your farm, to larger markets in Kampala and outside. Orange trees can yield for 20-30 years.