Onions are a moneymaker. According to Abbey Kazibwe, a farmer who owns Nsanja Agrochemicals, there is a big market for onions.
“We do not produce enough onions to sustain the local market. A lot of the onions on the market are imported from Tanzania,” he says.
Tanzania is the leading producer of onions and also supplies Kenya. Ugandan onions are exported to Europe, Asia and the US. However, there are no exact records of the total national production and export figures.
Onions can be grown in a wide range of climatic conditions. They can tolerate temperatures as low as -6ºC. However, good bulb formation requires temperatures from 15.5ºC, with an optimum temperature of 21-27ºC. This means that they can grow in most parts of the country.
In Uganda, however, most of the large-scale growing of onion farms (with fi ve to 10 acres) is done in Sebei region which comprises Kapchorwa, Bukwo and Kween districts.
Joseph Ggombya, an agronomist, says the average cost per kilogramme of onion seeds is sh800,000 to sh900,000.
An acre requires two kilogrammes taking the cost of seeds to about sh1.8m.
Ggombya puts the cost of labour and other farm inputs at about sh5m per season, making the cost of production around sh7m.
The total cost per acre includes the sh1.8m used to buy seeds, about sh1.5m used for clearing and ploughing the land, sh2m for labour to transplant and general maintenance of the seedlings from the nursery to the main farm, plus sh1.5m on fertilisers such as lime.
With a moderate 13 tonnes harvested at a moderate sh2,000 per kilogramme, the farm earns sh26m. There are two seasons per year and if the farmer employs irrigation, he can even have three seasons.
Soil requirements
According to Ggombya, onions do best in well-drained soils that are at least 650mm deep. Shallow soil may be utilised, but with proper adoptions in management practices. Examples of good management include proper transplanting, spacing and irrigation.
Ensuring a pH range of between 6.02–6.8. Lower pH levels can result in problems in regard to fertiliser uptake since one has to apply a lot of fertiliser for it to be effective.
To tell the pH, you must take soil samples for testing to a recognised laboratory such as Kawanda, Kabanyoro or any agriculture research centre certified to carry out soil testing. A single test sample costs sh30,000 and this can be done before every planting season.
Seedbed preparation
On well-drained soil, prepare a fi ne and even seedbed. If you can afford it, it is advisable to use seedling trays to ensure that little or no seed is lost during this process. Seedling trays are sold at agri-input stores at sh5,000 every 50 seedlings.
Alternatively, commercial plant raisers can help farmers raise healthy seedlings for use. If the soil pH is less than 6 or the available calcium is less than 2,300kg per hectare, apply agricultural lime at the rate of 2,500kg per hectare about eight to 12 weeks prior to planting. The total is around 50 bags of 50kg each.
Each 50kg bag of lime costs sh30,000, so the farmer spends around sh1.5m on lime. It takes at least two weeks for the lime to react with the acid in the soil to raise the pH and thus it should be applied before planting the onions.
Lime is applied once before planting. Transplanting Seedlings are usually ready five to six weeks after planting, when a majority of the seedlings’ necks are pencil– size (about 65 to 80mm) in diameter and 10 to 15cm tall.
Transplanting should be done either early in the morning or late in the evening.
“Transplanting when the sun is up affects the seedlings because it drains water from them,” Gombya says.
An acre can take as many as 250,000 seedlings.
Irrigation
There are several ways of irrigating onions. These include using the sprinkler system. It may be the small, low sprinklers or the water gun or even a drip irrigation system.
The sprinklers and the water gun are cheaper, since one unit can be moved from one part of around on the farm.
The drip system on the other hand is fixed on the farm and thus a farmer needs more than one system for a large farm.
A farmer can get a water gun, complete with a pump and pipes, costs sh3.5m, while laying a drip irrigation system on an acre may cost sh10m. Irrigate 3-5mm daily after transplanting, to keep the soil moist.
Direct seeded onions (onions planted from seeds without putting them through a nursery bed) growing under hot dry conditions may require two irrigation cycles per day — in the morning and evening.
Water shortage at any stage during growth may result in decreased yields. Adequate watering promotes good growth and helps keep the soil firm around the onions.
You are advised to water three times a week. Do not over-irrigate because this may cause onion bulbs to be soft with a poor shelf life. You can realise that you are over irrigating if the water is stagnant.
Onions can also be grown under a greenhouse, but it may be a waste of space and money, especially in Uganda, because the yields after 100 days may not match the costs of the green houses.
Weed management
According to Ggombya, onions develop slower than other vegetable crops and are more susceptible to weed competition, especially during the early growth stages. This can result in yield losses.
Weeds can be controlled successfully through either pre or post-emergence herbicides. Use only registered products from certified dealers.
Pest and disease control
Thrips are the major pest in onions. If not controlled, they can cause reduction in quality and quantity of produce. A number of diseases attack onions, but the major ones include downey mildew and purple blotch.
Most diseases that occur in onions can be controlled through management practices — by growing resistant varieties and chemical sprays.
Harvesting
Harvest when about 50% of the plants have dropped and shrunk and the bulbs visible from above the ground. The onions are lifted mechanically or by hand and put down on the farm to dry.
You then have to store them in a cool, dry well-ventilated store. If it is processed into powder, they can last for 12 to 20 months.
