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All you need to know about growing onions
Bulb onions require soils rich in organic matter and adequate soil moisture is required throughout the growing season. Photo by Lominda Afedraru
What you need to know:
Onions can be grown by direct seeding, which requires intensive management or one can decide to first establish a nursery bed, writes Lominda Afedraru
The numerous questions Seeds of Gold receives on onion farming attest to the fact that interest in the crop is growing.
Most of the farmers in Uganda engaged in growing onions do it for commercialisation with the aim of increasing their income for improved livelihood.
While most of those seeking information are beginners, a good number are practising farmers.
Several non-governmental organisations such as Association of Volunteers in International Service (AVSI) have taken to providing best practicing tips to organised groups countrywide.
In this article, we break down all that you need to know on farming onions successfully.
Requirements
Highest yields and best quality bulbs are obtained at more than 1,000m above sea level, although reasonable crop may be realised at lower altitudes. Bulbs form at relatively high temperatures.
Adequate soil moisture is required throughout the growing season for optimum yields. Bulb onions require soils rich in organic matter. Sandy loams are most suitable.
Varieties
Muzamir Twaibu Mwanga, an onion farmer from Kapchorwa District, explains that there are a number of onion varieties mainly identified by their shape. There are varieties with wide shapes and size. Others have white, yellow-brownish, purple colours. There are small pickling onions and large Spanish cultivars.
Propagation
Onions are propagated sexually by use of seeds or asexually through sets.
Where seeds are used, they may be established directly in the main field or started in a nursery and later transplanted when seedlings are pencil thick to the main field at a spacing of 30 by 10cm.
Nursery bed preparation
It is important for the farmer to organise a nursery bed to raise seedlings.
Make sure the soil is soft and the bed should be 1m by 10m to avoid movement made over the beds and for easy weeding process.
Make shallow holes between each line 5cm by 5cm and the beds should be raised to avoid soil erosion.
The beds must have trenches to provide water runway.
In the hole apply fertiliser and cover it with a thin soil layer. Plant the seeds and cover lightly with soil and apply mulches.
After planting irrigate the nursery bed liberally for the first 10 days and continue watering regularly.
Germination of seeds will take about 7-10 days after which the mulches are removed and used to make a shade above the tender plants which have not fully developed.
The shed is applicable to hot conditions but in Kapchorwa and other districts in eastern region such as Mbale and Sironko it does not apply.
The hybrid varieties will take between 30 to 24 days to get ready for transplanting but the local variety will take two months to transplanting.
Transplant when the seedlings have a thick base and a height of 15cm.
The seedlings should have three to five well-formed leaves at transplanting time.
Two weeks before transplanting reduce the shade to improve seedling survival rate in the field.
Planting onions
The farm must be organised by farmers ploughing it twice to make the soil soft. Transplanting must be done in a line running 3m in width and between the boxes there must be trench as water runway.
One acre of land requires one kilogramme of onions which has been raised in the nursery bed.
The mode of planting is just like making a nursery bed though not in raised form.
Before planting the soil must be sterilised to eliminate cut worms in the soil.
This can be done using rocket chemical spray or you can burn the soil using dry banana leaves.
The farm must be exposed to sunshine for photosynthesis to take place.
Soil needs to be well-drained, loose and rich in nitrogen; compact soil affects bulb development.
Add manure or compost to the soil before planting. Onion plants are heavy feeders and need constant nourishment to produce big bulbs.
Crop rotation is essential for onions and for the farmer to realise good yield. It is also essential to practice mulching during the growth period.
Weeding
Weeding can be using selective herbicides and hand picking is also good.
Fertilise every week and keep changing the fertiliser type from NPK to DAP to enable the bulbs grow bigger in size.
Cease fertilising when the onions push the soil away and when the bulbing process starts.
Do not put the soil back around the onions; the bulb needs to emerge above the soil.
Generally, onion plants do not need consistent watering if mulch is used. About one inch of water per week including rain water is sufficient.
Onions will look healthy even if they are bone dry, so be sure to water during drought conditions.
Harvesting and storage
When onions start to mature, the top foliage become yellow and begins to fall over. At that point, bend the tops down or even stomp on them to speed the final ripening process.
Loosen the soil around the bulbs to encourage drying. When tops are brown, pull the onions.
Clip the roots and cut the tops back to one inch.
Let the onions cure on dry ground alternatively suspended floor with wire mesh for four to five days depending on weather condition.
Always handle them very carefully—the slightest bruise will encourage rot to set in.
Allow onions to dry for several weeks before you store them in a root cellar or any other storage area.
Spread them out on an open screen off the ground to dry.
Store at 40 to 50°F (4 to 10°C) in braids or with the stems removed in a mesh bag or nylon stocking.
Once it is dry, store in sacks made of sisal and any open container which can allow aeration.
Marketing
After curing, it is recommended to pack the bulbs in open ventilated boxes/nets and store them in a cool dry environment, ready for the market. In major towns of Uganda one kilogramme of onions costs Shs5,000.
Pests and diseases
The common pests are thrips, aphids, onion maggots and cut worms which keep destroying the leaves.
The common disease is leaf blight which destroys the leaves thereby affecting the root formation.
Farmers can use curative method of prevention by spraying with chemicals such as tata master and ridomil.
If the leaves were browning and getting dried up, it will be cured and normal growth will continue.
However if the plant is not yet affected by any disease, farmers can use the preventive method by spraying the plants with fungicides such as mancozeb and greenzeb. Top dressing with urea when the plant is three weeks old is essential.
