Tips for managing bulb onions

I am Andrew from Luweero District and I plan to plant onions especially the bulb type. Please give me some tips and the general agronomy of the bulb type. 

Dear Andrew

Bulb onions, locally known as katungulu, is one of the most used vegetables in the world. It is used in cooked meals or raw salads as a flavour additive.

Onion farming can be profitable. Profitability is dependent on proper market identification, proper planning for labour especially during transplanting and weeding, and good post-harvest handling procedures.

The market

The onion market is enormous, given that almost all homes use onions as part of the ingredients of their daily meals. Currently, the cost of a kilogramme of onions ranges from Shs5,000 to Shs6,000 and goes higher when there is a shortage in the market.

At the markets, traders usually prefer the mid-sized onions to the larger onions. This is because home users prefer to use one onion once, with no remains as with large onions and also do not like cutting small onions. If you plan to cultivate the larger bulb varieties, you should target institutions and hotels as your market as they consume vast amounts of onions at a time. Other viable markets for onions aside from fresh produce markets include;

• Hospitals

• Primary and secondary schools

• Hotels and restaurants.

Health benefits

Onions are inexpensive, convenient vegetables that contain a multitude of nutrients that have various nutritional and health benefits. Some of the health benefits from onions include;

• Onions are particularly high in vitamin C therefore good for immune health, tissue repair and are necessary for iron absorption into your body.

• Onions also contain a high concentration of quercetin which is a flavonoid antioxidant. The antioxidant helps decrease heart disease risk factors such as high blood pressure.

Varieties

There are several varieties of onions. These varieties are based on the climatic conditions they do best in. These varieties include;

Red creole – It is very pungent taste characterizes this variety. It has a red, flat round, globular bulb appearance.

Bombay red – This variety does well in dry and warmer conditions. Its seeds Produce small to medium-sized bulbs, which are globe-shaped, deep purple-red colour and very pungent.

Others include Texas early grano, Neptune F1, Tropicana F1, Red star F1 and Red Passion F1.

Ecological requirements

Onions can grow in a variety of climatic conditions and soil characteristics. For optimal growth, onions will require;

Bulb onions grow well in well-drained soils. You can also grow onions in shallow soils if you adapt in your management practices. Sandy to silty loams with fine tilth is adequate, pH ranging from 6.0-6.8. This is to ensure your onions maintain good macronutrient uptake. An altitude of below 1900 metres above sea level.

The temperature of about 15 – 30 degrees Celsius. If the temperature exceeds 30 degrees Celsius, it hastens maturity leading to the production of small bulbs, consequently lowering the yields. Cooler temperatures also encourage the spread of leaf diseases.

Land preparation

You should plough your land as deep or ripped as possible. Onions do well in deep well-drained soils, and a good seedbed prepared, with all lumps broken up with a disc harrow.

Nursery preparation

You should make your nursery bed to raise your seedlings near the planting site to make it easier for you during transplanting. Follow the following guidelines while preparing your seedling nursery;

You should adjust the beds to be one metre wide while incorporating compost manure that is well decomposed.

The seedbed needs to be under a shade, or you can as well prepare a raised cover to protect seedlings from direct sunlight.

On the seedbed, make rows 15cm apart and drill the seed thinly 1cm deep.

Cover the seeds using soil and mulch. Onions take between 7-10days to germinate.

You should ensure that you water the seedbed daily but be careful not to flood it. After the seeds germinate, remove the mulch.

The onion seed rate ranges from 0.8-1.2kg per acre. It is essential to plan your timing very well to ensure that your onions mature when its demand is at its peak. This will ensure that you get maximum returns from your onions.

Transplanting onions

Seedlings are transplanted between six and eight weeks after sowing.  As you approach the intended day of transplanting, gradually reduce the rate of watering. This will make your seedlings stronger in terms of structure. Remove the shade cover to get the seedlings more used to stronger sunshine.

Before transplanting, you should irrigate your seedbed to avoid damaging your seedling as you pull it from the seedbed. You should also water the field a day before you intend to transplant.

Fertiliser requirements

Fertiliser plays a crucial role in the development of excellent and healthy onions. Before planting, you should apply 10-16tonnes of well-decomposed manure per acre. Ensure the manure is well rotten as fresh manure will cause the development of thick leaves at the expense of bulb formation. You can also add 80 kilogrammes of TSP to the fertiliser and incorporate it into the soil. You should top-dress your onions 30days after transplanting at the rate of 40 kilogrammes of CAN per acre.

Irrigation

Onions require light and frequent irrigation depending on the type of soil you have grown your onions in. Lighter soils such as sand will require more frequent water applications, but less water applied. Onions require just enough moisture during the growing stage. At the bulbing stage, the onions will require a substantial amount of water. You should reduce the watering towards the maturity stage.

Weed control

There are many ways weed control can be done while farming onions. Common weeds that grow alongside onions are Mexican marigold, star grass, sow thistle and thorn apple. Some of the weed control methods include;

Hand pulling-You can manually extract the weeds by pulling them by hand and burning them before they flower.

Chemical method- You can use herbicides such as Catapult 480SL and Predator 340EC to control the weeds. Use of chemicals is cost-effective and is also easy and fast to apply.

Intercropping onions

Intercropping is essential in ensuring you maximise your returns from your farm. It also has other benefits such as controlling pests such as caterpillars in vegetative plans. You can intercrop onions with other crops such as kales, lettuce and cabbages to deter caterpillar attacks on the leaves of the vegetative plants.

Harvesting

Onions usually become ready for harvesting at around 120 to 150 days after transplanting. You should harvest your bulb onions when 75 per cent of the tops of the crop have dried and fallen over. The onions are harvested by pulling and leaving the bulbs on the soil surface to begin the process of curing.

Post-harvest

Post-harvest care of onions involves the process of curing. Curing is whereby you dry the neck and outer leaves of the bulb. This prolongs the shelf life of the bulb by preventing moisture loss and attack by diseases. Curing can either be protected or done in the field.