Nursery Bed Management for Onions: Step by Step Guide

Successful onion (Allium cepa) production begins long before the bulbs form in the field, it starts in the nursery. Onion nursery bed management is the quiet foundation that determines seedling vigor, uniformity, and eventual yield. For onions, careful attention to soil preparation, moisture control, and seedling health at this early stage sets the tone for a productive crop. When the nursery is well managed, the field harvest tells the story.

NB: Examples of inputs used in this manual are from Uganda!

• Onion is propagated by seeds (fresh)

• Seed rate is 0.8 to 1.2 kg per acre and is sown in a nursery under a mulch cover

How to Set the Seedbed

• Use a tape measure, Harmer, wooden poles and a sisal rope to dig ridges 10 inch high above the ground, one meter wide and 10 meters long.

• Mix the top soil of the ridge with manure. Manure from ruminant animals is recommended (Goat, Cattle or Poultry) FYM 20 kg/m2.

• If the manure is fresh leave the bed for at least 3 weeks and then make a fine tilth. But if the manure is already decomposed enough, there should be a normal progress the following days.

• If you do not have manure you can use inorganic fertilizers like DAP 20g/m2 on the ridge and make a fine tilth.

• After mixing a fertilizer and making a fine tilth, use sisal ropes and tape measure to make rows across the ridge 15 cm apart. These are simple shallow lines 1cm deep where seeds will be sowed.

• Four ridges with rows of 15 cm apart and the above dimensions can accommodate 1kg of onion seeds. (250 grams of seeds per ridge).

How to Treat the Soil

• Treating the soil should be done in the morning hours on the day of planting

• After setting the beds, spray Glymark or any other  herbicide (30 ml in 20 liters) on the top soil 2-3 days before sowing

• Mix 5 spoons of indofil into 20 Liters of water or any other non-curative fungicide available and spray on the raised ridges on the day of sowing but before sowing.

• Mix 20-30 ml of bright down plus or any other curative fungicide available into 20 litres of water and spray on the ridge.

• Mix 20 -30 ml of Cyperforce or any other non-curative insecticide available into 20 Litres of water and spray on the ridge.

• Mix 20-30 ml of Ramida or any other curative insecticide into 20 litres of water and spray on the ridge.

How to Plant

• Planting should be done in the evening hours when the soil was treated in the morning.

• Onion seeds are very tiny and it is very exhaustive to plant one seed per hole.

• Measure 50 grams of onion seeds and mix with a cup of sand, this will ensure that only one seed falls into the hole. When two seeds fall in one hole, one has to die off hence making a loss.

• If you don’t have the equipment to measure the 50 grams of onions, get a 500 gram tin of onions and distribute it equitably into 10 cups or bottles of equal sizes, this will ensure each has 50 grams in it. Then mix each with a cup full of sand and shake vigorously.

• Sprinkle gently the sand-onion mixture into the rows, cover up with a very thin layer of fine soil with no clods.

• If you distributed the 500 gram tin into 10 cups, then 5 cups are recommended to cover only one ridge with the above discussed dimensions.

• After sowing, apply 2 watering cans per ridge to ensure enough water for germination.

• Mix 20-30 ml of Synergizer or any other starter foliar fertilizer available into 20 litres of water and spray on the top of the rows where seeds where planted.

• Sprinkle ash on top of the ridge, this will help create extra heat in the soil to enhance seed germination. 2-3 kg of ash can be applied on each ridge.

• Cover the top soil with dry mulches preferably dry grass, fresh grass may carry weed seeds on the bed. The mulch should be sizeable enough

• Mix 50 ml of Roket in 20 litres of water and spray on the mulches and in the sides and around the ridges to kill termites and other biting insects that may find habitat in the mulches.

Care Before Removing the Mulch

• Germination takes 5-10 days depending on the variety of the onions you planted.

• Irrigate the nursery bed regularly but do not do excessive watering for it delays germination. Apply water every after 3 days when rain is scarce and 4 days when rains are present

• Remove the mulch after achieving 50% germination of the seeds.

• The mulch should be removed in the evening to avoid sudden exposure to sunlight.

• Remember delay in removing the mulch leads:

Ø  Seedlings to bend and stretch in search of light.

Ø  Risk of uprooting or damaging seedlings during mulch removal. 

Care After Removing the Mulch

• Prepare a raised shade over the onion seedlings using wooden poles, dry grass and a few nails or ropes to make a simple roofing.

• When the shade is high the onions will be exposed to harsh weather. The recommended shade should be at a knee height.

• Cover the top of the shade with dry grass and watering should be done on top of the shade such that water falls on onions like rain drops.

• Continue with the same watering schedule, which is every after 3 days in scarce rains and 4 days when rains are present.

• From the sowing date, every after 7 days, apply a curative or non-curative fungicide, insecticide and a foliar fertilizer.

• At 4 weeks of seedling age:

Ø  Switch from starter foliar fertilizer for example Synergizer to a vegetative foliar fertilizer for example Maxi force.

Ø  This strengthens seedlings and prepares them to withstand transplanting shock.

• Keep the nursery bed weed free at all times, and ensure the bed surface is well levelled.

• Onion plants will bulb based on day length, not just size or age.

• Be aware of damping off (seedling fall). It happens due to poor drainage and inadequate water. It is treated by using a curative fungicide, also apply foliar fertilizer.

• On the 6th week when seedlings have 3-5 leaves trim them and apply a fungicide to prevent attacks from Downey mildew disease.

• While in the nursery bed some onions will start to bulb, this kicks off transplanting stage.

Pro Tip:

Rotate both the insecticides and the fungicides. Both fungi and insects have a tendency of mutating and developing resistance if the same chemical is used respectively. A farmer is recommended to have at least 4 different fungicides and 3 different insecticides sprayed at different intervals.

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