How to Produce Onion Seed:
Have you ever wondered how seed companies produce onion seeds?
I’ve wondered about it for a long time.
So I decided to do a little research.
My objective, “To uncover how seed breeders produce onion seed.”
My research uncovered very interesting things…
That I am sure they will excite you.
I discovered that onion seed breeders use two approaches to produce onion seed.
- Bulb to seed
- Seed to seed
For that reason, my discussion will explain the details of these two approaches.
Ready to know how to produce onion seed?
Bulb of Seed Method of Onion Seed production
In the Bulb to seed method, previously harvested bulbs are used to produce onions seeds.
Here is how it works.
The onion bulbs that were harvested and stored the previous season are replanted the following season.
Seeds are produced in the second season.
This method of producing onions is very expensive.
However, it has a big advantage.
It allows the grower to easily discard the off types, and the diseased or undesirable bulbs.
Because of this major advantage of the Bulb to seed, it is used to the preserve the onion seed stock.
Seed to Seed Method of Onion Seed Production
In this case, breeders use the seed as the initial planting material.
They grow the seed, the bulbs mature, and then they let them produce seed.
This onion seed production method has the following advantages;
- It gives a higher seed yield than bulb to seed method.
- The reason for the high yield is the closer spacing achieved when seeds are sowed…
- meaning that more bulbs will be produce and latter flower to produce seeds.
- Breeders invest less time in bulb establishment.
- Overall cost is lower than bulb too seed method.
The above reasons make the seed to seed method of onion seed production the most preferred.
The major disadvantage of this method is the production of off-types thus rouging is required.
Important Cultural Practices in Onion Seed Production
Some of the very important cultural practices have a role in ensuring the seeds produced are viable.
It’s important to pay close attention to pest and disease management when using seed to seed method.
Leave the field fallow for at least 4 years and ensure it’s free of perennial weeds and soil borne diseases.
Plow the soil to a depth of 10-15 cm.
Work it up until you achieve a firm seedbed.
Ensure the soil is friable, fertile and well supplied with humus.
Plant seeds at a depth of 1-3 cm in rows of a width of 50-70 cm at a rate of 4.5-6.7 kg per hectare.
Higher seed rates and close spacing yield more plants, thus more seed production.
In some varieties, more than one stalk is produced.
Where soil fertility allows, adequate and reliable irrigation or rain is present, the inter row spacing can be reduced to 30 cm.
Onions respond well to fertilizer application because rooting structure is shallow and limited to a depth of 5 cm.
It is important to add organic matter to improve soil moisture retention ability and soil structure.
An equivalent of 56 kg/Ha of Nitrogen should be applied as farmyard manure.
Application of nitrogen and potassium is not recommended at flowering because flowers become unattractive to bees; that are so important in pollination.
When the onions experience a copper deficiency, they become thin, poorly colored and have a poor bulb storage life.
This can be improved by application of 22 kg /ha of Cuso4.
Manganese deficiency common in onions; it is seen as leaf chlorosis. This is often observed in alkaline soils thus adding an acid based fertilizer e.g. ammonium sulfate will solve the problem.
Maintain the soil PH at 6.0-6.5 which is slightly acidic to prevent the incidences of manganese deficiency through regular soil testing. Ameliorate the soil PH when it becomes unfavorable.
You need a permanent source of water to keep soil moisture above 65% field capacity because the crop is shallow rooted. When the bulbs initiate flowering; stop irrigation.
Onions are poor competitors against weeds as they are shallow rooted. They have a poor canopy structure thus can be easily shaded by weeds.
Weeds also interfere with harvesting and become contaminants of crop seed. Effective weed control is achieved through proper cultivation, crop rotation or using selective herbicides.
- Pest and disease control
Many diseases and pests attack the onion plant.
- Umbel blight is caused by Botrytis alli infects the onion seed stalk consequently reducing seed yield and quality.
- Onion downy mildew is caused by Peronospara destructor that is common during cool season’s causes chlorotic lesions on leaves and root stalk.
- Pink root disease caused by Pyrenocheata tertris is a soil borne pathogen that infects onions at any stage of development and causes the root to turn pink then brown then black then die.
- Fusarium basal rot- caused by fusarium oxysporum causes yellowing, die back from the top of the leaves.
- Onion thrips feed on leaf surfaces causing them to turn white or silvery. They also feed on flowers, thus affecting seed formation.
- Scales are also a major problem of onions.
Harvesting and Threshing of Mature and Dry Onion Heads to Produce Onion Seed
Onion seed harvesting starts when onion heads containing some capsules
- Turn black
- Are opening.
The black color indicates that the seeds have ripened.
Although all onion seeds heads do not mature at the same time, most farmers do a once all harvesting when seed heads are about 30% mature.
The harvesting is done by hand.
Harvesters cut the plant 10-15 cm below the umbel head.
The cut umbel head is put in sacks and stored for 1-2 days.
After the 2 days, the seeds will be dry enough for threshing as the capsules become brittle, break easily thus releasing the small onion seed.
Once thrashing is done, dry the seeds at a temperature of 320 C until they achieve a moisture content of 10%.
Continue drying the seed then at a temperature of 430 C until a storage moisture content of 6% is achieved.
Conditioning of the Onion Seeds Produced in Readiness for Storage
After threshing, we condition the onion seeds to eliminate weed seed and chaff.
During the conditioning process, we eliminate light unviable onion seed.
Initial cleaning is done by an air screen cleaner and a gravity table.
The cleaner and gravity table allows the offloading of chaff and dirt on account of weight differences, heavy seeds sink on the other hand light seeds float and are unviable.
After the removal of chaff is over…
Wash and treat the clean onion seed using a suitable seed dressing chemical for not more than 3 minutes.
Once this is done, dry and store the seed.
Ensure that the seed moisture content is less than 10%.
How to Store of Onion Seeds After Harvesting
Onions seed deteriorate so fast when stored under hot, humid conditions.
In less than one year, they become unviable thus useless for planting.
However, proper storage will result to higher viability and germination rates.
Scientists have proven onions seed stored at a moisture content of 6%; will maintain their viability for 3 years.
Their viability increases by 100% to 6 years when stored at a moisture content of 3%, the viability.
Yields Per Acre of Onion Seed
Open pollinated onion varieties will like Red Creole will yield 550-800 kg per hectare.
However, for the hybrid varieties, 800-1200 kg of seed.
When one is aiming to produce bulbs, one hectare can produce about 12-20 tons of onion bulbs.
Most farmers prefer growing red creole variety because
It grows over a wide range of altitude
It is suitable for both open field planting and greenhouse planting.