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The variety chosen will reflect the end use for the bulbs ie fresh market (salads etc) or export and will be dictated by the location of the production area. . The choice of variety for a particular planting date is critical because bulb formation is sensitive to day length and temperature.. To produce a high yielding crop planting the right variety at the right crop density ) for a particular location is required. There are too many combinations to list so we suggest you speak to your local seed representative or local nursery for more information.
Onions (Allium cepa) are planted throughout the year depending on the region and climatic conditions although the usual planting period starts in February in the lower latitudes eg Lockyer Valley through to early spring in WA.
Seed can be planted on raised beds or flat ground depending on irrigation practice, soil type and available equipment. The use of precision planters is advisable to maximise yield.
A common plant spacing is 75mm between plants in rows 300mm apart ie around 450,000 plants per hectare; this planting density will give best yields. However, plant spacing can affect disease control and the size and shape of the onion. A uniform plant stand is required to produce bulbs of similar shape and size.
Germination time depends on soil temperature and can vary from 10days up to 28 days.
A primary requirement to obtain ideal plant stand is to use seed which has high germination levels (as determined by a recent test). If seed is retained from previous seasons then an updated germination test would be advisable.
Pre-emergent and post emergent herbicides can be used if you believe you may have a serious weed problem.
Many herbicides are available. The one selected will depend on the type of weeds present and the growth stage of the onion plants. Read the label to find out what weeds the chemical controls. (See agrichemical data on this site to find which chemical is registered for use on onions in your State).
Onions do need fertiliser but what type and how much depends on the soil type. The timing of fertiliser application is also important. All fertilising should be based on the results of a soil or leaf analysis. It is also essential to monitor plant nutrition using leaf and soil analysis. Apart from initial preplant fertiliser applications (ascertained from soil tests) subsequent applications of micronutrients and major nutrients may be required.
Plants are monitored for incidence of insect pest such as thrips or outbreaks of disease such as downy mildew . Spray programmes should be planned to maximise control and also minimise the risk of pests becoming resistant to the chemical.
Before using chemicals always read the label to determine if the chemical is registered for onions in your area. The label on the chemical container gives the registered rate of application and the withholding period. The label also tells you how to use the chemical and how to mix and apply the product safely (see agrichemical information on this site).
Onions are ready to harvest when 50 to 80 per cent of the tops have fallen. At this point all irrigation should have ceased and the crop can be lifted prior to harvesting and drying.
After maturation the onion crop is lifted eg by running a metal rod underneath the onion bulb severing the roots and killing the plant. Depending on area of production then the bulbs can be either
1. hand harvested, top and tailed manually, put into bags and sent to the market.
2. Put into bins (mechanically or by hand) and taken to storage sheds for curing (by fan forced air). When required for sale the bulbs can be passed over machinery to remove leaf and root residue then graded ( for size) and inspected for off types before packing into bins or bags as appropriate
3. Depending on the market (ie export or domestic) then bulbs are shipped on pallets or containerized and sent to wholesalers or the wharves for export.