What onion variety must I grow? And how?

Climate

• For vegetative growth optimum temperature range is 12-24o C.
• At bulbing temperature range is 22-28o C
• Onion is sensitive to photoperiod

Varieties

• Short-day cultivars: Texas Grano, Granex 33and  Pyramid
• Long-day cultivars: Australian brown

Soil requirements

• Deep well-drained soils are required as onions are sensitive to water logging
• Soil pH: 5.0-6.0

Time for Planting:

 Best time for sowing late February and March

Area                           Best time                                          Suitable Time

Highveld                     Feb. March                                 Jan., April., Sept., Oct., Nov

Middleveld                 Feb. March                                  Jan., April., Sept., Oct., Nov

Lowveld                     March. April                                Feb., May., June., Sept. Oct.

Seedling production

• Mix one hand full 2:3:2 (37)/ m2 of the seedbed
• Sow in shallow farrow 10 cm apart and cover with thin layer of soil or compost
• Cover with net to protect from high temperature and crusting from heavy rains
• A month after sowing topdress with LAN @ 50g/ 3m2 (handful)
• Seedlings ready for transplanting after 2 months (pencil size thickness)

Onion Sets

• The cultivar Pyramid is often used
• Seed is sown in open seedbed in August or Sep. and are left to mature in the seedbed (December harvesting).
• Bulbs are dried and stored in a dry place, and are replanted in February
• Ideal bulbs are about 20 to 25 mm in diameter

Land preparation

• Plough down weeds/ residues 2-4 weeks before planting (decomposition)
• Apply 15 t/ha kraal manure
• Onions require full sun and good soil drainage
• Onions have a relatively shallow root system, with most of the feeding roots occurring in the top 200 mm of the soil

Bed for transplanting preparation and planting

• Planting should be 1m  width and 15- 20 cm high with four rows spaced 20cm on either sides of the center (drip line)
•  For 1m beds, the distance from the center of one tire to the center of the tire on the opposite side will be 200 cm. This allows the tractor to pass through the field without intruding on the planted crop or compacting the soil around and under the planted crop. 
• Heavy pipe can be drug behind the tractor to flatten ridge tops, height of the remaining bed can be somewhat controlled by lengthening or shortening the chains.
• Use a fertilizer with the middle number higher than the other two, such as 10-20-10.
• Basal fertilizer: 100 g of 2:3:2 (22) or 2:3:4 (30) per 1 m2.
• Spacing in rows: 7-10cm but 5cm used if some will be sold green and not more than 2.5 cm deep

Water Management

• After transplanting, keep the soil moist for the first 5 days to overcome transplanting shock
• The soil profile should be wet to a depth of 50-60cm
• Avoid moisture stress during bulb formation and development

Top dressing and weed control

• Topdressing- 10g LAN+ 10g KCL/m2 every 3 weeks until bulb initiation
• Stop fertilizing when the onions start to bulb

Pest and disease control

• Common pest: thrips, cutworm, nematodes
• Common diseases: downy mildew, purple blotch, rust, white rot
• For thrips use
• Copper oxychloride and Bravo, every two weeks after transplanting can be used to prevent diseases
• Crop rotation can be used to avoid pests and diseases

Harvesting

• Green onions are harvested early, when bulbs reach market specification
• Dry bulbs are ready for harvest at 3-4 months after transplanting, neckfall is the indication of maturity
• Yield: 20-40t/ha