Onions are cultivated and used as a food item. They are usually served or cooked, as a vegetable or part of a prepared savory dish, but can also be eaten raw in salads.
Bulb onion varieties: Red creole, Bombay red, Texas Early grano (white), Red Pinoy, Red passion F1, Tropicana F1, Orient F1, Silvan F1, BGS 130, Flare F1, Red snack, Ruby F1, Red nice F1.
Spring onion varieties: Spring green bunching, white Lisbon, American flag, Italian giant.
Altitude: 500-2000m above sea level.
Rainfall: 500-700mm well distributed.
Soils: Well drained fertile soils with good water holding capacity, PH ranging from 6.0-7.0
Plough 2-3 weeks prior to planting, harrow the field 2-3 times to obtain fine tilth desirable for onion growing. Apply 40 tons of well decomposed organic manure or 400kg per every 100m2 and mix thoroughly with the soil.
Propagation and planting
Onions are grown from seeds sets or transplants. Transplant seedlings when they reach pencil thickness, about 6-8 weeks after sowing in the nursery. Plant at a spacing of 10cm by 8cm for seedlings raised on a nursery.
For direct seeding drill holes 2.5cm deep and 10cm apart, carry out thinning 4-6 weeks when seedlings attain 10-15cm height, let the plants be at 10cm by 8cm spacing or 10cm by 10cm.
Apply fertilizers in good time to supplement the required nutrients for proper crop performance. Apply 200kg TSP/DAP per hectare during planting and 300kg CAN per hectare 3-4 weeks after transplanting.
Keep onion field weed free throughout the growing period to avoid competition for growth resources. Carry out light hand weeding or use pre-emergence herbicides two weeks after transplanting.
Onion thrips: Irrigate the plants well, practice field hygiene.
Onion fly: Avoid soils with high organic matter, practice crop rotation, observe field hygiene, and solarize soil to destroy pupae.
Leaf miners: Preserve natural enemies such as parasitic wasps.
Downy mildew: Use certified seeds, plant resistant varieties, practice crop rotation, spray with suitable copper fungicide eg ridomil gold
Purple blotch: Plant resistant varieties, use wider spacing, crop rotation, practice good field hygiene, and spray using copper fungicide.
White bulb rot: Plant resistant varieties, use clean planting seeds, practice long rotation program roughly 8-10yrs.
Onion rust: Practice crop rotation and proper field hygiene
Fusarium basal rot: Practice crop rotation, avoid root injury, proper curing of onion bulbs before storage.
The crop is ready for harvesting 3-5 months for bulb onions and 2-4 weeks for spring onions after sowing. Grade the onions and package in net bags. Yield range between 7-10 tons per hectare depending on variety and management.