1. BACKGROUND
Distribution
In Limpopo province, onions (Allium cepa) are produced in all districts with Waterberg being the highest while Sekhukhune is the lowest.
Soil and Climatic Requirements
Onions grow on a wide range of soils. The best results can be obtained on loamy soils which are deep and well drained to a depth of 120 cm with a pH between 5,5 and 6,5. Onions grow best in temperatures ranging from 18 °C to 22 °C. Higher temperatures (25 –27 °C) will promote bulb formation, while lower temperatures (8–13 °C) will induce flowering.
2. CULTURAL PRACTICES
Planting
Soil should be loose to a depth of at least 75 cm and if heavy rain is expected in the early stages of growth, raised beds will reduce the effect of any waterlogging. Where seed is to be directly sown, even seed bed is vital in order to produce an acceptable stand. Onions can be sown directly, or seedlings can be transplanted. After transplanting, keep the soil moist for the first 5 days to overcome transplanting shock. Onions are planted at spacing of 7–10 cm in-rows and 20–25 cm inter-row.
Seed is sown at a depth of 1–2cm. Population of 700-800,000 plants ha-1 produces the highest proportion of medium-sized bulbs which are preferred by the South African market. Planting date in most areas of Limpopo province is February to April but the sowing time may be influenced by a micro-climate on a specific area.
Fertilization
N – 180 kg ha-1. 60 kg pre-plant, 60kg at 2 leaf stage 60kg at 4 weeks.
P – 100 kg ha-1. All applied as pre-plant.
K – 170 kg ha-1. 110 kg pre-plant, 60 kg 7-8 weeks prior to harvest.
Soil analysis is required for formulation of a detailed fertilisation programme.
Irrigation
Onions require approximately 400 to 600 mm of water during the growing season. Dryland production of onions is not recommended. Soil should not be allowed to dry out, especially during bulb formation. Do not irrigate onions for 3 weeks before harvesting.
Pest and disease control
Registered chemicals, proper crop rotation as well as field sanitation should be integrated to control all the pests and diseases affecting the crop.
3. CULTIVAR SELECTION
A medium sized bulb is preferred but there is also demand for smaller and larger bulb sizes. The largest demand in South Africa is for yellow (Ayoba, Duster, Harrier, Korimako,) or brown (Ayoba, Capricorn, Red Grano, Camilla, Cavalier, Chelsea, Copperhead, Cristalina, Fernanda, Gamay, Goblin, Komati, and Letaba) onions but there is a small market for red and pink varieties. Ayoba can’t repeat twice.
Sources
A PROFILE OF THE SOUTH AFRICAN ONION MARKET VALUE CHAIN 2021
Department of Agriculture, Forestry and Fisheries, Onions
Starke Ayres: Carrot Production Guideline, 2015