Abstract
The response of onion cv. Jaquar (Allium cepa L.) to sowing date and plant population was investigated in Bloemfontein (Free State Province, South Africa) during the year 2010. Jaquar seeds were sown on 11 and 25 May; and 8 June at five different populations (95, 83, 74, 67 and 61 plants m-2) in a randomized complete block design with each treatment combination replicated three times. Plant height and leaf number were measured 18 weeks after emergence. Bulb yield and quality (bulb mass, diameter, firmness and neck diameter) were recorded at harvesting. Significantly taller plants were obtained with the early sowing date (11 May) and a population between 61 and 74 plants m-2. Leaf production was not significantly influenced by any treatment. Bulb mass, yield and firmness were significantly higher with early sowing dates (11 or 25 May). Plant population significantly influenced bulb mass, but not yield. Bulb diameter increased as population decreased, irrespective of planting date. The three lowest populations (74, 67 and 61 plants m-2) yielded significantly harder bulbs than denser plants (83 and 95 plants m-2). The best sowing date for Jaquar in Bloemfontein was from 11 to 25 May at a population of between 61 and 74 plants m-2. Key words: Bulb diameter, bulb firmness, bulb fresh mass, bulb shape, leaf number, plant height, yield.
Highlights
The performance of onion (Allium cepa L.) is greatly influenced by environmental factors and agronomic practices
The primary objective of any producer is to attain high yields and for onions the final yield depends on the amount of vegetative growth before bulb initiation (Adjei-Twum, 1980 cited by Ibrahim, 2010)
Sowing of onions results in more vegetative growth (Mulungu et al, 1998), which reflects in the leaf area index (LAI) (Brewster, 1994)
Summary
The performance of onion (Allium cepa L.) is greatly influenced by environmental factors (photoperiod and temperature) and agronomic practices. The primary objective of any producer is to attain high yields and for onions the final yield depends on the amount of vegetative growth before bulb initiation (Adjei-Twum, 1980 cited by Ibrahim, 2010). Sowing date and plant population are the two major factors that influence the vegetative growth of onions. Sowing of onions results in more vegetative growth (leaf length and quantity) (Mulungu et al, 1998), which reflects in the leaf area index (LAI) (Brewster, 1994). The yield of late sown plants will be lower than earlier sown plants because leaf blade production switches to bulb initiation while the LAI and light interception is still low (Pakyϋrek et al, 1994; Brewster, 2008).
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