Response of onion (Allium cepa L.) to sowing date and plant population

[摘要] Field trials were conducted on the West Campus facility of the Department of Soil, Cropand Climate Sciences of the University of the Free State in Bloemfontein during 2009 and2010. The first trial during 2009 investigated the response of onion (Allium cepa L.)cultivars to sowing date. Cultivars namely; Charlize, Jaquar, Python and South Westerwere used in 2009. Onions were sown on 31 April, 7 May and 21 May during 2009. Thesecond trial was conducted during 2010, where cultivar Ceres Gold was used to replaceSouth Wester as the latter was no-longer available in the market and sowing was done on11 May, 25 May and 8 June. In both seasons, experiments were laid out as a randomizedcomplete block design with each treatment combination replicated three times. During2009, plant population of 41 plants m·2 was used, while in 2010 plant population of 61plants m·2 was used. Plots of 1.8 m2 were used with each plot having five rows. Each rowhad fifteen plants during 2009 and twenty two plants during 2010. Before planting, soilsampling and analysis were made, thereafter, fertilizers were applied as per soil analysisresults.A third field trial was conducted in 2010 to evaluate the three sowing dates (11 May, 25May and 8 June) with a combination of five plant populations (95, 83, 74, 67 and 61 plantsrn) using one onion cultivar ('Jaquar'). The experiment was laid out as a randomizedcomplete bock design, with three replications having 1.8 m2 plots. In each plot there werefive rows. A bulb storage trial was also conducted under room (±25°C) and cold roomtemperatures (±5°C). This was done for all field trial in both seasons.In a trial investigating response of cultivars to sowing date, better plant height, number ofleaves, bulb fresh mass, and yield were observed when sowing was done from the end ofApril to the end of May. Sowing date significantly influenced bulb and neck diameters onlyduring 2009. Bulbs were becoming more firm as sowing date was delayed, and theopposite was observed for bolting. Cultivar South Wester bolted more, followed by cultivarJaquar while other cultivars did not bolt. The shape of bulbs was not significantlyinfluenced by sowing date but it showed to be cultivar authentic. No split bulbs wereobserved. In a trial of sowing date and plant population, significantly taller plants were obtained withearly sowing date than the two later sowing dates. Leaf production was not significantlyinfluenced by sowing date. Sowing date and plant population affected bulb fresh mass,yield, bulb and neck diameters as well as firmness. Sowing date did not influence bulbshape while plant population did. None of the bulbs bolted from this trial.Mid-intermediate day cultivars ('South Wester' and 'Ceres Gold') recorded the shortestduration (105 days and 63 days respectively), while on average other cultivars werestored for 126 days in 2009 and 105 days in 2010. Storage disease (black mould),sprouting and loss of moisture from the bulbs were the contributing factors for reduction instorage duration. These factors were promoted by both field and storage conditions.Onion producers should have adequate information on the cultivars and the productionIn a trial of sowing date and plant population, significantly taller plants were obtained withearly sowing date than the two later sowing dates. Leaf production was not significantlyinfluenced by sowing date. Sowing date and plant population affected bulb fresh mass,yield, bulb and neck diameters as well as firmness. Sowing date did not influence bulbshape while plant population did. None of the bulbs bolted from this trial.Mid-intermediate day cultivars ('South Wester' and 'Ceres Gold') recorded the shortestduration (105 days and 63 days respectively), while on average other cultivars werestored for 126 days in 2009 and 105 days in 2010. Storage disease (black mould),sprouting and loss of moisture from the bulbs were the contributing factors for reduction instorage duration. These factors were promoted by both field and storage conditions.

[发布机构] University of the Free State