South Africa mainly produces oil seed sunflowers of which 86% is produced in the Free
State and North West provinces which are known for their sandy soils. Temperatures can
rise to 42°C in these soils when planting commences during November to January. These
conditions, in combination with other factors such as planting date and planting depth, soil
type, different cultivars, and seedling vigour, can influence the emergence rate of
sunflower seedlings. This will cause uneven stand which could affect the yield negatively.
In an attempt to evaluate the influence of soil factors and planting techniques on sunflower
emergence, three experiments were conducted in the greenhouse at the Department of
Soil, Crop and Climate Sciences of the University of the Free State. These experiments
evaluated the effect of seed size, planting techniques, and soil factors, and high soil
temperatures on the emergence rate of selected sunflower cultivars.
Three seed sizes (seed size one to three) of three cultivars (PAN 7049, PAN 7057, and
PAN 7063) were planted at two planting depths (25 and 50 mm respectively) during three
planting dates (September 2010, November 2010, and February 2011) to determine the
influence on the emergence rate of seedlings. It was found that a smaller seed size, such
as seed size three, emerged faster than larger seeds, seed size one.
The influence of two planting depths (25 and 50 mm) during the previously mentioned
planting dates with two soil types (Bainsvlei and Tukulu) on the emergence of sunflower
seedlings was also tested. Cultivar emergence was faster at 25 than at 50 mm. It was
also observed that the emergence rate was faster during February 2011 than during
September and November 2010. Although the emergence was faster during February
2011, above ground growth (plant height and dry weight) was greater during November
2010 than during September 2010 and February 2011.
The influence of four soil temperatures (35, 40, 45, and 50°C respectively) on the
emergence of sunflower cultivars was tested. An under floor heating wire (23 kW) was
attached to a galvanised metal grid and was used to simulate day and night temperatures
in the top soil. The grid and seed were placed at a depth of 25 mm (planting depth).
Emergence index declined gradually from 35 to 45°C, but a rapid decline in emergence
index was observed from 45 to 50°C. Emergence can be measured or calculated as an emergence index. Emergence is
determined as the moment that the seedling is visible above the ground and different
formulas exist to determine the emergence. Experiments differ from one another and
therefore different emergence index models were developed to accommodate the
experiment methods or crop that was used. It can therefore be concluded that differences
in emergence exist between cultivars. It is also necessary for producers to acknowledge
that soil factors and planting techniques play a vital role during planting until the seedling
emerge.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08192014-152545 |
| Date | 19 August 2014 |
| Creators | Schlebusch, L |
| Contributors | Dr AA Nel, Dr GM Ceronio |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-08192014-152545/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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