1. INTRODUCTION
Sunflowers are mainly produced in Southern Mpumalanga, in the Eastern North West Province and the Northern areas of the Free State. It is a large annual plant that is indigenous to the Americas. It gets its name from the shape, colour and size of the flower which depicts the sun ‐ hence sunflower. The stem of the plant is hairy and feels rough and the leaves have a coarse toothed and rough appearance. The head has many flowers on it which develop into seeds.
Sunflowers are grown for their seeds, which have high oil content of about 20 ‐ 30% of the seed. The oil which is extracted from sunflower seeds is used for manufacturing margarine, soap and paint, and also used for cooking. The residue which is left after extraction is a valuable cattle feed and is sold as Sunflower seed cake or meal. This cake or meal contains .40% Crude Protein, 10% Fat, 12% Fibre and is high in phosphorus. The seed or the whole head of the plant can be milled and fed to livestock, but must be fed in small quantities because of the high oil content. The marketing of sunflowers can be sold directly to a manufacturer. Sunflowers can be grown to make into silage, although the yield is much lower than maize silage and the palatability is poorer.
2. VARIETIES
There are many varieties of sunflowers and much research needs to be done to establish which cultivar is best suited to the production areas concerned. Descriptions of some varieties are as follows:
PAN 7057
This variety has been the top performer in the national trials for the last 2 years. It has a wide adaptability across all the production areas in South Africa with excellent oil yield of 43%. It is resistant to all forms of common rust and is a medium to late maturing variety which is ready to harvest in 150 – 155 days. The plant stands 170 cm high.
PAN 7063CL
This variety has a medium maturity season that is ready to harvest in 140 – 148 days. It has a high oil content of 42% with a plant height of 150 cm and it is resistant to the natural mutation of sunflowers and not genetically modified.
There are many other cultivars of sunflower such as: AFG 271, AGSUN 5261, DK 4040, HV 3037, Hysun 346, NK FERTI, Sirena and many other varieties.
3. PLANTING
CLIMATE AND SOIL
Sunflowers require a warm dry climate and thrive in areas with a mean daily temperature of 18 ‐ 25⁰C and are not suitable for cool humid areas. The mean temperature in January should be 19ºC and for the production of improved oil content, there should be a moderate temperature at seed development.
Sunflowers are more drought resistant and less susceptible to frost than maize but are very susceptible to eelworm infestation, and should never be grown on land that is likely to be used for tobacco. Sunflowers require a warm climate with a rainfall of 400 – 600 mm during the growing season and tolerate drought.
Sunflowers grow well on most soils provided they are well drained. They grow better on alkaline, very clayey or sandy soils than maize. They have a rooting depth of up to 2 metres; however they extract their water from 0.75 – 1.5 m depth. Sunflowers are sensitive to aluminium toxicity and boron deficiencies and do not do well in soils that crust easily, have poor drainage and sandy soils that are windblown. Ploughing and seedbed preparation is the same as for maize and a cultivation of the soil before the crop is planted will help to control weeds. The soil pH should be 4.5 and higher.
TIME OF PLANTING
This should be arranged so that the heads of the crop mature and dry out after the rains have finished.
Sunflowers should be planted from the beginning of December to the end of January.
The Planting depths vary from soil to soil. On clay soils the planting depth should be 25 mm, loam soils 30 mm and sandy soils 50 mm. The seed should germinate in 8 ‐ 10 days.
| Plants/ha | Spacing (mm) | Kg seed per ha | Potential yield (kg/ha) | ||||||||||||
| 25 000 | 900 x 450 | 2,5 | 1 000 | ||||||||||||
| 35 000 | 900 x 325 | 3 | 2 000 | ||||||||||||
| 40 000 | 900 x 275 | 4 | 3 000 | ||||||||||||
| 50 000 | 900 x 225 | 5 | 4 000 | ||||||||||||
Table 1: Plant Populations and Spacings
Once the crop has germinated and emerged, it can be treated exactly like a maize crop. The plant rows can be ridged up to support the plants and reduce lodging (e.g. the plant falling over and lying on the ground).
4. FERTILIZATION
When growing sunflowers on normal soils the following nutrients should be applied:
| Nitrogen | 0 – 45 kg per hectare | |
| Phosphorus | 35 – 70 kg per hectare | |
| Potash | 0 – 45 kg per hectare |
On very poor soils up to 80 kg/ha of Nitrogen can be applied. All fertilizer should be applied to the seedbed and harrowed or disced into the soil. One should not apply more than 30 kg/ha of Nitrogen at planting. One should also apply 1.5 kg/ha of Boron on sandy soils and 3 kg/ha on clay soils.
5. PESTS AND DISEASES
DISEASES
Rust: This is a seed‐born disease and can be controlled by the use of good seed which has beendressed with a seed dressing.
PESTS
Eelworms
These are a serious pest for sunflowers and can be controlled by the use of sound rotations. Do not grow the crop frequently on the same land and never in the same rotation as potatoes or tobacco.
Loopers
If the crop is attacked by looper caterpillars apply aluminium phosphide.
Birds
Grain‐eating birds can be a serious pest as they attack the heads of the plants and eat the seeds as they ripen.
Some protection can be obtained by using a variety of sunflower which turns its heads towards the ground as it ripens.
6. WEED CONTROL
Sunflowers in their first 6 weeks after planting are very sensitive to weed competition. Mechanical can be used but it is for a short period due to the rapid growth of sunflowers. This is the general method used but should be changed over to herbicides as the crop grows and equipment cannot gain access. The herbicides that are registered for sunflowers are: Trifluralin (pre‐planting), Alachlor (pre‐emergence of crop and weeds) and Haloxyfop‐R‐methylester (post‐emergent).
7. HARVESTING
The heads of the plants should be cut and harvested as soon as they are mature to reduce damage caused by birds and losses due to shattering i.e. the seed falling out of the head. Harvesting is done by hand. The heads are stored and then threshed by hand or a maize sheller. Threshing by hand should be done on a bare level surface such as a strip of cement.
Sunflower is ready to harvest when the moisture content of the seeds is at 10%. This happens when the sunflower heads have turned brown and it is like that for 80% of the crop.
Yields of seed for dry land are from 1 000 to 2 500 kg/ha, and under irrigation 4 000 kg/ha. If the crop is cut for silage before ripening, it will yield about 9 tons of green material.
