Sunflower oil is highly appreciated for its quality for cooking, its meal is popular in animal feed and it is a wonderful eye candy at the time of flowering. Every year, sunflowers blossoming in the whole of Europe on more than 4 million hectares. In Europe it is therefore the second most important oil crop cultivated. In order to achieve high yields, the choice of variety and the fertilization scheme has to be carefully adapted to the respective location.
Sunflower – a demanding oil crop
For germination, sunflower requires soils that warm up easily and about 150 frost-free days until harvest which is usually at the end of September. The total temperature demand during the growing season is high. Sufficient water supply at the time of flowering and persistently dry weather at the onset of maturity from August are very important.
- This demanding oil crop provides valuable yields when fertilization is specifically adapted.
- Sunflower has a high potassium requirement and is classified as chloride sensitive crop.
- Sulfur and magnesium are important nutrients to secure high oil content.
- The demand for the micronutrients boron and manganese is high.
Sunflower – best quality with sun, nutrients, and water
Owing to its high temeperature requirement, the cultivation of sunflower for oil production in the food sector is limited to climatically favorable regions. Sunflower can be successfully cultivated where grain maize varieties of the medium maturity group also ripen reliably. On the other hand, sunflower has a higher water requirement than maize during flower formation, which means adequate rainfall or irrigation, as well as soils with high water holding capacity are needed for a successful production.
Sunflower has an extensive tussock and fibrous root system which means that the crop has a good drought resistance during the rest of the growing season. Sunflower takes up large amounts of nutrients because of its large leaf and stem mass. Adequate nutrient supply by fertilzation during the vegetation is therefore important for good management of the crop.
The appropriate variety for the respective location must be selected in order to realize high yields.
Particular attention should be paid to the following criteria:
- Grain yield
- Oil content
- Early maturity
- Yield stability
- Disease tolerance
More facts about sunflower:
- An aspirational oil crop, sunflowers produce valuable yields when fertilizer is specifically adjusted.
- Sunflowers are chloride-sensitive and have high potassium requirements.
- Sulfur and magnesium are important to ensure oil content.
- The demand for the micronutrients boron and manganese is high.
The most important nutrients for sunflowers
Potassium – highest requirement for yield and quality
- Sunflower has a very high potassium requirement.
- During vegetation, about 300-400kg/ha K2O are taken up by the crop.
- Most of the potassium supply is needed to build up the large leaf and stem mass of the plants, while only about 80kg/ha K2O is contained in the seeds.
- Optimized potassium supply improves water utilization and increases resistance to drought.
- Potassium improves resistance to diseases and promotes sturdiness. This creates the basis for high yields.
- Potassium activates enzymes responsible for oil formation and therefore increases the oil content in the achenes.
- Due to the fact that sunflower is often cultivated in drier climates, where accumulation of chloride may occur, the use of potassium sulfate (SOP) is recommended.
Sulfur and magnesium – for securing the oil content
Sulfur – for protein formation and nitrogen efficiency
- With 40-50kg/ha S, sunflower has a similarly high sulfur requirement as canola.
- Optimized sulfur supply leads to more efficient nitrogen utilization. This has a positive effect on yield.
- Sulfur plays special roles in the fat metabolism of sunflower and is therefore indispensable for high oil contents.
An optimized sulfur supply leads to efficient nitrogen utilization. If there is a lack of sulfur, the nitrogen taken up cannot be converted into proteins, and a signal is sent to the roots to take up less nitrogen. Therefore, the plant's need for sulfur must be met for optimum nitrogen utilization.
Sulfur enables the plant to maintain its physiological processes optimally even under drought stress and to avoid or at least minimize yield losses. Sulfur is a component of the important antioxidant glutathione which, renders oxygen radicals, formed during drought stress, harmless and thus prevents necrosis of leaves and other plant tissues.
- A well-developed crop takes up about 50-70kg/ha MgO within a short period of time.
- An adequate magnesium supply guarantees a long-lasting assimilation of the sunflower leaves and therefore positively affects yield formation.
- Magnesium has a regulating effect on the citric acid cycle in cell respiration and in this way increases oil formation.
Boron and manganese – two important trace elements
- Sunflower has relatively high boron requirements.
- A crop that is well supplied with boron can optimally develop its tuft and fibrous root system, contributing to proper nutrient uptake from the soil.
- Boron also influences the growth of above-ground components. Deficiency, for example, leads to deformation of the flower heads and consequently to yield losses.
- Manganese is involved in the control of photosynthesis. This improves the assimilation performance of the sunflower and assimilation performance of sunflowers and has a lasting positive effect on yield.
- Through its regulating effect in fatty acid metabolism, manganese ensures a high oil content.
Sunflower fertilizer recommendations
Recommendation for soil fertilization
- 400-500kg/h Korn-Kali when fertilizing in the fall to meet the potassium requirement and at the same time secure the magnesium and sulfur requirement.
- 500-700kg/ha Patentkali when fertilizing in spring, e.g. on light soils, to cover the potassium supply and at the same time safeguard the magnesium and sulfur requirements without increasing the chloride content in the soil.
- 300-400kg/ha ESTA Kieserit gran. in the event of acute magnesium and sulfur deficiency.
Recommendation for foliar fertilization
For covering peak needs and controlling latent magnesium and sulfur deficiency, 15-25kg/ha EPSO Top in 5% solution is recommended. In case of severe deficiency or visible deficiency symptoms, the application rate can be increased up to 50kg/ha, split into two to four partial applications.
If additional boron or manganese is needed, 20-25kg/ha EPSO Microtop (5kg/100l water) is fertilized, possibly in several partial applications.