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
Due to their high temperature requirements, the cultivation of sunflowers for oil production in the food sector is limited to climatically favorable regions. Sunflowers can be successfully grown where grain corn varieties of the medium maturity group also ripen reliably. On the other hand, sunflower has higher water requirements than corn during flowering, so successful production requires adequate rainfall or irrigation and soils with high water holding capacity.
Sunflower has an extensive root network and fibrous root system, which means that the plant is well protected against drought during the rest of the growing season. Sunflower absorbs large amounts of nutrients due to its large leaf and stem mass. Adequate nutrient supply through fertilization during the growing season is therefore important for good management of the crop.
The variety suitable for the particular location must be selected in order to achieve high yields.
Particular attention should be paid to the following criteria:
- Grain yield
- Oil content
- Early maturity/required temperature sum
- Yield stability
- Disease tolerance
- Herbicide resistance
- Marketing direction (LO varieties with >70% linoleic acid content, HO (high oleic) varieties with >80% oleic acid content, striped birdseed varieties).
More facts about sunflower:
- As an emerging oil crop, sunflower provides valuable yields when fertilized selectively.
- 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.
- In wet years, sunflowers are vulnerable to diseases.
- Sunflowers achieve good nutrient mobilization due to intensive root growth.
- The nitrogen requirement of sunflowers is relatively low.
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 epsoTOP 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 epsoMICROTOP (5kg/100l water) is fertilized, possibly in several partial applications.