Oilseed rape is an important oil crop ant the oil is in high demand on the world markets as a high-quality edible oil because it has an almost optimal composition of saturated and unsaturated fatty acids. Moreover, oilseed rape is an important raw material for biofuel production, oleochemicals, pharmaceuticals and technical applications.
Oilseed rape for oil and energy
Oilseed rape cultivation has great advantages such as a broad crop rotation, an increased nutrient use efficiency or as an ideal previous crop for cereals. Oilseed rape has high requirements for nutrient supply. A high potassium availability from the soil or through fertilization is the precondition for an optimal yield formation.
- High nitrogen efficiency through potassium, magnesium and sulfur.
- Magnesium guarantees a high assimilate production through geen leaves and pods.
- Sulfur deficiency results in drastic yield decreases.
- Oilseed rape is a crop that particularly requires boron, thus boron fertilization should be standard for this crop.
Sucessful oilseed rape cultivation with an efficient nutrient supply
Oilseed rape production has many positive aspects for farmers and sustainable agricutulture. For example, loosening the crop rotation, increasing the nutrient efficiency of the soil or as an ideal pre-crop for cereals. Oilseed rape places high demands on the supply of nutrients, a high supply of potassium from soil reserves or fertilization is a prerequisite for optimal yield generation.
- High nitrogen efficiency through potassium, magnesium and sulfur.
- Magnesium guarantees full assimilation through green leaves and pods.
- A lack of sulfur leads to drastic losses in yield.
- Oilseed rape is a crop that requires boron, and drone fertilization should be a standard measure.
The most important nutrients for oilseed rape
Oilseed rape requires potassium
Oilseed rape has specific nutrient requirements. For optimum yield, it needs – in addition to nitrogen – above all potassium.
- In spring, at the beginning of the growing season, large amounts of potassium are taken up in a short time, as potassium uptake precedes biomass production.
- When the canopy is fully developed, an oilseed rape plant can contain up to 400kg/ha K2O.
- Depending on the development of the plant, it may have already absorbed 100kg/ha K2O ha by the beginning of winter.
- A good potassium supply increases the frost resistance of the plant and therefore leads to fewer losses in severe winters.
- Optimized water balance allows plants to better tolerate drought stress.
- The synthesis of oil is promoted by activating enzyme metabolism.
Magnesium and sulfur for high oil content in oilseed rape
- Most of the magnesium (Mg) required is absorbed before pod development.
- The magnesium requirement of oilseed rape is about 60kg/ha MgO.
- After a severe winter with large leaf losses, an adequate supply of magnesium is important for the development of new leaves.
- Improved assimilation by the plant, especially by the pods, has a positive effect on oil synthesis and total yield.
With a requirement of 50-70kg/ha sulfur, oilseed rape has a very high sulfur demand.
Optimal sulfur supply leads to more efficient utilization of nitrogen and therefore has a positive effect on yield.
Oil content is positively influenced by sulfur, as it is directly involved in the synthesis of fatty acids.
Mild temporary sulfur deficiency can be controlled until late budbreak by foliar applications of ESPO products without yield loss. Prolonged deficiency, however, can result in yield losses of up to 75%.
The uptake of magnesium in oilseed rape occurs in parallel with the uptake of sulfur (in terms of timing and quantity), so a combined application of both nutrients is recommended.
Organic fertilizers and farm manures are generally insignificant sources of sulfur for this demanding crop.
- Oilseed rape belongs to the group of boron-requiring crops.
- During the growing season, oilseed rape can absorb about 350-450g/ha boron.
- Swollen lower parts of the stems, stunted growth, development of root cavities, reduced growth of secondary lateral roots, and poor pod set after flowering are possible effects of insufficient boron supply that can affect yield.
- Therefore, it is advisable for oilseed rape growing areas to include boron content in soil analyses.
- Boron content should not be less than 0.2-0.5mg boron per kg soil in lighter soils and not less than 0.25-1.2mg boron per kg soil in heavy soils using CAT analysis.
Observing the supply of manganese on soils with high organic content
- Manganese supply bottlenecks occur mainly in soils with high organic matter content and/or high pH values or after lime applications.
- Manganese, like magnesium, influences the synthesis of chlorophyll and photosynthesis. This provides a high assimilation rate and has a positive effect on yield.
- The increased growth of secondary lateral roots improves the absorption of nutrients from the soil.
- Only in well-supplied crops, the full yield potential can be achieved.
- A foliar application of manganese should always be combined with an application of magnesium to avoid nutrient competition.
Fertilizer recommendation for oilseed rape
Fertilizer is applied in order to maintain the fertility of the soil so that its natural yield potential can be protected over the long term. This requires the maintenance of an optimal nutrient content in the soil. Nutrients removed with the harvest have to be replaced through an adequate application of fertiliser. Together with the replacement of removed nutrients adjustments have to be added for site specific losses (for example: leaching or erosion).
The total removal of a plant results from the nutrient uptake of the main crop (e.g. grain, tubers or beets) and the uptake of harvest residues (e.g. straw, leaves). If the harvest residues remain on the field, only the removed nutrients by the main crops have to be replaced.
Recommendation for soil fertilization
The table shows fertilizer recommendations calculated using the nutrient uptake of the main crops based on an optimal soil nutrient content. Adjustments for site-specific losses due to leaching, fixation, or erosion are not included.
Total removal (incl. harvest residues)
210kg K2O, 40kg MgO, 50kg SO3
Removal through main crop
40kg K2O, 20kg MgO, 40kg SO3
Recommendation for foliar fertilization
20-25kg/ha EPSO Top® or EPSO Microtop® in a 5% concentration for periods of high demand or to control latent magnesium and sulfur deficiency and deficiency of trace elements. Several split applications should be made between rosette and flowering stages. Especially for the high boron demand 400-600g/ha boron with EPSO Bortop® (2,5-5% concentration) is recommended.