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Kacper Łata

5 Dec 2022

Fertilizing winter rapeseed - how to do it right?

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Fertilization is a very important stage in the process of plant development. When growing rapeseed, it is worth taking advantage of this, as winter rapeseed is a crop with high nutrient requirements.

At the same time, rapeseed itself is the most important oilseed crop grown throughout Poland. The quality of the root system plays an important role in the wintering period, so in order to ensure the proper development of the cultivated rapeseed you need to have the right knowledge.

Soil requirements - how to prepare for sowing?

The soil resource for growing winter rapeseed should be rich in humus, microorganisms, calcium and general high culture. The most prosperous rapeseed will be obtained by sowing it on soils of the rye and wheat complexes of class I-III.

Winter rapeseed also needs soil with adequate acidity. The pH should be in the range of 6.0 to 7.0. When there is a lower level of soil acidity, the developed root system does not develop, which brings huge losses in yield.

At the moment when we do not have suitable conditions for rapeseed cultivation, we can consider liming the field, which improves chemical and biological values in poor soils. Its absence can lead to more frequent fungal diseases, a poorly developed root system and cracking of rapeseed siliques.

Fertilization of winter rapeseed with nitrogen and phosphorus - what is worth knowing?

In the autumn period, fertilizing winter rapeseed with phosphorus significantly affects the proper development of the root system. Why is this system so important? Because it ensures better winter hardiness of the plants and greater accessibility to water and nutrients, which makes the plants well nourished and less sensitive to any kind of drought.

Nitrogen fertilization is one of the most commonly chosen forms of fertilizer when growing canola. Nitrogen is one of the most yield-forming plant nutrients. 

Unfortunately, when fertilizing rapeseed, it is necessary to calculate the amount of nitrogen correctly, since a large amount of nitrogen provides accessibility to separate components such as sulfur. The supply of sulfur to plants partially determines the utilization of the given nitrogen, which ultimately reflects on the size, resistance and quality of plants.

Another important aspect is the proper selection of the form of nitrogen in the purchased fertilizer and timeliness in fertilization. The choice of form is most important in the first dose of nitrogen fertilization. It is recommended that a significant portion be the nitrate form (NO3), which allows efficient recovery of the leaf rosette.

Delayed topdressing will affect late flowering of rapeseed and pathological vegetative development of plants. The effects of late fertilization can be many, such as:

  • weaker development of the canes
  • slower plant growth
  • weak root system
  • plants may be of low abundance
  • poorer pollination of flowers
  • difficulty in harvesting

Effective use of nitrogen is possible, provided we stick to the right rules for using it. We should focus our attention on the spring dose of fertilizer, the purpose of which is to revive the damage done during the winter. The first dose should be about 2/3 of the planned dose of nitrogen fertilizer.

The time for the second dose of nitrogen is between 3 days and about 3 weeks after the first dose. Delaying the second dose can bring negative consequences such as, for example, oilseed rape lodging, prolonged flowering time or excessive vegetative growth (bushy plants).

Of course, a correct fertilization strategy for winter rapeseed is only possible at the time of a thoughtful process. It is necessary to take into account the moment of sowing, the weather that occurred during the winter period and current forecasts for future days.

Formula for calculating the required dose of fertilizer

It is necessary to prepare well for spring fertilization of winter oilseed rape, since nitrogen has a major impact on the yield effect of the crop. To determine the appropriate dose of fertilizer, you must first conduct a field survey to determine the abundance of nitrogen and other minerals in the soil. To determine the true abundance, 3 soil samples should be taken at different heights, such as:

  • 0 - 30 cm,
  • 30 - 60 cm,
  • 60 - 90 cm.

The recommended way to calculate the correct dose of fertilizer, is the following formula.

Spring dose of N = assumed seed yield (t) x nutrient needs for 1t of seed + straw - mineral N in the soil.

For the production of 5t/ha of rapeseed-it takes about 250 to 300 kg of N, since we need about 50 to 60 kg of nitrogen for 1 ton of seed. Obviously, the fertilizer dose includes nitrogen from mineral as well as natural fertilizers. What is worth remembering is to distribute the doses of fertilizer applied.

What else can rapeseed be fertilized with?

An additional option for fertilizing winter rapeseed is the use of phosphorus and potassium fertilizers. We use them in the pre-sowing period so that the soil, thanks to the soil water, absorbs the minerals that are given to it. Most often the solubility problem affects phosphorus fertilizers or those that have a partial phosphorus content. Therefore, this must be taken into account because this fertilizer needs more time to dissolve completely.

Therefore, if you have soil with low abundance, it is recommended to avoid phosphorus fertilizers. Fertilizing rapeseed with a two-component fertilizer, such as magnesium and sulfur, is often sufficient for the plants to provide them with autumn nutrients.

There are cases in which phosphorus-potassium fertilizers are also used in the spring. The susceptibility of plants to fertilization with potassium or other minerals depends largely on soil moisture.

Winter rapeseed in heavily moist soil will have brittle roots, in addition, minerals are prone to excessive leaching from the soil. So, when we are tempted to spring fertilization with potassium and phosphorus, we will positively affect the crop's nitrogen absorption. In order to enjoy the most beneficial use of fertilizer, it is necessary to start work in early spring still about 2 - 3 weeks before the start of vegetation.

Potassium with phosphorus and other components provides the needs of winter rapeseed with the necessary elements that positively affect the development of plants, strengthen winter hardiness, improve the efficiency of nitrogen processing and promote the expansion of the rosette of rapeseed. The element that thickens the cell and increases it is potassium. It is thanks to it that farmers can rest assured in winter, knowing that their crops will overwinter. 

Potassium itself is also involved in the judicious management of the soil's water resources, which protect plants from drought.

It is worth stocking up on other micronutrients, such as magnesium, manganese, molybdenum, boron, copper and zinc, for example. Such nutrients are used in the form of liquids found under the name "foliar fertilizers."

Often farmers also benefit from sulfur, which is used through topdressing. The mineral nitrogen content of the soil, thanks to sulfur, increases the possibility of its processing, has a positive effect on plant growth and has a huge impact on fat synthesis. 

Despite its pluses, it is important to remember that excess sulfur acidifies the soil, which can negatively affect the growth of rapeseed in the spring

Oilseed rape grows badly when the dose is incorrectly adjusted. Fertilizers containing sulfur should be shaped at 1/3 to 1/5 of the nitrogen dose. Plant resistance is in the hands of farmers, so it is worth preparing for nitrogen fertilization of rapeseed (basal fertilization), foliar fertilization, pathogens that may appear in the form of leaf browning and autumn fertilization of rapeseed with other elements.

What does foliar feeding consist of?

Foliar feeding is considered to be a basic preventive measure providing missing micronutrients to plants, by fertilizing rapeseed directly to the place of need, such as leaves, stem, flower, among others. This type of fertilization should be carried out in autumn, at the time of 6-8 leaves.

It is recommended to use such micronutrients as:

Boron - gets the necessary sugar into the roots, which helps winter hardiness. In Poland, there is often a shortage of this component, so it is quite often supplied in the form of fertilizers. Boron itself takes a significant part in the construction of plant cell walls, which increases the resistance of plants to various diseases and pests.

Iron - develops stronger mechanical tissue, which has a positive effect on the lodging of plants. In addition, iron supports the synthesis of lignins and stimulates the uptake of micronutrients.

Zinc - is responsible for proper plant immunity, supports the process of photosynthesis, and influences efficient nitrogen and hormone metabolism at the same time.

Molybdenum - builds nitrogen elements into protein structures, which affects the correct state of hormonal economy - provides greater security in the winter period and more efficiently regenerates plants after the winter period.

Manganese - inhibits growth and prepares the plant for dormancy, supports the proper uptake of phosphorus and promotes proper root development.

Copper - supports plants through proper nitrogen and hormone management, supports the process of photosynthesis creating a stronger and disease resistant plant.

Foliar fertilizers should be spread over at least two treatments. Using a fertilizer containing micronutrients we are able to support the plant during the winter to better overwinter, we take care of its proper development, and I act with the idea of creating an immune system against various diseases.

The most commonly chosen element is boron, which supports the reconstruction of cell walls, which reduces the risk of inferior plant formation and cracking. Fertilization itself should take place at the rosette stage and at the second date, which is the budding stage.

Despite the extra cost, it is worth fertilizing rapeseed so that significant amounts of nutrients are properly used while protecting the crop. Fertilizer makes plants use their full genetic potential and improves rapeseed's frost resistance. Significant amounts of micronutrients are welcome in medium-rich soil environments.


In conclusion, winter rapeseed is a crop that needs a lot of attention and care. Spring fertilization of rapeseed is just as important as fertilization in the fall pre-sowing and late autumn. In the life processes going on under the soil layer, deficiencies of some micro or macro elements can negatively affect the pile root system of winter rapeseed.

It is also important to remember that the spring dose of nitrogen should be spread over at least two fertilization processes. Cultivate oilseed rape in such a way that, through pre-sowing fertilization, we assist in the formation of a rosette of oilseed rape, which will be sufficiently large and well-fed. Do not forget about the abundance of soil, which should be refined in the fall and then in the spring.

The appearance of the field we find in the spring will be the result of our prior preparation. For this reason, we need to refine our actions so as to replenish those nutrients that have been washed out by heavy rainfall or acidic soil, while paying special attention to using the full potential of the nitrogen given, which is considered the most important ingredient in rapeseed cultivation.


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