Oilseed Rape- Internal Header.jpg

Blue Bags Grow Better Crops

Oilseed Rape

Average oilseed rape yields in the UK have changed little during the increase in popularity of the crop since the 1980’s.

Recommended list trials are demonstrating cumulative yield increases during this period that are not reflected in commercial agriculture.  Attention to detail through all crop management aspects will be required to achieve the potential it has in yield and quality.

The area planted to oilseed rape has trebled in the last 30 years meaning frequency in the rotation has increased which may suggest part of the yield challenge with less than 50% of rape now grown after a minimum 4 year break, but this is only one factor amongst various others including soil management, weed and disease management, but also nutrient management. Nitrogen rates have fallen by 30% and while Sulphur use has increased, there are still significant areas of rape not receiving fertiliser sulphur.

Use our fertiliser selector below to find out which fertiliser will best suit your crop and soil needs and access a blueprint for growth.

Start your CF Fertilisers journey today…


pH Level

A pH range of 6.5 to 7.0 is the optimum to cover availability of nutrients in an arable rotation. In the diagram below, the wider the band in each nutrient, the greater the availability.

Nutrient Uptake


P, K and Mg Status

Soil analysis should be conducted on a rotational basis so that 25% of the farm is sampled each year. Target Index at which crop removal rates of P & K should be made are :

  • Phosphate (P) Index 2
  • Potassium (K) Index 2-
  • Magnesium (Mg) Index 2

For indices higher or lower than target, adjust rates accordingly as shown in the Fertiliser Manual (RB209).

Once soil index is know use our fertiliser selector to access the best fertiliser system for your needs.

Crop Uptake

Nutrient uptake is limited in early spring, increasing rapidly during stem extension. Peak uptake is during May/June depending on nutrient followed by some reduction as the crop ripens. Note peak uptake of Potash will exceed that of Nitrogen and should be taken into account when formulating fertiliser recommendations.

Typical crop nutrient uptake in Winter Oilseed Rape kg/ha nutrient.

  In Spring  Peak Uptake  At Harvest 
Nitrogen  80  240  140 
Phosphate  40  130  130 
Potash  80  300  200 





 Crop Removal At Harvest

Crop removal of nutrient becomes the base point for recommendations of P & K.

Note removing straw increases Phosphate offtake by 8%, but increases Potash removal by over 80%. Where straw is removed, additional Potash will be required to maintain target levels.

Kg nutrient per tonne fresh yield  Phosphate  Potash 
Grain Only  14  11 
Grain and Straw  15.1  17.5 


For more information or advice call our Crop Nutrition Team on +44(0)151 357 5758 or email advice@cffertilisers.co.uk

Use our fertiliser selector to access a blueprint for fertilisation and product recommendations




Nitrogen is a key contributor to yield and protein formation.  It is supplied from:

  • Soil Mineral N (SMN)–available soil Nitrogen available for plant uptake
  • Additional Available Nitrogen (AAN) – organic Nitrogen which needs to be mineralised before it becomes available for crop uptake
  • Organic manures – supplying both readily available and organic Nitrogen which requires mineralising before crop uptake.
  • Minor amounts provided by wet and dry deposition.
  • Additional fertiliser Nitrogen


Soil Nitrogen supply =

soil mineral N + N likely to be mineralised during the growing season + Spring Crop N

 The most efficient form of Nitrogen in the UK climate is Ammonium Nitrate (Nitram®) as proven in the most extensive trial carried out in recent times by DEFRA in 2004/5. This NT26 trial series is recognised across Europe as the most credible data on Nitrogen use efficiency and went as far as to state that;

AN remains the best option for UK agriculture and early application of urea did not guarantee reduced ammonia losses.

Defra NT26




With atmospheric Sulphur deposition now less than 10% of the 1980 levels and most of the UK now getting less than 10kg S from this source, additional fertiliser Sulphur now essential in virtually all cropping.

Most efficient form of Sulphur is the Ammonium Sulphate form, in the correct ratio for crop requirement. Straight Ammonium Sulphate at 21%N 60% Sulphate (SO3) is unbalanced in N : S ratio:

  • Applying 50kg Sulphate for wheat would only apply 17kg N/ha
  • Applying 40kg N would apply well over twice the Sulphur requirement for Wheat.

Nitrogen and Sulphur have to be applied annually to crops in spring, soils cannot hold available supplies over winter efficiently. CF Fertilisers have a range of N:S analysis to suit ratios required and our trusted brand names of DoubleTop and SingleTop are regularly used throughout Britain.

Oilseed rape is one of the most responsive crops to Sulphur both in yield and oil content. Oil content will be reduced before yield losses are seen in Oilseed Rape.

Use our product selector to access a fertiliser recommendations and blueprints for wheat growth. 


Phosphate and Potash

Phosphate and Potash have major functions in crop production, heavy clay soils typically being more Phosphate deficient and medium / lighter soils being more Potash deficient.

Since the early days of oilseed rape growing in the early 1980’s, applied levels of P & K have declined, this is a concern given arable rotations generally are now running a deficit on P & K.

Up to year 2000 P & K application exceeded removal.

Since year 2000 crop removal has exceeded fertiliser application.

The data below does not account for manures applied which will reduce but in many cases not eliminate soil nutrient deficits.

Peak uptake of Potash in oilseed rape can exceed 300kg/ha requiring adequate soil reserves and significant Potash application.

Phosphate and Potash Uptake

Whilst traditionally applied in autumn or over winter, Phosphate and Potash can be applied as a single dressing in spring, together with Nitrogen and Sulphur and save additional workload on the farm.



While still a major nutrient, Magnesium not typically in deficient supply, but in some regions where Magnesium applications are required and particularly where roots are in the rotation, Calcined Magnesite is the usual source.

For more information or advice call our Crop Nutrition Team on +44(0)151 357 5758 or email advice@cffertilisers.co.uk

Use our fertiliser selector to access a blueprint for fertilisation and product recommendations


Maximum profitability from crop nutrition in oilseed rape depends on correct calculation of Nitrogen and Sulphur requirements and timing of these applications to achieve crop quality required for your market.

Nitrogen rates of between 180 and 240kg N/ha (depending on soil nitrogen supply), in combination with application timings, follow the canopy management principles are key to achieving good yields. 

It is essential to apply Sulphur to all oilseed rape crops at a rate of 80-100kg SO3/ha to optimise yield performance and quality.  Do not be tempted to exceed this level of application as oil can be compromised and increase glucosinolate levels.  Oilseed rape establishment responds to autumn applied N.  A maximum of 30kg N/ha is allowable in an NVZ and follows the code of good agricultural practice.

Balancing organic N supplies with applied fertiliser can target the correct rates more accurately and profitably.

In the case studies below, on the left the soils have generally had higher mineral N reserves that haven’t been fully accounted for and the crop has been over fertilised where normal farm practice has been used. On the right, where mineral N contribution has been accurately assessed the target N level at harvest is much closer.

 Crop balance accuracy

Whether oilseed rape is grown for industrial or food purposes, high oil content is a desirable requirement commanding premiums or deductions for oil levels typically over or under 40% respect.

Accuracy of N calculation is critical to get the balance between yield and quality.  There is evidence that applications of late N (mid to late flowering) reduces oil content.  Therefore application of late N to increase yield should be made no later than yellow bud/ early flowering.


For more information about our Services or advice please contact us on +44(0)151 357 5758 / advice@cffertilisers.co.uk 




CF Fertilisers have had 30 years of experience with Nitrogen recommendations.

Our customers who use our advice and services achieve above average yields and if applicable, are able to achieve this extra yield without compromising malting premiums from increased grain N levels.


N-Min® and N-Calc service

Assessing the amount of Nitrogen the soil contributes to the growth of the Oilseed Rape crop during the growing season is key to assessing the optimum rates to apply.

A patented analysis makes N-Min® service unique in accuracy of Nitrogen recommendation.

Don't just take our word for it, these farmers have had great results year on year.

A Sulphur recommendation will also be provided in a product to suit your system.

So get in touch today to unlock the potential on your farm +44 (0)151 357 3738 or email advice@cffertilisers.co.uk


For more information about our Services contact our Crop Nutrition Team on +44(0)151 357 5758 or email advice@cffertilisers.co.uk



Each field on your farm is individual with its own characteristics and nutritional requirements. Follow our step by step guide and unlock the potential on your farm today.

  1. Identify crop to be grown, intended market and crop quality requirement.

  2. Annually use the N-Min® analysis and Nitrogen Calculator (N-Calc) to understand the Soil Nitrogen Supply.

  3. Sample ¼ of the farm each year and analyse for soil pH, P, K and Mg.

    Target Values to maintain in arable rotations  
     Soil pH 6.5 (5.8 on peat soils) 
     Soil P  Index 2
     Soil K  Lower Index 2(2-)
     Soil Mg  Index 2
  4. The N-Min analysis is the only test that measures both Soil Mineral Nitrogen (SMN) and Additionally Available Nitrogen (AAN) to accurately quantify the Total Nitrogen available during the growing season.

  5. Annually review phosphate and potash applications to ensure that optimal levels are maintained. It is important to allow for any surplus or soil deficit situations due to the under or over application of phosphate or potash to previous crops in the rotation.

  6. Use N-Calc to work out the N requirement of Cereals and Oilseed Rape. 

  7. Annually check that the fertiliser spreader is in good working order and is calibrated to specific spreading width.

  8. Ensure that accurate records are kept of any fertilisers and organic manures applied.

Contact us for fertiliser advice, our expert team of FACTS qualified advisers are on hand to provide you with the latest advice in fertiliser management and nutrient plans.