Growing brassicas: Have you thought it through?

Thursday 17.05.2018 , News

There are a number of options available to farmers when choosing forage crops, but there are three fundamental questions to answer before deciding on the most cost-effective type of forage crop for your livestock production system.

  1. When do you want to utilise the crop?
  2. When will the land for growing the forage crop become vacant?
  3. How many animals do you need the crop to feed?

General guidelines for sowing

Site selection

  • When choosing a field for growing forage crops for out–wintering, choose a field that will dry out quickly and does not have an extreme slope. The field should not be close to watercourses or water supplies (cross–compliance is a consideration).
  • Ideally choose fields where grass production is falling and it can be incorporated into a grass reseeding program.
  • Club root is a threat to brassicas so a one in five-year rotation is advised to keep club root levels low.

Sowing advice

  • Soil test prior to sowing.
  • Soil pH is critically important and should be at least 6.0 (optimum is 6.2 to 7.0). Crops will perform best under good soil pH and fertility status.
  • Spray off the old sward with glyphosate.
  • If min–till, use a minimum of 2 bags of gran lime.
  • Seed is generally sown into a cultivated seedbed, but can also be direct drilled or broadcast (if broadcasting you will need to increase the seed rate).
  • Sow seeds into a fine, firm seedbed at a maximum depth of 10mm to ensure uniform germination.
  • Roll after sowing.
  • Monitor the crop closely for weeds and pests and control as appropriate.

Benefits of Brassicas

Brassicas are low in fibre and supplementing with a fibre source e.g. baled silage is critical for animal health. In addition, ensure animals will have constant access to fresh water when grazing the crop. Kale and the hybrid brassicas (a rape x kale cross) are the most common brassica forage options for British & Irish farmers.


Kale is suitable for sheep and cattle grazing. Maris Kestrel is the most popular variety of kale in the UK and Ireland due to its exceptionally high leaf: stem ratio and high feed value. It has high digestibility and a long utilisation period and animals can utilise the entire plant.

Sowing guidelines 


  • Kale sowing date: May to early June
  • Kale seeding rate: 2.5-3.0 kg /acre (increase to 3.5 kg/acre if broadcasting)
  • Kale utilisation: November to February

Kale X Rape Hybrids

The hybrid brassica, Redstart (Rape x kale cross) offers the highly beneficial combination of rapid growth ability and good all-year-round performance. The forage rape genes give it the ability to grow quickly, while the kale genes deliver excellent winter hardiness.

Redstart is mainly used as a high-energy protein crop for out–wintering cattle and sheep. Redstart can be grazed more than once if sown early, if so take care with the first grazing to ensure the main stem remains intact to protect the crop for future regrowth.

Sowing guidelines

Redstart Hybrid Brassica

  • Redstart sowing date: Mid-June to mid-August (earlier sown will allow repeat grazing)
  • Redstart Seeding rate: 3.5-4.0 kg /acre
  • Redstart Utilisation: August to February

Fertiliser for Brassicas

Brassicas have a high requirement for N and P and an adequate supply of these nutrients is critical to maximise the yield potential of the crop. At soil Index 3, Kale and Redstart will require 100 kg N/ha (split dressing), 30 kg P/ha and 170 kg K/ha. It is advisable to fertilise the crop of Redstart after grazing to ensure sufficient nutrients for regrowth but always remain within your N and P allowances within the nitrates directive.

Grazing management

When it comes to grazing the crop, there are a few guidelines that should be followed so that the stock really benefit from the crop and don’t experience any setbacks:

  • Introduce stock slowly – allow 1-2 hours access and build up to full–time access after 7-10 days
  • Provide access to roughage e.g. silage bales – place bales in the field during the summer or at sowing as this will avoid machinery travelling the field in winter (reduce soil damage) and reduce workload.
  • Strip grazing will maximise utilisation and minimise wastage
  • Graze in long narrow strips to ensure all animals can graze at the same time and also to minimise trampling of the crop at feeding.
  • Provide minerals/ bolus animals – speak to your vet to ensure animals receive the necessary minerals
  • If sown on a hill always graze downhill
  •  Ensure constant access to fresh water