12th September 2022

Brassicas can break the cycle

According to Limagrain’s Scottish seed specialist adviser John Heaphy, a crop of brassicas will be especially beneficial in pest control, following the withdrawal of the pesticide used to control leatherjackets and frit fly.

“A brassica mixture, such as the rape, kale and stubble turnip Autumn Keep – or Meat Maker for those wanting a crop for autumn and winter grazing – can be ready for grazing by October and will provide a high protein and high energy balanced diet.”

Limagrain trials have shown that crops of forage rape and stubble turnips can produce more than 3.5 tonnes of dry matter per hectare – and up to five tonnes for stubble turnips – with crude proteins around 18% for stubble turnips and 19 to 20% for forage rape and ME values of 11MJ/kg DM. Similar energy values are seen in kale crops, with 16 to 17% crude protein and dry matter yields per hectare of eight to 10 tonnes.

Mr Heaphy stresses the ease and speed of establishment of forage rape and stubble turnips. “This is a real advantage as there’s less chance of pest problems; insects like flea beetle don’t have as much time to cause damage as the crops grow faster than some of the other fodder crops. Forage rape, which will be ready for strip grazing 12 or 13 weeks after sowing, has become more popular in Scotland following the wet summers in 2012 and 2013 when the establishment of other crops was very tricky.”

Likewise, stubble turnips have ‘staying power’. “They can be left in the ground and grazed to suit the farm system,” he adds. “They just keep growing and are relatively winter hardy.”

However, Mr Heaphy draws attention to the important role of using brassicas as a vital part of pest management, now that the pesticide chlorpyrifos – that controlled pests like frit fly and leatherjackets – has been withdrawn.

“These pests can cause serious losses in established grassland and devastate new leys,” he adds. “So growers need to take a more integrated approach to pest management and one good measure is to use a brassica as a break crop, to break the lifecycle of these pests by removing their food source.”

Mr Heaphy suggests that Scottish growers can take a crop of silage off a pasture in June then sow a straight brassica crop or a catch crop mixture for autumn and winter feed, then reseed in spring.

“This is ideal for Scottish growers as they will usually get a good silage crop by the end of June, then they would cultivate and leave the land fallow for two weeks prior to sowing a forage rape, stubble turnip, kale, or better still, a mixture. This land can be ploughed the following March and sown with a grass seed mixture in April. This strategy can reduce the threat from grassland pests and maximise forage production.”



High yielding and economical crop to grow
Flexible utilisation period – can be fed through autumn and winter to suit
Growing costs £496 per hectare*

Performance (Limagrain trials):
Dry matter: 8-10 tonnes/ha
Crude protein:16%-17%
ME: 10-11 MJ/kg DM


Forage rape and hybrids
Fast growing, leafy catch crop
Forage rape and rape kale hybrids grow in poorer soils and on exposed sites
Growing costs £408 per hectare*

Performance (Limagrain trials):
Dry matter: 3.5-4 tonnes/ha
Crude protein:19%-20%
ME: 10-11 MJ/kg DM


Stubble turnips
Fast growing
Protected from frost damage and some varieties have excellent disease resistance
Growing costs £305/ha*

Performance (Limagrain trials):
Dry matter: 3.5-5 tonnes/ha
Crude protein:17%-18%
ME: 11 MJ/kg DM

* Based on data from Kingshay Farming Trust

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