Tillage focus: Spring oilseed rape seed is providing a niche crop for tillage farmers

While the summer brought a host of sunny days and dry weather, flowering was delayed in spring oilseed rape crops; but growers waited patiently to cut their crops as close to a moisture content of 9% as possible.

AgriLand visited Gary Pearson’s spring oilseed rape crop in Rathangan, Co. Kildare, last week. Checking the crop before harvest was Denis Dunne, who works as an agronomist for Seedtech and monitors seed oilseed rape crops throughout the season and across the country.

While this year’s weather prolonged the season, all crops have now been harvested.

Gary Pearson cutting his crop of oilseed rape

Seedtech has built up a strong hybrid seed production business over the past number of years; the produce of which is exported.

Seed crops can only be grown in ground free of oilseed rape for at least 12 years. Five years has to be left between root crops – such as potatoes or beet – to limit disease.

“We can go back after 12 years if the ground is clean, but we are really looking for virgin oilseed rape land. Gary is very good. In three to four years, there will be no oilseed rape volunteers in the ground; but we still have to follow the protocol. We’ll grow the seed rape after continuous cereals or grass.”

Denis Dunne checking a crop of seed oilseed rape

Denis explained that Clearfield technology has helped with weed suppression in oilseed rape crops, especially where charlock or runch might have pit a grower off growing seed rape in the past.

If a spray has a 95% efficiency, as a conventional grower, you’re delighted; but for us, that 5% that would get through is unacceptable.

“We supply workers that rogue the fields at least twice in the season to make sure that the variety is pure to its line. The group of workers we know the varieties to pull by the size of the flower – that’s how you know – or some flowers with pollen on them will be pulled as well.

“All of these crops are checked by the department three times – at the vegetative stage, flowering and after the male crop has been taken out.”

Pollinating a seed crop

In order for seed crops to be pollinated, female and male plants are sown in alternate rows across the field.

“After drilling I walk the crops a lot to keep an eye on how the crop is growing and get ahead of any problems. A lot of our growers have never grown rape before so we help them with advice on fertiliser and sprays.”

Denis explained: “Because the male and female plants are two different varieties, they may flower at different times. As a result, a male variety that will flower before the female is chosen.

“We’re looking for the variety off the female. The male is a conventional variety and the female is sterilised; it can’t produce pollen. It can only take the pollen off the male; that’s why there has to be an isolation of 1km from other oilseed rape crops, so that it can’t take pollen from somewhere else.”

The 1km isolation is from any oilseed rape crops; not just seed crops.

It can be really tricky to get growers if there is a lot of oilseed rape in an area.

Bee-keepers set up hives in some seed crops and this helps with pollination.


Farmers are paid a land payment for growing the seed crop. They can lock into a price during the year and are then paid a seed bonus once the seed is certified.

“There’s a seed bonus and a land payment. Farmers know both of these when they are sowing. It is up to the farmer when they want to lock in on the price.”


“Most people don’t bale the straw. The reason why they grow oilseed rape is because it’s a break crop; so, they look at the straw as added value going back into the ground.”


Denis explained that, because some of the crop is taken out, yields are lower than a commercial crop of oilseed rape. However, the payment for the seed crop works out much higher.

Spring growers can expect crops to yield 0.6t/ac and winter crop yields are significantly higher at 1t/ac.

The costs of growing a seed crop are higher than conventional rape; but these costs are more than off-set by the land payment (€200/ac), seed bonus (€400/t) and grain payment (€400/t) in 2018. The land payment is structured to reduce the risk on the grower in a difficult season.

“It works out approximately 50% more profitable than conventional oilseed rape. It competes very well for someone who is looking to change their rotation.”