Planning for winter oilseed rape
The recently released Department of Agriculture, Food and the Marine (DAFM) Basic Income Support for Sustainability (BISS) figures show the crops grown in Ireland this year, and make for some very interesting reading.
The cereal area has fallen by 6% but when proteins and oilseeds are included, the decline in the tillage area is only 2%. This is largely down to the fact that the area of winter oilseed rape (WOSR) has increased significantly again for harvest this year to just over 20,000ha, up from 14,000ha in 2022. This is exactly double the area harvested in 2021 when just over 10,000ha were claimed.
At a time when tillage crops have been in decline, WOSR has become extremely popular with farmers for a number of reasons. It’s not just the more reliable varieties that are now available, which help to improve the profit margins. The other benefits including spreading the workload, soil structure improvements and grass weed control have also helped to increase its popularity. Again in 2023, many growers were able to reduce the amount of nitrogen (N) required to grow the crop, by measuring the green area index (GAI) of the crop in early spring. This was a significant saving given the cost of fertilisers.
Early drilling
Early drilling is essential for growing oilseed rape. August-drilled crops generally perform better than September-drilled ones, and it may be easier to prevent pigeon grazing of large canopies, which in turn will reduce the amount of N needed. The following tips are a useful guide when growing oilseed rape crops:
- Sowing date - mid-August to early September – ideally pre September 10; however, seedbed quality (i.e., fine and firm) is as important as sowing date.
- Variety - the DAFM Recommended WOSR list is the best source of information on the main varieties. Conventional varieties or hybrids can be sown in August, but in September you should only use hybrids. Look for varieties with good traits such as light leaf spot (LLS) resistance and pod shatter resistance.
- Seeding rate - sow 60-80 seeds/m2 to establish 30-50 plants/m2 in the spring. Varietal differences in vigour, thousand seed weight, along with seedbed conditions and sowing date must be accounted for. Poor seedbeds and later sowing will need higher (10%) seeding rates.
- Weed control - field history is important as pre-emergence weed control is still the most effective. Volunteer cereals, cleavers and grass weeds are the main competitive weeds and do most damage early in the crop’s growth. Apply pre-emergence or early post-emergence treatments. Options include Butisan S/Rapsan 500 (1.5L/ha) or Katamaran Turbo (2.0-2.5L/ha) within 48 hours of sowing. Graminicides such as Falcon, Fusilade, etc., can also be used to control grass weeds, while Astrokerb will give control of broadleaf and grass weeds later in the season.
Clearfield varieties offer an opportunity to grow oilseed rape in fields where brassica weeds such as charlock, hedge mustard, etc., are a problem. The herbicide Cleranda is specially developed for Clearfield varieties and not only does it control charlock, it also controls groundsel, fumitory, poppy and speedwells. However, Cleranda can only be used on Clearfield hybrid varieties.
Clubroot
One area of concern that has appeared in some crops over the last two years is clubroot. There have been a number of reports of the disease in crops around the country. This can usually be traced back to poor rotation or the intensive use of brassica cover crops in schemes such as the Green Low-carbon Agri-environment Scheme (GLAS).
Clubroot has become an issue in some crops
Clubroot is a soil-borne disease that lives on hosts such as volunteer rape plants, brassica weeds, or weeds such as shepherd’s purse. To avoid the problem keep rotations as wide as possible and avoid the use of brassica catch crops.
This article first appeared in the Teagasc Tillage Advisory newsletter for August. Access the newsletter here.
Also read: The multiple benefits of catch crops