The area of oilseed rape grown in the UK has declined significantly over the past decade, but with strong demand domestically and for export, the crop still provides a profitable and effective break in the cereal rotation. Making small changes to improve all aspects of the crop’s production can incrementally drive yield to maximise the potential of oilseed rape.
But which areas are best to focus on for the greatest incremental gains?
Selecting varieties with the right genetics for your situation can make a significant impact on potential yield and returns. Getting the right balance of early growth, vigour, disease resistance and other characteristics will depend on drilling date, expected pressure from cabbage stem flea beetle (CSFB), and intended market.
DEKALB’s plant breeding programme has resulted in winter oilseed rape varieties with genetics to suit a range of situations and markets, with robust disease resistance, and agronomic traits that improve yield, oil quality, and standing ability.
Variety selection should take account of the need to grow away quickly to out-pace CSFB at establishment, and the ability to stand until harvest. For early sowings, the speed of early growth should be weighed against the risk of developing excessively forward crops into the winter, and not all varieties are suited to this early slot. Rapid development is, however, very useful in later drilling, when it coincides with increasing CSFB pressure. Here, hybrids can provide the fast growth and early vigour required, with establishment schemes offered by some breeders, including DEKALB to provide additional reassurance and support.
DK Extremus is a very high yielding hybrid with high oil content and vigorous establishment. Traits include rapid autumn growth, helping the crop to grow away from CSFB and other autumn pressures, and strong early spring regrowth for CSFB larvae tolerance.
Other genetics to take into account include pod-shatter resistance to aid harvest timings, and disease resistance, particularly Phoma and light leaf spot, and clubroot where this disease poses a threat.
DK Exstar, a triple 8 breakthrough variety from DEKALB offers high yields and oil content with an exceptionally robust agronomic package, including disease rating of 8 for Phoma and light leaf spot, and a 9 rating for lodging resistance, plus pod shatter resistance. While DK Plastic is a step-up in performance and reliability for clubroot-resistance varieties, offering strong yield performance and a range of DEKALB yield protecting traits, including double Phoma resistance, pod shatter resistance, vigorous establishment, and rapid autumn growth to cope with challenging autumn conditions, including CSFB.
With the loss of neonicotinoid seed treatments, the threat of turnip yellows virus (TuYV) spread by aphids has increased. Hybrid variety DK Excited provides resistance to TuYV along with a range of yield-protecting traits, including Phoma and pod shatter resistance.
For growers with cruciferous weed pressure in oilseed rape fields, Clearfield varieties which have an in-built tolerance to specific imidazolinone herbicides offer an opportunity to get on top of these weed problems, without sacrificing yield.
DK Imprint CL is a new generation Clearfield hybrid from DEKALB which offers strong agronomic performance, including pod shatter resistance, lodging resistance and double Phoma resistance.
Finally, consider the market opportunities for choosing varieties with HOLL (high oleic, low linolenic
or HEAR (high erucic acid rape) genetics, which can provide additional returns if the crop meets contract specifications.
DEKALB’s V316OL is a HOLL variety that is fully recommended by AHDB for the UK, and offers high yields with excellent oil quality.
Lengthening rotations to once every four years or longer can help to reduce pressure from CSFB and certain diseases.
Sclerotia, the resting bodies of Sclerotiniaformed in affected OSR crops and susceptible vegetable crops can persist in the soil for several years. Avoiding other brassica species, including cover crops or vegetable crops susceptible to Sclerotinia within the rotation, and increasing the OSR rotation to four years can also help to reduce the risk of infection.
Ideally, drilling date should be dictated by soil moisture rather than calendar date, but the increasing trend towards early drilling means attention to variety choice, timing, and technique is required.
Seed rates warrant consideration, since Bayer’s trial results show that populations of 20 to 40 plants per square metre result in bigger plants, with thicker stems which offer more resilience to CSFB larvae in the spring. Higher seed rates not only increase the cost of production (and the losses if the crop fails) but denser crop stands with plants with thinner stems are more likely to suffer from CSFB larvae in the spring, with a resulting impact on yield.
Ensuring that preceding cereal straw is either baled or chopped and spread evenly is important, but drilling shallowly into moist soil is critical. Crops need to germinate quickly and grow away at pace, to lessen the threat from CSFB attack.
Seedbeds must be in good condition, with uncompacted soil that enables good rooting penetration. If fields need soil remedial work, or seedbeds are poor, it is better to wait until soil conditions are more optimal.
Moving the soil as little as possible, and ensuring good seed-to-soil contact, with fertiliser (nitrogen and phosphate) accurately applied alongside the seed, will help optimise conditions for germination and early growth.
Stubbles can be left long, or a companion crop sown to help disguise the emerging crop from CSFB.
Later drillings are likely to benefit from more reliably moist soil to aid germination, but at the risk of coinciding with greater CSFB migration. In areas where CSFB is less of a threat, drilling later allows time for optimal seedbed preparation and opens up the choice of varieties.
Cereal volunteers and competitive broad-leaved weeds can impair establishment, so taking out these weeds early will support good, early growth. Oilseed rape offers opportunities to tackle difficult-to-control grass weeds such as black-grass with different chemistry, which is another advantage of retaining the crop within the rotation.
Preserving the green leaf area in crop canopies is a significant driver for yield. So, managing foliar disease throughout the crop can be influential in driving returns. Phoma and light leaf spot are the main diseases in the autumn and early spring, while Sclerotinia needs attention once the crop is in flower.
Bayer’s SpotCheck service can help to identify Phoma and light leaf spot in the crop, enabling protectant fungicides to be applied in time.
The threat of light leaf spot is driven by the weather, and the proximity to recently-harvested OSR crop where wind-blown ascospores can lead to early infection. Early-drilled crops are at increased risk of infection, so choosing varieties with resistance can help reduce the reliance on fungicides alone. Depending on conditions, the risk of light leaf spot infection will usually continue through the winter and into spring. Applications of protectant fungicides such as Proline or Aviator (which will also treat Phoma) during the autumn, before stem extension or even afterwards, may be required depending on the conditions.
Later drilling increases the risk of Phoma infection, but again, choosing varieties with genetic resistance can support better disease management alongside timely application of effective fungicides.
Crops are most at risk of Sclerotinia from the onset of flowering when airborne ascospores land on petals and fall to infect leaves in extended periods of wet or humid weather. Lodged crops are particularly at risk. With no varietal resistance to Sclerotinia, timely applications of an effective fungicide, such as Aviator, will provide protection during the key flowering period.
Harvest intervals for glyphosate must be adhered to, so assessing the crop regularly will help to time sprays according to expected harvest date. However, spraying too early can reduce oil content and immature pods will result in an increase in the quantity of red seed at harvest.
Crop maturity will vary across a field, so taking 20 samples from a representative area and number of plants, and not just near the headlands, will provide a more accurate view of how close the crop is to desiccation.
Pod shatter can be avoided by selecting varieties with resistance, or by using a pod sealant if pod shatter is a risk and desiccation is delayed. All DEKALB varieties include pod shatter resistance, which provides some flexibility during variable summer weather.
While early drilling can markedly reduce the impact of adult CSFB grazing, moving drilling forward from its main mid-late August window brings with it a number of challenges that need to be addressed to make the most of this change.
Time has to be the primary consideration in establishing OSR within a tight early window when harvest workloads are at their peak. This puts the premium on careful planning and management to ensure success without compromising wheat combining, in particular.