Varietal Choice is more than just yield
The potentially high profit margins enjoyed by oilseed rape growers this year mean that variety selection has become more critical and some industry experts are advising farmers to look at a range of variety selection criteria this autumn, not just yield.
Richard Fenwick, independent seed specialist acknowledges that farmers choose rape varieties for their consistent, high yields, but they should also make more provision for varieties with a strong agronomic package that makes crop management more cost-effective, particularly in a climate when input costs are rising so rapidly."
"Other factors such as low biomass, good disease resistance and stem stiffness can all make the crop easier and cheaper to manage and so more profitable to grow."
He considers choosing a low biomass crop, such as Astrid and the new candidate variety Alienor from Grainseed, makes a significant difference to the overall growing costs. "With shorter less bulky varieties, less volume of plant material goes through the combine, improving harvesting efficiency by up to 25%. Drying down is faster at harvest, too. A faster work rate at harvest reduces stress on the workforce and machinery. When fuel prices are so high, this increased efficiency can reduce costs directly."
Low biomass varieties such as Astrid and Castille are already popular with growers because of their excellent, consistent yields plus their ease of management. "There are some significant height differences between varieties now - Astrid is 142 cms, Castille 144 cms, Alienor 147 cms, Winner and Epure are 159 cms, and Dimension 163 cms. Overall hybrids tend to be taller and bulkier and, if growers chose to grow them, they must be prepared for the ensuing management issues, all of which have a cost implication," says Richard.
"And when you consider potential losses due to disease, it makes sense to choose a variety with high resistance ratings, even if it yields slightly less. A yield difference of 3% is equivalent to less than £50/ha, which can easily be recouped in improved disease protection," considers Richard Fenwick.
Richard points out that in practical terms few growers grow rape today without using fungicides. "High disease ratings give insurance against disease and a back-up for fungicide treatments, particularly if the fungicide programme isn't quite as comprehensive as the HGCA trials programme."
John Hardy of Grainseeds reports that there is also a wide variation of disease resistance, with hybrids tending to have lower resistance overall. "Published stem canker ratings for HGCA Recommended conventional varieties are: Astrid 7.2, Castille 5.9, Expert 5.8, Canti 5.3, Temple 5.3, Lioness 5.2, NK Grace 4.8, Catana 4.4 and Winner 4.3. for hybrids Flash has a 4.7 rating and Excalibur 5.0 for Phoma.
Light Leaf Spot resistance ratings are 6.7 for Temple and NK Grace, 6.0 for Lioness, 5.9 for Es Betty, Canti and NK Bravour 5.8 for Expert and Winner, 5.7 for Astrid and 5.0 for Castille. For the hybrids Flash has a 5.5 rating, Excalibur 6.2 and Excel 5.6."
"Rape diseases cause significant economic impact. Light Leaf Spot can cause losses of up to 1.5 t/ha, valued at over £500/ha with rape at £350/tonne. HGCA forecasting for Light Leaf Spot for 2008 shows the East of the country at 38%-53% infection, the North between 53-68% and 25% in the South. The well documented and rapid rise in the threat of this damaging disease right across the UK means that high levels of innate resistance have become much more important to growers. Our new candidate variety Alienor has an 8 rating for Light Leaf Spot as well as Phoma," says John.
"Phoma can cause losses up to 50%, but 0.5-1 t/ha is common, giving losses valued at £175-350/ha. HGCA forecasting for this damaging disease predicts 63% infection in the South, 49% in the East and 25-28% in the North. In fact 60% of all rape is grown in a high Phoma risk area. Most rape grown in the UK is at risk from diseases and it is beneficial to grow a variety with good disease resistance," says Mr Hardy.
Another key variety characteristic focused on by variety expert Mr. Fenwick is stem stiffness. "Lodging can be a serious problem in rape, not just the impact on yield, which can be as high as 30% but also the impact on spraying and harvesting. Choosing a variety that is short with good stem stiffness minimises the risk of lodging and is another key selection criteria that can impact on yield and gross margins."
Finally Richard considers early flowering and early maturity to be preferable. "It is important to get the crop off early so as not to impinge on barley and wheat harvest. Early flowering varieties such as Alienor help with timeliness, workload and rotations, an advantage at a busy time of year. Later maturing varieties can have a detrimental effect on harvest and rotations."
Overall Richard Fenwick urges farmers to look further than just yield, to calculate the potential losses from a range of threats and consider carefully the full range of variety characteristics before making their final variety choices.
For further comment and information, please contact
1) John Hardy, Director, Grainseed Ltd on 01379 871073 or 07836 582436 or via email at john@grainseed.co.uk
2) Richard Fenwick, Cambridge Arable Technologies on 01954 204837 or by email at richard@richardfenwick.co.uk