Crop record-keeping data shows an alarmingly high number of oilseed rape varieties being grown commercially across the UK – and this could be contributing to a stagnant national average yield.
Plant breeders have made a huge effort to produce new and improved rapeseed varieties in recent years, with about 100 now entering the National List system each year. despite the national crop being about 600,000ha.
This is relatively small when compared with wheat, which sees about 2m hectares drilled each year and a similar number of new varieties put forward for examination.
Candidates that have made it on to the AHDB Recommended List over the past decade have achieved a 2% year-on-year yield increase in trials and consistently hit more than 5t/ha, but the national average continues to flounder at about 3.2t/ha.
Anonymous grower data from Farmplan’s Gatekeeper record keeping software shows that in harvest year 2014, at least 69 varieties were planted by UK growers
In 2015, this rose to 77, dipped to 70 in 2016, then went back up to 73 in the harvest year (see graph 1, below).
Niab oilseed rape variety expert Simon Kightley says this is far too many and could be a contributory factor in stagnant national on-farm yield figures’ failure to improve.
“In the early days of oilseed rape production, you would see a single variety take a 50% market share, such as Winner or Castille, but we are no longer in that situation. It is much more fragmented now.
“As it’s so fragmented, I don’t think we are seeing the development of national yield we would expect if growers were selecting the very best varieties in trials,” he notes.
Graph 2 shows that about 30-40% of the sample area was planted with varieties not on the Recommended List in the four harvest years between 2014 and 2017.
When delving into specific varieties not on the Recommended List in the four years, some are dated and have a 10-15% yield gap to the newest and highest-yielding types in trials.
While growers need a mix of varieties to spread risk and established performers will maintain a presence on farm while new and unproven varieties are adopted, Mr Kightley says the data clearly demonstrates that some growers might not be moving on as quickly as they should.
There are also numerous “second tier” varieties that narrowly missed out on the Recommended List but have made it into drilling plans.
Simon Oxley, head of crop production systems at AHDB, says while many of these varieties might perform adequately in the field, the job of the Recommended List is to promote improvement.
This is achieved by ensuring newly recommended varieties have a balance of features to potentially provide a more consistent economic return, compared with older varieties.
“There has been a focus recently on selecting new varieties on the list which demonstrate improvements in disease resistance to light leaf spot in combination with high gross output,” says Dr Oxley.
There are several factors at work within this trend, including the many “second tier”, varieties, and Mr Kightley believes it is quite reasonable for seed companies to continue to promote them and try for market share in an effort to recoup some of their investment.
“Realistically, to have a viable seed trade, we have to live with this, as the alternative is a monopoly by fewer breeders and seed companies and seed prices would inevitably be pushed up,” says Mr Kightley.
There is also the poor economic climate pushing down on crop margins, he adds, which results in a strong temptation for growers to opt for serviceable varieties with cheaper seed cost than the top recommended varieties.
“This is especially the case in the cabbage stem flea beetle affected ‘hotspots’, where growers are becoming very wary of buying expensive seed and then losing the crop.”
It should be noted that some of the niche oil varieties, such as high erucic acid (Hear) and high oleic, low linolenic (Holl) varieties, are often not on the Recommended List and would represent a small proportion of the non-recommended varieties.
The Recommended List showcases the very best varieties to help levy payers improve yields and farm profit and both Mr Kightley and Dr Oxley believe the most progressive growers are following it closely.
“My experience [is] most of our farmer members at Niab are very aware of varieties and are quick to take up those offering improvements,” says Mr Kightley.
Dr Oxley adds those leading growers and agronomists are part of the decision process for recommending new varieties, with scope for varieties with innovative traits – such as turnip yellows virus resistance – to be fast-tracked in the Recommended List.
This leaves it up to the market to decide if these varieties, which may have lower yields, are going to be commercially successful.
“What’s clear is it’s those varieties with high gross outputs, but weaknesses against disease leading to a reliance on high inputs of fungicides, which are not going to make the grade,” explains Dr Oxley.
On the current 2017-18 east/west list, 11 of the top varieties are separated by just one least significant difference (LSD) for yield in trials and should provide an adequate range of high-yielding cultivars with agronomic characteristics to suit growing conditions across the UK.
“If all things are equal and there is enough seed there, then the full set of 22 varieties must surely be enough. Having 73 [in harvest year 2017] just makes no sense at all,” adds Mr Kightley.
Growers taking note of regional advice
The insight into oilseed rape variety trends shows growers are planting varieties suitable for their region, as proposed by AHDB lists (see graphs 3-6).
The Recommended List shows a UK gross output, with a further split into the east/west and north region, reflecting the different challenges of growing the crop in opposing extremities of the UK.
Northern growers have typically favoured varieties with good standing power, light leaf spot resistance and early maturity, while further south, a good phoma stem canker score is an additional consideration.
Mr Kightley says it is positive growers are using regional advice, but also believes there is some crossover.
“I am sure that it must be incredibly difficult for the Recommended List committee to get it right all the time at the candidate selection stage, as it has to make selections based on a handful of early trials.”
“Some varieties can evolve from their original labelling as the strength of trials data improves year to year. Nikita was a good example of this, being originally pigeon-holed in the North, but now having a UK-wide recommendation following last harvest’s results.”
Dr Oxley says the new UK system introduced for the 2017-18 list now allows all candidate varieties to be grown in all regions, so UK-wide information exists for those that may only be recommended for a single region.
“Anastasia is a good example of a variety that has universal appeal, but was recommended for one region, he adds.
The next 2018-19 edition of the oilseed rape Recommended List will show untreated yields and the reintroduction allows growers to see potential yield reduction in the absence of fungicides.
With challenges in effectively managing disease – particularly light leaf spot – this will become increasingly important.
“Growers selecting Recommended List varieties have free access to independent, annually updated information on variety performance and any changes in resistance. Growers selecting varieties not on the list will be more reliant on breeders’ trials,” adds Dr Oxley.