Oil Seed Rape - A Year to Forget

A far more encouraging start to this season leaves most winter oilseed rape growers happy to put last year well behind them. While 2012/13 will go down as an OSR season almost everyone would like to forget, its experience holds valuable lessons anyone keen to improve the consistency of their cropping would do well to remember.

This is the conclusion of Agrii national oilseed rape specialist, Philip Marr’s assessment of the relative performance of a wide range of commercial crops as well as results from the company’s OSR performance-stretching Technology Centre and Farm trials and demonstrations across the country last year.

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photo © farm-images.co.uk

Interestingly, he finds no one part of the UK or specific growing system faring better than any other under the combined onslaught of the cold, wet autumn, unrelenting slug and pigeon attack and the coldest, latest spring for more than 50 years.

“We saw some excellent 6t/ha-plus yields from Essex in the south to Forfar in the north, mainly from drillings before August 26th,” he reported. “But alongside them – often just a field or so away – many crops sown later or in less good conditions struggled to do a third of this. And a good 20-25% of the national area drilled never made it to harvest.

“Having said that, a number of the crops pulled out in March and April should really have been left in. At the same time, some of those that were left in should almost certainly have been pulled out. It’s easy to have hindsight, I know. But then that’s what we get by learning from experience.”

Last season really underlined Philip Marr’s faith in the recovery abilities of winter rape. Even he was surprised, however, to see yields of well over 3t/ha and up to 4t in some cases from crops with populations as low as 12 plants/m2 and so little apparent potential going in to May. All the more so after seeing them go backwards so rapidly in the face of up to five weeks of cold easterlies around Easter.

“In all my years working with the crop I’ve never seen OSR suffer like this,” he said. “Most plants came into March small and well behind anyway. Our weather station data across the country showed the ground was far too cold for them to really get going until well into April. The east wind was brutal. And with no spring crops to feed on or canopy to deter them, the pigeons were unrelenting.

“Many September-sown crops that looked alright in February had little, if any top growth to speak of by the time the growing season actually started. Which is why so many of them were given up as lost causes, even those which actually still had plenty of potential.

“This clearly shows the danger of judging the OSR book by its covers,” insisted Philip Marr. “What’s below the ground counts at least as much as what you can see above it. Without exception, the crops that went on to deliver decently despite far lower than normal populations had a good 2-3” of root in February or March. Equally, those that looked just about OK but disappointed at harvest were almost invariably lacking in the root department.

“The lesson is clear. Rooting is every bit as important as GAI in OSR decision-making in the spring. In fact, I’d go so far as to say it counts for more. And not just when the chips are down either. In a growthy season – as the current one promises to be for many – well-rooted crops are far less likely to lodge. This makes the winter and early spring use of growth-regulating fungicides and rooting stimulants especially important.”

Also crystal clear from Philip Marr’s review of the season is the superior performance of hybrids over pure line varieties under challenging conditions, particularly at seed rates low enough to allow them to express their more robust early rooting and branching abilities.

This has been far more apparent under Agrii’s best farm practice trial regimes than under the protocols of Recommended List trials. At the same time, though, the season has confirmed a number of characteristics especially valuable in allowing some hybrids to deal with challenging conditions noticeably better than others.

“Last year showed just how important it is to have varieties that develop faster in the autumn,” he stressed. “Our work shows that the fastest autumn developers need 300-350 fewer day degrees to reach five leaves than the slowest developers. This was an immense advantage with temperatures at the sort of premium they were last autumn and winter.”

Mr Marr accepts such varieties may present more of a management challenge where sown early in good conditions at higher-than-ideal seed rates and without robust autumn and spring growth regulation. While height is something that can be managed, though, he insists that the one thing we’ve learnt from the past season is the importance of having a crop to manage.

“Equally obvious too has been the value of varieties that develop faster in the spring,” he added. “This ensures sufficient lateral bud development before increasing day length puts a stop to it by triggering stem extension. By enabling noticeably greater branching last year, it allowed these varieties to make more of the excellent – though very late – flowering – conditions that proved the season’s saving grace.

“The ability of varieties with well-waxed leaves to survive late icy blasts is another thing we’ve really learnt from our 2013 experience. This character also appears useful in resisting contact herbicide damage.”

Alongside the sort of resilience shown by the best of today’s fast developing hybrids and the importance of judging crops by what’s below the ground as much as above it, Philip Marr sees one over-riding lesson to learn from the trials and tribulations of last year’s oilseed rape cropping.

“Always farm by conditions not the calendar,” he stressed. “In some cases last year the conditions proved too much for any crop. Even though everything may be against them, though, we can now be confident the right varieties going into half-reasonable seedbeds well into September can give a decent result; especially where rooting isn’t compromised by pushing-up seed rates too much in an attempt to compensate for the conditions.

“However thin and unpromising they may appear as late as mid-April too, we’ve also learnt that decently-rooted crops should always be left in the ground, while there should be serious question-marks over better-looking ones that may be lacking in the rooting department.

“Who knows what the current season has in store ? Very different its challenges will almost certainly be. But we’d do well to keep hold of the valuable hindsight we’ve gained from the season we’d like to forget if improving OSR consistency is our key objective.”


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