Oilseed rape has had a tricky couple of years, but its popularity has remained strong as a recent survey by CPM and BASF has shown, and getting it off to the best start could ensure it continues a top crop for the future. CPM reports.
The seemingly easy way at the start is not always best.
By Melanie Jenkins
Care and attention to detail right from pre-emergence could well be the key to delivering a successful oilseed rape crop.. The impact of addressing individual pressures, such as cabbage stem flea beetle, may have been overplayed in terms of how much they have contributed towards crop-emergence issues, according to a survey carried out by CPM and BASF.
In recent years, the majority of farmers (74%) said their OSR area had stayed the same. This is despite issues surrounding neonicotinoids, blackgrass and volatile prices. Defra statistics show harvest 2015 saw a peak of around 650,000ha of OSR combined, which fell back to 560,000ha at harvest 2017.
Crop failure – often cited as the reason for delaying expenditure on the crop – is not as widespread as thought, with average crop failure over the past three seasons less than 10% over 80% of growers reporting less than 20% of their crop had failed in recent years. The survey reveals there’s scope to significantly improve establishment success, however. What’s more, it may be the fear of crop failure that’s encouraged growers to delay herbicide applications, rather than an actual occurrence, experts have suggested.
Cabbage stem flea beetle was less of an issue last autumn, with 15% of growers reporting it as a problem, compared with 19% in 2015/16, although this could reflect a general trend towards spring cropping, which is good for many agronomic reasons. “Spring cropping is an important inclusion, but growers don’t want to put all their eggs in that basket,” notes Clare Tucker at BASF. OSR is an important profitable crop when grown well with thought paid to good establishment, she points out.
“It’s a good option for tackling blackgrass as growers can use herbicides with different modes of action in their programmes against it compared with cereals.”
Sarah Cook at ADAS agrees that OSR has a place in the rotation. “People are interested in growing it as they can use propyzamide with it, which is vital for killing blackgrass.”
Don’t give up on OSR because of weeds, she adds. “The key is to get the crop to establish well.”
Farmers already know how to grow OSR and have an understanding of it, says Clare. As a result they’ve spread out rotations, showing they have a good sustainable approach.
“Flea beetle has become more of an issue and some response has been to chuck OSR seed in and wait and see, which is quite a chancy thing to do. The crop may struggle to emerge, often unevenly, making it vulnerable to the pest. Or if it all emerges it’s over-thick with spindly poorly rooted plants which will be more vulnerable to disease, winter weather and poor yield potential.
“But once it’s drilled, farmers have already committed to a crop, so it’s a question of adapting to the challenges,” says Clare. There are good practices developed before flea beetle became such an issue, she says. These involve using optimum seed rates, good soil structure, ensuring seed to soil contact, preserving seedbed moisture and sometimes starter fertiliser to get it away.
Clare points out that the recommended seed rates are best and that drilling should take place when conditions are right. “Don’t worry so much about the date, but more about the conditions and getting the seedbed right.”
OSR wants to go into winter with 8-10 true leaves, more than 8mm root collar diameter at the base of the stem and more than 8g of root mass. A well established, even crop has greater tolerance to pigeon damage, phoma, winter wet and cold weather and flea beetle larvae. It has more root resource to fight back in the spring.
But does this make a difference when it comes to weeds? According to the survey, blackgrass is the biggest weed issue for OSR growers with 39% of respondents suffering with it more than other weeds. “Blackgrass is a headline weed of course,” says Clare. “There’s a reasonable armoury of chemicals for use with OSR, given it’s getting tougher taking it out in other crops.”
However, farmers may be reluctant to apply a herbicide until they have a crop up, says Mark Hemmant at Agrovista. “Therefore, residuals like metazachlor have been applied post rather than pre-em. But they work better pre-em and effective weed control is particularly important for wide row crops.”
Taking weeds out early to remove the competition and get good establishment is key and Clare suggests that if broadleaf weeds can be taken out early, they should be. “There are more spray days in Sept than in the months of Oct, Nov and Dec combined. Added to that, if you spray late you can cause more soil damage.” So take advantage of the better weather and start the weed control early, she advocates.
Going early also avoids complications having to work around clethodim spray intervals, with Katamaran Turbo or Banastar (dimethenamid-p+ metazachlor+ quinmerac) good early options, she advises. Even where Astrokerb is planned later, either of these options removes the weed competition early and also removes the weeds Astrokerb won’t control.
“It’s worth noting that Astrokerb is weak on cranesbill and cleavers, which were the biggest issues for 8% and 7% of the survey respondents, respectively. These are less of a problem where Shadow or Banastar is used before it.”
Kerb and Astrokerb were the most commonly used products in the survey, with 53% and 48% of respondents claiming to use these most, where the main target will be blackgrass.
Mark agrees. “Some growers have relied heavily on Astrokerb for broadleaf weed control,” he says. “But it’s applied late and can prove unreliable, so do something before that’s tailored to the weed problems.”
With blackgrass, Clare recommends using a three-pronged attack of early residual, clethodim and propyzamide to make sure you do as good a job as possible and the different modes of action makes resistance management sense.
Charlock was the next biggest burden behind blackgrass for the survey respondents, with 21% of growers citing it as their biggest weed issue. “Charlock has become more of a problem, but Clearfield OSR provides a good answer here. Whereas, bifenox is the only herbicide option in non-Clearfield OSR crops, it’s unreliable and can cause crop damage,” says Clare.
Some growers are so beset by charlock that they can’t grow conventional varieties anymore, says Sarah. “It’s impossible to kill it in OSR unless you grow a Clearfield variety.”
In the survey, 45% of respondents said they’re using a metazachlor co-form, as opposed to only 18% using solo metazachlor. One issue around early solo metazachlor herbicide application is that if conditions are dry, the weeds will grow too big before moisture brings the applied product to the emerging roots, says Clare.
“Unlike metazachlor, dimethenamid-p is also taken up by the weed shoots as they emerge, so it doesn’t require the same moisture levels to give reliable control.” This is particularly true if you want to wait until crop emergence – when you can see the rows – before applying the herbicide.
Mark says that Agrovista has been looking at a phenmedipham mixed with a residual which, when applied early post-em has very good results. “We all understand the desire not to spend money on a crop that might fail and a simple solution seems to be mixing a residual with phenmedipham.” It gives growers an opportunity to take out chickweed, poppy, cranesbill and shepherd’s purse, among others.
“Growers who’ve gone from pre-em sprays to early post-em can be a bit dissatisfied, which is why the mix with phenmedipham can help,” he adds.
Mark warns growers to keep stewardship and water issues in mind with herbicide programmes though. “Check restrictions of each product brand and take care to avoid drift.” It’s also worth remembering to keep an eye on the stewardship rules for the coming autumn as these haven’t been firmed up.
Another option growers are turning to is the Clearfield system. With 45% citing brassica weed control and 34% citing general broadleaf weed control as benefits, it has obvious appeal for those fighting weed burdens. “The initial attraction is that growers can wait until the crop is up and then they can spray and it has a wide weed-control spectrum, taking out pretty much all broadleaf weeds,” He continues.
Clearfield varieties are becoming much more widely adopted, says Mark. “It’s an easy, reliable solution and with concerns surrounding erucic acid, the area should increase this year. It’s a nice option for farmers to have and most who’ve tried it have been satisfied with it. If not, it’s because they’ve maybe left things too late with other weeds.”
Varietal choice is much better now, he adds. “There’s not such a yield penalty, but if you don’t have a brassica weed problem, then there are other herbicide options.” Clare advises that for best weed control, target 1-4 true leaves of the weeds, achieve good coverage using a medium spray and allow a minimum of two hours for good rain fastness.
And it’s the early attention that produces winning crops, she says. “Growers want crops which are easy to manage throughout the season, but the seemingly easy way at the start is not always best. Attention paid at the beginning of the crop’s life, getting it away well, removing weeds early makes the whole job easier for the rest of the year.”
Flying high with a thriving crop
Congratulations to James Cox from Glos who responded to the survey and has won a fabulous prize of a DJI Mavic drone.
He completed the tie-breaker question with the answer judged best on what makes an excellent OSR herbicide. “A product that reduces crop competition and seed contamination to allow the OSR to thrive and perform,” was his response.
The poetic flair of Alistair Marr Cambs also impressed the judges. He responded “works well for my situation, without any fuss or complication, no red-tape nor derogation but leaves me feeling adulation.” and receives a BASF goody bag.
To take part in the next survey, make sure we have the correct details for you by emailing angus@cpm-magazine.co.uk
