As featured in Arable Farming Magazine
Sheep add to OSR resilience
by Arable Farming Essential Varieties Supplement July 2022 Issue
Careful variety selection and using sheep to graze the fields are among the OSR risk management tools employed by one Midlands oilseed grower.
Grazing forward crops with sheep is part of the extra flexibility Staffordshire grower Rob Atkin is building into his oilseed rape growing at Field Hall Farm, Uttoxeter, to cope with the increasingly uncertain climate.
It proved especially valuable this season for earlier sowings on fertile silt ground going into the winter far too thick for comfort following excellent establishment and one of the growthiest autumns in recent memory.
All 11.4 hectares of the DK Excited drilled on August 5, 2021, were grazed for a week in mid-November, together with a section of the Agrii iFarm’s variety trial field as a demonstration.
This and the rest of Atkin Farm’s 50ha of the crop – mainly split between DK Excited and DK Exalte – were sown from mid-August.
Responsibility In a cost sharing agreement with a local shepherd, who takes responsibility for fencing and flock management, sheep have been part of the family’s 450ha mixed arable and beef business for a while now, grazing off the stubble turnips that continue to be their favourite cover crop ahead of spring barley.
Although this is the first time sown OSR has been grazed, sheep were put onto a small area of well-grown OSR volunteers ‘too good to waste’ and taken through to harvest last season with some success.
Despite minimal inputs, this ‘crop’ delivered 2.5 tonnes/ha.
Last year Mr Atkin also found how useful sheep grazing could be in taking out spring barley volunteers as well as black-grass and particularly problematic brome from a small area of winter wheat.
So, in a farm-scale trial he also gave ewes access to the most forward 15% of his 200ha of winter wheat this season, grazing September and early October crops of Graham and Fitzroy on the farm’s heavier Keuper Marl ground to three different heights in February.
“Having access to sheep, we wanted to see if we could make better use of them,” he says.
“My grandfather always found them valuable on his winter barley.
So, I guess we’ve come full circle.
“Continuing to grow winter barley means we’ve been able to move our OSR sowing forward to make sure it gets away from the large numbers of game birds we have here as much as cabbage stem flea beetle [CSFB].
“Thankfully, they have never been really bad on our oilseed rape so far.
But they’ve ravaged our stubble turnips in the past, making us acutely conscious of the risk they pose.
“As well as nursing the crop through its first few critical weeks, leaving a decent length of straw and spreading sewage sludge ahead of OSR drilling may be useful in preventing serious beetle damage.
Equally valuable here are the vigorously establishing, ast-developing Dekalb hybrids we always choose and the healthier soils we have been building by reducing tillage and giving our ground plenty of FYM as well as sewage sludge every year.
“When our five-year rotation puts the OSR on our most fertile ground, though, this approach and the sort of autumn and winter we’ve had this season brings with it other challenges.
“By last November our early-sown crop, in particular, dwarfed our labradors with a worryingly over-thick and over-forward canopy.
Which is where the sheep were really useful, removing almost all the foliage and with it, we very much hoped, early disease as well as any CSFB larvae.
They also opened up the crop well and provided extra manure.
Careful “It certainly took courage, and we were very careful to move them on quickly.
Immediately after grazing the crop looked pretty bare – particularly one area that was taken down a little too far.
“Even this recovered well as the crop grew away strongly from winter, however.
In fact, it probably had a better structure going into stem extension than the later-sown crops we didn’t graze.
Come harvest, our yield maps will make very interesting viewing.”
With green area indices going into February very much lower than they would otherwise have been, the farm was not able to economise as much on nitrogen as it might have done.
Even so, healthy soil mineral nitrogen levels have led to a cut in rates of around 10% to just under 200kg/ha.
Better structured canopies with less residual disease after the grazing have also enabled worthwhile spring fungicide and PGR economies.
Hybrid Although limited by the late frosts and poor summer light levels, Mr Atkin was pleased with the 3.9t/ ha he brought in from the DK Excited he tried for the first time last year, alongside the 3.8t/ha of his DK Exalte – itself up more than half a tonne on 2020.
He sees the new hybrid’s rather slower leaf development going into winter, together with its strong disease resistance, TuYV resistance and standing power making it well suited to earlier drilling.
Its strong and rapid spring development is also proving just what is needed after winter grazing.
“Rather than going for the highest yields, we want to get a consistent 4t/ha-plus from our OSR every year with the least possible risk,” he says.
“Earlier drilling with the most suitable variety is a key part of this.
Every bit as important, though, is getting the seed into moisture evenly with good seed to soil contact.
“As we’ve moved away from the plough to progressively less tillage since 2003, we’ve tried all sorts of ways of establishing our OSR, from drilling after a big set of Simba discs and Cultipress to Stocks-seeding down the legs of a Shakaerator subsoiling to 12-18 inches.
“The Shakaerator remains an important part of our approach but only ahead of drilling.
Much better soil structure means we now run it at barely 6-8in following sewage sludge application.
This guards against any immediate obstacle to rooting from previous trafficking without disturbing the surface and losing crucial soil moisture.
“We’d like to direct drill the OSR without any cultivation, as we do wherever possible with our cereals, but we continue to find a little timely mechanical structuring works wonders in ensuring consistent OSR establishment and early development.”
Vital too in the family’s experience is reliably even sowing at a shallow depth.
Sowing behind the subsoiler leg in the past used to leave seed all over the place in the profile, leading to protracted emergence and much greater vulnerability to early pest attack.
Consistent This has been overcome by drilling to a consistent 1.5cm – initially with a tined Horsch CO4 but now even more accurately with the disc system of the recently acquired Amazone Cirrus with its variable seeding capability.
To capture as much soil moisture as possible, the drill is run as closely behind the Shakaerator as workloads allow, then followed in equally short order by a Cambridge roller.
Sowing rates are deliberately kept down to around 40 seeds/sq.m.
A companion crop of buck wheat and berseem clover was included with the later-sown OSR for the first time this season – in a 2:1 mix with the seed – more to improve crop rooting and growth than as a defence against CSFB.
While its absolute financial value may never be quantifiable, the combination of nitrogen fixing from the clover and phosphate mining from the buckwheat is seen as a valuable addition to establishment assurance.
“The most important thing for us is to get our crops out of the blocks running,” says Mr Atkin.
“They also need to have get up and go in spring.
As well as vigorous establishment and rapid early development, we choose our varieties for the most robust all-round strength.
This includes disease resistance, standing power and pod shatter resistance so we can manage the harvest for the least weather and combining losses.
“That way we are firmly on the front foot with our management and have the greatest flexibility to match our agronomy to whatever the season throws at us.
“We always like to have well-grown oilseed rape going into winter.
But we are equally conscious that having it too thick and forward coming into spring can get in the way of developing the most efficient light-intercepting canopies as well as increasing light leaf spot pressure.
“With sheep in our armoury in addition to the traditional seed, fertilisation and crop protection tools, it looks as if we may have a very valuable extra risk management tool,” says Mr Atkin.