This season’s oilseed rape cropping appears to have seen a significant shift in location across the UK, but with little change in the overall area being grown, according to latest AHDB monitoring.
While establishment challenges have resulted in a reduced area through the Flea Beetle hotspots of central and eastern England - with one iOSR grower taking his entire 300 ha out of the rotation - in other areas growers have significantly increased their OSR cropping, buoyed by the prospect of higher oilseed values and a profitable break crop option.
With most iOSR growers reporting crops having come through the winter well, there is optimism for a push for higher yields to take advantage of better prices. But they are also mindful last season’s great hope, was largely dashed by dismal dull weather over the early summer - which restricted pod fill, seed size and oil content.
This spring, agronomy decisions have been focused around developing green leaf area and crop canopy structure to allow best use of available sunlight, and to keep the healthy green leaves for longer that will drive yield.
Oxfordshire farm manager, Rufus Dudfield, has been looking to increase the inherent fertility and potential of his ironstone soils with farmyard manures and biosolids. The 250 hectares of oilseed rape in the rotation has been a key beneficiary with stronger rooting and maintaining a longer, healthy growing season.
With his establishment and early season agronomy set to produce higher Green Area Index (GAI) crops, the focus turns to nutrition and disease control that is targeted to make best use of the leaf area.
He says: “We’ll apply nutrients little and often wherever possible, to keep crops growing. Last year, for the first time, we also used Toprex to encourage side branching and greater leaf area.
“Where we can build the plant structure to develop more leaves, it will make all the better use of Amistar green leaf retention.”
Rufus says Sclerotinia control with Amistar has always been reliable and, even if there is no disease, the control of late foliar diseases and the health of plants has kept the crop noticeably greener. “We get the ups and downs of OSR yields like all growers, but I do believe it helps us to be more consistent year-on-year with yields and oil content.
“Oilseed rape has an extremely important role in the farm rotation and, if we can continue to improve its consistency and results, it will continue to be the prime break crop,” he added.
Despite battling Flea Beetle on the Bedfordshire/Cambridgeshire borders, iOSR grower, Russ McKenzie has kept faith with the crop on the 750ha family farm. Improved soil structure, min-till and the adoption of hybrid varieties has helped to get crops away from damage, although some patches are borderline for sufficient plant numbers.
“Plants are a bit smaller than I would like this season, but 70% is ok,” he reports. “The hybrid varieties are showing their value again this year, with generally strong autumn establishment and better early spring growth.”
Russ says GAIs at the beginning of February were assessed at typically between 0.65 and 0.7, with only had a couple of fields pushing close to 1.0. That was a bit behind what he plans as normal, but was hoping to perk up with early N at 40-50 kgs/ha.
“We have tweaked our N timings a bit this year, so hence the lower first dose than the normal 70-85 kgs/ha.
“We tissue test for trace elements to get a snapshot of what's happening and what demand there might be; we regularly see our OSR crops being short of molybdenum and magnesium, although boron can fluctuate a bit more.”
Further west, in Northamptonshire, Brinxworth, farming arable director, Ian Matts, reported some big forward crops came out of the winter, but says pigeon feeding in early February has stripped back the leaf on some areas. He has also seen some clubroot effects and suffered some frost kill, but only on relatively small areas.
“Assessing GAI, with the Yara app in early Feb, indicated the early drilled crops had taken up around 110 kg N/ha, compared to later drilled crops 30 kg/ha. The drilling date was the overriding factor in plant size, although ground that received sewage sludge in the autumn is certainly moving fastest in early spring.”
While conditions delayed early N applications by two to three weeks, all crops were destined to have received a small proportion of annual N by mid-March, when field movement permitted.
“Nitrogen rates will be determined by the N-Sensor, but I anticipate it should be relatively low this season - maybe around 180kg N/ha - in two splits and both with sulphur.”
Ian explains he sent in a sample from each block of OSR cropping for leaf analysis, which showed magnesium as the main issue and key focus for now, with some slightly low in calcium and manganese to address, plus boron on the clubroot sites. “I will then be aiming for a late dressing of foliar N during flowering,” he advises.
Oilseed rape relies entirely on photosynthesis to put on yield post-flowering, according to Syngenta field technical manager, James Southgate. “Unlike cereals, there is no evidence OSR can move carbohydrate energy reserves around the plant to drive oilseed yield, which makes green leaf area so essential,” says. “Low radiation levels in May and June last year coincided with pod fill; it was simply too dull for pods to reach their full potential.”
So in the field, it’s the green leaf which growers should look to preserve, he says. “An application of Amistar at yellow bud to early flowering is the best timing to prolong the green leaf area.”
In ADAS trials the GAI in an OSR crop was prolonged by as much as 0.5 from the end of flowering for up to a month from 1.0 l/ha of Amistar at flowering, he says.
James says, more recently, Sclerotinia pressure has tended to increase later in the season with applications at mid-flowering giving the best disease control.
“The greening effect still happens at the later timing, although to a lesser degree. Field trials have shown the improved plant health it brings also helps combat the effects of Verticillium wilt. Even in a year with low Sclerotinia incidence, you still get the economic yield benefit from higher yield and greater oil content of seed from an Amistar application,” he adds.
Good autumn establishment has seen crops come through the winter well and evaded the effects of pest pressures for both the northern Lincolnshire and southern Berkshire farms of Sutton Estates, managed by Chris Baylis.
Although Light Leaf Spot was much later to start this season, he reported low levels of disease had become evident throughout the crops.
“Disappointingly we are also seeing Cabbage Stem Flea Beetle larvae damage in some of the side shoots emerging from the base of the stem but hopefully only a low %. It is a growing concern.”
He highlights the big leaves of his DK Extrovert in the ground had seen some larger GAI recoding this season, with an average of 1.0 in Lincolnshire, and slightly ahead in Berkshire at 1.25, with crops drilled in 500mm bands.
With the strong growth, March N applications ranged from 60-80 kg N/ha, depending on GAI. “The first application is aimed at canopy retention, leaving the final 120 kg/N/ha to be applied later, typically at yellow bud, or as late as we dare,” he adds.
He points out canopy management, with a combination of nutrition and PGR, is aimed to develop a uniform crop coming into flower, which can minimise the impact of pollen beetle and, wherever possible, avoid the need to control.
“We are finding that, over recent seasons, seed weevil has become more of a threat later in the season.”
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