Arable News

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Establishment compared at rotational study

NIAB TAG’s unique ‘Sustainability Trial in Arable Rotations’ (STAR) project is in its 10th year

NIAB TAG’s unique ‘Sustainability Trial in Arable Rotations’ (STAR) project is in its 10th year. Dominic Kilburn attended a recent open day at its base in Otley, Suffolk.

This year, for the first time at NIAB TAG’s Sustainability Trial in Arable Rotations (STAR) project, Otley in Suffolk, slug monitoring has been carried out within the trial plots to observe any differences in populations in respect to both cultivation and rotational changes.
As part of the project’s long-term cropping plan, winter wheat variety Skyfall was sown across all trial plots this season following a combination of winter cropping (OSR), spring cropping (oats), continuous wheat (wheat) and alternate wheat/fallow (fallow), and established using the four different cultivation systems (see Box opposite).
Speaking at the event, NIAB TAG adviser Neil Watson (left) said that although slug numbers across all rotation and cultivation systems were initially high last autumn, the ploughed plots had the lowest number by comparison across all crop rotations in the project when first measured in early October. “Ploughed land (irrespective of rotation) started with the lowest populations probably because of the mortality during ploughing itself. The highest pressure initially was seen in deep, non-inversion, cultivation plots,” he said.
In terms of rotational differences in pressure, results suggested that numbers of slugs in traps were lower in the spring cropping rotation (irrespective of cultivation).
However, specifically focusing on the winter rotation where wheat followed OSR, and considered to be a high-risk slug scenario, numbers of slugs were higher than the spring rotation where wheat followed spring oats.
“When considering the affect of cultivation systems in the winter rotation when measured in mid-October, the plough had the highest burden in terms of slug numbers, with shallow cultivation showing the least,” Mr Watson added.
“In terms of slug monitoring and subsequent slug pellet applications, growers must be aware that, although ploughing can hit numbers initially, it can take slugs a long time, sometimes up to a month, to emerge through the cracks in deep cultivations,” he suggested.
“Don’t think they have gone just because you can’t see them after deep cultivations,” stated Mr Watson, adding that, “in reality there is always a certain level of slug populations in fields and there are certainly more slugs in deeper cultivations than shallow, because of the looseness of the seedbed.”
Although slug emergence and not control was the primary purpose of the trials, the performance of slug pellet material Sluxx (ferric phosphate) was monitored after the first application applied on 13th October, contributing to a big impact on slug numbers immediately after the first application, noted Mr Watson.
Supporting the trials work is crop protection company Certis whose technical manager, Nigel Riches, said that the message of “continual monitoring” for slugs was critical. “Growers must get into the habit of being more watchful for slugs because if the weather is right for them, they will be in the crop.
“This is only the first year of slug monitoring in the trial and we are hoping to be able to repeat it and see what the differences are each season,” he said.
His colleague, Certis product manager for arable crops, Inez Cornell (left) added that with the loss of slug pellet active methiocarb for use in potato crops, and the awareness of the problems presented by metaldehyde being found in water, growers are seeking alternative products for the control of slugs and that ferric phosphate can be an important part of a slug control programme. “High quality ferric phosphate pellets are providing control on a par with metaldehyde-based alternatives,” she commented, pointing out that because Sluxx pellets are water insoluble, they remain on the surface and available for ingestion by slugs much longer than pellets containing metaldehyde.
“Ferric phosphate also remains active in cold weather, adding to the pellets, good performance in challenging conditions,” she added.
According to Inez, once Sluxx pellets are ingested, feeding stops immediately and the slugs go underground to die, rather than corpses being found on the surface.
“Juveniles also find the pellets attractive and their control helps interrupt the breeding cycle,” she concluded.

Yields and margins

Also speaking to farmer members at the event was NIAB TAG’s Ron Stobart who said that when comparing mean winter wheat yield data (over four years across the rotation), in relation to the different cultivation systems represented at STAR (and at NIAB TAG’s New Farming Systems site at Morley, Norfolk), and comparing ‘winter and spring’ and ‘all’ rotations; the shallow cultivation approach had the lowest yields.
“This yield loss is possibly more pronounced on the lighter soiled NFS site in Norfolk, where lighter soils are more prone to loss of structure and need some deeper rectification,” he commented.
In practice, Mr Stobart said that the differences were small (up to 0.3t/ha).
“However, despite the plough providing the best yields overall when comparing cultivations in all rotations, it is not giving us the best margins (#486/ha), compared with shallow (#499/ha), ‘managed’ (#506/ha) and, best performing, deep tillage (#516/ha),” he explained.
Mean wheat yield in regard to rotation (irrespective of cultivation system) over the same period indicates that there is relatively little difference in yield between ‘winter’, ‘spring’ and ‘fallow’ rotations, however a yield reduction of about 2.5t/ha is apparent in ‘continuous wheat’, he said, highlighting that the loss had been due to crop population and grass weed issues.

OSR yields
Mr Stobart said that oilseed rape yields at the STAR site had been similar when comparing plough and deep tillage cultivations but there had been a much bigger drop off in yield to shallow cultivation performance.
“In terms of OSR margins, deep tillage was best and the plough has done well too. That said, I’m not suggesting everyone resorts to the plough to establish oilseed rape, as ploughing resulted in slower early autumn growth, but this is good yield data and, using 36 x 36m plots, it reflects how this would have yielded on farm,” he added.

Weed control
NIAB TAG’s John Cussans (left) said that non-inversion cultivation systems and the continuous wheat rotation have resulted in the greatest density of grass weeds at the site, with meadow brome being the worst offender. “However, we’ve also seen high grass weed levels when wheat is alternating with a spring crop,” he pointed out.
“People use different techniques to establish crops and if it works on their farm then they should continue to do it. Shallow, non-inversion methods can be the worst in terms of grass weeds, but if it works for you then that’s OK. But don’t use a min-till system just because it’s fashionable – it’s a whole system approach,” he stressed.
While establishment practices may vary from farm to farm, Mr Cussans pointed out that the one common factor that linked growers having success at controlling grass weeds was that of attention to detail. “There’s not one magic solution out there and you can make any rotation work – but only if attention to detail is given to every operation.”
Mr Cussans continued: “If you are drilling in October, rather than September, grass weed populations will be lower, herbicides will work better in the available moisture and control will be better. However, if the weather turns bad later in the autumn prior to finishing the planned winter acreage, then it’s better to be flexible and walk away from it if conditions are not right for drilling.
“It’s much better to then plan for a good spring crop rather than try and establish, in bad conditions, what will be a poorly competitive crop,” he added, concluding that getting good, experienced and independent advice was also key where growers needed it.
*The STAR project, hosted by Suffolk farmer John Taylor, is supported through the Chadacre Agricultural Trust and the Felix Thornley Cobbold Trust. It contributes to the AHDB-funded ‘Platforms to test and demonstrate sustainable soil management’; a collaborative project delivered through NIAB TAG and the James Hutton Institute.

STAR overview
NIAB TAG’s 10-year Sustainability Trial in Arable Rotations (STAR) study examines the interaction between four different cultivation methods and four crop rotations on heavy Hanslope soil. The project uses farm scale equipment on large, 36 x 36m plots, with the overall aim of comparing the impact of rotation and cultivation on weed burden, soil condition, crop yields and margins.

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