Arable News

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Agronomy Update

Patience with seedbed preparation and timely pre-em sprays are vital strategies with late-sown winter wheat, advises our Norfolk-based agronomist

Patience with seedbed preparation and timely pre-em sprays are vital strategies with late-sown winter wheat, advises our Norfolk-based agronomist.

Most growers have some wheat left to drill and, with care, excellent crops can still be achieved, says Agrovista’s Craig Green, who points out that many are delaying operations on land affected by difficult black-grass. Others have fields to sow following maize or sugar beet.
Whatever the reason, patience is the key, Craig advises. “We need to ensure nothing is mauled in. A poor seedbed means a poor crop.”
Wheelings will need to be removed after maize, he notes. After beet, he advises lifting compacted soils to let further rain percolate through before considering the options.
“If you can drill, even if that means waiting for a frost, then do so, otherwise consider leaving the field for spring barley or oats.”
Where wheat is sown this autumn, Craig advises following with pre-emergence chemistry immediately the drill has left the field to ensure optimum control of black-grass and other problem weeds.
“If you can drill, you can roll and spray – that way nothing gets missed, and you’ll reap the maximum benefits of delayed drilling.”

Spray recommendations
Craig is including Avadex (tri-allate) in all his spray recommendations. “I don’t worry which order the chemistry goes on – the important thing is to get it on,” he says.
He’ll advise Herold (diflufenican + flufenacet) plus Liberator (diflufenican + flufenacet), each at 0.3-litres/ha, to provide 240g of flufenacet and 90g/ha of DFF, plus Anthem (pendimethalin) at 3-litres/ha to provide 1,200g/ha of pendimethalin, preceded or followed by full-rate Avadex.
“Avadex must be applied accurately to optimise control. A boom applicator is best, but for most people this means hiring in a contractor. It can be applied from a granule distributor mounted on the drill or rolls, but this must be calibrated properly.”
Craig will also add Remix, an oil-based adjuvant, to his pre-em spray. Agrovista trials show this can provide an extra five per cent control of black-grass by holding the chemical in the surface layer of the soil, especially important with later drillings when rainfall is likely to increase.
“Remix keeps the chemistry working for longer without adding much to the price,” adds Craig.

Slug alert
Slugs should also be monitored carefully. “Seedbeds are likely to have more clod so there will be more open seed and conditions will be damper. Drains are likely to be running, or to do so soon after rain, so I’ll avoid metaldehyde and use ferric phosphate instead.”
Once conditions deteriorate and good seedbeds can no longer be achieved, there is no point in forcing seedbeds, he stresses.
“Things are best left until spring. If wheat remains the first choice, some varieties can be drilled safely through February, it may be better to opt for a true spring variety such as KWS Willow or Mulika.
“They are both capable of producing high yields as well as thick canopies that help smother out spring-germinating black-grass.”

Phoma infection
The phoma threat to oilseed rape raised in last month’s report has become a reality, with infection noted at the time of writing in west Norfolk, says Craig (right).
Growers should spray when 10-20 per cent of plants are infected with at least one lesion, says Craig.
“Smaller crops are at higher risk as infection grows down the leaf petiole into the stem, so it has less distance to travel. Nights are now colder, and crop growth is slowing, so the risk of phoma in these crops is increasing.”
Small plants should be treated with a low 0.25-litres/ha dose of Difcor (difenoconazole) plus amino acid product TerraSorb at 2-litres/ha to boost vigour. “Backward crops need pepping up to help them develop enough going into the winter.”
This should be followed by a November-applied Frelizon (penthiopyrad + picoxystrobin) at 0.5-litres/ha to control light leaf spot and will mop up remaining phoma. This can be applied with Kerb (propyzamide) or Crawler (carbetamide), he adds.
Caryx (mepiquat chloride + metconazole) will replace Difcor as the first treatment on bigger crops to provide early growth regulation as well as disease control. Craig recommends 1-litre/ha.
“Watch out for late aphids too,” he adds. “Spray 0.3-litres/ha of Biscaya (thiacloprid) as soon as they are seen to help prevent the transmission of turnip yellows virus.”
*Craig Green is an agronomist with Agrovista, based at Great Ellingham, Norfolk ([email protected]).


  • Written by: Farmers Guide
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