Hold off with N application
Hold off with N application
Wheat crops across the
country are well advanced,
making changes to
nitrogen, PGR and fungicide
strategy essential to
safeguard yield. We provide
some baseline advice
BE prepared to delay nitrogen applications this spring, especially where crops are forward and tillering has been prolific, advises Keith Norman, technical director of Velcourt.
"But growers must know what they are dealing with before they draw up a plan, so get into the field and check tiller numbers per plant and plants per square metre," he says.
Optimum yields come from 550-600ears/sq m, so that should be the final target.
Nitrogen
Early nitrogen applications help plants retain tillers, so avoid them where populations exceed 100 plants/sq m, he advises.
"Even where plant counts are spot on, at 70-100/sq m, there is still unlikely to be a need for early nitrogen.
"Only crops with too few tillers will benefit from nitrogen in early March. Remember that around 1000 tillers/sq m are needed by GS31/32."
Farmacy agronomist Robert Jack agrees. "Crops are not short of nitrogen this year, as soil reserves are good, so do not apply any fertiliser nitrogen before the onset of stem extension."
Going by growth stage rather than calendar date will be essential, he adds. "The crop starts to have a huge demand at GS31/32, so get the fertiliser on at the start of stem extension before the crop gets hungry."
The main nitrogen dose should go on as close to terminal spikelet as possible, Mr Norman agrees. "Make sure you know when that is."
Plant growth regulators
Lodging pressure is much higher than for the past two years, so PGR use will be critical, believes Mr Norman.
"Get an early grip on lodging by using a split Cycocel programme, then follow with a Terpal-type product about a month later," he says. "The two types of product should be used in sequence for the best results."
Disease control
Lush, forward crops are more likely to harbour disease, so be vigilant for mildew and septoria.
"The combination of early drilling, big canopies and mild conditions is conducive to disease, and mildew was around before Christmas," notes Mr Norman.
Eyespot is less of a concern at present, he says. "There is no sign of it in our trials, but if we have another cold snap, it may come in. And it is not just a GS31 disease, it can come into crops right up until flag leaf." *
Well grown wheats need first nitrogen splits delaying, so tiller counts drop, yield potential is protected and severe lodging avoided , says Velcourts Keith Norman.
1 Early nitrogen Wont be needed this year, except where take-all threatens.
2Tiller numbers Aim for 1000 tillers/sq m by GS31/32.
3Plant population Optimum yields come from 550-600 ears/sq m.
4 Nitrogen strategy Get main dose on for start of stem extension; use more splits where leaching is a risk.
5Nitrogen dose Calculate according to soil mineral nitrogen, soil type and crop requirements.
6Lodging High risk, especially where seed rates were not reduced.
7PGR Use split chlormequat programme at GS30/31, follow up with Terpal at GS37.
8Mildew Seen in crops pre-Christmas, check now and use quinoxyfen if required.
9Septoria Expect higher infection levels.
10 Eyespot Can come into crops up until flag leaf. Consider lower threshold than 20% tillers infected.
Totally different appearance
"September-drilled wheats look more like they were sown in August," reports John Spink of ADAS. Crops are twice as far forward as last year, with far greater tillering making it crucial to hold off early N.
At ADAS Rosemaund, Claire winter wheat had 10 tillers in January, compared with 2-3 the same time last year. "We are looking at a completely different crop."
Good nitrogen mineralisation in the autumn is another reason to delay N use. Crops may well have taken up 60kg/ha already. "If the stems are made weaker, that increases the leverage and the likelihood of lodging."
The exceptions are second and third wheats at risk from take-all, where early N is needed to feed crops before root systems fail.