20 February 1998

Easy on inputs despite growth surge – warning

By Andrew Blake

RAPID crop growth following balmy weather and high soil temperatures should not mean knee-jerk use of nitrogen or growth regulators.

Just because fields are dry and machines can travel, do not feel obliged to treat forward barleys and wheats, agronomists advise.

Most crops are already well tillered, so inputs at this stage could do more harm than good, they say. Only some backward stands and those with take-all may merit extra stimulation.

Some early Sept-drilled wheats in sheltered southern areas are already at the start of stem elongation (GS30), claims ADAS. Only 1-2% fall into that category, but further warm weather could see many more at that stage before long, says principal consultant John Garstang.

There are two main dangers, he explains. "After the mild winter there are some very thick crops with high tiller numbers about. If we get a dry summer grain quality could be terrible."

Extra early stem extension makes both wheat and barley ears more vulnerable to April frosts, he adds.

Unless cooler conditions return growers could face big growth regulator and fungicide bills on over-thick crops. "It is just the sort of expense we dont want to contemplate in a year like this."

Very forward crops might justify a first split growth regulator if the weather stays warm. But his main message is to resist the temptation to apply nitrogen now.

Levington Agricultures Ian Richards echoes that advice. There is little sense in top dressing knee-high crops at least until the first two weeks of March, he says. "There is no point in trying to develop a lot of crop at this time of year."

In East Anglia there is a marked difference between cereals sown either side of Sept 10, says Doug Stevens of Morley Research Centre.

"The earlier ones went into moisture and got away well." But a dry spell delayed later emergence and means most are only slightly more advanced than normal.

Main need on the well-tillered stands is to ease back on nitrogen and apply it later rather than sooner, says Mr Stevens. "We need to get 50% of the tillers out and the sooner they go the better."

Steve Cook of Hampshire Arable Systems says day length should keep crops at GS30 for a while. "But they are tillering madly which is worrying. We have got five to six tillers a plant which is far too many."

Two rather than three N dressings could be the norm this season. Regulators at this stage could merely encourage unwanted growth, he adds.

The only crop justifying pre-March N for independent agronomist Charles Malone in Suffolk is one with take-all. It has already had 30kg/ha and Axis root stimulant to help it along.

&#8226 Western barometer grower Steven Mackintosh reports Buster and Consort wheat at first node (GS31) with up to nine tillers a plant in low seed rate stands. "We pulled back one or two tillers by delaying the first 40kg/ha N until last week." A 2 litres/ha spray of straw-strengthening chlormequat also leaves him feeling more confident.

FORWARD CEREALS

&#8226 Aim to lose tillers.

&#8226 Delay nitrogen top dressing.

&#8226 Avoid recreational pgr use.

&#8226 Beware of take-all.

&#8226 Treat manganese deficiency.