30 June 2000

Use expensive seed dressings with care

EARLY appearance of take-all in wheat crops across the main production areas this season is likely to trigger widespread interest in seed dressings capable of reducing the fungal impact for autumn sowings.

But they should be used carefully as they are an expensive input, warns ProCams technical director David Ellerton. "They are not like the old seed dressings of 20 years ago. Modern ones are more targeted and more expensive. They must be integrated with the appropriate sprays."

Adapting crop husbandry changes to complement their use will be essential, he says. ProCam has issued guidelines to help growers minimise take-all pressure (see panel).

As cereal production intensifies under the new area aid regime, take-all is bound to become more widespread, he reasons. In recent seasons there has been a noticeable build-up of trouble, with crops in 1998 suffering the worst losses for many years.

Last year there was less, but worrying levels were still seen, and ProCam agronomists are beginning to see a lot this season, says Mr Ellerton.

"If we are running into a dry spell crops with shallow and poorly developed root systems, a legacy of the wet autumn and winter, could struggle as roots fail to find sufficient moisture. In this state they would be vulnerable to take-all attack, with any further loss of rooting having a big impact on yields and profits."

The move to early drilling and reduced seed rates is likely to increase the risk of trouble.

In 1998 ProCam noticed a 1.75t/ha (14cwt/acre) difference between early sown first wheat and early sown second. That yield gap narrowed as drilling was delayed.

Last season there was a 1.3t/ha (10.5cwt/acre) difference between first and second wheats grown by the top 25% of growers in the companys management survey which includes 4000ha (10,000 acres) of wheat grown on farms from Yorkshire to the south coast. &#42

Tackling take-all


Risk factor Cultural control

Continuous cereals Switch to a rotation.

Early sowing Sow high risk crops later.

Variety choice Choose more tolerant types – Napier,

Cockpit, Consort better than most.

High seed rates Reduce rates.

Loose seedbed Consolidate, reduce tillage.

Poor soil structure Correct drainage and compaction

problems.

Grass weeds Remove grasses/couch before break.

Alkaline soils Lime before break crop not cereals.

Nutrient deficiency Correct P, K, Mn deficiencies.

Nitrate nitrogen Switch to ammonium nitrate or sulphate.