10 August 2001

DELAYEDDRILLINGFORBLACKGRASS

EARLY wheat drilling may be top of growers agendas this season, after last autumns washout.

But Essex grower David Chennells is adamant that sowing date restraint and modern mixed herbicides are the keys to beating blackgrass on his heavy clay.

His 400ha (1000 acres) Highlands Farm at Rettendon has most types of blackgrass, including sensitive and mixed populations of enhanced metabolism and target-site resistance.

But if he retains his tight rotation of two winter wheats followed by oilseed rape, uses the right herbicides and avoids drilling too early, he believes he can keep on top of the weed. "We are on the winning side of it, I think."

Mr Chennells is well aware of the trend for drilling to start from late August. But he remains committed to sowing first wheats in the last week to 10 days of September, and second wheats in early October.

"It is tempting to go early if conditions look right. And if it was not for blackgrass I would. But if we pushed too far we would be swamped."

Equally, he recognises the risks of drilling too late.

So sowing dates are a fine balance between maximising yield potential, waiting until peak blackgrass germination has passed, and still being able to get a drill over the land.

"Once it gets late enough for the blackgrass pressure to be completely off, you have lost a lot of yield in wheat. And on our heavy land, once it gets wet you might as well shut the gate."

Without modern mixed chemistry the delayed drilling approach would not have succeeded.

"We have better chemicals nowadays. A few years ago, it was basically just IPU. Then we moved to Avadex (triallate) followed by IPU and trifluralin."

"More recently we have used a Hawk (clodinafop-propargyl + trifluralin) or Hawk plus Lexus (flupyrsulfuron) mix." Advice comes from AICC member Debbie Wedge.

"We use mainly full rates otherwise we would soon run into trouble, says Mr Chennells.

"Modern chemicals such as these give us a high degree of control. But there is no let up. You have got to keep everything buttoned down using the right rotation, not drilling too early, and using the right chemicals in oilseed rape.

"Our blackgrass is patchy. We have some fields that we have to keep an eye on more than others.

"We still use some IPU and trifluralin, but we are losing the battle in places with this. We still use Avadex. In severe infestations we now follow up with Hawk plus Lexus, and on less severe we will use Hawk." &#42

HIGHLANDS FARM

&#8226 Sensitive and resistant populations.

&#8226 Delayed drilling key defence.

&#8226 Underpinning of modern herbicides.

&#8226 Losing battle with IPU/trifluralin.