25 September 1998

Seed rates need tuning to match sowing date

The Arable Research

Centres latest detailed

Descriptive Lists for winter

wheat and barley contain a

wealth of information for

members. Andrew Blake

extracts some messages for

a wider audience

FAILING to trim seed rates can dilute the yield advantages of early sown winter wheat.

That is the clear message from ARC trials on nine varieties (seven UK Recommended) at four sites last season.

"It is only when you start to drop the seed rate that you pull in the full benefits of early drilling," says director, Mike Carver.

The experiments compared yields from pre-Sept 15 sowings at 100, 200/250 and 350/400 seeds a sq m with those from early Oct drillings at 350/400.

Sticking to the conventional, relatively high rate in September depressed average output by 1.2%. Easing to 200/250 allowed the early sowings to outstrip those in Oct by 3.9%. But pulling back to 100 gave them an average 5.1% edge.

Benefits from early sowing varied greatly between sites, most benefit coming from the mid-way seed rate which shaded Oct sowing by 19% at Caythorpe, Lincs. At the other extreme, at Cirencester, Glos, no Sept sowing outperformed the later one. But the 100 seeds a sq m approach was adrift by only 0.3%, whereas the 350/400 drilling was 5.2% down.

"The results show there are yield benefits from early sowing, but only if you make the right rate adjustments," says Dr Carver.