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SOME commonly held myths about wheat growing are dispelled in the latest publication from the Arable Research Centres, according to director Mike Carver.
Second wheats do not always yield less than first crops and early drilling is no sure route to higher output, he warns.
Variety performance in second and continuous wheats and on land infected with soil-borne wheat mosaic virus are new features in the ARCs Descriptive List 2000/2001.
This years list, the eighth in an annual series produced with HSBC Agriculture, has also been extended to cover 12 crops. Previous lists were confined to winter wheat and barley.
Dr Carver says the 114-page booklet offers the most comprehensive source of variety information and agronomy available to combinable crop growers.
When it comes to second wheats no varieties, with one possible exception, yield relatively better or worse than when grown as a first wheat, he says. "Equinox is probably the only example which doesnt do quite so well."
Relative performances as continuous wheats are also remarkably similar. Season, soil type and other factors such as take-all pressure have a much bigger bearing on performance, he says.
This harvest some second wheats even outyielded firsts. The average of 30 varieties in the second slot in Warks was 9.34t/ha (3.78t/acre). Grown as first wheats the same 30 gave only 9.09t/ha (3.68t/acre).
In Kent, the second wheat yield reduction was only 3.6%, but in Northants it was 22.6%. "This shows how dangerous it can be to budget on a rule of thumb penalty of 10-15%."
Yields in ARC continuous wheat trials since 1994 have also varied greatly. In 1996 the average was 5% better than that of first wheats. But in 1999 those in the long wheat run produced 21% less, he says. "It all depends on individual circumstances."
ARC has long trialled early and late drilling for wheat and this years results reinforce the companys views.
While useful as a management aid, early sowing must not be viewed as a technique to increase yields, says Dr Carver. "At some sites early September crops have yielded over 2t/ha less than conventionally drilled crops when averaged over a number of varieties.
"If you are sowing early you must adjust seed rates. Our trial at Bainton in Yorks was a classic example of why growers should not rush down the early drilling road."
ARC work has found big differences in the susceptibility of varieties to wheat mosaic virus, much as recorded in France (Arable Sep 29). Equinox has been particularly hard hit, says Dr Carver.
Studies, part HGCA-funded, on Barley Mosaic Virus confirm the need to identify the mix of virus on infected land.
"The message is that while it is important to differentiate the types, there are still some varieties which are technically susceptible but perform well."
ARC members have plenty of trial results to digest in the latest Descriptive List, says Mike Carver.
ARCBainton wheat trial*
Sowing date Seeds/sq m Yield t/ha
Sept 2 100 9.27
Sept 2 200 8.65
Sept 2 400 7.66
Sept 24 350 10.32
*Average of 13 varieties.