14 April 1995

Testing methods under attack

TESTING varieties under typical farming conditions rather than the artificial regime of untreated or completely protected provides a valuable insight into their true potential.

That is the argument that has underpinned the variety trials run by Arable Research Centres for years. And this year it is being expanded with a sequence of additional trials to provide more practical advice for arable farmers.

"Weve always been concerned that NIAB data doesnt reflect how the crop is grown," says ARC director Dr Mike Carver. "Very few people grow wheat with no sprays, or with four or five." What ARC trials do is mirror "local farm practice" – applying a spray programme which is considered to be the most appropriate for each site and season, he explains.

That shows local farmers how varieties will perform on their farms. And it also provides useful data on which to base the ARCs national descriptive lists, Dr Carver maintains .

He counters criticism that the extra subjectivity erodes the value of the results. A site managers decisions could have more effect on the responsive varieties than the less responsive ones, he acknowledges. But NIABs intensive use of fungicides to exclude disease has its own weaknesses.

Excessive fungicide, particularly at the first and last spray timings, can hit yields, he says. "Trials show you can expect a 4-5% yield reduction from applying an ear-wash fungicide when it isnt needed."

Indeed, ARC trials results have consistently given a similar level of statistical accuracy as the NIAB trials, he adds.

"There is no perfect way of running a trials system to satisfy everybody. You either try to exclude disease or you use local farm practice. Each has its strengths and both can be criticised."

With that in mind, ARC has expanded its targeted variety trials. This year varieties will also be tested using a single fungicide spray at flag leaf emergence (GS39). Other sites will show the effect of growing malting barley varieties under a malting-type fertiliser regime. &#42

&#8226 Inputs by local farm practice reflect practical farm systems.

&#8226 Tailored inputs avoid negative effects of excess fungicides.

&#8226 Results still statistically valid for ARC variety lists.

&#8226 New trials test malting barley regime, early/late sowings, and one-pass fungicide input.

Variety testing using local fungicide programmes is as valid as NIABs all or nothing approach, argues ARCs Mike Carver.