10 September 1999

ARCagronomic advice aids practical cropping

Strob variety effects unclear

Three seasons of ARCtrials comparing strobilurin and triazole fungicide-based programmes on a wide range of wheat varieties show no clear trends. The average yield lift from using strobilurins on 30 varieties in Lincs this year was 4.8%. But in Glos, where yields were much the same, there was no difference.

Variations in individual responses over the years make the picture even murkier, Mike Carver suggests. The most responsive has been Shamrock, averaging a 12.1% increase. But the same variety has displayed a range of -2% to + 36%, he says.

"I used to think that we might be able to find varieties which respond to strobilurins better than others. Now I am not so sure."

By Andrew Blake

HOT on the heels of last weeks variety results, Arable Research Centres has issued agronomic information to aid crop management. Drilling date and rate and fungicide responses are most striking.

Most ARC members received detailed information this week. Headline messages for a wide range of varieties provide a taster of what is on offer.

"The key is that we are directing our members to some very interesting varieties and agronomic trends that otherwise they might know nothing about," says director Mike Carver.

Top yielder nationally, Marshall, has been tested at ARC for only two years. But others, such as Chaucer and weak-strawed Maverick, did well at most of ARCs 15 sites from Yorks to Somerset over three seasons. "It shows they are not flashes in the pan."

Only one of 13 new varieties, a possible biscuit wheat from Nickerson with good Septoria tritici resistance, has outyielded Savannah in pre-DL trials at eight sites.

The trials also show low seed rates do not always suit early drilling. Depending on site and variety, the most cost-effective seed rate for early drilling can range from 100 to 400 seeds/sq m. "Clearly low seed rates are normally best, but rates must be increased in poor seed-beds," warns Dr Carver.

Sowing first wheat before Sept 15 paid off at Bainton, Yorks and Cirencester, Glos, with mean yield increases over later drilling of 4.1% and 7.3%. But at Wye in Kent and Kettering in Northants, the same approach cut average output by 10.8% and 4.7%. The trends were the same irrespective of seed rate.

Nationally the best early-sown variety was Claire – at all seed rates. Weston also did relatively well at higher rates. Riband was clearly unsuited last year.

Beyond that the trials pinpointed big differences in the most cost-effective approach, based on seed at £225/t and £71/t grain. For Consort in Yorks 400 seeds/sq m was best in 1999, whereas 250 was adequate elsewhere. But just 100 seeds/sq m was sufficient in Yorks for Buchan, Equinox, Riband and Savannah.

ARC trials also question the value of three spray fungicide programmes compared with flag leaf-only spraying. Extra response averaged 6.8% over five years.

However, varieties and locations differ. "In the past we have tried to discover what we call zero-option varieties, those which you might not even have to spray. But we have struggled to find them." Three years of work highlight scope for cuts in Abbot, Malacca and Rialto. "But decisions must be based on local conditions and not national generalisations."

ARCWHEATFINDINGS

&#8226 Non-recommendeds do well.

&#8226 Early optimum seed rates vary.

&#8226 Unexpectedly low fung response.

&#8226 No clear strobilurin trends.