3 July 1998

Dull weather and lodging putting yield prospects in shade

By Andrew Blake

MORE sunshine is desperately needed to dispel increasing gloom over combinable crop yields, say specialists.

June sunlight levels have been the lowest for 30 years, notes Velcourts technical director, Keith Norman.

"Some barleys have seen hardly any sun since the ears came out." With about 40% of yield coming from the awns, potential is clearly slipping away, he believes.

With grain fill already under way dull weather reducing photosynthesis is also limiting wheat output. "It is affecting us daily. There will be a lot more single figure crops than double ones this year." Aborted grain sites, obvious in some crops, suggest plants are compensating for shortage of carbohydrate caused by poor photosynthesis, he explains.

The greening effects of strobilurin fungicides are alleviating some of the problems, he says. "We have seen some good benefits and there should be a good payback. But overall it is not looking good."

Individual stem carbohydrate reserves, mainly soluble sugars which together account for as much as 3t/ha (1.2t/acre) of output according to HGCA research, are lower than normal, says John Foulkes, crop physiologist at Notts University. But high stem numbers could help.

Canopies for light interception are also slightly larger than normal because of unusually free-tillering earlier on, notes Dr Foulkes. "That could be helpful. Given standing crops and good disease control there is time for good yields yet. But it will need average radiation or above," he says.

Lack of sunshine has already eaten into wheat yields, though barley output is harder to call, according to Julian Hayes, ADAS head of arable. "We could be looking at up to 1t/ha off the long-term average," he predicts. "But there is still a long way to go."

Boxworth-based colleague John Garstang believes sunny weather may return too late for shallow rooted crops to benefit. "If it stays gloomy yields could drop further. If it turns hot and sunny a lot of crops could turn their toes up pretty quickly."

YIELD DAMPENERS

&#8226 Too little sunshine.

&#8226 Low stem sugars.

&#8226 Shallow rooting.

&#8226 OSR pod shading.