24 August 2001

Wider WOSR rows are not just for tall types

By Andrew Blake

OILSEED rape varieties do not have to be tall to do well when sown in wide rows, judging by yields from a Kent farm.

But weed control needs to be top notch to cope with extra pressure.

Jo Picketts experience at Rentain Court Farm, Chartham, near Canterbury, shows the establishment advised for getting the best from relatively weak-stemmed Escort works equally well for shorter, stiffer Canberra.

"We used to grow Apex, but switched to Escort last year," says Mr Pickett, who had a total of 33.6ha (83 acres) of winter rape. "A neighbour had had good results and it has done well for us, yielding 32cwt/acre under minimum tillage."

But still hankering after the ease of combining of a shorter variety, he also sowed a ploughed field half with Canberra and half Escort. Both were drilled at twice the normal 11.5cm (4.5in) row width.

No reduction in seed rate to compensate for the wider rows was made, both being sown at 5kg/ha (4.5lb/acre).

Given similar overall treatments throughout the season, including ammonium sulphate for first top dressing, the Canberra at 4.3t/ha (35cwt/acre) outyielded the Escort by 0.5t/ha (4cwt/acre). It also ended up 30cm (12in) shorter, says Mr Pickett.

"It has been really interesting. Establishment is nearly always a problem on our mainly chalky ground, and the thing I liked about the wider spacing was that it gave us nice bushy rows. They were a bit like mini-hedges and much easier to see when we needed to go through it early on."

Although trials show that under ideal conditions thinner more uniform stands should be the target, such stands are more vulnerable to pigeons and slugs, he says.

"I am a great believer in safety in numbers. But now that I have seen how well it works I may be tempted to drop the rate a bit this year, perhaps to 4.5kg/ha."

Achieving the wider 23cm (9in) spacing with the Kuhn/Accord power harrow/drill combination was straightforward. "I just used some tissue paper to block off every other spout. I shall definitely be trying it again this year."

Continental growers have long used wider rows as a form of canopy management to get more sunlight to the base of rape crops to boost podding and minimise lodging, says Hutchinson agronomist James Short, who advises Mr Pickett.

"With tall varieties it is a bit like giving them a crutch to help. A lot of people have tried it here, but in practice it has not always worked."

One downside is potentially increased weed competition. "With more space weeds have a better chance, so if you are going to use wider rows you have to be on top of your weed control programme." Timely Butisan S (metazachlor) or Katamaran (metazachlor + quinmerac) is the best defence, he suggests.

Conditions last season made all varieties noticeably shorter than usual, so a different result might be expected in a more normal year, Mr Short admits.

Having seen the encouraging outcome, he anticipates a slight seed rate cut this year. "I do believe in drilling at a fairly low rate to establish 60-80 plants/sq m with conventional varieties. But going too low in the first year with wide rows would have been an unnecessary risk. We shall decide on the day – we cannot compromise establishment too much."

One problem with extra low rates is the inability of some conventional drills to sow without bunching. The logical progression is towards precision sowing, but widespread volunteers could thwart that move on many farms, he believes. &#42

WOSR MINI-HEDGES

&#8226 Wider rows, same seed rate.

&#8226 Tall & short types equally suited.

&#8226 Extra weed competition risk.

&#8226 Trim seed for more uniformity?