Direct drilled osr not suited to dry seasons

Oilseed rape establishment and nitrogen use efficiency were just two trials to come under the spotlight at this year’s Cambridge Arable Technologies (CAT) winter conference. Louise Impey reports.

Direct drilling oilseed rape is extremely risky in a dry autumn and is likely to be less effective than other forms of establishment, according to independent variety expert and CAT member, Richard Fenwick.

“We’ve now had two years of trials results which show how poor crop establishment can be with direct drilling,” he said.

In 2007, Mr Fenwick tested 10 varieties across four different seed-bed preparation systems – plough and cultivation, direct drill, min-till and subsoil drill (see table).

“No matter whether it was a conventional or a hybrid variety, none of them did well in the direct drill situation,” he said. “In fact, we only achieved 18% establishment with conventional varieties and not much more with the hybrids.”

Although he accepted that it was dry when the crops were drilled on 6 September, Mr Fenwick said that this was the second successive set of CAT trials to give the same result.

Seed to soil contact

“You need good seed to soil contact with oilseed rape,” he added. “This hasn’t been happening with direct drilling.”

Having too few plants established in the autumn meant that there was room for pigeons to land in the crop, causing further losses, he noted.

“We’ve also noticed that the plant’s tap root is limited in the direct drilled plots. It seems as though it hits a pan with this method, which then limits its uptake of nutrients and water, having an effect on yield.”

A closer look at individual varieties showed some differences, he continued. “Castille was the highest yielding variety in every establishment method. Es Antonia and Excel also performed consistently.”

However, the semi-dwarf types didn’t fare at all well with direct drilling. “Even though they are hybrids, this system doesn’t seem to suit them at all,” Mr Fenwick concluded.

OSR establishment trials

Average yield of all varieties (t/ha)

Conventional

Hybrid

Plough and cultivate

3.6

3.4

Min-till

3.5

3.2

Direct drill

2.9

2.7

Subsoil drill

3.5

3.0

Source: Cambridge Arable Technologies

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