Think hard before ploughing in oilseed rape crops

Oilseed rape growers are being urged to persevere with backward crops as they emerge from winter as long as weeds are under control.

Many crops are looking poor and patchy coming into early spring although many agronomists advise growers to wait before throwing in the towel.

A survey last autumn by crop consultant ADAS said UK oilseed rape autumn drillings were down 10%, and a fifth of the crop in the ground might not be viable and may have to be ploughed up.

“Don’t judge crops too early. There is very little that can beat a half-decent crop of oilseed rape,” says Mark Hemmant, technical manager at adviser Agrovista.

He suggests waiting for some growth from the crop before making a final decision and says he has seen a plant population as low as five plants/sq m yield a more than respectable 4t/ha.

Agronomists say thick crops rarely make high-yielding ones, and the crop’s huge power of recovery often see a thin population come up trumps.

Thin crops can be encouraged with nitrogen fertiliser although weed control for troublesome infestations of chickweed and blackgrass can be a problem.

Richard Elsdon, technical manager at United Oilseeds, stresses the importance of good weed control if growers are looking to encourage backward crops.

“As long as your weed control is good the crop will give you a better return than anything you could plant in the spring,” he says.

For extremely backward crops, Mr Elsdon suggests a light dressing of 20kg/ha of nitrogen just to see if this will encourage the crop into strong growth.

Even plants the size of a one pence piece at this stage of the season can produce reasonable crops, as if they have survived until now then they can create a good crop by the summer, he adds.

“As long as your weed control is good the crop will give you a better return than anything you could plant in the spring,” Richard Elsdon, United Oilseeds

Weed control is critical at this time of the year with herbicide choice limited and growers reliant on carbetamide (Crawler) for controlling chickweed and blackgrass.

Time is running out for this type of application as it can only be used safely until the end of February.

If growers decide to plough in the crop and have already have used a residual herbicide propyzamide (Kerb), then options are limited to largely spring oilseed rape or pulse crops.

Patchy crops are also a problem, but patching up is not always an option as Mr Elsdon says repairing damaged areas with spring oilseed rape could bring a crop “plagued” with pollen beetle.

Independent agronomist Patrick Stephenson says despite a challenging year growers can still aim at a yield of 4t/ha, but warns input costs could well be higher than usual.

“Diseases such as light leaf spot and phoma will be difficult to control on these backward crops because they have such a short distance to travel to the stem, so investment will be needed,” he says

“One of the first things that growers should be doing, though, is getting a nitrogen application on,” he says from his base in North Yorkshire.

Normally, growers wouldn’t be looking at putting anything on until the beginning of March, but Mr Stephenson advises getting half of the normal dressing on as soon as conditions allow.

“You’ve got to feed it a little bit and often to try and stimulate it and get it growing, so this early application followed by the rest at the conventional time will be important,” he says.

Mr Stephenson predicts up to 10-20% of oilseed rape could be ploughed up across his area of northern England, but still urges growers to think twice before giving up on it.

“Half a crop of rape will probably be better than half a crop of spring barley that you’ve had to spend another lot of money on,” he notes.

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