LOOK after those fields of oilseed rape. They may be your most valuable combinable crop and not just a convenient break crop.
For many growers in eastern and southern England, rape may be in line to produce a better gross margin than even first wheats which are far more likely to have agronomic care lavished on them.
The potential top return from rape – if end prices remain buoyant after next harvest – is sufficient to justify extra care this autumn in sending crops into the winter with the protection they deserve.
This surprising ascendancy for oilseed rape among the combinable crops is underscored by the commercial gross margins obtained on 20,000ha (50,000 acres) monitored by the Hertfordshire-based ProCam Group in East Anglia and the south-east of England.
Rape was the clear leader with the best gross margin at the 1996 harvest and, while waiting for actual figures from this years harvest, ProCam has recalculated the 1996 yields at 1997 prices to get much the same ranking.
David Ellerton, group technical director, says low grain prices and relatively mediocre yields this year have affected growers morale.
"All of them are saying where do we go from here? and asking whether they should change the proportions of the crops they grow and how much they should spend on those crops," he points out.
The group survey for 1996 shows clearly that the best gross margins came from oilseed rape, first winter wheats and peas, followed by continuous winter wheat, winter barley, second wheat, spring barley, winter beans and linseed.
Rape had a gross margin in 1996 of £909/ha (£368/acre) compared with £843/ha (£341/acre) for winter wheat, based on an amalgam of milling and feed wheat prices averaging £107/t. Peas slotted into third place with a gross margin of £857/ha (£347/acre) from last harvest.
Recalculating the gross margins using this years lower end prices drops the gross margin for each of the top three by about £200/ha (£81/acre) but their ranking stays much the same.
Rape yields this year have been much the same as, or better than, in 1996, says Mr Ellerton, and the rapeseed price has increased over the £140/t figure used in the recalculation.
"The first reason for growing oilseed rape is profit but it is also an entry for first wheat, the second most profitable crop," he adds.
Although the ProCam survey shows rape in fourth position as the best crop to precede winter wheat, the influence of different break crops on wheat yield are not that great at the top end.
Peas provide the best entry, just ahead of naturally-regenerated set-aside, both producing following wheat yields in 1996 around the 8.5t/ha (3.44t/acre) mark. Wheat yield after spring beans was slightly less, while after winter oilseed rape or winter oats yields averaged about 8.25t/ha (3.34t/acre).
Oilseed rape also provides the cereal grower with an opportunity to clean up difficult weeds such as sterile or soft bromes and blackgrass using herbicides which are not safe to be used in the cereal crop.
Mr Ellerton suggests growers consider ways of maximising the potential of their oilseed rape crops again in 1997-98. Early drilling will have set most crops up well for good yields but attention must be paid to the broad-leaved weeds which could smother out plants or hamper full establishment.
"Grass weeds and volunteers can cause up to 40% yield losses in certain circumstances and must be treated as necessary," he says.
Volunteers are frequent this year in rape crops which have followed wheat or barley. Cabbage stem flea beetle also started to appear in a few crops in mid-September. Phoma and light leaf spot have regularly been seen in fields over the last few years.
The ProCam survey shows that the best gross margins are achieved by those growers who apply a fungicide in the autumn and again at stem extension.