Archive Article: 2001/03/31

31 March 2001

Gallic ways with N on oilseed rape

FRENCH arable growers are taking a more targeted approach to nitrogen applications. Reglette Azote Colza is a tool developed by Cetiom, Frances national agency for oilseed rape, to identify how much nitrogen to apply to oilseed rape.

It is essentially a slide rule to guide application rates according to foliage weight and visual in-field assessments. In early spring, the grower makes a visual appraisal of the crop, or weighs representative foliage samples from one square metre in the crop. These assessments are matched with N application rates, ranging from 150kgN/ha to 210kgN/ha, recommended on the slide rule.

Fife grower Gordon Rennie is already a fan: "I appreciate the tool has been developed and calibrated for French farmers. However, the same principles apply in Scotland and I intend to make revisions, if necessary, for Fife growers," says Mr Rennie who farms 284ha in Elie.

He aims to use the tool to help make adjustments according to variety and spatially variable applications within the field – but without the use of a satellite. "The kit requires that ultimate tool, the farmers foot," he explains. "I believe that nitrogen is by far oilseed rapes most important component. Ive had crops, which received sufficient nitrogen, yield 5t/ha."

"If farmers rely on RB209 advice or similar spreadsheets, they follow a broad brush approach to their crops nitrogen requirements, and theres a danger that crops which have potential to harvest 5t/ha will not receive sufficient nitrogen, while those with a lower yield potential will receive an overdose."

"We need to increasingly finely tune inputs to realise crop potential, minimise waste and improve the units overall efficiency and profitability. Testing for soil nitrogen does not provide an accurate answer due to our regions vagaries of soil type and climate. However, I believe the Cetiom kit will go a long way to achieving an accurate solution as far as oilseed rapes nitrogen inputs are concerned. It challenges the farmer or adviser to look at crop canopy, start scoring individual fields and then use the kit to match nitrogen requirement more accurately to yield potential."

A simple visual method of determining the ideal date to apply the first spring N dressing to winter wheat is being advocated by advisers in eastern France. A trial plot of just a few square metres is sown in each field in the autumn at double the normal seed rate to the rest of the field. When the leaves in these plots turn yellow in spring it is time to get the spreaders out, say advisers from the Lorraine Chamber of Agriculture.

Last year the simple system worked well on 102 different French farms. The resultant first day of application for spring N differed by up to 21 days from the date chosen by traditional means. The average yield between the visual method and traditional methods was similar, but protein content was 0.5% higher – averaging 11.7% – on wheats using the visual assessment of leaves turning yellow in the trial plot for N application.

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