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Advanced Oilseeds Need Careful Management

Date Added: 23/11/2009

Despite exceptionally dry autumn conditions, many winter rape crops across the Midlands and south of England look too far advanced for this time of year and have grown too quickly, believes Richard Elsdon, technical manager for United Oilseeds.

"We have inspected crops that have in excess of 50 plants per square metre, with many plants already showing up to eight true leaves," Mr Elsdon describes. "Whilst this may look good in the field, this is not where crops should be and they will require careful management throughout the winter and spring to safeguard final yields."

In the interest of high yields at harvest time, crops should be less dense with thinner canopies so that the lower branches of each plant can access the necessary sunlight during the summer months to develop full and fruitful seed pods.

"Similar conditions going into 2007 gave equally advanced crops which produced very mediocre yields at harvest," Mr Elsdon warns.

Mr Elsdon also cautions that it is too late for plant growth regulators (PGR) to have an effect on the most advanced crops. But he believes that there are other advantages to be gained from maintaining existing PGR programmes.

"It is still advisable to apply a growth regulator which is effective against phoma to prevent the spread of the disease in high risk areas," he states. "And for less advanced crops, it is not too late for a PGR to prevent excessive top growth. Unfortunately, for those crops that have already started to develop a stem it is too late for regulators to be effective."

On a more positive note, Mr Elsdon believes that dense crops will be less susceptible to pigeon damage and will be better equipped to out-compete any lingering broadleaved weeds. He also believes that many crops will be able to manage without an application of early spring nitrogen.

"Applying nitrogen to crops that are already well advanced will lead to runaway spring growth and an overly dense canopy. A better policy is to delay spring nitrogen until the crop is almost at the green bud stage and has received a spring PGR application. This will reduce fertiliser costs and give optimal plant height and canopy cover."

In order to assess the timing and rate of spring nitrogen applications, Mr Elsdon advises growers to monitor the Green Area Index (GAI) of their crops. "Without an experienced eye it can be difficult to accurately assess the GAI of a crop using traditional methods. But there are a number of online tools, such as BASF's GAI canopy tool which can give an accurate green area assessment through the use of digital photographs.

"Using these new tools is vital for farmers to control runaway crops and optimise the timing and application rates of spring nitrogen."

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