Getting the early agronomy of winter crops right is crucial a recent tillage conference heard.

Seedtech director, Dr. Tim O’Donovan, gave an agronomy update on a range of winter crops, during his presentation to the AgriCare tillage conference.

Where oilseed rape (OSR) is concerned, he confirmed the threat of light leaf spot at the present time.

This is a fungal disease, which has become a challenge in Ireland over recent weeks in the wake of the recurring wet weather.

“I would strongly advise farmers to spray OSR crops with Proline, or an equivalent product, as soon as possible,” O’Donovan said.  

Light leaf spot can be found in the crop as early as October, and so it is vital to familiarise yourself with symptoms from the very start of the growing season.

As a polycyclic disease, it continuously releases spores and can spread at an alarming rate, making early identification vital.

Early symptoms appear as white sugar-like spores, forming in a circular pattern, on either the top or underside of the leaf. Untreated crops can suffer yield losses of 50% or more.

Fertiliser for winter crops

With regard to the fertiliser requirements of OSR crops, O’Donovan strongly advised the use of Green Area Index (GAI) values.

It is then a case of subtracting the GAI-estimated figure from the crop’s total N requirement to work out the amount of artificial fertiliser that should be added to meet its full yield potential.

O’Donovan pointed out that a combination of GAI-based estimates and organic manures can allow OSR growers secure 2t/ac final yields with relatively low mineral nitrogen inputs.

Meanwhile, the area of winter hybrid rye grown in Ireland continues to increase.

The Seedtech representative explained that the crop has the smallest seed size of all the cereals grown in this part of the world.

“This can create problems where seed sowing depths are concerned,” he said.

“When placed at 2-3cm below the surface, seed germination and subsequent plant development rates will be optimal.

“However, there were instances last autumn of rye seed being placed at a depth of 3″.”

He explained that the seed did germinate. However, the resulting tillering rates were below those that would be expected and the end result was a drop-off in final crop yields.”

Where winter barley is concerned, O’Donovan stressed the need to manage crops precisely during the early stages of their development.

“Barley is a sink limited crop. In practical terms this means that all the yield-related management decisions must be taken by the beginning of April,” he continued.

“After that, it’s very much window dressing.

“The fungicide and growth regulator regime followed during the month of March is critical in determining the final yield of winter barleys.”