Check crops with care in wake of long cold spell

17 January 1997




Check crops with care in wake of long cold spell

By Andrew Blake

CEREALS and oilseed rape seem to be emerging from the prolonged cold spell well. But crops not yet recovering should be checked to find the cause, advises ADAS.

In parts of the east, especially where snow cover was limited, cereals have lost leaves through wind scorch, says Huntingdon-based agronomist John Garstang. What remains is generally green and strong and should grow away, with little yield loss.

Crops on light land prone to frost heave need assessing to determine root damage. Plants separated from most of their roots in a solid frozen lifted layer of soil are unlikely to survive, says Mr Garstang. But those with deeper connections should survive, albeit with some leaf and tiller loss.

Avoid N

The temptation to apply nitrogen to chivvy backward cereals along should be avoided, he warns. Crops are unlikely to benefit from such early top-dressing, even with the thaw, and unused fertiliser risks pollution, he explains.

Morley agronomist Doug Stevens agrees. "I certainly would not contemplate any N until at least the second half of February."

Leatherjackets, more numerous than usual in some areas, are an added threat to struggling crops. ADAS advice is to check carefully down the drill rows for signs of damage – yellowing and shoot severing – after eliminating frost heave as a cause. The trigger for an insecticide spray on late-sown wheat is an average of five pests a metre of drill, it suggests.

Wheat bulb fly egg hatch is already under way, with levels of 15% noted in Cambs and Lincs. At Morley, where sugar beet canopies were good, few problems in following wheats are expected. But wheats after thinner crops may soon need treatment, says Mr Stevens.

Cold weather and pigeons have taken their toll on oilseed rape. But just because leaves have been removed, growers, especially those with unsprayed crops, should not assume they are free of phoma disease. "It will be in the plants by now," says Mr Garstang. "Light leaf spot is also expected to make an appearance soon, if the weather becomes damp and mild."

Herbicide check

Onset of the thaw is a good time to gauge the effectiveness of late autumn herbicides and the frosts impact on weeds, he adds. Any large cleavers surviving the Arctic conditions may need treating next month as they start to grow away.

The cold snap is expected to spur more seed-bank wild-oats into germinating this spring. That view is echoed by Mr Stevens. "It tends to wake them up."

Looking further ahead, Mr Garstang says low winter rainfall is of growing concern.

"It is the biggest worry in the eastern counties." Some parts with long-term annual averages of 560mm (22in) had only 330mm (13in) of rain in 1996. Morley had just 39.2mm (1.5in) in December against its 56.4mm (2.2in) 27-year mean.

lCereals and rape in Scotland, where winter weather has been kinder than further south, generally look very well, according to Stuart Wale of Aberdeen SAC. &#42


POST-THAW ADVICE


&#8226 Inspect cereals for:

– soil heave

– plant and leaf loss

– discoloration

– pest damage.

&#8226 Assess weed control.

&#8226 Avoid early nitrogen.

&#8226 Check oilseed rape for:

– phoma

– light leaf spot.


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