Adas enhanced fears for the UK wheat harvest by saying that wet conditions had prevented farmers from a late catch-up on winter sowings, and raising its estimate of the proportion of the crop at risk.

The consultancy, which in November cautioned that growers had been able to plant only 25% of winter wheat thanks to persistent damp, said that there had been "no significant drilling" since because of further rains.

Rainfall between September and February averaged 50% higher than normal.

"A few [farmers] have tried broadcasting and others have drilled in the frost, but over all there has been little increase in the area of winter wheat drilled since November," Adas said, in comments released minutes after European Commission grain officials cautioned over "excessive precipitation" in the UK.

'Very poor growth'

Much of what has been planted as struggled with slugs encouraged by the wet conditions, and with high soil water levels, besides compaction from what fieldwork has been done.

"Saturated soils reduce oxygen availability for the roots, resulting in some very poor growth on the wettest fields, especially on heavier ground," Adas said.

"Of the [wheat] crops that have been drilled many have struggled to establish in cold, wet soils resulting in low plant populations with reduced levels of tillering."

The consultancy raised to 10%, from 7%, the proportion of UK winter wheat "estimated to be of questionable viability", forecasting that "at least half" of that area will be reseeded with spring crops.

'It has been terrible'

The data suggest a sharp drop in UK wheat production in 2013-14 even assuming a rise in spring plantings of the grain and a recovery in yield from last year's 20-year low of 6.7 tonnes per hectare.

Spring wheat typically yields far less than autumn-sown varieties, although tends to be of higher quality.

Indeed, at Gleadell, the UK grain merchant, trading manager Jonathan Lane said that data implied a crop well below the roughly 12m tonnes the market has appeared to be trading.

Strategie Grains has forecast a total UK soft wheat crop of 12.4m tonnes, with Gleadell forecasting a figure near 11m tonnes.

"It has been terrible, which people appreciate when they go out and actually look at the crops," he told Agrimoney.com.

'Serious levels of damage'

Adas was less downbeat on winter barley, if cautioning that "the reduced tillering over winter due to the cold and wet soils may mean that some crops will have reduced yield potential".

Oats that were drilled in the optimal autumn sowing window "have survived the cold, windy, wet conditions of the winter better than the other cereals".

However, the consultancy restated a forecast that 20% of winter oilseed rape was of "questionable viability", and of which at least half was expected to be reseeded.

"Late drilling, wet soils and slug pressure all combined to give poor establishment in a significant proportion of winter oilseed rape crops, with low plant numbers and small, slow-growing plants a feature of many crops.

"Slugs have caused serious levels of damage in oilseed rape and have been responsible for the failure of many crops," with pigeon grazing "likely to put the viability" of backward crops at risk, and phoma, a fungal disease, is "widespread".

Gleadell has forecast a UK rapeseed crop as low as 1.7m tonnes – down by one-third year on year, although many market forecasts are at about 2.0m tonnes or above.