The return "with a vengeance" of wet weather may prompt many UK farmers to abandon their last standing wheat, besides rendering spring barley and oats harvests the slowest in recent memory, and piling on "misery" for potato growers.

While the harvest of the UK wheat crop is close to completion - after a dry spell at the start of the month allowed farmers to catch up on a rain-delayed start - rains over the weekend left growers facing "saturated soils, ponding in fields and some flooding", Adas said.

"There are still crops elsewhere on the higher land and in wet patches of fields that may prove impossible to harvest following the latest rain," the consultancy said.

In Scotland, where "there have been serious harvest difficulties caused by the wet conditions", further rain forecast for the coming week "will hamper the completion of the winter wheat harvest".

Abandoned barley

The poor conditions look set to ensure a historically poor UK harvest ends on a dismal note.

Adas restated a forecast of yields coming in "towards the lower end" of a range of 6.8-7.2 tonnes per hectare, implying the worst result in 20 years, with the specific weight, a key quality measure, dropping 70.7 kilogrammes per hectolitre, the lowest on records going back to 1977.

And the harvest slowdown was reflected in other cereals too, with the spring barley harvest slowing to a crawl, and becoming the latest in recent years.

"There are still crops dotted around the rest of England and Wales that have not been harvested due to poor ground conditions," Adas said.

"The latest rain and the harvest logistics mean that many of these patches may not be harvested."

For oats, harvesting stalled at 85% complete, compared with nearly all typically by now.

'Perfect storm of misery'

The wet conditions have also slowed the potato harvest, which was 27% complete as of Monday, roughly half the usual rate, according to the British Potato Council.

The low figure reflects, besides recent rains, the knock-on effects of damp spring weather, which delayed sowings, and the wettest summer in a century, which slowed crop development and raised disease pressures.

Confirmed outbreaks of potato blight have more than doubled this year, the council said, warning that producers faced a "perfect storm of misery" given also that many farmers were on fixed contracts, meaning they would be unable to pass on higher costs.

"The combination of low yielding potato crops, increased crop spraying costs and increased wastage from problems such as greening, soft rots and growth cracks has massively increased the average cost of producing a tonne of potatoes," council chairman Allan Stevenson said.

Price dynamics

According to analysis group Andersons, farmers' costs have soared from £140 a tonne to £190 a tonne.

Potatoes achieved an average price of £184.77 a tonne last week, with relatively low contract prices offsetting £252.77 a tonne for free-market crop.