Openfield revealed a hit from a poor UK export performance last season, even as shipments remain weak this marketing year, and are forecast to attract "strong competition" in 2014-15 too.
The UK's biggest agricultural co-operative, owned by 2,700 farmers, said it had fallen to breakeven in the year to the end of June, from a £2.6m pre-tax profit the year before, despite raising revenues by 8% to £710m.
The drop in profit reflected efforts to sell deliveries from a poor-quality grains crop, thanks to persistent rains, with wheat, the UK's main cereal, showing the lowest average bushel weight on records going back 35 years.
"Conscious of the difficulty many UK farmers had with their poor quality grains, Openfield determined, as a policy, to work tremendously hard to market those crops in the most advantageous way possible from a members' perspective," James Dallas, the co-operative's chief executive, said.
"This undoubtedly had a negative impact on our profitability," although he added that the policy "is entirely consistent with our co-operative principles".
One way in which profits were hit was in a tripling to £1.8m in interest charges thanks to the cost of maintaining larger inventories while finding markets for grains.
"The primary impact on the Openfield business of the 2012 harvest was the disappearance of the export markets for UK crops, which resulted in longer stock holdings," the co-operative said.
The comments come as in wheat the UK, usually a net exporter, is amid a season in which shipment volumes have, again, proven weak, reaching 225,702 tonnes in the first half of 2013-14, from July to December, the lowest in 12 years.
This is a reflection of a relatively small wheat harvest last year, of 11.9m tonnes, thanks to poor autumn sowing conditions the year before, again because of persistent rains, but implying a reduced threat of inventory service costs for exporters.
However, an inventory backlog could potentially prove more of an issue next season, with the UK placed for a large recovery in wheat production this year, thanks to better autumn sowing conditions, but potentially facing a tough rivalry shifting surplus supplies on to world markets.
Data on Monday from the HGCA crop bureau estimated winter plantings in England and Wales up 19% at 1.815m hectares.
"The higher wheat area increases the likelihood of the UK being able to return to being a net exporter of wheat in 2014-15," HGCA senior analyst Helen Plant said.
However, wheat area "is also expected to remain high across Europe and, with limited crop issues so far, the UK may face strong competition in export markets".
The result of this year's harvest this year will depend in part on the degree of damage in the UK from one of the wettest starts to a year on record, which brought an average of 259mm of rain to England and Wales over January and February.
"Winter crops will survive some flooding, but submersion can affect tillering, plant survival and crop viability," the Adas crop bureau said in a crop survey on Monday.
"Wheat's ability to survive long periods of waterlogging is dependent on its stage of growth, with impacts greatest in plants that have not started to tiller before waterlogging occurs."
Adas added that there were "no serious or widespread pest problems", although thanks to the wet and relatively warm conditions "disease pressure is relatively high this season, with yellow rust and brown rust widely reported in susceptible varieties with early treatment likely".
Other winter grains, and autumn-sown rapeseed, have also "established well", although the oilseed is showing some evidence of light leaf spot, which "will be targeted with fungicides, as soon as farmers can travel on the land" when soils dry up.