According to The Australian Financial Review, CBH expects Western Australia, which produces 40 per cent of the nation's harvest, to deliver 8.1 million to 8.4 million tonnes of grain, more than 30 per cent below average and the lowest crop since 2006-07.

"This one will really hurt because some growers will have had three bad years in a row," CBH's general manager operations, Colin Tutt, said.

Economists said good seasonal conditions in South Australia, Victoria and NSW would offset falling ­volume from WA.

However, economists and industry experts have warned that Australia faced export bottlenecks, with forecasts for bumper crops on the east coast putting strain on logistics infrastructure.