Australia's wheat inventories may surge to between 8 million and 10 million metric tonnes by Sept. 30 from as much as 7.3 million tonnes a year ago as coal-mining companies' fight for rail capacity led to transport bottlenecks in the eastern states.

The Australian Bureau of Agricultural and Resource Economics and Sciences forecast a wheat crop at 26.2 million metric tonnes, short of 2010's record 26.3 million tonnes. Exports may climb to a record-high 20.4 million metric tonnes in the year from Oct. 1 from 18.7 million tons, the agency announced on Sept. 13.

Harvesting begins in October and a second crop may help delay a 23 per cent drop in global prices in September.

Wheat for December delivery improved 0.2 per cent to $6.2525 a bushel on the Chicago Board of Trade on Tuesday.

New South Wales and Queensland grains exports share part of their transport infrastructure problems with the coal mining companies. Australia is the world's largest exporter of coal. It expects export earnings from the coking coal to leap 29 per cent to A$37 billion in the year to June, with shipments growing 11 per cent to 156 million metric tonnes, the Bureau of Resources and Energy Economics said Sept. 20. Profits from thermal coal may increase 29 per cent to A$18 billion.