Australia's official agricultural commodity forecaster, ABARES, has reaffirmed its estimates of a record breaking wheat harvest this season, at 32.6 million tonnes, up 35 per cent on last year's harvest.

It's the latest in a string of estimates from local and global forecasters of a global bumper harvest, something that's weighed on grain prices all season.

ABARES' estimate for total 2016/17 production compares to the recent International Grains Council's estimate of 28.3 million tonnes, which is the same as the latest USDA call.

Locally, in an October report, NAB analysts said "we would be looking to national production over 29 million tonnes (29.4 according to our framework), but given the uncertainty we have held our forecast at 27.6 million tonnes this month".

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ABARES forecasters, in the report, said "favourable seasonal conditions in most cropping regions during spring boosted the production potential of crops, which were generally in very good condition at the end of winter".

The country's total harvest of all key winter crops is pegged at 52.4 million tonnes, including a record-breaking 10.6 million tonne barley crop and the third-biggest canola crop at 3.6 million tonnes.

Flood and frost

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The big question mark hanging over the crop report is the extent of frost damage in Western Australia, which won't be fully known until harvest is completed.

Farmers and agronomists have been warning the severe frost event would impact grain quality, forcing premium crops to be sold at lower grades.

In Victoria, where extensive September flooding water-logged soils and delayed harvest by a number of weeks.

Globally, farmers in competing grain exporting nations, like Canada, the United States, the Black Sea, Russia and South America have also produced bumper crops.

Combined with record-low shipping rates, Australia's competitive advantage for selling grain to south east and north Asian ports is being eroded.

"I think what we'll be hearing from early next year is that growers are holding back grain from the market because the prices at the moment are obviously below cost of production for a number of people," Grain Producers Australia chairman Andrew Weidemann.

"When you see low prices, that generally drives high prices, extra consumption goes up because of the low prices and that will drive the economy again.

"So overall I think that things look pretty positive."

In NSW the last week to ten days of warm to hot weather has allowed the harvest to move at a frantic pace.

Bulk handler GrainCorp's Supply Chain Manager Nigel Lotz said, on individual days, record amounts of grain have been delivered to a number of silo sites.

"Coonamble currently holds 340 thousand tonnes and the previous record was 303 thousand and across the state in total, the overall amount in storage was 4.7 million, up 2.5 in just one week.

"We have had some problems with rail maintenance on the tracks and there have been some long delays at individual sites but overall, considering the huge volume, it has been progressing reasonably well."

"Growers are pretty happy with the big yields they are getting and now they just want the prices to crank up a bit."