The reduction was a result of the poor season and difficult harvest conditions, ABS said.
Stocks of milling grade wheat grain were 4.2 million tonnes at the end of September 2011, a decrease of 870,000 tonnes from the previous month. Stocks of feed grade wheat grain were at 4 million tonnes at the end of September, a decrease of 672,000 tonnes, or 14% from the end of August 2011.
At the end of September 2011 Australia's bulk storage of wheat grain was estimated at 8.3 million tonnes, which was a decrease of 16% compared to August 2011. Stocks were up 3.1 million tonnes or 61% compared to September 2010.
All states reported decreases in stocks of wheat grain compared to August 2011, following the expected pattern of post-harvest decline.
New South Wales and Australian Capital Territory stored the largest amount of grain at 3.4 million tonnes despite a fall of 11% from August 2011.