Export commodity prices fell to a four year low in March.
The Reserve Bank of Australia's index of commodity prices was 2.0 per cent lower in foreign currency terms in the month.
Coking coal, steaming coal and iron ore were the main culprits for the fall, but base metals prices were also lower.
Rural commodity prices, led by wheat, provided some offsetting gains, the RBA said.
The March level of the index was 28 per cent below the July 2011 all-time high, and the lowest since March 2010.
And the momentum of prices appears to be negative.
The RBA said estimates for iron ore, coking coal and thermal coal export prices are based on market information on prices actually received.
But current market prices are even lower.
"Using spot prices for these commodities, the index declined by 4.6 per cent in March in SDR terms (an average of four major foreign currencies), to be around 18 per cent lower over the past year," the RBA said.
Although the foreign currency index was 13 per cent lower in March than a year earlier, the index rose by 2.3 per cent in terms of Australian dollars, thanks to the local currency's depreciation over the same 12 months.
