Commodity prices have fallen for 11 months in a row.
The ANZ Bank's monthly Commodity Price Index fell 0.9 percent January compared with the previous month and the Bank says a lower dollar will help exporters in coming months.
The index is seven percent lower than a year ago.
Casein led the decline last month, falling by 14 percent, with increased supplies from New Zealand and Europe weighing on prices.
Wool fell by six percent and beef continued to ease from record highs, declining by three percent.
That offset gains in whole and skim milk powder, which rose due to tightening supply, while lamb and skins prices rose as well.
Kiwifruit and apples remained unchanged, while forestry prices were little changed.
ANZ said its indexes use monthly averages, and are yet to fully reflect the impact of sharp falls in the dollar in the second half of January.