The index eased 1.3% in September for a cumulative drop of 4% since the peak in May. Ten commodities recorded falls in prices, three lifted and four were unchanged.
The New Zealand dollar weakened across the major trading currencies. When converted into a local currency measure, the ANZ New Zealand dollar commodity price index lifted by 0.4% - the first monthly rise since March.
While there had been a retracement in commodity prices in both local and international terms over the past few months, the overall level of both series remained elevated.
"The level of commodity prices in world terms is 94% higher than the long-run average. In New Zealand-dollar terms, the NZD index is 44% higher than the long-term benchmark," Mr Williams said.
The largest fall was in the price of apples which fell 23% last month, consistent with the traditional seasonal easing in fruit prices in the northern hemisphere as the price premium for southern exporters petered out.
That seasonal trend was also reflected in a 4% drop in kiwifruit prices. Aluminium prices had also dropped by 4%.
Butter prices led the overall fall in dairy prices, dropping 3% followed by a 2% drop in skim milk powder prices. The price of logs, beef, wool and cheese all eased by 1%, while sawn timber prices slipped by 0.25%.
Seafood prices posted a small lift, rising 0.5%, with smaller rises of 0.25% in sheep meat and skins. Wood pulp, casein, whole milk powder and venison were unchanged from a month earlier.
New Zealand exported $221 million of venison in the 12 months to August, representing one of the lowest annual levels in five years.
The export of velvet, deer hides and other co-products pushed the total deer industry export figure to more than $250 million.
The deer farming industry has put increasing effort into extending the reach of venison in export markets, Mr Williams said.
The largest share (about a third) of exports continued to be shipped to Germany. The next largest destinations were mainly European countries, the United States and Hong Kong.
The world price of venison had always been on a "rollercoaster ride". Influences included economic conditions in Germany, variations in supply from New Zealand, changing tastes of consumers and resistance to price peaks, he said.
A Silver Fern Farms market update on September 23 said venison production remained at relatively low levels, with national processing numbers through August more than 17% less than a year ago, and the lowest August production levels since 1995.
Market demand remained solid, but there were concerns over economic conditions in Europe and the chance of a repeat of 2008, when consumers' spending collapsed and chilled volumes were not consumed.
Demand for chilled venison overall appeared well balanced with supply, given prices for all chilled venison items remained at or near historic highs in euro currency terms, the update said.
