The price of the country's main commodity exports fell in December, led by weaker prices for dairy, meat and horticulture.
The ANZ Bank's Commodity Price Index fell 1.8 percent last month as the improvement in dairy prices came to an end, and there was softness in world prices for some fruit and lamb.
However, there was some offset with higher prices for forestry and aluminium.
A rise in the New Zealand dollar during the month also reduced earnings for local producers.
ANZ Bank agri-economist Con Williams said 2015 was a year to forget, with prices down nearly 13 percent, although the overall decline in the currency helped to cushion the impact on producers.
There was little prospect of any significant improvement this year and the worst-affected producers, such as dairy farmers, would have little choice but to squeeze their costs further.
"I think a lot more businesses think these lower prices unfortunately are going to stay around for a bit longer period than earlier anticipated, so they're just trying to restructure their business models accordingly," Mr Williams said.
A weaker New Zealand dollar would help to cushion the impact of lower prices, he said.
