Terra Industries, the fertilizer maker fighting takeover by rival CF Industries, has announced fourth quarter earnings more than doubled and said it is upbeat about its prospects.

Terra's earnings for the October to December period jumped to $165.7m from $69.7m a year before, on revenues 20% higher at $683.5m.

The rise reflected increases of up to 80% in the prices of its fertilizers, which more than offset sharp falls in volumes sold. Terra shifted 16% less urea ammonium nitrate than a year before, and 30% less ammonium nitrate, and, like many rivals, mothballed some production facilities over the winter.

Michael Bennett , the Terra chief executive, said the group had "delivered strong fourth quarter results in a difficult environment".

He added that "fundamentals appear to be improving for spring", with the market for nitrogen-based fertilizers helped by a rebound in demand from farmers, who have been deterred by the high prices.

The 3% drop in US corn plantings estimated by some economists "could be more than offset by the estimated 5% of nitrogen applications that growers missed last fall and will be looking to make up this spring", Mr Bennett said.

In the longer term, the impact on stocks of a cut in corn planting this season could create "a stronger outlook for the 2009 second half and 2010 first half", he added.

Terra was also being helped by a drop in the price of natural gas, a major raw material. The forecast five-year low in nitrogen prices over the next 12 months put Terra on course for "strong margins".

Terra shares stood $0.20 higher at $23.43 in late trade in New York, a premium of 3.2% to the price implied by CF Industries' all-share offer.