CF Industries Holdings Inc. (CF) extended the expiration date of its exchange offer for all outstanding shares of rival Terra Industries Inc. (TRA), which the fertilizer producer has been trying to buy since January.

The latest move comes as three fertilizer producers, which also includes Agrium Inc. (AGU), are looking to take advantage of the drop in sector stock prices since last summer to buy up production capacity ahead of an expected rebound in prices.

In its latest effort, CF extended the offer for Terra's stock to June 12, shortly after Terra is required to hold its annual meeting by stockholders. CF said all terms and conditions of the exchange offer remained unchanged.

As of the market close on Thursday, CF said a total of 19,370 shares of common stock had been tendered in the exchange offer.

Previously, Terra had been required by its own bylaws to hold its annual meeting by May 15, but earlier this month, the company amended the bylaws to give it more flexibility with setting the date.

CF initially offered to buy Terra in January in a deal valued at $2.1 billion. It later sweetened its bid to $3.07 billion. At the same time CF has been pursuing Terra, it has been fending off a takeover bid by larger rival Agrium. On Tuesday, CF shareholders backed three directors up for re-election at the company's annual board meeting, signaling an endorsement of the company's direction.

Earlier this week, Terra Industries reported its first-quarter net income dropped 70% on falling demand for nitrogen products, while CF posted a 53% drop in its profit as mark-to-market items masked improvements in revenue and total volume.

CF's shares were unmoved in after-hours trading at $71.09, as Terra's shares were even at $27.90.

-By John Kell, Dow Jones Newswires; 201-938-5285; john.kell@dowjones.com