Using the exact language it did two weeks ago, Terra Industries Inc. (TRA) again rejected a takeover offer from rival CF Industries Inc. (CF) on Tuesday. CF had sweetened its bid Monday to $3.07 billion.

The two companies and Agrium Inc. (AGU) are in a three-way tussle for position in the fertilizer industry. The struggle comes as fertilizer producers look 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.

As they said on March 11 after rejecting a $27.50-a-share offer, Terra Chairman Henry Slack and President and Chief Executive Michael Bennett said Monday's new $30.50-per-share bid "substantially undervalues" the company and would deliver less value than Terra would achieve independently.

While announcing on Monday its boosted all-stock bid for Terra, CF also recommended shareholders reject rival Agrium's hostile bid for CF, initially valued around $3.6 billion. It added that Agrium can afford to price its offer at more than $100 a share instead of its current per-share bid of $72.

In recent trading Tuesday, CF shares were up 3.9% at $73.99 while Terra gained 1.9% to $27.93 and Agrium added 1.4% to $39.17.

-By Tess Stynes, Dow Jones Newswires; 201-938-2473; tess.stynes@dowjones.com