(Fertilizer item updated for stock-price movement.)SIOUX CITY, Iowa ( TheStreet) -- After more than a year of rejecting CF Industries' ( CF) advances, Terra Industries' ( TRA) board said Wednesday that CF's latest and highest-price offer trumps a bid it had already accepted from the Norwegian fertilizer giant, Yara Industries. In a press release issued Wednesday, Terra used the phrase "Superior Proposal" to describe CF's raise, and said that it has notified Yara of its plan to terminate the buyout agreement the two had struck less than a month ago if Yara doesn't return with a better offer. Under the terms of the initial deal, Yara would have acquired Terra for $41.10 a share in cash. CF's latest bid, made last week and reversing an announced decision in January to give up on its hostile pursuit of Terra, comprises $37.15 in cash plus nearly a tenth of a share of CF stock. The offer had a per-share value of about $46.74, based on Tuesday's closing stock prices. Yara, which will convene a special meeting of its board on Thursday, now has five days to raise a counteroffer; or it can simply take its break-up fee ($123 million) and head home. Also in a statement Wednesday, CF said it had sent a merger agreement to Terra. Stephen Wilson, CEO of the Deerfield, Ill., company, reiterated its chief arguments for a CF-Terra combination: "We believe that Terra is worth more to CF Industries than to any other acquirer, given the strategic benefits of the transaction, including synergies, which only CF Industries can achieve." Wilson added, "Any offer from Yara must be heavily discounted for the substantial risks and length of time associated with closing." If CF, which began a tender offer for Terra's shares last week, is able to complete the purchase of its smaller rival it will have likely dashed the hopes of its own hostile suitor, Agrium ( AGU), which has been pursuing CF almost as long as CF has pursued Terra. Early in Wednesday's regular session, Terra shares were advancing 59 cents, or 1.3%, to $46.42, on heavy volume. CF shares sank at the opening bell, but by 10:00 a.m. EDT they had inched into the green, trading higher by 25 cents to $100.88.