Shares in CF Industries slumped nearly 8% despite Canada's Agrium, in a third bid sweetener, adding $240m to its offer for the US fertilizer group.

Agrium, terming its latest terms "best and final", gave CF shareholders until November 18 to accept the $4.5bn cash-and-shares bid, which it said valued its US target at a "compelling" multiple of underlying earnings.

The bid raised by $5 per CF share, to $45 per share, the cash element of Agrium's offer, valuing CF stock at $92.99 at the time of the announcement.

However, CF shares slumped by more than $7 to $78.78 in early deals in New York before recovering some ground to close at $79.90.

'Shareowners disappointed'

Analysts blamed the share decline on discontent that Agrium had not come in with a richer sweetener.

"A lot of CF shareowners would have been thrilled with a $100 [a share] offer, and will be very disappointed today," analysts at Sterne Agee said.

The US broker added that it expected CF to reject Agrium's latest offer as "inadequate", and to say investors were better off with current strategy, which includes a hostile bid for Terra Industries, a rival American fertilizer group.

CF said it would "in due course review the latest revised proposal", while noting that the multiple of underling earnings outlined in Agrium's bid is lower than the ratio CF itself is offering for Terra.

'Final opportunity'

Agrium chief executive Mike Wilson said that the company was prepared "immediately" to sign up to a deal, having gained the necessary finance and "addressed" all Canadian and US antitrust concerns.

"CF stockholders must tender their shares by November 18 to send an unambiguous message that they want this deal with Agrium at this price."

Agrium in June received 62% acceptance from CF shareholders for a lower bid - also termed "best and final" - but the ballot result was not, under Delaware law, binding on the US group's board.

The Canadian fertilizer giant may need the support of more than 80% of shareholders to "get CF's board's attention", Sterne Agee said.

Agrium shares jumped 4.0% to finish at Can$53.27 in Toronto.