For Agrium Inc., this is déjà vu. Just 18 months after the company fended off an assault from activist shareholder Jana Partners LLC, it is now in the crosshairs of an even bigger U.S. activist. ValueAct Capital Management LP revealed in a filing on Friday that it has acquired almost 8.2 million Agrium shares, or 5.7%…

Agrium Inc. targeted by another activist investor