The board, which invests on behalf of the Canada Pension Plan, says U.S.-based Jana hasn't made a compelling case for change at Agrium's board of directors.
"While we agree that opportunities for improvement exist, we are of the view that the dissident's nominees do not represent the best alternative for optimizing long-term value creation, particularly in light of Jana's proposed director compensation structure," the CPPIB said in a posting on it website.
As a result, the CPPIB said it was throwing its support behind all of Agrium's nominees and would not support any of those put forward by Jana, including that of managing partner Barry Rosenstein.
Earlier, two major proxy advisory firms came out with different conclusions about how shareholders should vote in the hotly contested battle for control of Agrium Inc.'s board of directors.
Glass, Lewis & Co. LLC has recommended that its clients vote for all 12 of nominees put forward by the Calgary-based Agrium.
But Institutional Shareholder Services came out in favour of two of Jana's five alternative nominees, Rosenstein and David Bullock, a former CFO of Graham Packaging.
Among the Jana proposals for increasing value, the one that has garnered the most attention has been to break off Agrium's retail business into a separate company.
However, it also wants the company to cut costs, better manage capital and improve corporate governance.