The new buyback authorization comes on top of its existing authorization, which still has $850 million remaining.
The Plymouth, Minn., company also said that starting Oct. 1, it would reduce its production of phosphates by 500,000 tons in 2019 by idling its Louisiana operations in an effort to reduce inventory.
Despite the production slowdown, Mosaic expects strong fertilizer application in the fall and a more balanced global supply/demand outlook by 2020.
"Phosphate prices have declined further through the summer, with excess imports continuing to enter the U.S. on top of high channel inventories," Chief Executive Joc O'Rourke said in a statement.
"We expect our move to idle production to tighten supply and rebalance the market. Mosaic will prioritize shipments to meet key customer needs through the idling period."
Mosaic shares were down 31% in 2019 through Monday. They're trading up 4.2% to $21.03 on Tuesday.