The Mosaic Company reported fourth-quarter net income down 79%, as falling prices for crop nutrients potash and phosphate ate into profits. Per-share earnings of 30 cents fell short of consensus by 14 cents a share. However, profitability concerns aren't making a dent in investor appetite. Shares are up after the board approved a $1 billion share repurchase program. Management already approved a buyback program in December which would see the company repurchase 43.4 million Class A shares within the first seven months of 2014.