2/18/2021 By Rod Nickel WINNIPEG, Manitoba, Feb 18 (Reuters) - Global sales of potash fertilizer look to hit record highs this year, helped by a spike in crop prices, but cautious North American producers are keeping a lid on supplies. Canada's Nutrien Ltd and U.S.-based Mosaic Co have benefited as crop prices climbed to multi-year highs, helped by strong Chinese demand. "We believe there is a cyclical recovery in agriculture underway," Nutrien Chief Executive Chuck Magro said on a conference call. As crop prices rise, farmers have greater incentive to apply fertilizer and maximize yields. Nutrien predicts the largest U.S. corn plantings in five