UPDATE 1-PotashCorp buys 9.5 pct in Heringer to expand in Brazil

SAO PAULO, March 2 (Reuters) - Potash Corporation of Saskatchewan Inc, the world's largest fertilizer company by market value, agreed on Monday to pay about $56 million for a 9.5 percent stake in Brazilian rival Fertilizantes Heringer SA, the latest effort by Potash to grow in Latin America's largest economy.