U.S. President Donald Trump's tariff decisions since he took office on January 20 have shocked financial markets and sent a wave of uncertainty through the global economy.Here is a timeline of the major developments:February 1 - Trump imposes 25% tariffs on Mexican and most Canadian imports and 10% on goods from China,

President Trump said Japan and South Korea would face tariffs of 25 percent unless they reached an agreement with the United States. Other countries received notice of higher levies.

Higher tariffs on nearly all major U.S. trading partners are piling pressure on farmers already struggling with soaring agricultural supply costs and elevated rates.