This is a BBC Latin America report on the causes and the latest news of the agrarian strike in Colombia. It's in Spanish, but you can use your web browser's translator if you don't speak Spanish. Namely, the author points to the free-trade agreements that Colombia has recently signed with the US and the EU, among others, as the major factor degrading the quality of life for the Colombian peasantry. An earlier bout of trade liberalization in the 90s destroyed Colombia's production of large-scale grains like wheat or lentils, and other commodities like cotton, but peasants focused on high-value, mainly perishable goods to maintain a decent income. These products like dairy and potato have now also had their protections taken away, so basically the small farmer has had his last leg taken out from under him.
At any rate, today the government has agreed to set up some sort of negotiating table with peasants, so we'll see how that works out.