Sitting by a fireplace in the Kimberley family's living room in Des Moines, Iowa in February 2012, Xi Jinping, then China's vice-president, chatted with the Iowan family about life on their farm.

Xi was given a tour of Kimberley Farm and asked specific questions: How long the grain was stored, and how the storage temperature controlled?

"What surprised me was his profound understanding of agriculture and his awareness of its crucial role in the world," Rick Kimberley recalled.

The highlight of the tour came when the Kimberley family showed Xi one of their tractors. To everyone's surprise, Xi climbed up into the tractor and tried his hand at operating the machine.

"A stronger Sino-US cooperation in agriculture is good for the people of the two nations, as well as for ensuring world food safety," said Xi during the visit.