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Charlie Neibergall, Pool, Associated Press
Rick Kimberley presents a model tractor to Chinese Vice President Xi Jinping during his visit to Kimberley's family farm, Thursday, Feb. 16, 2012, in Maxwell, Iowa.

DES MOINES, Iowa — Agriculture officials from the United States and China are gathering in Iowa to discuss ways to feed the world, and Chinese Vice President Xi Jinping (shee jihn-ping) is seeing how local farmers help in that effort.

Xi climbed into the cab of a John Deere tractor Thursday at a 4,000-scre farm outside Des Moines.

Xi asked fifth-generation farmer Rick Kimberley how he knows when to sell the grain. Kimberley says that's "probably the toughest part of farming — to market our crops."

The visit came shortly after Xi opened the agricultural symposium and announced that the U.S. and China would sign a five-year deal to guide discussions on food security, food safety and sustainable agriculture.

U.S. Secretary of Agriculture Tom Vilsack says the agreement strengthens cooperation between the world's largest agricultural producers.