This week’s revelation that a Chinese billionaire and member of its Communist Party is the second-largest foreign owner of farmland in the US sparked outrage among politicians, who want to know why Chen Tianqiao’s $85 million purchase was a secret for nearly a decade. Chen, a co-founder of Shanda Interactive Entertainment, bought nearly 200,000 acres of farmland in Oregon in 2015 at about $430 an acre, according to the Land Report, a magazine that focuses on private land ownership in the US. However, his purchase of the acreage does not appear in government records of land ownership by foreign investors,...