Howard Audsley, who wears dark glasses and has his hair cut short in a crew cut, has been driving his Toyota truck through the state of Missouri for the past 30 years to assess the value of farmland. Barreling down the flat roads of Saline County, Mo., on a recent day, Audsley stopped his truck at a 160-acre tract of newly tilled black land. The land sold for $10,700 an acre last February, double what it would have gone for five years ago.
