SOUTHERN TEXAS GRAIN DIFFERENTIALS ADJUSTED Posted county prices in 99 southern Texas counties have been changed to reflect only one market differential instead of the usual two-terminal market pricing system, a senior Agriculture Department official said. Interior grain and soybean prices in the affected counties will now be based solely against the Texas Gulf. Prior to the change, county prices were also priced against the Amarillo market. The changes were made to better reflect local market conditions, said Ralph Klopfenstein, deputy administrator for commodity operations at USDA. "The Texas Gulf has always been the dominant market in those counties. Amarillo never became effective for that area," Klopfenstein told Reuters.