DES MOINES, Iowa (AP) – During a summer of drought, the U.S. Department of Agriculture says Iowa’s corn crop likely will plunge 19 percent below last year’s production. The crop is forecast at nearly 1.92 billion bushels, based on Aug. 1 conditions.  A USDA report released Friday says the yield is forecast at 141 bushels an acre, which would be the lowest figure since 1997.  Soybean production is forecast at 406 million bushels, which would be nearly 13 percent under last year’s figure.  Soybean yield is forecast at 43 bushels an acre, which would be 7.5 bushels under last year.