Average corn yields top­ped 200 bushels per acre in more than one-third of Iowa’s counties last year, according to estimates released last week by the USDA’s National Agricultural Statistics Service. A total of 39 counties had average yields above 200 bushels per acre (bpa), led by Marshall County at 226 bpa. Grundy,  Delaware,  Tama  and  Ida counties rounded out the top five with yields over 222 bushels. The low reported yield was 149.4 bpa in Adair County. Six counties didn’t have yields reported due to...