DES MOINES, Iowa (AP) — This year’s corn harvest is ahead of schedule with 4 percent in already compared with just 1 percent at the same time last year. The harvest is three to four weeks ahead of schedule in most of the corn belt because an unusually warm spring allowed farmers to plant earlier. Most expected a good year then, but the U.S. Department of Agriculture has been reducing its estimates of the nation’s harvest amid a severe drought centered over the Midwest. It now says it expects the least amount of corn since 2006, although the tally won’t be certain until the harvest is done. It is significantly ahead of schedule in some places. The USDA reported Monday that in Tennessee and Missouri, the harvest was already 18 percent complete.