Many corn fields across Iowa had significant variation in plant emergence and early-season growth within fields. Uneven emergence and plant heights are caused by several factors, including variation in soil temperature, seeding depth, residue distribution, soil crusting, and soil moisture, etc. Iowa producers dealt specifically with variable soil temperatures this year, which have now caused variable plant heights and vigor. How much can plant height vary before it causes a real yield loss? And based on this, should we have replanted more? Four percent of Iowa's corn acreage was replanted this year (National Agricultural Statistics Service [NASS], 5 June 2006).