Plant nutrients referred to as micronutrients are essential for crops, but are needed in very small amounts. Prior research in Iowa and neighboring states showed inconsistent corn and soybean grain yield responses to micronutrient applications, except for Zn in corn. This report summarizes results of two studies with corn and soybean, one with application to the soil and the other with application to foliage, which were conducted from 2012 through 2014. The micronutrients evaluated were boron (B), copper (Cu), manganese (Mn), and zinc (Zn).