Micronutrients are essential plant nutrients that are needed in very small amounts. Prior research in Iowa and neighboring states since the 1950s showed inconsistent corn and soybean grain yield responses to micronutrient applications, except for zinc in corn. This report summarizes results of two studies with corn and soybean rotations, one with application to the soil and the other with application to the foliage, which were conducted from 2012 through 2014. The micronutrients evaluated were boron (B), copper (Cu), manganese (Mn), and zinc (Zn).