Crop heat units (CHU) are the amount of cumulative heat over the growing season. Growing Degree Days (GDD) are also a measurement of heat to track crop development throughout the season, mainly for determining crop maturity. Check out this article to help determine your GDDs: www.beckshybrids.com/Blog/ArtMID/841/ArticleID/2177/Agronomy-Talk-Corn-and-Soybean-Early-Season-Emergence.