Guidelines for comparisons among different maize maturity rating systems

Several systems are extensively used to rate maize (Zea mays L) maturity in North America, including growing degree days, crop heat units, and Minneso ta relative maturity rating days, Correspondence between the different syst ems varies with the temperature range of the environment, because of differ ent bases of calculation and unit size. However, general guidelines for con version from one system to another would aid communication among researcher s, producers, distributors, and extension personnel, particularly where reg ional preference for one system exists, but information developed in anothe r region is shared. Simple regression equations were developed from a data set with 4 years, 28 hybrids, and 19 locations (between 39 degrees and 48 d egrees N tot). Coefficients of determination were greater than or equal to 0.91, indicating that these equations could be used as a general guideline to compare maturity ratings developed using the different systems.