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In the United States, much grain sorghum [Sorghum bicolor (L.) Moench] production area has shifted to maize (Zea maps L.) during the last 25 yr, which has been partially due to grain yield differences between these crops. The objective of this study was to document the rate of grain yield increases for maize and sorghum hybrids from 1950 to 1999 in rainfed and irrigated environments in eastern Nebraska. Across all production environments and years, maize produced 1.7 to 4.3 Mg ha(-1) greater yield than sorghum. The rate of yield increase was approximately three times faster for maize than sorghum but varied with production environments. The highest rate of yield increase (0.050 Mg ha(-1) yrl) was found for rainfed, high water-holding capacity soil conditions; the second highest rate of increase was for irrigated maize (0.028 Mg ha(-1) yr(-1)). The rate of sorghum yield increase under all environments and maize under rainfed, low water-holding capacity soil conditions was low at 0.010 to 0.015 Mg ha(-1) yr(-1): Pearson correlations indicated that the number of ears (panicles) per square meter had the highest association with yield (r = 0.68 for maize and r = 0.59 for sorghum) while both the number of kernels per ear (per panicle) and kernel weight were significantly correlated to yield for both crops. Yield component analysis for maize shows that yield increases with introduction year resulted from increased number of ears per square meter and kernel weight, while sorghum saw no significant correlation between yield and yield components.