B REAKAGE susceptibility and hardness of three yellow dent corn hybrids were determined for kernels separated into 6 size and shape categories and equilibrated to 12.3 and 14.7% moisture (wet basis). Measurements for breakage susceptibility by severe impact from the Wisconsin Breakage Tester (WBT) and by a grinding action from the Stein Breakage Tester (SBT) were determined by sieve and by a green dye test to analyze for severe, moderate, and minor breakage. Measurements for hardness by

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... were determined by near infrared reflectance wave-length of 1680 nm and Stenvert Hardness Tester parameters. Mechanical breakage at harvest was influenced more by kernel size, shape and structure characteristics then by kernel hardness properties. There were high correlations between and among physical properties (test weight and kernel density), composition (oil, protein, ash, and carbohydrate), hardness, and SBT values. Size and shape of the kernel and of the germ were interrelated and related to severe and moderate breakage from WBT and severe breakage from SBT. Results suggest that the 6.35-mm round hole sieve could be used along with the 4.76-mm sieve to provide SBT data on both hardness and brittleness. WBT results were several times higher than SBT results at both moistures.