Oat Grain Density Measurement by Sand Displacement and Analysis of Physical Components of Test Weight

Test weight or bulk density of oats (Avena sativa L.) has a major influence on the monetary value of oat grain. We hypothesize that test weight can be attributed to grain density and packing efficiency. We have measured oat grain volume and density by a sand‐displacement method and derived the packing factor for six oat cultivars grown in three environments. Volumes of individual grains were 31–38 mm³ and were highly correlated with grain mass. Grain densities were 0.96–1.03 g/cm³. Packing efficiency, defined as the space proportion occupied by the grains, was 53–55%. Regression analysis suggested that 78% of the variation in test weight could be attributed to grain density. Size fractionation of grain by sieving and analysis by digital image analysis indicated that smaller grains within an oat sample packed more efficiently than larger grains and larger grains in a sample were less dense than the smaller grains. Analysis of oat grain components indicated groat densities were ≈1.29 g/cm³ and hull densities were ≈0.69 g/cm³. The difference in densities between groat and hull provide a physical basis for the recognized relationship between groat percentage and test weight.