Influence of oat kernel size and size distributions on test weight

Test weight is one of the most important characteristics for evaluating grain quality in oats. This study evaluated the role of oat kernel size and size distributions on test weight. Oat kernel size was measured from digital image analysis, sequential sieving and mean kernel mass of original oat samples and their different size fractions. Data from ten genotypes and eight environments indicated that smaller sized kernel fractions derived by sieving had higher bulk density than those from the larger sized kernel fraction. The smaller kernels also had greater groat percentages, indicating greater kernel density in smaller size fractions. To investigate a possible packing effect of different kernel sizes on test weight, the summation of volumes of size fractions was compared with the volume of the original sample. Our results indicated no significant differences between the volumes of the original sample and the sum of the volumes of their size fractions. This indicated that oats of uniform size packed just as efficiently as a mixture of different size kernels. A similar experiment evaluating bulk densities of the different size fractions reached the same conclusion. These results indicate that the test weight drops observed in seed cleaning, where the smaller kernels are removed, are due to the removal of the most dense kernels in the sample, and not to a packing effect, where smaller kernels might fill in spaces between larger kernels.