Volume and Density Measurements of Single Sorghum Grains versus Sample Test Weight

Highlights An imaging system with a rotating pedestal was designed/fabricated to collect 36 images per revolution/seed. A computer program converted the 36, 2-dimensional images into a 3-dimensional model of the seed. Individual seed volumes and densities were determined on a set of sorghum samples. Sorghum sample test weight was determined after dockage was removed and correlated with seed densities. Abstract. Sorghum production is on the rise in the United States, and breeders need rapid methods to assess grain quality. One of the most important metrics of grain quality is test weight, with low test weight sorghum having poor quality and marketability. Many image methods use 2-dimensional images to obtain 2-dimensional data of single seeds. In this study, we developed a revolving 3-dimensional imaging instrument to obtain seed thickness more accurately and to determine the volume of single sorghum seeds. By including single seed weights, seed density can be determined. Using a diverse set of sorghum samples with varying test weights, we assessed whether composite density calculated from single seeds was correlated with test weight and bulk density. For these experiments, the bulk test weights were measured for a set of uncleaned sorghum samples and ranged from 51 to 59 lb/bu. When dockage was removed with an aspirator, test weight values of the samples improved to 55 to 61 lb/bu. We then separated the sorghum seeds into four size categories (small, medium, large, and extra-large) and determined single seed volumes and density using our 3-D instrument. A single seed was placed on a revolving pedestal and imaged every 10°. The imaging software collected 36 images per seed during the 360° of rotation. Then, those 2-D images were processed to form a 3-D model of the seed, and individual seed volumes were computed. The volumes of the individual sorghum seeds were ~9, ~14, ~21, and ~28 mm 3 for the small, medium, large, and extra-large sizes, respectively. Each single grain was weighed, and the individual seed densities were calculated. Composite grain density values from single-seed measurements ranged from 1.22 to 1.33 mg/mm 3 and were linearly correlated with the clean-sample test weight values (R 2 = 0.71).