Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Manjit K. Misra


This study was conducted to evaluate the effectiveness of a gravity table for separating seed corn into fractions of different quality, and to correlate the physical and physiological properties of each fraction of seed corn;Five lots of seed corn with five sizes (unsized, large flat, large round, small flat, and small round) were conditioned through two types of gravity table (pressure and suction type). The original sample, obtained before the gravity table separation, and four fractions (heavy, medium heavy, medium light, and light) obtained from the discharge edge of each gravity table, were analyzed for physical (bulk density, weight of 100 seeds, volume, specific gravity, terminal velocity, purity, breakage susceptibility, and pericarp injury), physiological (standard germination, cold germination, conductivity, and field emergence), and chemical composition (NIR protein, oil, and starch contents);Both gravity tables performed similarly as determined by the seed quality of various fractions. Flat seed corn was better in seed quality than round seed corn. The gravity table was efficient in separating seed corn into fractions of different quality along the discharge edge of the gravity table deck. However, when the initial seed quality of a lot is high, only marginal improvement in seed quality was obtained. The light seed obtained from the low side of the gravity table did not meet the seed requirement and must be discarded. The medium light fraction may be re-conditioned to recover fractions of acceptable seed quality. Bulk density was the best physical property of the seed corn correlated with the physiological quality of the seed. Weight of 100 seed may be also used, but bulk density is preferable due to its higher relationship with field emergence than seed weight.



Digital Repository @ Iowa State University,

Copyright Owner

Leopoldo Baudet



Proquest ID


File Format


File Size

206 pages