Alternative methods for density grading of sugarbeet seeds: A proposal

Sugarbeet seeds are selected on "gravity tables" to provide high density seeds that exhibit superior germination and emergence to non-selected seeds. Use of gravity tables allows separation under dry conditions, thus, the seeds do not require drying before treatment and packaging. However, the advent and increased use of seed priming and other preconditioning treatments obviate the need for keeping seeds dry, and opens alternative, and possibly more useful methods of gravity grading that involve moistening of seeds. We propose two methods of achieving gravity-based seed separation with moist seeds. 1) Premoistened seeds could be dispensed into a stream of flowing water. Seeds with densities less than 1.0 (that of water) would float, whereas those with greater densities would sink in the flowing water, with the velocity of sinking being dependant upon their relative densities. Passage of the moving stream of seeds and water through a set of baffles would allow separation of seeds into discrete, preselected density classes. 2) Alternatively, mixtures of seeds and water could be pumped into hydrocyclones. The flow of material into these devices produces a cyclonic flow within them that causes centrifugal separations of materials that then can be drawn off in a binary separation. Either of these proposed grading methods seems likely to provide improved gravity-based separations that may provide planting seed of improved quality.