Development of seed agglomeration technology using lettuce and tomato as model vegetable crop seeds

Seed agglomeration is a coating technology with the purpose to sow multiple seeds of the same seed lot, or multiple seeds of different seed lots, varieties or species. The objective of this study was to develop agglomeration technology by producing single agglomerates or pellets using lettuce and tomato as model vegetable crop seeds. Physical properties of dry and wet pellets were measured and seedling emergence assessed. Pellets were formed by a molding technique with a mixture of filler, binder, and seeds. Diatomaceous earth (DE) was used as the filler, and two binders were tested: polyvinyl alcohol (PVA) and a commercial organic binder. Each binder solution was mixed with DE, and seeds were added during the agglomeration process. Oval and cylindrical pellets were molded with known compression forces. Cylindrical pellet strength increased, as PVA binder concentration increased from 8% to 16% and pellet strength was greater for pellets produced with 3kg than with 1kg compression. The percent seedling emergence and speed of emergence were not affected by a compression force of 1kg and 3kg for PVA-pelleted lettuce and tomato, respectively compared to the non-pelleted control. Cylindrical pellets formed using the commercial organic binder at 1 and 3kg force without lecithin showed significantly less seedling emergence and speed of emergence for lettuce seed; no significant differences were observed for tomato seed. Seedling emergence and speed of emergence for lettuce seed from oval pellets formed with the commercial organic binder and lecithin at 1kg and 3kg compression grouped with the non-pelleted control. Cylindrical pellets made without lecithin and with the commercial organic binder using 3kg compression force containing three tomato seeds produced plants with greater combined leaf area, fresh and dry weight than plants grown from single non-pelleted seeds, 26 days after being sown in the greenhouse.