In this work, pellets were produced in a small concrete mixer like machine (pan), where seeds rolled over one another, receiving gradually and alternately coating (stuffing) and cement (adhesive) ingredients, until they reached the required size. Seeds were then dried and classifified. Lettuce seeds were pelleted with fine sand, coarse sand, fine lime or coarse lime, using bentonite diluted in water at 7,5%, or polivinil acetate glue (PVA) at 30%, as cement. A portion of these pellets were covered with a thin layer of lime plus PVA. The small pellets made of fine sand plus lime with or without the fine finish cover presented the best results. Rates of germination and seedling development were similar to those obtained with bare seeds. Lime usage delayed seedling growth, being more pronounced on larger pellets. Using lime plus PVA glue resulted in the most physical resistance, whereas the use of sand plus bentonite, resulted in the least resistance; fine finish enhanced the pellet resistance. Pellets with PVA glue were more resistant than those with bentonite. Coats of sand were most quickly dissolved, although pellets tested dissolved in less than one minute. The water content in each type of pellet was less than 0.45%, with low higroscopicity (less than 0.6%).
Lactuca sativa; coat; pelleting; resistance; higroscopicity.