Resumen
Production of onion (Allium cepa) seedlings for transplants is done directly in flat soil conditions or in trays using reduced cell volumes and high plant density conditions, without consideration of the possible effect that reduced cell volume can have on crop growth. Therefore, the objective of this study was to evaluate the production of onion seedlings in two seedbed systems and their subsequent behavior in the field. Seedling production and transplant establishment were determined with a long-day type of onion (cv. Grano de Oro) in the Metropolitan Region of Chile (33°-34° south latitude) from 2004 to 2005. The production of covered root transplants was performed in trays with 286 (18 cm3), 432 (10 cm3) and 814 (5 cm3) cells each, equivalent to plant densities of 1144 (low), 1728 (medium) and 3256 (high) plants·m-2, respectively. The production of bare root transplants was done in boxes with equal plant densities as in the tray system. Next, plants obtained from each seedbed system and plant density were field transplanted. Based on the results obtained, neither plant density nor transplant production system affected the pseudo stem diameter 25 days after emergency (DAE). At 77 DAE, the pseudo stem diameters were 3.8 and 5.2 mm, the root dry weights (DW) were 4.8 and 6.2 g·plant-1 produced in high and low plant density, respectively. This suggests that the tray system had a minor effect on plant development. At 23 days after transplanting (DAT) differences in the pseudo stem diameter between the three densities were obtained, although differences between the bare and covered root systems were not statistically significant. Plants obtained from high-density seedbeds showed a smaller pseudo stem diameter and lower canopy DW than plants produced in low-density seedbeds until 84 DAT. At harvest, no differences were observed in formation or among the quality categories of the onion. Therefore, it is feasible to produce onion seedlings to be transplanted with bare roots or covered roots, produced in high-density boxes or in 5 cm3 cells, without affecting the final quality of harvested onion bulbs. Los almácigos de cebolla (Allium cepa) se siembran en suelo o en contenedores (alvéolos) de reducido volumen, en alta densidad, sin considerar el efecto del tamaño del contenedor en el crecimiento del cultivo. Con el propósito de estudiar el efecto del sistema y densidad de la almaciguera se realizaron dos ensayos (almácigo y transplante) en la Región Metropolitana (entre 33,3º y 34º lat. sur), Chile. Se empleó cebolla cv. Grano de Oro, cultivar de día largo destinado para guarda, en la temporada 2004-2005. La siembra de almácigos para transplante a raíz cubierta se estudió en contenedores con 286 (10 cm3), 432 (10 cm3) y 814 (5 cm3) alvéolos, correspondiendo a 1144 (D1), 1728 (D2) y 3256 (D3) plantas/m2 y para trasplante a raíz desnuda en cajoneras, con iguales densidades, bajo invernadero. Hasta 25 días después de emergencia (dde) la densidad y el tipo de almaciguera no influyeron el diámetro del cuello. A 77 días, D3 presentó un diámetro de cuello de 3,8 mm·planta-1 y D1 5,2 mm·planta-1; el peso seco (PS) radical fue de 4,8 y 6,2 g·planta-1, respectivamente, con menor efecto en plantines de contenedores. Los plantines se transplantaron al aire libre, cuando éstos alcanzaron 5 a 6 mm a nivel de cuello. A los 23 días después del transplante (ddt), hubo diferencias en el diámetro de cuello entre las tres densidades de planta, pero no hubo diferencias significativas entre transplante a raíz cubierta o desnuda. Las plantas provenientes de D3 mostraron menor diámetro de cuello y PS de canopia, hasta 84 ddt. En cosecha no hubo diferencias entre densidades en categorías de calidad y malformaciones de bulbos.