During onion cultivation employing the transplanting system, initial stage of plantlet development is dependent on environmental conditions and agronomic management. This research was carried out in order to study the effect of sowing depth and density on damping-off and onion plantlet quality, developed in seedbeds where Pinus sp. dried leaves were used as mulch. Experiments were performed at Epagri - Experimental Station in Ituporanga, using cultivar Bola Precoce, between May and July (1993), and a creolle population between June and August (1993, 1994). The experiment was laid out in a complete randomized block design, with three replications, and 3 m²/plots. For a plant depth of 2 cm, best plantlets were obtained at sowing densities up to 3 g/m² of seeds. For a sowing density of 3 g/m² of seeds, best plantlets were obtained at plant depths of 1 and 2 cm. For seeds sown at a depth of 4 cm, damping-off of onion cotyledon-leaves significantly increased and plantlet survival was reduced. Plantlets obtained with a sowing depth of 1 cm displayed a significantly lower fresh weight of plant, in comparison with plantlets obtained when sown at 2 and 4 cm depths. Sowing densities higher than 3 g/m² reduced plantlet weight and number of plantlets able to transplant. Damping-off increased with sowing density only in 1994. The different sowing densities employed (2, 3, and 5 g/m²) did not affect emergency, stand, or plantlet survival.
Allium cepa; germination; stand; diseases; plantlet average weight
