The determination of the optimal density of plants per hectare considering species, cultivar, growing region and the system adopted is very important for the economic viability of the vegetable crop activity. We evaluated the effects of five plant densities (200, 250, 300, 400 and 600 thousand plants/ha) in different spatial arrangements on the yield and quality of bulbs of onion cultivar Empasc 355-Juporanga. The experiment was carried out at Epagri, Santa Catarina state, Brazil, from May to December 2010. We evaluated the cycle, productivity, post-harvest losses, crop return and biometric characteristics of the plants. The experimental design was randomized blocks, "split plot" in time, with four replications. The increasing of planting densities had no effect on commercial productivity of bulbs (36.19 t ha-1) and on the productivity of bulbs in classes 3 and above (31.91 t ha-1) and in the conservation of bulbs after three months of storage. However, this procedure resulted in the acceleration of the cycle of the cultivar (about seven days), reduction of the diameter and fresh mass of bulbs and increase of the total yield of bulbs (from 33.58 to 41.92 t ha-1) and yield of bulbs of class 2 (from 0.28 to 10.92 t ha-1). The achievement of higher quality bulbs (class 3) is obtained when using densities between 400,000 and 600,000 plants ha-1. Considering the costs of labor, in transplant and harvest operations, and prices paid to growers, the cost/benefit analysis indicates an increase of US$ 426.53 per hectare in the profitability by using densities of 600,000 plants ha-1.
Allium cepa; plant arrangement; postharvest; profitability
