the study of effect of planting date and density on marketable yield and bulb characteristics of an onion population from behbahan

This study was conducted to determine the optimum planting date and density for a selected population of Behbahan onion for two years. Experiment was conducted as a split factorial based on RCBD design with four replications. Main plots consisted of four planting dates from 6 September to 23 October with 15 day intervals. Sub plots consisted of combinations of three row spaces (20, 30 and 40 cm) and three plant spaces (5, 7.5 and 10 cm). Marketable yield, bulb weight and diameter, total soluble solid and bulb dry matter percentage were measured. Analysis of variance showed significant effects (at 1% probability level) of planting date, row spacing and plant spacing on marketable yield. Planting at 21 September produced the greatest marketable yield (42460 kg ha-1). Marketable yield decreased by delaying the planting date. Plants with 20 cm row spacing (43780 kg ha-1) had a greater marketable yield than plants with  20 and 30 cm row spacing ( 34970 and 28570  kg ha-1, respectively). Plants with 5 cm space produced greater bulb yield than those with 7.5 and 10 cm (35400 and 31310 kg ha-1, respectively (. Decreasing the planting density led to increase in bulb weight, diameter and neck diameter. According to the results for the Behbahan onion population, planting at 21 September (in nursery) and transplanting with 20 × 5 cm distances (100 plants m-2) with a marketable yield of 60240 kg ha-1 may be recommended for Behbahan climatic conditions.