Effects of Planting Date and Planting Density on Bulbing Date, Yield and Agronomic Traits of Improved Population of Behbahan Onion

The present study was conducted in split factorial based on RCBD with four replications at Behbahan Agricultural Research Station during 2011-13 cropping seasons, to determine the suitable sowing date in nursery and plant density in farm for improved population of Behbahan onion. Main plots consisted of four planting dates 6 September, 21 September, 6 October and 21 October. Sub plots were combination of three row spacings (20, 30 and 40 cm) and three plant spacings (5, 7.5 and 10 cm) as factorial. Earliest time of bulbing was estimated using bulbing ratio and statistical method of cusmus. In the first year bulbing occurred between photoperiods of 12 h and 3 min (17 March) and 13 h and 16 min. (27 April). In the seconed year bulbing occured between photoperiods of 11 h and 35 min. (1 March) and 12 h and 46 min. (9 April). Bulbs were harvested when 50-80% of top foliage had fallen and collapsd. Planting date of 21 September produced the highest yield (52.62 tha-1), however difference of yield between planting dates of 6 and 21 September was not significant. Planting date of 6 September had the maximum bolted plants (17.5%). By delay in planting date, bolted plants percent was decreased. Yield of plants with 20 cm row spacing (51.52 tha-1) and 5 cm plant spacing (47.92 tha-1) was higher than plants with the other row and plant spacings. Reduced planting density decreased bolted plants percent. According to the results, sowing of improved population of Behbahan onion on 21 September in nursery and transplanting with 20× 5 cm distance (100 plants per m2) is recommended for behbahan area.