Effects of Onion Set Transplanting Date on Physiological Response, some Vegetative Characteristics and Yield of Onion Genotypes in Behbahan Region

This experiment was conducted to determine the best transplanting date to earliness the onion, at Behbahan Agriculture Research Station for two years (2012-2014). Experiment was performed in factorial based on RCBD with three replications. The factors were four onion genotypes, including: Improved population of Behbahan onion, Ramhormoz landrace, Primavera and Texas Early Grano cultivars and three transplanting dates, including :23rd September, 7th and 23rd October. To produce sets, 10-12 g seeds of onion genotypes were sown per square meter in late February and sets were harvested in late January. Based on the results, threshold of day length related to bulbing for Primavera cultivar was shorter than for other genotypes. The highest total and marketable yield was produced on 23rd October transplanting date. Percent of bolted plants and doubling bulbs decreased by delaying transplanting date. The minimum bolted plants and doubling bulbs belonged to Primavera cultivar. The highest total and marketable yield as well as mean bulb weight obtained from primavera cultivar. Interaction effect of genotype and transplanting date showed that the most total and marketable yield was produced by Primavera cultivar on 23rd October transplanting data and marketable yield of this cultivar on transplanting date of 23rd September was about 25% lower than transplanting date of 23rd October. Nevertheless, due to 20-30 days crop earliness in transplanting date of 23rd October and 50% reduction in onion price at this time of the season, and also by considering this fact that the farmers will obtain more income from the 23rd September transplanting date, therefore this date is recommended for transplanting of Primavera onion set in Behbahan region.