Effects of planting time on the growth stages and oil and seed yield of soybean in Ardabil region, Iran

In order to study the effects of different planting dates on growth stages and oil and seed yields of soybean varieties, an experiment was conducted as a factorial based on a randomized complete block design with three replications at the Agricultural Research Station of Islamic Azad University, Ardabil Branch in 2009. The first factor was planting date at four levels (27 May, 5, 15 and 26 June) and the second factor was Williams variety and L17 line of soybean. The results showed that there were significant differences between planting dates for traits like plant height, days from sowing to first flowering, days from sowing to first pod initiation, oil percentage, seed yield, oil yield, growth period and days from sowing to seed formation. Interaction effects of planting date and varieties were not significant for all evaluated characteristics. Planting dates of 27 May and 5 June were not statistically different and were the same for plant height, days from sowing to first flowering, days from sowing to first poding and oil percantage. Planting date of 27 May had the highest values for seed yield, oil yield, growth period and days from sowing to seed formation. Results of this research showed that becaues of short growth period in Ardabil region, soybean could not reach to its potential yield and it seems that the planting date of 27 May is more suitable than other planting dates in Ardabil cold climate.