Abstract

In order to study the effects of different planting dates on the grain yield of soybean cultivars, an experiment was conducted as factorial in the form of randomized complete blocks design with three replications at the research farm of Ardabil (Iran) in 2009. In this experiment, the first factor of sowing date included four levels (27 May, 5, 15 and 26 June) and the second factor included cultivar Williams and line L₁₇. The results showed that there was not meaningful difference between cultivars under study for all traits, while there was meaningful difference between different sowing dates for all traits being studied except number of seeds per pod. Also, the interaction of planting date and cultivar was not meaningful for all traits under study. Sowing dates of 27 May and 5 June were placed in one group for number of pod in main bough, height of each plant and a weight of 100 seed. Also the mentioned traits had the highest in the expressed sowing dates. Sowing date of 27 May had the highest amount for pods per sub-bough, number of nodes per sub-bough, number of nodes in the main bough and the final yield.

Key words: Sowing date, soybean, vegetative and reproductive traits, yield.