Effect of planting date and plant density on phenology and yield of soybean in Ardabil Region, Iran

The study was carried out in Agriculture Research Station of Ardabil Branch, Islamic Azad University, Ardabil, Iran in 2009 as a factorial experiment based on a Randomized Complete Block Design with three replications. The first factor was planting date from May 20 until June 29 with 20-day intervals. The second factor was plant density at three levels of 20, 30 and 40 plants m-2 and the third factor was cultivar including Williams and LW17. It was found that planting date significantly influenced days to 50% emergence, 50% flowering and 50% pod formation at 1% probability level. The effect of planting date was significant on grain yield per plant and per unit area, pod number per plant and single-grain weight at 1% and on grain number per pod at 5% probability level. Plant density significantly impacted days to 50% flowering and 50% pod formation at 1% probability level. The changes in plant density (between 20 and 40 plants m-2) did not significantly influence grain yield per unit area, pod number per plant and single-grain weight, while grain yield per plant and pod number per plant were significantly affected by plant density. Grain yield and yield components did not have significant differences for the studied traits. Cv. LW17 was less sensitive to the changes in plant density than cv. Williams, so that the highest and lowest grain yield per plant of cv. Williams was obtained at plant densities of 20 and 30 plants m-2, respectively.