Evaluation the effects of mother plant planting date and density on germination and vigor of soybean seed

High temperature during seed set and seed filling can reduce yield and seed quality. In order to evaluate the effect of high temperature during planting date and also plant density on soybean seed quality, an experiment was conducted at two locations, namely, Seed and Plant Certification and Registration Institute in Karaj and Agricultural and Natural Resource Center of Moghan, in 2013. The studied factors were included planting date (5th of May, 5th of June and 5th of July), plant density (300, 400 and 500 thousand plant/ha) and soybean varieties (Williams and L17) were sown in the rate of 40 plants per m-2 at 5th May, 5th June and 5th July. The experiment was conducted as a factorial based on a randomized complete block design (RCBD) with three replications. The results of standard germination test showed that in Moghan area, the highest normal seedling percentage (92.1%) was obtained at fifth of June and in Karaj area, it (96.2%) was gained at fifth of July. In addition, it was noticed that cv. L17 in Moghan and cv. Williams in Karaj had the highest normal seedling percentage. The results of accelerated aging test was cleared that the normal seedling percentage in karaj was more than Moghan area and it showed that the quality of seed that were produced in Karaj was better than Moghan area. There was no significant difference between areas in 300 and 400 thousand of plant/ha and in these both density, the result of Karaj was better than Moghan area, but there was significant difference between normal seedling percentage after accelerated aging test in Karaj (77.6%) and Moghan (58%) in 500 thousand plant/ha. The highest seedling vigor index (11.75) was obtained in 400 thousand plants/ha at fifth of July in Karaj area and the lowest rate of it (5.41) was observed in 300 thousand plants/ha at fifth of June in Karaj area.