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To determine the best cultivar and planting date in Isfahan region, an experiment was conducted on different soybean cultivars during 1981 and 1982. In 1981 , yields of 17 cultivars were compared and late maturing cultivars (with growing periods of more than 150 days) were eliminated. Soybean cultivars of S.R.F. 450, Clark, Williams, and Woodworth had the highest seed yield, respectively. In
1982, the experiment was continued with 11 Cultivars and two planting dates. As a result, S.R.F. 450 and Williams cultivars at May planting and Clark, Woodworth, and Williams cultivars at June planting had the highest seed yield. From yield components, seed number had the most important role in seed yield increase. In general, It was concluded that medium maturing cultivars, with growing period of 100-140 days had the.highest seed yield in Isfahan region, and early maturing cultivars with growing periods of 90—131 days are suitted for late planting dates.