effect of canopy temperature on protein and sugar soluble content, oil and yield of soybean in karaj and moghan areas

in order to study the canopy temperature effect on protein and soluble sugar, oil percentage and yield of soybean in different planting dates, an experiment was conducted as factorial based on randomized complete block design with three replications in karaj and moghan areas during 2012-13. the studied treatments were included cultivar (‘williams’ and ‘l17’) and planting date (5th of may, 5th of june and 5th of july). results showed that the soluble protein content was not affected by studied factors. the highest oil percentage (22.38%) in both areas was related to first planting date, also second and third planting dates with 18.8 and 17.72% respectively were arranged in the next levels. in karaj area, the maximum rate of soluble sugar (73.17 mg/g grain) was obtained at third planting date but in moghan area, it (72.12 mg/g grain) was observed at second planting date. furthermore the highest yield (3679 kg/ha) was attained at second planting date in both areas while also third and first planting dates with 3160 and 3000 kg/ha were putted in the next levels. results showed that although the oil percentage at 5th of may planting date was higher than the other planting dates, but the rate of yield and soluble sugar were decreased at this planting date, because of encountering the pod set and grain filling stages with higher temperature. so, in order to prohibition of this problem occurrence, it is suggested that soybean doesn’t plant in may and it be postponed until the mid of june.