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In order to the evaluate the effect of planting dates on phenological traits, plant height, pods per plant and seed yield of rapeseed spring varieties, a split-split plot experiment based on randomized complete block design with four replications was conducted during 2 years at Agriculture Research Station of Baykola, Mazandaran, Iran. Treatments were planting dates (September 29, October 9, October 19, October 29 and November 8) as main plot and sub-plots were three cultivars ( Hyola401, Option500 and RGS003. All the traits were affected by planting date and variety. The mean values of seed yield of Hyola401, Option500 and RGS003 were 3274, 2898 and 3040 kg ha-1, respectively and Option500 and RGS003 had not statistically significant difference. Non significant interaction effects of planting dates and varieties for seed yield indicated that yield reduction of the varieties in late planting dates had similar trend and Hyola401 and Option500 had the most and the least seed yield, respectively. Seed yield reduction at late planting date was related to insufficient vegetative growth before flowering stage. Significant positive correlation between plant height and number of pods per plant was the main reason that in late planting date reduction of plant height imposed reduction of pods per plant and finally seed yield was decreased.

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In order to evaluate the effect of different nitrogen fertilizer levels on physiological traits, plant height, yield components, and seed yield of rapeseed genotypes a split-plot experiment based on a randomized complete block design with three replications was carried out at the Baykola Agriculture Research Station, Mazaandaran during 2010-11. Four levels of nitrogen, as urea fertilizer, including of 0, 70, 140 and 210 kg ha-1 were considered as main plots and four rapeseed genotypes including of L7, Zafar, RGS003 and Hyola401 were considered as subplots. The result of analysis of variance revealed that the traits, including number of days to flowering, number of days to end of flowering, number of days to maturity, plant height, siliques pods per plant, seeds per silique, seed yield and oil yield were significantly affected by nitrogen levels. Genotype effect was significant effect on all the traits except seeds per silique. Hyloa401 and Zafar respectively with 3831.2 and 3893.7 kg ha-1 of seed yield, and also 1638 and 1591 kg ha-1 of oil yield were classified at the same statistical group. Non significant interaction effects of nitrogen fertilizer application and genotypes were achieved for all of the studied traits, indicated that the trend of variation of these traits due to nitrogen levels were similar in all genotypes. A significant positive correlation of seed yield with the other studied the traits, except days to flowering, indicated that increasing of nitrogen level application made increasing of the traits and finally seed yield.

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In order to determine the appropriate sowing dates, seed rates and their interaction effects on yield and yield components, oil and protein contents of soybean variety Sari, a split-plot experiment based on a randomized complete blocks design with four replications was carried out at Qaemshahr Gharakeil Agriculture Research Station in 2009. Five sowing dates including 15^th May, 31^th May, 15^th June, 1^th July and 16^th July were considered as main plots and three different seed rates including 60, 75 and 90 kg ha^-1 as the sub-plots. The results showed that all of yield components were affected by sowing dates and also seed rates had a significant effect on the number of pods per plant. Although due to increasing seed rates, yield components, such as pods per plant were decreased, but because of the increasing number of plants per square meters, seed yield not decreased significantly. Therefore for economically saving 60 kg ha^-1 of seed rates will be preferred. In this study high mean value of seed yield, biological yield and 1000-seed weight was achieved in first sowing date and all of the yield component characters were decreased in late sowing dates. Harvest index was increased in late sowing dates and it was not significantly affected by seed rates. Sowing dates and seed rates had not significant effects on oil and protein percentages, but due to significant effects of sowing dates on seed yield, oil and protein yields were significantly affected by sowing dates. In this study higher seed yield was belonged 60 kg ha^-1 of seed rate in first and second sowing dates which have not significant statistically differed.