| Summary: | In order to find suitable cultivar and N-topdress rates in corn planted after wheat harvest, a field experiment was conducted in Isfahan University of Technology Experiment Farm located at Shervedan, Falavarjan in 1994. The experiment design was a split plot with a randomized complete block arrangement and four replications. Main plots were four N-topdress rates (0, 90, 180, and 270 kg/ha) and the subplots were three corn hybrids (S.C.I08, S.C.301, and D.C.370). N-topdress rates had no effect on the stages of plant development (50% emergence, transition, pollination and physiological maturity). Also there were no significant effects on the number of leaves per plant, LAI, plant height and plant dry weight measured at pollination stage for different N-topdress rates. As expected, plant development stages differed among hybrids except that of time until 50% emergence. Differences in the number of leaves per plant, LAI, plant height and dry weight of plant measured at pollination stage were highly significant among hybrids. D.C. 370 had the highest values for all of these characteristics. Dry matter accumulation during growing season increased as the N-topdress rates were increased for the hybrids. Also N-topdress rates x hybrid interaction was significant for biological yield. Grain yield, number of seeds per ear, 100-seed weight and biological yield were affected by N-topdress rates and hybrid. Higher grain yield of D.C. 370 can be attributed to greater number of seeds per ear. The results of this study suggest that D.C. 370 with 90 kg/ha N-topdress rate can be used after wheat harvest in Isfahan.
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