Investigating the trend of changes of physiological growth indices of maize (Zea mays L.) in different sowing dates at Varamin climate conditions

In order to investigate the effect of sowing date on the physiological growth indices of maize, an experiment was performed in the form of randomized complete blocks with three replications in Varamin at 2015 year. The treatments included five sowing dates (9th of April, 21th of May, 18th of June, 30th of June and 15th of July) and the cultivar of Karoun (single cross 701) used. In each of the 5 to 7 day periods of each plot, 5 plants were randomly selected and the traits studied in connection with this study included: total dry weight, leaf area and leaf dry weight to draw the curve of physiological growth indices of maize plants during the growing season. The results showed that the effect of sowing date was significant on the maximum leaf dry weight, total dry weight, leaf area index (LAI), relative growth rate (RGR), crop growth rate (CGR), specific leaf area (SLA) and fresh yield. In the meantime, the fourth sowing date (30th of June) had the highest maximum leaf dry weight, total dry weight, leaf area index, CGR and fresh yield, and the second sowing date (21th of May) was superior to the rest of the sowing dates in terms of maximum RGR and SLA. The CGR was reduced in different sowing dates after reaching its maximum and eventually became negative. According to the results of this study, maize sowing in the first decade of July can be recommended for Varamin region.