The Effects of Planting Date on Grain Yield and Yield Components of Rice Cultivars

This research was conducted in order to investigate the effects of planting date on the grain yield and yield components of three rice cultivars in Khouzestan climatic conditions (South-west Iran), this research was conducted as a split plot using Randomized Complete Block Design (RCBD) with three replications in the 2010 cropping season in the research field of Khuzestan Agricultural Research and Natural Resources Center(Shavoor agricultural research station). In this research, the dates 5 th May, 25 th May, and 15 th June were considered as the main factor in the main plots, and the rice cultivars Hamar, RedAnbarbou, and Danial were regarded as the secondary factors in the sub plots.The results showed that planting date significantly affected grain yield, biological yield, harvest index, 1000 grain weight, fertility percentage, the number of filled grains per panicle and the number of fertile tillers. The second planting date exhibited the highest grain yield with an average of 6018.3 kgha -1 and the first planting date assumed the lowest grain yield. The cultivars had a significant difference in terms of the abovementioned attributes. Danial and Hamar cultivars featured the highest grain yield with averages of 5591 and 55549 kgha -1 respectively; the lowest amount belonged to Red Anbarbou cultivar.Theinteraction effects of planting date and cultivar was significant on all attributes except for panicle length. The highest grain yield belonged to Danial cultivar in the second planting date with an average of 6902.6 kgha -1 while the lowest was obtained for Red Anbarboucultivar on the first planting date. Both delayed and early planting resulted in the decline of grain yield of rice cultivars. The reason for these reductions was the shortening of the vegetative growth period in delayed planting, andthe coincidence of the flowering stage with environmental high temperaturesin earlier planting dates compared to the desirable state. Thus, Danial cultivar on the second planting date is recommended for cropping in Khouzestan climate conditions.