Effect of Planting Date and Irrigation Intervals on Yield and Yield Components of Rice (Oryza sativa L.) in Rasht Region

This study was carried out to investigate the effects of irrigation intervals and different planting dates on the yield and yield components of rice. A split-plot design based on randomized complete block design was used with three replications, at Rice Research Institute of Iran (Rasht) in 2016 and 2017. The main factor was irrigation at four levels (full flooding, 5, 10 and 15 days irrigation intervals) and the secondary factor was planting date at three levels (April 21, May 11, and May 31). The results of analysis of variance showed that irrigation and planting date had a significant effect on the yield of rice at 1% probability level. The highest amount of biological yield was obtained in full flooding and 5-day irrigation interval, with an average of 10960 and 10238 kg/ha, respectively, and in May 11 and April 21 planting dates with an average of 10553 and 10397 kg/ha, respectively. The highest 100-grain weight was obtained in May 11 and May 31 planting dates, the maximum number of panicle per plant was observed in full flooding treatment, and in May 11 planting date and the highest number of filled grains was observed in full flooding treatment. The maximum number of hollow grains was observed in 15 and 10-day irrigation intervals and May 31 planting date. The results showed that the full flooding irrigation with a yield of 4271 kg/ha had the highest grain yield. The 10 and 15 days irrigation intervals had less grain yield than flood treatment and  5-day irrigation interval treatments. In two years of the experiment, the planting date of May 11 had the highest grain yield with an average of 3820 kg/ha. In this experiment, the May 11 planting date had the most favorable environmental conditions for growth and had a good yield-stability.