Abstract

In order to determine the best irrigation withholding time in four varieties of rice, an experiment in factorial statistical format based on complete randomized block design was conducted. This experiment took place in National Rice Research Institute situated in Rasht township (Guilan province, North Iran) in 2008. First factor included four rice varieties (v₁ = Khazar, v₂ = Sepeed Roud, v₃ = Hassani, and v₄ = Binaam). The second factor included three drought periods (d₁ = 1 week after flowering, d₂ = 2 weeks after flowering, and d₃ = 3 weeks after flowering). The statistical analysis results almost in most measured traits showed significant difference at 1% probability level. The highest grain yield of 5635.8 kg/ha was obtained of Sepeed Roud variety. Also, the interaction effect of V₂d₃ with 6000 kg/ha was recorded the maximum grain yield. But since one of the goals for conducting this study was to determine a variety with short-water-necessity period in water deficiency years of cultivation, it is recommended that V₂d₁ level with grain yield of 5325 Kg/ha be used even though it has a lower yield.

Key words: Rice varieties, irrigation withholding time, yield, yields components, Iran.