ABSTRACT
Two field experiments were conducted during the two consecutive rice growing seasons 2020 and 2021 at the experimental farm of Sakha Agric. Res. Station, Kafr Elsheikh, Egypt to study effect of four irrigation intervals i.e.1- irrigation every 3 days (control) (I₁), 2- Irrigation every six days (I₂), 3- Irrigation every nine days (I₃) and 4- Irrigation every twelve days (I₄) on growth , yield and yield attributes of three rice genotypes i.e., 1- Giza 178 as inbred rice cultivar, 2- Egypt hybrid 1 and 3- Egypt hybrid 2 . The experimental design was split plot with four replications.
The obtained results showed that prolonging irrigation intervals from 3 to 9 or 12 days significantly reduced flag leaf area (cm), stomata conduces ,transpiration rate , CO₂ net assimilation rate, plant height (cm) ,number of panicles m^-2 , panicle length (cm), number of branches/panicle  , number of filled grains /panicle,1000 grain weight(g) ,  grain yield (t ha¹), biomass yield (t ha¹) and harvest index in both seasons. On the other hand, leaf temperature increased with increasing irrigation intervals from 3 to 9 or 12 days in both seasons.
Regarding genotypes variation results indicated that Giza 178 rice variety  significantly exceeded Egypt hybrid 1 and Egypt hybrid 2 in flag leaf area, leaf temperature , transpiration rate, Co₂ net assimilation rate, plant height, number of panicles m^-2, panicle length, ,1000 grain weight,  grain yield, biomass yield  t and harvest index  in both seasons . 
The interaction effect among irrigation intervals and rice genotypes was significant on all studied traits except number of filled grains /panicle in both seasons.
       At irrigation every 12 days Giza 178 rice variety gave the highest grain yield as compared with Egypt hybrid 1 and Egypt hybrid 2 in both seasonsـ