Two field experiments were conducted at the Experimental Farm of Rice Research and Training Center, Sakha, Kafr El-Sheikh, Egypt during 2011 and 2012 seasons to investigate the effect of irrigation intervals (continuous flooding and Irrigation every 6 or 8, 10 days), organic and mineral fertilization (control, 160N + 40P+ 60K kg/ha, compost at 5 t/ha, 40N + 10P+ 15K kg/ha + compost, 80N + 20P+ 30K+ compost, 120N+ 30P+ 45K kg/ha + compost and 160N+ 40P+ 60K kg/ha + compost) on the growth, productivity, technological characters of grains and some rice water relations of two hybrid rice genotypes (Egyptian hybrid 1 and SK2046 hybrid). The results obtained could be summarized as follows:
1- The data indicated that continuous flooding followed by irrigation every 6 days recorded the highest values of most growth characters (dry matter production, Leaf area index, crop growth rate, days to heading and number of tillers), yield and its components (number of panicles, panicle length, number of total grains/panicles, sink capacity, panicle density, 1000-grain weight, panicle weight, grain yield, straw yield, biological yield and harvest index), grain quality (hulling, milling and head rice percentages) and grain chemical analysis (N,P,K % and protein %). On the other hand, irrigation every 10 days recorded the highest values of days to heading, unfilled grains and broken rice % in both seasons.
2- Egyptian hybrid 1 recorded the highest values of most growth characters, yield and its components, grain quality and chemical analysis of grains. However, SK2046 hybrid recorded the highest values of panicle length, unfilled grains % and broken rice % in both seasons.
3- Fertilization systems had a marked effect on characters studied in favor of fertilization with application of 160N+ 40P+ 60K kg/ha + compost, 160N + 40P+ 60K kg/ha and 120N+ 30P+ 45K kg/ha + compost which they gave the highest values of most growth characters , grain yield and its components , grain quality and chemical analysis of grains. However, unfertilized plants gave the lowest values of most characters studied.
4- It can be concluded that it is possible using the irrigation system every 6 days with the application of mineral fertilizer of 120 Kg N + 30 Kg P2O5 + 45 kg K2O / ha + organic fertilizer of 5 ton compost / ha for saving the amounts of irrigation water by about 10% as well as mineral fertilizer of NPK by about 25 % with insignificant minimum reduction in grain productivity of hybrid rice genotypes.