Abstract :
Irrigation intervals and potassium levels were studied using Giza179, GZ7112 and Sakha106 rice genotypes at the experimental Farm of Rice Research and Training Center (RRTC) Sakha, Kafr El-Sheikh, Egypt, during 2012 and 2013 seasons. Four irrigation intervals treatments namely; continuous flooding (W), irrigation every 4 days (4W), irrigation every 8 days (8W) and irrigation every 12 days (12W), as well as five rates of potassium; 0 (K0), 36 (K1), 72 (K2), 108 (K3) and 144 (K4) kg K2O/ha were used. The field experiments were laid out in a split-spit design with four replications. The irrigation treatments were applied in the main plots, the rice genotypes were placed in the sub- plots and the potassium rates were put in the sub- sub plots. The main obtained results indicated that Giza179 produced higher grain yield and its attributes followed by GZ7112 rice line under continuous flooding (W) without any significant decrease in yield up to 8W and then significantly decreased under12W treatment. The amount of water saved due to increasing irrigation intervals compared to continuous flooding were (10.36 and 8.37 %) for Giza179 and (10.50 and 10.36%) for GZ7112 under 4W treatment and (17.81 and 23.66%) for Gzia179 and (13.33 and 18.44%) for GZ7112 with 8W treatment, while under 12W water saved was about 23.91 and 27.90 % with reduction in grain yield about 22.42 and 24.71 % in 2012 and 2013 seasons respectively. Over both season using Giza179 and GZ7112 rice genotypes which gave higher yield about (9.70 and 9.33 t/ha), water saved (20.73 and 15.88 %) and water use efficiency (0.90 and 0.81 kg/m³) for both genotypes respectively. It means that the total water input ranged from 11260.88 and 10006.80 m³/ha (which equal about 4700 m³/fed) under 8W treatment using Gzia179 rice variety compared with national average which reaches to 1428.57 m³/ha (which equal about 6500 m³/fed). The application of potassium up to 108 K2O/ha (K3) significantly increased rice yield and relatively mitigated the undesirable effect of water stress resulted in increase the WUE and water saved %.
