Field experiments were conducted in 2014 and 2015 at Sakha Agriculture Research station, Kafr El-Sheikh (31° 07' N Latitude, 30° 57' E Longitude) at North Nile Delta, Egypt to study the effects of raised beds, irrigation intervals and ammonia gas injection levels on productivity of irrigation water (PIW) of rice. A split split plot design with four replications was used. Ammonia gas injection levels were devoted to the main plot, irrigation treatments were allocated in sub-plots and rice planting methods were arranged in sub sub-plots. Ammonia gas injection levels were 70 unit nitrogen N (F1), 80 units (F2) and 90 units (F3). Planting methods treatments were transplanting in flat, as a traditional method (M1), and transplanting in raised beds only (M2). Irrigation intervals were irrigation every four days after transplanting (I1), irrigation every six days after transplanting (I2), and irrigation every eight days after transplanting (I3). Results showed that there was no significant difference on GY between I1 and I2 while there were a significant difference on SY, BiomY and other yield components between I1, I2 and I3. The highest values of SY, BiomY and other yield components were obtained from I2 compared to I1 and I3. As for planting treatments, GY, SY and BiomY increased by 20.8%, 40.4% and 31.7% respectively under M2 compared with M1. There were no significant differences on GY and its attributes between F2 and F3 except SY and BiomY.
Mean values of water applied for M1 received the highest amount of IWA to be 14338 m3 ha-1 compared to M2 which was 10443 m3 ha-1, respectively. The amount of water used in M2 is a feasible amount to grow rice with a 27.2% saving of water. Higher value of PIW of I2 proved its superiority over I1 and I3 treatments by 16% and 7%, respectively. Planting methods treatment M2 increased NUE by 21% compared to M1. The highest values of NUE were recorded for I1 and I2 without any significant differences between them whereas the lowest one was obtained from I3. Also, the highest mean value of NUE was obtained under F1whereas the lowest was under F3.
Therefore, M2 could be applied by the farmers' under irrigation interval of I2 and 80 units N as ammonia gas injection (F2) because it saved irrigation water by 36% and increased NUE by 17% compared to M1 x I1 x F1 which in normally practiced in North Delta, Egypt, without any reductions in GY.