MAXIMIZING WATER AND N FERTILIZER USE EFFICIENCIES UNDER MAIZE CROP AT NORTH DELTA

Field experiment was conducted at Sakha Agricultural Research Station farm, Kafr El-Sheikh Governorate during the summer season of 2008, maize (zea mays) plants (variety mono parid 10) was cultivated. N-mineral fertilizer was applied as urea (46%).Split plot design was used; main plots were irrigation treatments namely: Surface irrigation (I₁), Semiportable sprinkler: (I₂), Minisprinkler (I₃), Floppy sprinkler (I₄), Surface drip (I₅) and Subsurface drip  (I₆). Sub plots were nitrogen fertilization treatments namely: 100 % soil application (N₁), 100 % fertigation (N₂), 75 % fertigation + 25% soil application (N₃), 50 % fertigation + 50% soil application (N₄) and 25 % fertigation + 75% soil application (N₅). The main résults could be sammarized as follows:
The lowest value of water applied under maize crop (48.06 cm) was achieved under subsurface drip system. and the highest value (63.03 cm) was recorded under surface irrigation system. While, the highest amounts of water stored under maize roots zone (49.08 cm) was obtained under floppy sprinkler system, and the lowest amount (45.31 cm) was found under subsurface drip system. The highest value of water consumptive use by maize crop was recorded under surface irrigation system (53.89 cm), and the lowest value was detected under subsurface drip system (38.17 cm). The most extracting portion of soil moisture by plant roots occurs in the upper 15 cm. The maximum value of water application efficiency (94.27%) was obtained from subsurface drip system, and the minimum (76.59%) was obtained from surface irrigation. The highest values of FWUE under maize crop (1.18 kg m^-3) was achieved under surface drip system. and the lowest value (0.79 kg/m³) was recorded with semiportable sprinkler system The highest value of CWUE to maize crop (1.56 kg m^-3) was achieved under surface irrigation system., and the lowest value (0.97 kg m^-3) was recorded under semiportable sprinkler system. The longest plants were recorded with I₁ system, and the shortest plants were obtained with I₆ system. The longest plants (159.66 cm) were recorded with N₁ (surface irrigation), and the shortest plants (148.66 cm) were obtained under N₅ (subsurface irrigation system).Treatment I₅ obtained the highest value of leaf area (806.53 cm²) and I₆ produced the lowest value (597.38 cm²). Nitrogen  application rate had significant effect on leaf area. The highest nitrogen application rate (N1) recorded 712.85 cm², while the lowest nitrogen fertilizer application rate (N₅) recorded 683.26 cm²(LA).  
The longest ear length (22.5 cm) was recorded from I₁ and the shortest ear length (11.58 cm) was recorded with (I₆). The effect of nitrogen fertilizer application rates, N₁ gave the longest ear length (19.09 cm) compared with the shortest ear length recorded with N₅ (17.58 cm).The interaction between irrigation systems and nitrogen application rates was highly significant effect on ear length.
       There was high significant effect of irrigation systems on ear diameter. I₁ gave the highest ear diameter (9.4 cm).  The lowest ear diameter was obtained by I₆ (5.92 cm). Ear diameter was highly significantly affected by changing the nitrogen fertilizer application rate.  The highest ear diameter (8.35 cm) was recorded by using N₁ and the lowest and (7.23 cm) was recorded by using N₅ . Where I₁ gave the highest weight of 100 grain (50.18 g) as compared with (I₆) (34.12 g). N₁ gave the highest grain yield (2347.11 kg fed^-1).  The lowest grain yield was recorded under N₅ (2053.83 kg fed ^-1). Concerning the interaction effect between irrigation system and nitrogen application rate on grain and straw yield it was high significant.
The highest grain yield (2625.5 kg fed^-1) was recorded from I₁ while the lowest grain yield (1865 kg fed^-1) was recorded with I₂.
The highest values of N use efficiency to maize grain (20.21), was recorded with I₁. and the lowest values (13.87 kg/N unit) was achieved under I₂.   Concerning the N-recovery (%) of maize grain yield, the highest value of N-recovery to maize grain (30.79%) is achieved with I₅ and the lowest value (19.19 %) was recorded under I₂. N-use efficiency and N-recovery % attributed to N₂ is higher than the same obtained by N_1. The highest values of N-use efficiency were obtained by I₆ N₂ (21.78 kg/N) and the lowest one was detected under I₆ N₁ (10.35 kg/N unit).
Data indicated that N-recovery increased with increasing N level.  The highest value of N-recovery % was found under I₅ and N₂ (35.40% grain and 18.16% straw), whereas, the lowest one was found under I₂ and N₁ (13 % grain and 10.49% straw)