Two field experiments were carried out at Giza Agric. Exp. and Res. Sta., Fac. Agric., Cairo Univ., during 2015 and 2016 seasons to determine growth, yield and water use efficiency under different levels of irrigation water for increasing agro – economic feasibility. The treatments were the combinations between three applied irrigation water levels (75, 100 and 125% of the recommended water applied) and six cropping systems (50% soybean + 100% corn, 100% soybean + 100% corn), traditional solid corn, solid corn (mixed system), traditional solid soybean and solid soybean (mixed system). The experimental design was split plot design with four replications. The results indicated that LAI of soybean and corn were affected significantly by applied irrigation of water. Soybean LAI was affected significantly by cropping systems, meanwhile corn LAI was not affected. Soybean solid culture had the highest values for soybean LAI as compared to those of intercropping cultures. Intercropping soybean with corn (100% soybean + 100% corn) and application 3750 m3 of irrigation water/fad produced the highest LAI of both components as compared with the other treatments. Seed yields per plant and per fad and HI were not affected significantly by levels of applied irrigation water but the converse was true with number of pods per plant and seed index. Most of corn traits were affected significantly by applied irrigation water. Traditional solid soybean culture had the highest values of number of pods and seed yields per plant and per fad as compared to those of intercropping systems. Intercropping soybean with corn decreased seed yields per plant and per fad by about 47.94 and 55.76%, respectively, as compared with those of traditional solid culture of soybean. Applied irrigation water levels x cropping systems did not affect significantly all the studied soybean traits. Conversely, applied irrigation water x cropping systems affected significantly all the studied corn traits except number of harvested plants and grains weight/ear. LER ranged from 1.39 to 1.52. RCC of soybean was greater than 1 of intercropping cultures indicating yield advantage compared with traditional solid culture of soybean. The values of aggressivity of intercropping soybean was negative for all combinations indicating that soybean is dominated component, but corn was the dominant crop in the present study. Intercropping soybean with corn under the application of 75% of recommended applied irrigation water achieved the highest WUE of economic and biological yield. Net return of intercropping soybean with corn was varied between treatments from L.E. 2523 per fad by intercropping 50% soybean with 100% corn that received 75% of applied irrigation water to L.E. 3784 per fad by intercropping 100% soybean with 100% corn that received the highest level of applied irrigation water.
