This study was conducted to investigate the effect of deficit irrigation on radiation capture, radiation use efficiency (RUE) and water use efficiency (WUE) in maize production, and to assess how these factors impact biomass production in water stress environments. Five irrigation levels were investigated: a full irrigation treatment with a water depth of 60 mm (I1), and four deficit irrigation treatments with depths of 50 (I2), 40 (I3), 30 (I4) and 20 mm (I5). Crop water stress index values indicated treatments I2 and I3 caused mild water stress while I4 and I5 caused severe stress. Water deficits significantly (p<0.05) reduced leaf area index compared to full irrigation. The reduction in biomass for I2 to I5 ranged between 7 and 43% relative to I1. In I1, the RUE was 3.46 g MJ-1, while mild and severe water stress significantly reduced it to 3.11 and 2.69 g MJ−1, respectively. A reduction in both intercepted photosynthetically active radiation and RUE contributed significantly to biomass reduction. Mild and severe water stress improved the WUE within range of 2 and 25% and 10 and 34%, respectively. The results suggest that in mild water stress environments, high RUE aids in minimizing production losses, and in cases of severe water stress, the reduced ability to capture and utilize radiation is compensated by improving the WUE.