Water Requirement of Corn (Zea mays L.) for Fall Season of Central Iraq Under Full and Deficit Irrigation

The objective of this study was to estimate water requirement and water use efficiency of corn (fall season) under full and deficit irrigation. A field experiment was carried out at the Experimental Research Station, Soil and Water Resources, Ministry of Science and Technology, 30 km south east of Baghdad, Iraq. The experimental design was a split plot in three replicates. The main plots were the full and deficit irrigation treatments: Full irrigation (control) and four deficit irrigation treatments at stages of establishment, vegetative, flowering, and yield formation. The sub-plots were two varieties. The amount and time of irrigation were determined based on soil water depletion measured by neutron moisture meter. The control treatment showed the highest ETa and was 416 mm for the synthetic variety. Whereas the irrigation deficit treatments caused significant decrease in ETa compared to the control and the decrease was 5-12% depending on the stage of growth. Similar behavior was observed for the hybrid variety. These values represent nearly 50% of those values estimated for the central part of the country. The contribution of the groundwater in water requirement was estimated by 10-22%. Although the amounts of water applied in the irrigation deficit treatments were less than those of the control, they resulted close yield with no significant differences. The highest yield was 9.1 obtained for the control and the lowest 7.6 ton/ha for the irrigation deficit at flowering, which reflected the sensitivity of this stage for the irrigation deficit.