Effect of regulated deficit irrigation scheduling on water use of corn in southern Taiwan tropical environment

The enhancement of common irrigation practices can substantially contribute to sustainable water development. This study was conducted to determine an effective water application depth for improving agricultural water use (irrigation water use efficiency (IWUE) and water use efficiency (WUE)) in surface irrigated corn production, and to determine an effective rooting depth for irrigation planning in a tropical region. The effect of five irrigation treatments on corn growth, yield and root extraction patterns were investigated and assessed. The treatments included a full irrigation treatment with a water application depth of 6cm (T5), and four deficit irrigation (DI) treatments with depths of: 5cm (T4), 4cm (T3), 3cm (T2) and 2cm (T1). Irrigation water was applied to all treatments when soil moisture for T5 was depleted by 40%. Seasonal water applied varied from 235 to 555mm while the seasonal crop evapotranspiration ranged from 331 to 605mm. Results revealed all treatments sustained varying levels of water stress except for T5. Corn grain yield ranged from 567.13gm−2 in T1 to 911.26gm−2 in T5, a significant increase (P<0.05) of 37.7%. Similarly, there were significant differences in biomass ranging from 1012.64 to 1774.05gm−2 and leaf area index ranging from 3.99 to 5.83m2m−2. The highest WUE of 1.79kgm−3 and IWUE of 2.41kgm−3 were observed for T3 and T5, respectively, whereas the lowest was found in T5 with respective values of 1.52 and 1.63kgm−3. Results indicate that it is possible to implement DI strategies for reducing agricultural water use without significant impact on grain yield. Treatments T3 and T4 offer water savings of 29% and 14% respectively in irrigation application with a 10.5% and 8.6% insignificant reduction in grain yield relative to T5. Further, agricultural water productivity can be enhanced by employing a rooting depth of 60cm when planning irrigation application amount.