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Improving irrigation water management is becoming important to produce a profitable crop in South Texas as the water supplies shrink. This study was conducted to investigate grain yield responses of corn (Zea mays) under irrigation management based on crop evapotranspiration (ETC) as well as a possibility to monitor plant water deficiencies using some of physiological and environmental factors. Three commercial corn cultivars were grown in a center-pivot-irrigated field with low energy precision application (LEPA) at Texas AgriLife Research Center in Uvalde, TX from 2002 to 2004. The field was treated with conventional and reduced tillage practices and irrigation regimes of 100%, 75%, and 50% ETC. Grain yield was increased as irrigation increased. There were significant differences between 100% and 50% ETC in volumetric water content (?), leaf relative water content (RWC), and canopy temperature (TC). It is considered that irrigation management of corn at 75% ETC is feasible with 10% reduction of grain yield and with increased water use efficiency (WUE). The greatest WUE (1.6 g m-2 mm-1) achieved at 456 mm of water input while grain yield plateaued at less than 600 mm. The result demonstrates that ETC-based irrigation can be one of the efficient water delivery schemes. The results also demonstrate that grain yield reduction of corn is qualitatively describable using the variables of RWC and TC. Therefore, it appears that water status can be monitored with measurement of the variables, promising future development of real-time irrigation scheduling.
