Daily evapotranspiration prediction from Louisiana flooded rice field

During 1995, daily evapotranspiration (Et) from a flooded rice field was ca lculated with a water balance equation using measured values of water revel , precipitation, irrigation, seepage, and tailwater runoff. Stagewise Et wa s 6.3, 8.1, and 6.8 mm/d for the vegetative, flowering, and yield formation stages, respectively; average daily Et was 6.8 mm/d. Grass reference Er (E t-r) combination models Penman-Monteith, FAO-Penman, and 1963 Penman were e valuated for their capabilities to predict rice Et using dairy weather data . Daily Et,was also calculated by summing up hourly values with the Penman- Monteith method. The Penman-Monteith (daily) method had a coefficient of de termination (R-2) of 63.7%, as compared with 62.9, 60.0, and 61.7% for Penm an-Monteith (hourly), FAO-Penman, and 1963 Penman methods, respectively. Cr op coefficients (K-c) using the Penman-Monteith (daily) model were 1.39, 1. 51, and 1.43 for the vegetative, flowering, and yield formation stages, res pectively. Developed K-c values were verified using limited rice Et data in 1996. The K-c values underpredicted rice Et by 3.7%, which was acceptable for water management.