Evaluation the Effif iciency of Simple Equation for Estimating Evapotranspiration and Changes of Soil Moisture in Sugarcane Field

Abstract

Evapotransiration is a key part for water cycle and can be used as a tool to improve water use efficiency and increase sugarcane yield. The Penman-Monteith FAO-56 (PM-56) has been widely used to estimate the evapotranspiration rate. However, the unavailability of local weather data has largely restricted its application. This study evaluated the simple equation and linked to water balance model for estimating soil moisture in the sugarcane field. Soil moisture in sugarcane yield was measured using Time Domain Reflectometry (TDR) soil moisture sensor and automatically recorded by data logger. The experiment was conducted in Khon Kaen Field Crops Research Center during March to September, 2014. Sugarcane cultivar KK3 was planted in plot site 36x40 m with spacing 1.20x0.50 m. After that, simple equations were developed for estimating evapotranspiration and changes of soil moisture in sugarcane field. Comparison the simple equation with Penman-Montieth FAO-56 (PM-56) and Priestley-Taylor (PT) for evapotranspiration and compared with experiment and Canegro model for soil moisture. Simple equation performance was evaluated using the statistical parameters such as cofficient of determinatron (R²), root mean square error (RMSE) and normalized root mean square error (NRMSE). The result showed that the simple equation was excellent for evapotranspiration estimation comparing to PT. The total evapotranspiration was not significantly different from PT equation (2.2%) but lower than PM-56 19.1%. The simple equation was the good estimation of soil moisture with the NRMSE 10.2%. The results indicated that the evapotranspiration and soil moisture in sugarcane field can be estimated by the simple equation.