A Methodological Comparison of Evapotranspiration Estimation for Coconut MATAG ( Cocos nucifera ) Seedlings in Tropical Nursery Conditions

This study was conducted at Universiti Putra Malaysia (UPM), located at a latitude of 3° N, in a rain shelter nursery on the rooftop of the Faculty of Engineering. The primary aim was to compare the performance of three evapotranspiration (ETc) estimation methods Blaney-Criddle, Hargreaves-Samani, and Penman-Monteith for Coconut MATAG ( Cocos nucifera ) seedling growth during nursery stages. The study spanned two cultivation seasons, each lasting 12 to 15 weeks, to account for potential seasonal variations. Data were collected from January to December 2023. The methodology involved calculating monthly ETc values using a crop coefficient (Kc) of 0.8, with climatic data gathered from a centrally located weather station within the rain shelter nursery to minimize the influence of direct rainfall. The findings revealed that the Blaney-Criddle method consistently provided the highest ETc estimates (7.67 mm/day in March to 8.1 mm/day in July), while the Hargreaves-Samani method yielded lower values (3.28 mm/day in February and December to 3.76 mm/day in July). The Penman-Monteith method showed moderate estimates, ranging from 3.84 mm/day in January to 4.96 mm/day in July. The study highlights the significant variability among methods, emphasizing the importance of selecting an appropriate estimation model for irrigation planning in tropical coconut MATAG nurseries.