Comparative Assessment of Evapotranspiration Estimation Methods for Coconut (Cocos nucifera) Seedling Growth in the Nursery Phase

Abstract

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 (Cocos nucifera) growth during nursery stages. The study spanned two cultivation seasons, each lasting 12 to 15 weeks, to account for potential seasonal variations. The data was collected from Jan-Dec 2023 and the methodology involved calculating monthly ETc values using a crop coefficient (Kc) of 0.8, with the data collected using the weather station located in the middle of 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, ranging from 7.67 mm/day in March to 8.1 mm/day in July. The Hargreaves-Samani method produced lower ETc values, varying from 3.28 mm/day in February and December to 3.76 mm/day in July. The Penman-Monteith method showed moderate ETc estimates, ranging from 3.84 mm/day in January to 4.96 mm/day in July. The conclusions drawn emphasize the significant variability between the methods, highlighting the importance of method selection in optimizing irrigation schedules for coconut cultivation in tropical nursery conditions.