Reference evapotranspiration estimation inside greenhouses

Abstract

Because of the large area occupied by a class A pan, alternative methods have been sought to estimate reference evapotranspiration (Eto) inside greenhouses. The objective of this work was to compare ETo estimated by different methods inside and outside a greenhouse. A class A pan (CAPi), a reduced pan (RPi) and an atmometer (Ai) were installed inside a greenhouse, and another class A pan (CAPo) was installed outside. ETo estimates, obtained by CAPi, RPi, and Ai were 56%, 69% and 63% of those estimated by CAPo, respectively. A simple linear regression showed positive coefficients R = 0.94 for the RPi and the CAPi, R = 0.91 for the Ai and the CAPi, R = 0.70 for the CAPi and the CAPo, R = 0.66 for the RPi and the CAPo, and R = 0.62 for the Ai and the CAPo. ETo needs to be estimated inside greenhouses and it is possible to use reduced pans or atmometers to estimate the ETo inside the greenhouse. Equipment replacement would increase the available space inside the greenhouse.