Articles
USE OF WEIGHING LYSIMETER AND BOWEN-RATIO ENERGY-BALANCE FOR REFERENCE AND ACTUAL CROP EVAPOTRANSPIRATION MEASUREMENTS
Article number
537_14
Pages
143 – 150
Language
Abstract
The use of precision (load cell) weighing lysimeters has been demonstrated as one of the most effective methodologies for precise hourly reference and actual crop evapotranspiration measurements to be used in validation studies of empirical methodologies for Reference Crop Evapotranspiration (ETo and ETr) estimation, comparison of different methodologies for actual crop evapotranspiration measurements (ETc), as well as for crop coefficients (Kc) studies.
The relative scarcity of weighing lysimeters data is mostly due to their high prices and complexity for construction and installation.
The use of micro-meteorological stations (Bowen-Ratio Energy-Balance, BREB) are, in turn, widely used for evapotranspiration measurements due to their relatively low cost and installation simplicity.
The main objective of the present study was to calibrate the load cell response of a 6 m2 weighing lysimeter, validate the use of BREB for hourly ETo measurements and use of its climatic variables to be applied in the Penman-Monteith equation for hourly ETo estimations.
The data analysis showed good agreement between BREB and grass lysimeter.
For those days when reference crop was close to the standard, the Penman-Monteith equation showed good results predicting ETo. Load cell field calibration showed that both 6 wire and 4 wire full bridge connections could be used with their respective regression coefficient.
However, the 6 wire connection was more advisable since it accounts for the tension drop along the cable.
The relative scarcity of weighing lysimeters data is mostly due to their high prices and complexity for construction and installation.
The use of micro-meteorological stations (Bowen-Ratio Energy-Balance, BREB) are, in turn, widely used for evapotranspiration measurements due to their relatively low cost and installation simplicity.
The main objective of the present study was to calibrate the load cell response of a 6 m2 weighing lysimeter, validate the use of BREB for hourly ETo measurements and use of its climatic variables to be applied in the Penman-Monteith equation for hourly ETo estimations.
The data analysis showed good agreement between BREB and grass lysimeter.
For those days when reference crop was close to the standard, the Penman-Monteith equation showed good results predicting ETo. Load cell field calibration showed that both 6 wire and 4 wire full bridge connections could be used with their respective regression coefficient.
However, the 6 wire connection was more advisable since it accounts for the tension drop along the cable.
Authors
J.J.B. Yrissarry, F.S. Naveso
Keywords
Schedule, load cell, reference crop, Penman-Monteith, Extremadura, Spain
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