Lisímetros de pesagem para medidas de evapotranspiração em estufa

Abstract

Weighing lysimeters are used for the purpose of determining water balance components, especially for evapotranspiration and evaporation. Within all know methods, lysimeter is considered the most accurate, but in order to obtain reliable data, their calibration must be performed in situ. The objective of this work was to calibrate 12 lysimeters to verify measurements’ linearity and the existence of hysteresis, besides evaluating the equipment's accuracy. The lysimeters had diameter and depth of 30 cm, with one load cell in each lysimeter for determination of mass variation, connected to a data acquisition and storage system. The calibration was performed by comparing the load and unload know mass (kg) with the load cell reading (mV). The calibration data were linear, presenting a significant mass correlation in response to voltage. The angular and linear coefficients varied from 762.78 to 1187.8 kg mV-1 and -499.99 to -798.00 kg, respectively. The absolute error ranged from 0.03 to 0.54, showing a high accuracy of the lysimeters. The accuracy for mass variation was 0.79 mm and the Willmott concordance index was 0.99, showing the good agreement between the estimated and observed values. It can be concluded that lysimeters are suitable for crop evapotranspiration determination.